ISO/TS 24560-1:2022

Tissue-engineered medical products — MRI evaluation of cartilage — Part 1: Clinical evaluation of regenerative knee articular cartilage using delayed gadolimium-enhanced MRI of cartilage (dGEMRIC) and T2 mapping

This document provides a principle to determine the parameter settings and operating methods for the evaluation of the composition and structure of articular cartilage by dGEMRIC and T2-mapping MRI in humans with a typical example of the methods; each are distinct MRI technologies that allow for noninvasive observation of soft tissue characteristics. The methods provided in this document are intended for application in the evaluation of the clinical effects of tissue-engineered cartilage or other cartilage regeneration products used in the knee joint, and are also applicable for the evaluation of regenerative cartilage in other joints, although some modification of parameters is needed. This document describes a longitudinal evaluation of the water content, the glycosaminoglycan (GAG) concentration, and the concentration and orientation of collagen fibres in regenerative cartilage when using dGEMRIC and T2-mapping techniques in 1,5 T or 3,0 T magnetic resonance imaging equipment.

Produits médicaux issus de l'ingénierie tissulaire — Évaluation du cartilage par IRM — Partie 1: Évaluation clinique de la régénération du cartilage articulaire du genou par séquences IRM tardives après injection de gadolinium (dGEMRIC) et cartographie T2

General Information

• Status: Published
• Publication Date: 13-Jul-2022
• ICS: 11.040.40 - Implants for surgery, prosthetics and orthotics
• Technical Committee: ISO/TC 150/SC 7 - Tissue-engineered medical products
• Drafting Committee: ISO/TC 150/SC 7 - Tissue-engineered medical products
• Current Stage: 6060 - International Standard published
• Due Date: 28-Oct-2023
• Completion Date: 14-Jul-2022

Standards Content (sample)

TECHNICAL ISO/TS
SPECIFICATION 24560-1
First edition
2022-07
Tissue-engineered medical
products — MRI evaluation of
cartilage —
Part 1:
Clinical evaluation of regenerative
knee articular cartilage using delayed
gadolimium-enhanced MRI of
cartilage (dGEMRIC) and T2 mapping
Produits médicaux issus de l'ingénierie tissulaire — Évaluation du
cartilage par IRM —
Partie 1: Évaluation clinique de la régénération du cartilage
articulaire du genou par séquences IRM tardives après injection de
gadolinium (dGEMRIC) et cartographie T2
Reference number
ISO/TS 24560-1:2022(E)
© ISO 2022
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ISO/TS 24560-1:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

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ISO copyright office
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Phone: [phone]
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Website: www.iso.org
Published in Switzerland
© ISO 2022 – All rights reserved
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ISO/TS 24560-1:2022(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Principles ..................................................................................................................................................................................................................... 3

5 T2 mapping evaluation in human knee articular cartilage ................................................................................... 4

5.1 Characterization parameters and methods ................................................................................................................. 4

5.2 T2 value measurement process ............................................................................................................................................... 6

5.2.1 Post-processing of imaging ....................................................................................................................................... 6

5.2.2 Measurement method .................................................................................................................................................... 6

5.2.3 ROIs of regenerative cartilage ................................................................................................................................ 7

5.2.4 ROIs of normal control cartilage .......................................................................................................................... 8

5.3 T2 value evaluation ............................................................................................................................................................................ 8

5.3.1 Purpose of evaluation .................................................................................................................................................... 8

5.3.2 In vivo evaluation of regenerative cartilage with T2 value ......................................................... 8

6 dGEMRIC evaluation in human knee articular cartilage .......................................................................................... 9

6.1 Characterization parameters and methods ................................................................................................................. 9

6.2 T1 value measurement process ............................................................................................................................................ 11

6.2.1 Post-processing of imaging .................................................................................................................................... 11

6.2.2 Measurement method ................................................................................................................................................. 11

6.2.3 ROIs of regenerative cartilage .............................................................................................................................12

6.2.4 ROIs of normal control cartilage .......................................................................................................................12

6.3 ΔR1 value calculation .................................................................................................................................................................... 12

6.4 ΔR1 value evaluation .....................................................................................................................................................................12

6.4.1 Purpose of evaluation .................................................................................................................................................12

6.4.2 In vivo evaluation of regenerative cartilage with ΔR1 values ................................................13

7 Acceptable standard for MR evaluation ...................................................................................................................................14

7.1 Requirements for MR equipment ........................................................................................................................................ 14

7.2 Requirements for MR parameters...................................................................................................................................... 14

7.3 Requirements for the MR longitudinally evaluation ......................................................................................... 14

7.4 Exclusion criteria .............................................................................................................................................................................. 14

8 Limitation .................................................................................................................................................................................................................15

Annex A (informative) Example of measurement results ..........................................................................................................16

Annex B (informative) Introduction of T1ρ MR Imaging technology ............................................................................26

Bibliography .............................................................................................................................................................................................................................28

iii
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ISO/TS 24560-1:2022(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 150, Implants for surgery, Subcommittee

SC 7, Tissue-engineered medical products.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
© ISO 2022 – All rights reserved
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ISO/TS 24560-1:2022(E)
Introduction

Tissue-engineered cartilage has shown desirable results for the repair of cartilage defects, and histologic

findings indicate that the repaired tissue has a hyaline-like cartilage structure. Kang H.J. et al., Zheng

M.H. et al. and Behrens P. et al. reported that the histologic change after matrix-associated autologous

[1-3]

chondrocyte implantation/transplantation (MACI/MACT) was a hyaline-like cartilage. The knee

articular cartilage can also be repaired or regenerated via other tissue engineering approaches using

other seed cells such as mesenchymal stem cells or even by tissue regeneration free of external seed

[4-6]

cells . MACI and other approaches lead to a maturation of the cartilage matrix over time with the

development of an organized collagen architecture. For long-term follow-up of regenerative cartilage,

clinical scores and morphological evaluations are commonly used. Furthermore, histological evaluation

from arthroscopic biopsies provides a gold standard for morphological and biochemical assessments

of regenerative cartilage tissue. However, this process is invasive and unacceptable for patients after

cartilage repair surgery. Magnetic resonance (MR) is a noninvasive technique that can be used for the

evaluation of a cartilage microstructure. Xu X and other researchers reported that MR-based biochemical

imaging techniques, such as delayed gadolinium-enhanced MRI of the cartilage (dGEMRIC) and T2

[7-12]

mapping, show the capability of evaluating the biochemical character of articular cartilage . The

T2 relaxation time is sensitive to the content of effective hydrogen atoms, and thus to the concentration

[13]

of collagen, the main component of cartilage extracellular matrix . Besides, the orientation changes

in the collagen network of articular cartilage produce the depthwise T2 anisotropy through the magic

[14]

angle effect . The dGEMRIC technique enables an indirect estimation of the fixed charge density (FCD)

[15]

of cartilage, which mainly arises from the aggregated proteoglycan biomacromolecules . Since both

collagen and proteoglycan components are important for determining the functional characteristics

of cartilage, a combination of T2 mapping and dGEMRIC techniques provides a better evaluation of

articular regenerative cartilage. Therefore, standardization of T2 mapping and dGEMRIC techniques is

needed for the evaluation of regenerative articular cartilage.

This document is intended to guide the clinical biochemical evaluation of regenerative articular

cartilage with MR. dGEMRIC and T2 mapping are recommended for the clinical evaluation of

regenerative cartilage. These techniques have been used for patients who received tissue-engineered

cartilage implantation or transplantation (MACI/MACT). The validation data from different hospitals

are provided Annex A.

This document provides general principles for imaging and the measurement method of T2 mapping

and dGEMRIC of knee cartilage using 1,5 T or 3,0 T MRI equipment. These techniques are also applicable

for other articular cartilage, such as the ankle joint, hip joint, and shoulder joint, but the imaging

parameters should be adjusted and modified for better image quality.
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TECHNICAL SPECIFICATION ISO/TS 24560-1:2022(E)
Tissue-engineered medical products — MRI evaluation of
cartilage —
Part 1:
Clinical evaluation of regenerative knee articular cartilage
using delayed gadolimium-enhanced MRI of cartilage
(dGEMRIC) and T2 mapping
1 Scope

This document provides a principle to determine the parameter settings and operating methods for the

evaluation of the composition and structure of articular cartilage by dGEMRIC and T2-mapping MRI

in humans with a typical example of the methods; each are distinct MRI technologies that allow for

noninvasive observation of soft tissue characteristics.

The methods provided in this document are intended for application in the evaluation of the clinical

effects of tissue-engineered cartilage or other cartilage regeneration products used in the knee joint,

and are also applicable for the evaluation of regenerative cartilage in other joints, although some

modification of parameters is needed.

This document describes a longitudinal evaluation of the water content, the glycosaminoglycan (GAG)

concentration, and the concentration and orientation of collagen fibres in regenerative cartilage when

using dGEMRIC and T2-mapping techniques in 1,5 T or 3,0 T magnetic resonance imaging equipment.

2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
pulse sequences
train of programmed radio frequency pulses and gradient pulses

Note 1 to entry: In MRI, it is a time protocol for encoding images to obtain k-space data.

3.2
number of averages

number of repeated acquired identical MR signals from the same programmed pulse sequence

3.3
voxel

three-dimensional cuboid representing the minimum unit comprising a three-dimensional image

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ISO/TS 24560-1:2022(E)
3.4
pixel
two-dimensional cuboid representing the minimum unit comprising an image
3.5
field of view
FOV
width and height of an imaged region
Note 1 to entry: It is expressed in cm by cm or mm by mm.
3.6
matrix

array of scalars arranged in frequency encoding direction and phase encoding direction in a two-

dimensional MR image

Note 1 to entry: It is typically expressed in number of pixels in frequency encoding direction by number of pixels

in phase encoding direction.

Note 2 to entry: In MRI, the scalars in the array are called pixel of the matrix.

3.7
slice thickness
thickness of the imaging plane
Note 1 to entry: It is expressed in cm or mm.
3.8
signal-to-noise ratio
SNR
single number obtained by dividing the image signal by the image noise
3.9
region of interest
ROI
user-defined area on an image in which parameter of interested is calculated
3.10
echo time

time from the centre of the 90-degree excitation RF-pulse to the centre of the echo

Note 1 to entry: It is expressed in ms.
3.11
repetition time

time interval for repetition of the basic unit of magnetic resonance pulse sequences

Note 1 to entry: It is expressed in ms.
3.12
proton density-weighted image
PDWI
magnetic resonance image reflecting the concentration of protons in tissue
3.13
matrix-associated autologous chondrocyte implantation/transplantation
MACI/MACT

procedure involving expansion of autologous chondrocytes and seeding the cells onto a three-

dimensional biomaterial scaffold
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ISO/TS 24560-1:2022(E)
3.14
scaffold

support or structural component or delivery vehicle, or matrix, consisting of synthetic and/or naturally-

derived material(s), for modulating the biological properties or transport of administered and/or

endogenous cells and/or binding/transport of bioactive agents

Note 1 to entry: Biological properties include (but are not limited to) adhesion, migration, proliferation, and

differentiation.
[SOURCE: ASTM F2312 -11: 2020, Clause 4]
3.15
gradient recalled echo
GRE
MR sequence that generates gradient echoes as a consequence of echo refocusing
3.16
delayedgadolinium enhanced MRI of the cartilage
dGEMRIC
pre-contrast and post-contrast T1 mapping of cartilage
3.17
longitudinal relaxation time

time taking for the longitudinal magnetization to recover approximately 63 % of its initial value after

being flipped into the magnetic transverse plane by a 90° radiofrequency pulse
Note 1 to entry: It is expressed in ms.
3.18
transverse relaxation time

time taking for the magnetic resonance signal to irreversibly decay to 37 % of its initial value after

being flipped into the magnetic transverse plane by a 90° radiofrequency pulse
Note 1 to entry: It is expressed in ms.
3.19
T1 mapping
two-dimensional spatial distributions of T1 value of tissue
3.20
T2 mapping
two-dimensional spatial distributions of T2 value of tissue
3.21
longitudinal relaxation rate calculated as 1/T1
4 Principles

Articular cartilage is a type of hyaline cartilage that is characterized by an extracellular matrix that

[16]

contains a fine network of collagen and proteoglycan . In regenerative articular cartilage, it is

important to evaluate whether the implanted tissues regenerate to hyaline or hyaline-like cartilage

with time. MRI is a noninvasive technique that can provide an indirect method for assessing the

composition and microstructure of articular regenerative cartilage, including content and organization

[12],[17]

of the collagen network and the proteoglycan, as the main component in the extracellular matrix .

Delayed gadolinium enhanced MRI of the cartilage (dGEMRIC) is a technique pertinent to the T1

relaxation-time measurement that uses the negative ionic charge of gadopentetate dimeglumine (Gd-

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ISO/TS 24560-1:2022(E)
2- 2-

DTPA ) to map the fixed charge density of the cartilage GAG. Gd-DTPA is repelled by negatively

charged GAGs and is therefore negatively related to the local proteoglycan concentration. Consequently,

Gd-DTPA accumulates in areas of low GAG content, and a cartilage will have a shorter T1 relaxation

time in these regions. The ability to measure spatial variations in the cartilage GAG concentration in

vitro with dGEMRIC has been validated biochemically and histologically using both bovine and human

cartilage. The feasibility of using dGEMRIC in vivo has also been demonstrated, and the interpretation

[18-21]

of MR images as representing a GAG distribution is supported by literature evidence . The GAG is a

component of normal hyaline cartilage that is critical to its mechanical strength. Thus, as a noninvasive

method of indirectly monitoring the GAG concentration in cartilage, dGEMRIC is a potentially useful

method for assessing regenerative cartilage.
[22]

T2 mapping usually involves imaging at several echo times along the T2 decay curve and T2

relaxation time of different tissues can be calculated after data processing. In cartilage, changes in the

T2-relaxation times are dependent upon the quantity of water and the integrity of the proteoglycan–

collagen matrix. T2 relaxation time mapping provides an indirect assessment of the collagen structure

and orientation as it relates to the free water content. The presence of unbound water molecules slows

the loss of transverse magnetization following an RF pulse, such that regions of cartilage with more free

water have higher T2 relaxation times. In healthy cartilage, the collagen matrix traps and immobilizes

water molecules. When this structured matrix breaks down, the extra space is filled with free, unbound

water, and leads to elevated T2 relaxation times. The correlation between T2 relaxation time mapping

[23],[24]

and the collagen content has been validated, both in vitro and in vivo . The T2 value of cartilage is

a dipolar interaction due to the slow anisotropic motion of water molecules in the collagen matrix and

[14],[25]

varies as a function of the collagen arrangement in the static magnetic field , the strength of this

interaction is orientation-dependent and reaches its minimum at an angle of 54,7 (between the static

field and the axis of interacting protons, the so-called “magic angle”. Consequently, T2 changes along

cartilage thickness are reported to follow the orientational changes in the collagen fibril network.

Using appropriate arrangement of the articular surface with respect to the B0 field the resulting

laminated appearance in T2 maps approximately corresponds to the histological collagenous zones: the

superficial zone (orientation of collagen fibrils parallel to the articular surface), the transitional zone

(random fibril orientation) and the deep or radial zone (fibrils perpendicular to the articular surface

and perpendicular to the bone), which reveals the spatial collagen architecture in articular cartilage.

This spatial variation is a marker for hyaline-like matrix organization after cartilage repair.

MACI/MACT uses biomaterial scaffolds (natural or synthetic materials) as a carrier and seeds cells of

autologous chondrocytes. The repaired tissue can develop an organized collagen network, which is the

[1-3],[26],[27]

basis for histological characterization of normal hyaline articular cartilage over time . It is

possible to longitudinally evaluate the water content, the GAG concentration, and the concentration and

orientation of collagen fibres in regenerative cartilage after MACI/MACT by using the dGEMRIC and T2

mapping techniques.

In this document, T2 mapping and dGEMRIC data obtained from subjects who received MACI using

different MRI equipment are included Annex A.
5 T2 mapping evaluation in human knee articular cartilage
5.1 Characterization parameters and methods

The 1,5 T or 3,0 T magnetic resonance imaging equipment and multichannel phased-array knee coil

are recommended for T2 mapping examination of knee cartilage. It is recommended to use the same

field strength equipment for longitudinal evaluation to avoid the influence of static magnetic field B0

on the relaxation time of the tissue. Before MRI examinations, the subject should rest for more than

30 min to avoid mechanical loading by exercise, which can influence the T2 value of knee cartilage. B0

and B1 shimming is highly recommended before scanning the T2-mapping sequence for every patient.

Sagittal proton density-weighted images with fat saturation (FS-PDWI) and three-dimensional gradient

recalled echo (3D-GRE) pulse sequences are recommended for morphological evaluation of cartilage.

3D-GRE pulse sequences with spoiled gradient (such as SPGR, FLASH, and VIBE) or steady-state free

precession (such as DESS) can be chosen in different MR manufactures. The pixel size in plane of the

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ISO/TS 24560-1:2022(E)

3D-GRE pulse sequence should be consistent with pixel size in plane of the T2 mapping sequence, which

can ensure the accuracy of the image fusion registration.

A regularly repeated phantom test is recommended to ensure the status and stability of the MR system.

Phantom-based quality control is required after any change in the MR system hardware and software.

The protocol of T2 mapping consists of a sagittal, multi-echo spin echo pulse sequence for T2

measurement. Table 1 lists the recommended imaging parameters of T2 mapping in 1,5 T and 3,0 T MR

equipment, as a reference.
Table 1 — Recommended Magnetic resonance parameters of T2 mapping evaluation
T2 mapping
Parameters
1,5 T 3,0 T
FOV (mm x mm) 160 × 160 160 × 160
TR (ms) range 1 200 to 2 000 range 1 200 to 2 000

multiple TE (no less than 4 echo times), more multiple TE (no less than 4 echo times), more

echo times corresponds to more accurate echo times corresponds to more accurate
TE (ms)

T2 calculation, and the maximum echo time T2 calculation, and the maximum echo time

should be shorter than 80 ms should be shorter than 80 ms

Parallel the acceleration factor should be no larger the acceleration factor should be no larger

acquisition than 2 than 2
Matrix no less than 256 × 256 no less than 320 × 320
Pixel size in plane
no larger than 0,6 × 0,6 no larger than 0,5 × 0,5
(mm )
Number of
1 or 2 1 or 2
averages (NA)
Slice thickness
3 is recommended (ranging 3,0 to 4,0) 3 is recommended (ranging 3,0 to 4,0)
(mm)
Image plane sagittal plane sagittal plane
Number of slices no more than 30 slices no more than 30 slices

NOTE The parameters were suggested to be adjusted with different MR equipment and different signal-receiving coil.

MR examination of PDWI and T1-weighted 3D-GRE pulse sequences should achieve the following

standards:

a) the field of view (FOV) should be no larger than 160 mm × 160 mm and no smaller than 140 mm ×

140 mm;

b) the pixel size in plane of the PDWI pulse sequence should not be larger than 0,5 mm × 0,5 mm in 3,0

Tesla MRI equipment and should not be larger than 0,6 mm x 0,6 mm in 1,5 Tesla MRI equipment;

c) a 3,0-4,0 mm slice thickness is suggested in the PDWI pulse sequence;

d) for image matching, some parameters, such as FOV, the scanning centre and slice thickness, are

suggested to be kept the same for both PDWI and T2 mapping;

e) the voxel size of the 3D-GRE pulse sequence should be isotropic and not larger than 0,5 mm ×

0,5 mm × 0,5 mm in 3,0 Tesla MRI equipment and should not be larger than 0,6 mm × 0,6 mm ×

0,6 mm in 1,5 Tesla MRI equipment;

f) the fat-saturation technique is suggested in PDWI and 3D-GRE pulse sequences, such as water-

excitation or fat water separation methods;

g) imaging with high resolution can require multiple signal averages in 1,5 Tesla MR equipment for a

higher signal-to-noise ratio (SNR);
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ISO/TS 24560-1:2022(E)

h) if images are acquired with fat suppression, lowering the imaging bandwidth improves the overall

SNR.
5.2 T2 value measurement process
5.2.1 Post-processing of imaging

Post-processing of the multiple images generated by the T2 mapping sequences can be performed

online on the scanner or offline using algorithms written in separate programs, such as MATLAB (the

MathworksInc, Natick, MA). Automated processing on the scanner typically generates a pixel-by-pixel

map of T2 relaxation times, and the T2 maps can be overlain on anatomical images through image

registration. Generally, sagittal PDW images and 3D-GRE images are recommended for morphological

evaluation of regenerative cartilage and native cartilage. PDW images are sensitive to the signal

abnormality of regenerative tissue, and 3D-GRE pulse sequence is used to obtain anatomical images for

its high resolution. T2 map images can be registered to 3D GRE images for verification of regenerative

cartilage and native cartilage (see Figure 1).
5.2.2 Measurement method

T2 relaxation time is obtained by pixel-wise mono-exponential fitting of signal decay at different echo

times, and discarding the first echo for curve fitting is recommended in post-processing to minimize

[28]

the error in T2 . If the regenerative cartilage showed longer T2 component not covered by the entire

ETL, bi-exponential curves including the offset as an additional parameter should be applied and the

corresponding model can be manually selected in the MATLAB software for imaging processing.

The SE pulse sequence signal intensity (S) shall be calculated by Formula (1).
SM=×()11−−expT()RT//×−expT()ET2 (1)
where
S is the SE pulse sequence signal intensity;
M is equilibrium longitudinal magnetization;
TR is the repetition time;
T1 is the longitudinal relaxation time;
TE is the echo time;
T2 is the transverse relaxation time.

When TR>>T1, (1-exp(-TR/T1)) approaches 1. When TR is not much longer than T1(mostly in multi

echo spin echo T2 mapping sequence), TR is fixed, and the T1 value of the tissue is also relatively fixed

...

© ISO 2022 – All rights reserved
ISO/TS 24560-1 (E)
ISO TC 150/SC 7
Date: 2022-06-07
Secretariat: JISC
Tissue Engineered Medical Products –-engineered medical products — MRI
Evaluationevaluation of Cartilage–cartilage — Part 1: Clinical
Evaluationevaluation of Regenerative Knee Articular Cartilage Using
Delayed Gadolinium-Enhancedregenerative knee articular cartilage using delayed
gadolimium-enhanced MRI of the Cartilagecartilage (dGEMRIC) and T2
Mappingmapping
TS stage
Warning for WDs and CDs

This document is not an ISO International Standard. It is distributed for review and comment. It is subject to

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Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of

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© ISO 2021
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ISO/TS 24560-1:2022(E)
© ISO 2022

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no

part of this publication may be reproduced or utilized otherwise in any form or by any means,

electronic or mechanical, including photocopying, or posting on the internet or an intranet, without

prior written permission. Permission can be requested from either ISO at the address below or ISO’s

member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.orgwww.iso.org
Published in Switzerland
4 © ISO 2022 – All rights reserved
iv © ISO 2022 – All rights reserved
---------------------- Page: 3 ----------------------
ISO/TS 24560-1:2022(E)
Contents

Foreword ..................................................................................................................................................................... i7

Introduction ................................................................................................................................................................ 8

1 Scope ................................................................................................................................................................ 1

2 Normative references ................................................................................................................................ 1

3 Terms and definitions ................................................................................................................................ 1

4 Principles ....................................................................................................................................................... 4

5 T2 mapping evaluation in human knee articular cartilage ........................................................... 6

5.1 Characterization parameters and methods ........................................................................................ 6

5.2 T2 value measurement process .............................................................................................................. 7

5.3 T2 value evaluation .................................................................................................................................. 10

6 dGEMRIC evaluation in human knee articular cartilage ............................................................... 12

6.1 Characterization parameters and methods ...................................................................................... 12

6.2 T1 value measurement process ............................................................................................................ 14

6.3 ΔR1 value calculation ............................................................................................................................... 15

6.4 ΔR1 value evaluation ................................................................................................................................ 16

7 Acceptable standard for MR evaluation ............................................................................................. 19

7.1 Requirements for MR equipment ......................................................................................................... 19

7.2 Requirements for MR parameters ....................................................................................................... 19

7.3 Requirements for the MR longitudinally evaluation ..................................................................... 19

7.4 Exclusion criteria ....................................................................................................................................... 19

8 Limitation..................................................................................................................................................... 15

Annex A (informative) Example of measurement results ......................................................................... 21

Annex B (informative) A introduction of T1ρ MR Imaging technology ................................................. 34

Bibliography ............................................................................................................................................................. 36

Foreword ..................................................................................................................................................................... iv

Introduction ................................................................................................................................................................. v

1 Scope ................................................................................................................................................................ 1

2 Normative references ................................................................................................................................ 1

3 Terms and definitions ................................................................................................................................ 1

4 Principles ....................................................................................................................................................... 4

5 T2 mapping evaluation in human knee articular cartilage ........................................................... 5

5.1 Characterization parameters and methods ........................................................................................ 5

5.2 T2 value measurement process .............................................................................................................. 6

5.3 T2 value evaluation .................................................................................................................................... 8

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ISO/TS 24560-1:2022(E)

6 dGEMRIC evaluation in human knee articular cartilage ................................................................. 9

6.1 Characterization parameters and methods ........................................................................................ 9

6.2 T1 value measurement process ............................................................................................................ 11

6.3 ΔR1 value calculation ............................................................................................................................... 12

6.4 ΔR1 value evaluation ................................................................................................................................ 13

7 Acceptable standard for MR evaluation ............................................................................................. 14

7.1 Requirements for MR equipment ......................................................................................................... 14

7.2 Requirements for MR parameters ....................................................................................................... 14

7.3 Requirements for the MR longitudinally evaluation ...................................................................... 14

7.4 Exclusion criteria ....................................................................................................................................... 14

8 Limitation ..................................................................................................................................................... 15

Annex A (informative) Example of measurement results .......................................................................... 16

Annex B (informative) A introduction of T1ρ MR Imaging technology .................................................. 24

Bibliography .............................................................................................................................................................. 26

6 © ISO 2022 – All rights reserved
vi © ISO 2022 – All rights reserved
---------------------- Page: 5 ----------------------
ISO/TS 24560-1:2022(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national

standards bodies (ISO member bodies). The work of preparing International Standards is normally

carried out through ISO technical committees. Each member body interested in a subject for which a

technical committee has been established has the right to be represented on that committee.

International organizations, governmental and non-governmental, in liaison with ISO, also take part in

the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all

matters of electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directiveswww.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patentswww.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT),see

www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 150, Implants for surgery, Subcommittee

SC 7, Tissue-engineered medical products.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at
www.iso.org/members.htmlwww.iso.org/members.html.
© ISO 2022 – All rights reserved 7
© ISO 2022 – All rights reserved vii
---------------------- Page: 6 ----------------------
ISO/TS 24560-1:2022(E)
Introduction

Tissue-engineered cartilage has shown desirable results for the repair of cartilage defects, and

histologic findings indicate that the repaired tissue has a hyaline-like cartilage structure. Kang H.J. et al.,

Zheng M.H. et al. and Behrens P. et al. reported that the histologic change after matrix-associated

[1-3 ]

autologous chondrocyte implantation/transplantation (MACI/MACT) () ) was a hyaline-like cartilage.

The knee articular cartilage couldcan also be repaired or regenerated via other tissue engineering

approaches using other seed cells such as mesenchymal stem cells or even by tissue regeneration free

[4-6 ]

of external seed cells ( ). . MACI and other approaches lead to a maturation of the cartilage matrix

over time with the development of an organized collagen architecture. For long-term follow-up of

regenerative cartilage, clinical scores and morphological evaluations are commonly used. Furthermore,

histological evaluation from arthroscopic biopsies provides a gold standard for morphological and

biochemical assessments of regenerative cartilage tissue. However, this process is invasive and

unacceptable for patients after cartilage repair surgery. Magnetic resonance (MR) is a noninvasive

technique that can be used for the evaluation of a cartilage microstructure. Xu X and other researchers

reported that MR-based biochemical imaging techniques, such as delayed gadolinium-enhanced MRI of

the cartilage (dGEMRIC) and T2 mapping, show the capability of evaluating the biochemical character of

[7-12 ]

articular cartilage ( ). . The T2 relaxation time is sensitive to the content of effective hydrogen atoms,

[13 ]

and thus to the concentration of collagen, the main component of cartilage extracellular matrix ( ). .

Besides, the orientation changes in the collagen network of articular cartilage produce the depthwise T2

[14 ]

anisotropy through the magic angle effect ( ). . The dGEMRIC technique enables an indirect estimation

of the fixed charge density (FCD) of cartilage, which mainly arises from the aggregated proteoglycan

[15 ]

biomacromolecules ( ). . Since both collagen and proteoglycan components are important for

determining the functional characteristics of cartilage, a combination of T2 mapping and dGEMRIC

techniques provides a better evaluation of articular regenerative cartilage. Therefore, standardization

of T2 mapping and dGEMRIC techniques is needed for the evaluation of regenerative articular cartilage.

This document is intended to guide the clinical biochemical evaluation of regenerative articular

cartilage with MR. dGEMRIC and T2 mapping are recommended for the clinical evaluation of

regenerative cartilage. These techniques have been used for patients who received tissue-engineered

cartilage implantation or transplantation (MACI/MACT). The validation data from different hospitals

wereare provided in this document as an annexAnnex A.

This document provides general principles for imaging and the measurement method of T2 mapping

and dGEMRIC of knee cartilage using 1,5 T or 3,0 T MRI equipment. These techniques are also

applicable for other articular cartilage, such as the ankle joint, hip joint, and shoulder joint, but the

imaging parameters should be adjusted and modified for better image quality.

The International Organization for Standardization (ISO) draws attention to the fact that it is claimed

that compliance with this document may involve the use of a patent.

ISO takes no position concerning the evidence, validity and scope of this patent right.

The holder of this patent right has assured ISO that he/she is willing to negotiate licences under

reasonable and non-discriminatory terms and conditions with applicants throughout the world. In this

respect, the statement of the holder of this patent right is registered with ISO. Information may be

obtained from the patent database available at www.iso.org/patents.
8 © ISO 2022 – All rights reserved
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---------------------- Page: 7 ----------------------
ISO/TS 24560-1:2022(E)

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights other than those in the patent database. ISO shall not be held responsible for identifying

any or all such patent rights.
© ISO 2022 – All rights reserved 9
© ISO 2022 – All rights reserved ix
---------------------- Page: 8 ----------------------
TECHNICAL SPECIFICATION ISO/TS 24560-1:2022(E)
Tissue Engineered Medical Products –-engineered medical
products — MRI Evaluationevaluation of Cartilage–cartilage —
Part 1: Clinical Evaluation of Regenerative Knee Articular
Cartilage Using Delayed Gadolinium-Enhancedevaluation of
regenerative knee articular cartilage using delayed gadolimium-
enhanced MRI of the Cartilagecartilage (dGEMRIC) and T2
Mappingmapping
1 Scope

This document provides a principle to determine the parameter settings and operating methods for the

evaluation of the composition and structure of articular cartilage by dGEMRIC and T2-mapping MRI in

humans with a typical example of the methods; each are distinct MRI technologies that allow for

noninvasive observation of soft tissue characteristics.

The methods provided in this document are intended for application in the evaluation of the clinical

effects of tissue -engineered cartilage or other cartilage regeneration products used in the knee joint,

and are also applicable for the evaluation of regenerative cartilage in other joints, although some

modification of parameters is needed.

This document recommendsdescribes a longitudinal evaluation of the water content, the

glycosaminoglycan (GAG) concentration, and the concentration and orientation of collagen fibersfibres

in regenerative cartilage when using dGEMRIC and T2-mapping techniques in 1,5 T or 3,0 T magnetic

resonance imaging equipment.
32 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO/TR 16379:2014, Tissue-engineered medical products — Evaluation of anisotropic structure of

articular cartilage using DT (Diffusion Tensor)-MR Imaging

ISO/TS 21560:2020, Tissue-engineered medical products — General requirements of tissue-engineered

medical products
There are no normative references in this document.
43 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminologicalterminology databases for use in standardization at the following

addresses:

— ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp

© ISO 2022 – All rights reserved 1
---------------------- Page: 9 ----------------------
ISO/TS 24560-1:2022(E)

— IEC Electropedia: available at http://www.electropedia.org/https://www.electropedia.org/

3.1
pulse sequences

train of programmed radio frequency pulses and gradient pulses, in MRI, it is a time protocol for

encoding images to obtain k-space data

Note 1 to entry: In MRI, it is a time protocol for encoding images to obtain k-space data.

3.2
number of averages

number of repeated acquired identical MR signals from the same programedprogrammed pulse

sequence
3.3
voxel

three-dimensional cuboid representing the minimum unit comprising a three-dimensional image

3.4
pixel
two-dimensional cuboid representing the minimum unit comprising an image
3.5
field of view
FOV
width and height of an imaged region (expressed in cm by cm or mm by mm)
Note 1 to entry: It is expressed in cm by cm or mm by mm.
3.6
matrix

array of scalars arranged in frequency encoding direction and phase encoding direction in a two-

dimensional MR image (

Note 1 to entry: It is typically expressed in number of pixels in frequency encoding direction by number of

pixels in phase encoding direction).

Note 12 to entry: In MRI, the scalars in the array are called pixel of the matrix.

3.7
in-plane resolution

capability of the sensor to observe or measure the smallest object clearly with distinct boundaries,

given by = FOV/matrix size (typically expressed in mm by mm)
3.8
slice thickness
thickness of the imaging plane (
Note 1 to entry: It is expressed in cm or mm).
2 © ISO 2022 – All rights reserved
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ISO/TS 24560-1:2022(E)
3.98
signal-to-noise ratio
SNR
a single number obtained by dividing the image signal by the image noise
3.109
region of interest
ROI
a user -defined area on an image in which parameter of interested is calculated
3.1110
echo time

the time from the centercentre of the 90-degree excitation RF-pulse to the centercentre of the echo (

Note 1 to entry: It is expressed in ms).
3.1211
repetition time

time interval for repetition of the basic unit of magnetic resonance pulse sequences (expressed in ms)

Note 1 to entry: It is expressed in ms.
3.1312
proton density-weighted image
PDWI
magnetic resonance image reflecting the concentration of protons in tissue
3.1413
matrix-associated autologous chondrocyte implantation/transplantation
MACI/MACT

procedure involving expansion of autologous chondrocytes and seeding the cells onto a three-

dimensional biomaterial scaffold
3.1514
scaffold

support or structural component or delivery vehicle, or matrix, consisting of synthetic and/or naturally-

derived material(s), for modulating the biological properties (including, but not limited to, adhesion,

migration, proliferation, and differentiation) or transport of administered and/or endogenous cells

and/or binding/transport of bioactive agents

Note 1 to entry: Biological properties include (but are not limited to) adhesion, migration, proliferation, and

differentiation.
[SOURCE: ASTM F2312-11:2020, Clause 4]
3.15
gradient recalled3.16
gradientrecalled echo
© ISO 2022 – All rights reserved 3
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ISO/TS 24560-1:2022(E)
GRE

MR sequence that generates gradientsgradient echoes as a consequence of echo refocusing

3.17
3.16
delayedgadolinium enhanced MRI of the cartilage
dGEMRIC
pre-contrast and post contrast T1 mapping of cartilage
3.1817
longitudinal relaxation time

the time taking for the longitudinal magnetization to recover approximately 63 % of its initial value

after being flipped into the magnetic transverse plane by a 90° radiofrequency pulse

Note 1 to entry: It is expressed in ms.
3.18
transverse relaxation time

time taking for the magnetic resonance signal to irreversibly decay to 37 % of its initial value after

being flipped into the magnetic transverse plane by a 90° radiofrequency pulse (expressed in ms)

3.19
Note 1 to entry: It is expressed in ms.
3.19
transverse relaxation time

the time taking for the magnetic resonance signal to irreversibly decay to 37% of its initial value after

being flipped into the magnetic transverse plane by a 90° radiofrequency pulse (expressed in ms)

3.20
T1 mapping
two -dimensional spatial distributions of T1 value of tissue
3.2120
T2 mapping
two -dimensional spatial distributions of T2 value of tissue
3.2221
longitudinal relaxation rate calculated as 1/T1
54 Principles

Articular cartilage is a type of hyaline cartilage that is characterized by an extracellular matrix that

[16 ]

contains a fine network of collagen and proteoglycan etc. ( ). . In regenerative articular cartilage, it is

important to evaluate whether the implanted tissues regenerate to hyaline or hyaline-like cartilage with

4 © ISO 2022 – All rights reserved
4 © ISO 2022 – All rights reserved
---------------------- Page: 12 ----------------------
ISO/TS 24560-1:2022(E)

time. MRI is a noninvasive technique that can provide an indirect method for assessing the composition

and microstructure of articular regenerative cartilage, including content and organization of the

[12 ],[17 ]

collagen network and the proteoglycan, as the main component in the extracellular matrix ( , ). .

dGEMRICDelayedgadolinium enhanced MRI of the cartilage (dGEMRIC) is a technique pertinent to the

T1 relaxation-time measurement that uses the negative ionic charge of gadopentetate dimeglumine

2- 2-

(Gd-DTPA ) to map the fixed charge density of the cartilage GAG. Gd-DTPA is repelled by negatively

charged GAGs and, is therefore, is thus negatively related to the local proteoglycan concentration.

Consequently, Gd-DTPA accumulates in areas of low GAG content, and a cartilage will have a shorter

T1 relaxation time in these regions. The ability to measure spatial variations in the cartilage GAG

concentration in vitro with dGEMRIC has been validated biochemically and histologically using both

bovine and human cartilage. The feasibility of using dGEMRIC in vivo washas also been demonstrated,

and the interpretation of MR images as representing a GAG distribution wasis supported by literature

[18-21 ]

evidence ( ). . The GAG is a component of normal hyaline cartilage that is critical to its mechanical

strength. Thus, as a non-invasivenoninvasive method of indirectly monitoring the GAG concentration in

cartilage, dGEMRIC is a potentially useful method for assessing regenerative cartilage.

[22 ]

T2 mapping usually involves imaging at several echo times along the T2 decay curve ( ) and T2

relaxation time of different tissues can be calculated after data processing. In cartilage, changes in the

T2-relaxation times are dependent upon the quantity of water and the integrity of the proteoglycan–

collagen matrix. T2 relaxation time mapping provides an indirect assessment of the collagen structure

and orientation as it relates to the free water content. The presence of unbound water molecules slows

the loss of transverse magnetization following an RF pulse, such that regions of cartilage with more free

water have higher T2 relaxation times. In healthy cartilage, the collagen matrix traps and immobilizes

water molecules. When this structured matrix breaks down, the extra space is filled with free, unbound

water, and leads to elevated T2 relaxation times. The correlation between T2 relaxation time mapping

[23 ],[24 ]

and the collagen content has been validated, both in vitro and in vivo ( , ). . The T2 value of cartilage

is a dipolar interaction due to the slow anisotropic motion of water molecules in the collagen matrix

[14 ],[25 ]

and varies as a function of the collagen arrangement in the static magnetic field ( , ), , the strength

of this interaction is orientation-dependent and reaches its minimum at an angle of 54.,7 (between the

static field and the axis of interacting protons, the so-called “magic angle”. Consequently, T2 changes

along cartilage thickness are reported to follow the orientational changes in the collagen fibril network.

Using appropriate arrangement of the articular surface with respect to the B0 field the resulting

laminated appearance in T2 maps approximately corresponds to the histological collagenous zones: the

superficial zone (orientation of collagen fibrils parallel to the articular surface), the transitional zone

(random fibril orientation) and the deep or radial zone (fibrils perpendicular to the articular surface

and perpendicular to the bone), which reveals the spatial collagen architecture in articular cartilage.

This spatial variation is a marker for hyaline-like matrix organization after cartilage repair.

MACI/MACT uses biomaterial scaffolds (natural or synthetic materials) as a carrier and seeds cells of

autologous chondrocytes. The repaired tissue may be able tocan develop an organized collagen

network, which is the basis for histological characterization of normal hyaline articular cartilage over

[1-3 ],[26 ],[27 ]

time ( , , ). . It is possible to longitudinally evaluate the water content, the GAG concentration,

and the concentration and orientation of collagen fibersfibres in regenerative cartilage after

MACI/MACT by using the dGEMRIC and T2 mapping techniques.

In this document, T2 mapping and dGEMRIC data obtained from subjects who received MACI using

different MRI equipment are included in the Annex A.
© ISO 2022 – All rights reserved 5
© ISO 2022 – All rights reserved 5
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ISO/TS 24560-1:2022(E)
65 T2 mapping evaluation in human knee articular cartilage
6.15.1 Characterization parameters and methods

The 1,5 T or 3,0 T magnetic resonance imaging equipment and multichannel phased-array knee coil are

recommended for T2 mapping examination of knee cartilage. It is recommended to use the same field

strength equipment for longitudinal evaluation to avoid the influence of static magnetic field B0 on the

relaxation time of the tissue. Before MRI examinations, the subject should rest for more than 30

minutes min to avoid mechanical loading by exercise, which can influence the T2 value of knee cartilage.

B0 and B1 shimming is highly recommended before scanning the T2-mapping sequence for every

patient. Sagittal proton density -weighted images with fat saturation (FS-PDWI) and three-

dimensional GRE gradient recalled echo (3D-GRE) pulse sequences are recommended for

morphological evaluation of cartilage. 3D-GRE pulse sequences with spoiled gradient (such as SPGR,

FLASH, and VIBE) or steady-state free precession (such as DESS) can be chosen in different MR

manufactures. The pixel size in plane of the 3D-GRE pulse sequence should be consistent with pixel size

in plane of the T2 mapping seq
...

TECHNICAL ISO/TS
SPECIFICATION 24560-1
First edition
Tissue-engineered medical
products — MRI evaluation of
cartilage —
Part 1:
Clinical evaluation of regenerative
knee articular cartilage using delayed
gadolimium-enhanced MRI of
cartilage (dGEMRIC) and T2 mapping
Produits médicaux issus de l'ingénierie tissulaire — Évaluation du
cartilage par IRM —
Partie 1: Évaluation clinique de la régénération du cartilage
articulaire du genou par séquences IRM tardives après injection de
gadolinium (dGEMRIC) et cartographie T2
PROOF/ÉPREUVE
Reference number
ISO/TS 24560-1:2022(E)
© ISO 2022
---------------------- Page: 1 ----------------------
ISO/TS 24560-1:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
PROOF/ÉPREUVE © ISO 2022 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TS 24560-1:2022(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Principles ..................................................................................................................................................................................................................... 3

5 T2 mapping evaluation in human knee articular cartilage ................................................................................... 4

5.1 Characterization parameters and methods ................................................................................................................. 4

5.2 T2 value measurement process ............................................................................................................................................... 6

5.2.1 Post-processing of imaging ....................................................................................................................................... 6

5.2.2 Measurement method .................................................................................................................................................... 6

5.2.3 ROIs of regenerative cartilage ................................................................................................................................ 7

5.2.4 ROIs of normal control cartilage .......................................................................................................................... 8

5.3 T2 value evaluation ............................................................................................................................................................................ 8

5.3.1 Purpose of evaluation .................................................................................................................................................... 8

5.3.2 In vivo evaluation of regenerative cartilage with T2 value ......................................................... 8

6 dGEMRIC evaluation in human knee articular cartilage .......................................................................................... 9

6.1 Characterization parameters and methods ................................................................................................................. 9

6.2 T1 value measurement process ............................................................................................................................................ 11

6.2.1 Post-processing of imaging .................................................................................................................................... 11

6.2.2 Measurement method ................................................................................................................................................. 11

6.2.3 ROIs of regenerative cartilage .............................................................................................................................12

6.2.4 ROIs of normal control cartilage .......................................................................................................................12

6.3 ΔR1 value calculation .................................................................................................................................................................... 12

6.4 ΔR1 value evaluation .....................................................................................................................................................................12

6.4.1 Purpose of evaluation .................................................................................................................................................12

6.4.2 In vivo evaluation of regenerative cartilage with ΔR1 values ................................................13

7 Acceptable standard for MR evaluation ...................................................................................................................................14

7.1 Requirements for MR equipment ........................................................................................................................................ 14

7.2 Requirements for MR parameters...................................................................................................................................... 14

7.3 Requirements for the MR longitudinally evaluation ......................................................................................... 14

7.4 Exclusion criteria .............................................................................................................................................................................. 14

8 Limitation .................................................................................................................................................................................................................15

Annex A (informative) Example of measurement results ..........................................................................................................16

Annex B (informative) Introduction of T1ρ MR Imaging technology ............................................................................26

Bibliography .............................................................................................................................................................................................................................28

iii
© ISO 2022 – All rights reserved PROOF/ÉPREUVE
---------------------- Page: 3 ----------------------
ISO/TS 24560-1:2022(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT),see

www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 150, Implants for surgery, Subcommittee

SC 7, Tissue-engineered medical products.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
PROOF/ÉPREUVE © ISO 2022 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/TS 24560-1:2022(E)
Introduction

Tissue-engineered cartilage has shown desirable results for the repair of cartilage defects, and histologic

findings indicate that the repaired tissue has a hyaline-like cartilage structure. Kang H.J. et al., Zheng

M.H. et al. and Behrens P. et al. reported that the histologic change after matrix-associated autologous

[1-3]

chondrocyte implantation/transplantation (MACI/MACT) was a hyaline-like cartilage. The knee

articular cartilage can also be repaired or regenerated via other tissue engineering approaches using

other seed cells such as mesenchymal stem cells or even by tissue regeneration free of external seed

[4-6]

cells . MACI and other approaches lead to a maturation of the cartilage matrix over time with the

development of an organized collagen architecture. For long-term follow-up of regenerative cartilage,

clinical scores and morphological evaluations are commonly used. Furthermore, histological evaluation

from arthroscopic biopsies provides a gold standard for morphological and biochemical assessments

of regenerative cartilage tissue. However, this process is invasive and unacceptable for patients after

cartilage repair surgery. Magnetic resonance (MR) is a noninvasive technique that can be used for the

evaluation of a cartilage microstructure. Xu X and other researchers reported that MR-based biochemical

imaging techniques, such as delayed gadolinium-enhanced MRI of the cartilage (dGEMRIC) and T2

[7-12]

mapping, show the capability of evaluating the biochemical character of articular cartilage . The

T2 relaxation time is sensitive to the content of effective hydrogen atoms, and thus to the concentration

[13]

of collagen, the main component of cartilage extracellular matrix . Besides, the orientation changes

in the collagen network of articular cartilage produce the depthwise T2 anisotropy through the magic

[14]

angle effect . The dGEMRIC technique enables an indirect estimation of the fixed charge density (FCD)

[15]

of cartilage, which mainly arises from the aggregated proteoglycan biomacromolecules . Since both

collagen and proteoglycan components are important for determining the functional characteristics

of cartilage, a combination of T2 mapping and dGEMRIC techniques provides a better evaluation of

articular regenerative cartilage. Therefore, standardization of T2 mapping and dGEMRIC techniques is

needed for the evaluation of regenerative articular cartilage.

This document is intended to guide the clinical biochemical evaluation of regenerative articular

cartilage with MR. dGEMRIC and T2 mapping are recommended for the clinical evaluation of

regenerative cartilage. These techniques have been used for patients who received tissue-engineered

cartilage implantation or transplantation (MACI/MACT). The validation data from different hospitals

are provided Annex A.

This document provides general principles for imaging and the measurement method of T2 mapping

and dGEMRIC of knee cartilage using 1,5 T or 3,0 T MRI equipment. These techniques are also applicable

for other articular cartilage, such as the ankle joint, hip joint, and shoulder joint, but the imaging

parameters should be adjusted and modified for better image quality.
© ISO 2022 – All rights reserved PROOF/ÉPREUVE
---------------------- Page: 5 ----------------------
TECHNICAL SPECIFICATION ISO/TS 24560-1:2022(E)
Tissue-engineered medical products — MRI evaluation of
cartilage —
Part 1:
Clinical evaluation of regenerative knee articular cartilage
using delayed gadolimium-enhanced MRI of cartilage
(dGEMRIC) and T2 mapping
1 Scope

This document provides a principle to determine the parameter settings and operating methods for the

evaluation of the composition and structure of articular cartilage by dGEMRIC and T2-mapping MRI

in humans with a typical example of the methods; each are distinct MRI technologies that allow for

noninvasive observation of soft tissue characteristics.

The methods provided in this document are intended for application in the evaluation of the clinical

effects of tissue-engineered cartilage or other cartilage regeneration products used in the knee joint,

and are also applicable for the evaluation of regenerative cartilage in other joints, although some

modification of parameters is needed.

This document describes a longitudinal evaluation of the water content, the glycosaminoglycan (GAG)

concentration, and the concentration and orientation of collagen fibres in regenerative cartilage when

using dGEMRIC and T2-mapping techniques in 1,5 T or 3,0 T magnetic resonance imaging equipment.

2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
pulse sequences
train of programmed radio frequency pulses and gradient pulses

Note 1 to entry: In MRI, it is a time protocol for encoding images to obtain k-space data.

3.2
number of averages

number of repeated acquired identical MR signals from the same programmed pulse sequence

3.3
voxel

three-dimensional cuboid representing the minimum unit comprising a three-dimensional image

© ISO 2022 – All rights reserved PROOF/ÉPREUVE
---------------------- Page: 6 ----------------------
ISO/TS 24560-1:2022(E)
3.4
pixel
two-dimensional cuboid representing the minimum unit comprising an image
3.5
field of view
FOV
width and height of an imaged region
Note 1 to entry: It is expressed in cm by cm or mm by mm.
3.6
matrix

array of scalars arranged in frequency encoding direction and phase encoding direction in a two-

dimensional MR image

Note 1 to entry: It is typically expressed in number of pixels in frequency encoding direction by number of pixels

in phase encoding direction.

Note 2 to entry: In MRI, the scalars in the array are called pixel of the matrix.

3.7
slice thickness
thickness of the imaging plane
Note 1 to entry: It is expressed in cm or mm.
3.8
signal-to-noise ratio
SNR
single number obtained by dividing the image signal by the image noise
3.9
region of interest
ROI
user-defined area on an image in which parameter of interested is calculated
3.10
echo time

time from the centre of the 90-degree excitation RF-pulse to the centre of the echo

Note 1 to entry: It is expressed in ms.
3.11
repetition time

time interval for repetition of the basic unit of magnetic resonance pulse sequences

Note 1 to entry: It is expressed in ms.
3.12
proton density-weighted image
PDWI
magnetic resonance image reflecting the concentration of protons in tissue
3.13
matrix-associated autologous chondrocyte implantation/transplantation
MACI/MACT

procedure involving expansion of autologous chondrocytes and seeding the cells onto a three-

dimensional biomaterial scaffold
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3.14
scaffold

support or structural component or delivery vehicle, or matrix, consisting of synthetic and/or naturally-

derived material(s), for modulating the biological properties or transport of administered and/or

endogenous cells and/or binding/transport of bioactive agents

Note 1 to entry: Biological properties include (but are not limited to) adhesion, migration, proliferation, and

differentiation.
[SOURCE: ASTM F2312 -11: 2020, Clause 4]
3.15
gradient recalled echo
GRE
MR sequence that generates gradient echoes as a consequence of echo refocusing
3.16
delayedgadolinium enhanced MRI of the cartilage
dGEMRIC
pre-contrast and post contrast T1 mapping of cartilage
3.17
longitudinal relaxation time

time taking for the longitudinal magnetization to recover approximately 63 % of its initial value after

being flipped into the magnetic transverse plane by a 90° radiofrequency pulse
Note 1 to entry: It is expressed in ms.
3.18
transverse relaxation time

time taking for the magnetic resonance signal to irreversibly decay to 37 % of its initial value after

being flipped into the magnetic transverse plane by a 90° radiofrequency pulse
Note 1 to entry: It is expressed in ms.
3.19
T1 mapping
two-dimensional spatial distributions of T1 value of tissue
3.20
T2 mapping
two-dimensional spatial distributions of T2 value of tissue
3.21
longitudinal relaxation rate calculated as 1/T1
4 Principles

Articular cartilage is a type of hyaline cartilage that is characterized by an extracellular matrix that

[16]

contains a fine network of collagen and proteoglycan . In regenerative articular cartilage, it is

important to evaluate whether the implanted tissues regenerate to hyaline or hyaline-like cartilage

with time. MRI is a noninvasive technique that can provide an indirect method for assessing the

composition and microstructure of articular regenerative cartilage, including content and organization

[12],[17]

of the collagen network and the proteoglycan, as the main component in the extracellular matrix .

Delayedgadolinium enhanced MRI of the cartilage (dGEMRIC) is a technique pertinent to the T1

relaxation-time measurement that uses the negative ionic charge of gadopentetate dimeglumine (Gd-

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2- 2-

DTPA ) to map the fixed charge density of the cartilage GAG. Gd-DTPA is repelled by negatively

charged GAGs and is therefore negatively related to the local proteoglycan concentration. Consequently,

Gd-DTPA accumulates in areas of low GAG content, and a cartilage will have a shorter T1 relaxation

time in these regions. The ability to measure spatial variations in the cartilage GAG concentration in

vitro with dGEMRIC has been validated biochemically and histologically using both bovine and human

cartilage. The feasibility of using dGEMRIC in vivo has also been demonstrated, and the interpretation

[18-21]

of MR images as representing a GAG distribution is supported by literature evidence . The GAG is a

component of normal hyaline cartilage that is critical to its mechanical strength. Thus, as a noninvasive

method of indirectly monitoring the GAG concentration in cartilage, dGEMRIC is a potentially useful

method for assessing regenerative cartilage.
[22]

T2 mapping usually involves imaging at several echo times along the T2 decay curve and T2

relaxation time of different tissues can be calculated after data processing. In cartilage, changes in the

T2-relaxation times are dependent upon the quantity of water and the integrity of the proteoglycan–

collagen matrix. T2 relaxation time mapping provides an indirect assessment of the collagen structure

and orientation as it relates to the free water content. The presence of unbound water molecules slows

the loss of transverse magnetization following an RF pulse, such that regions of cartilage with more free

water have higher T2 relaxation times. In healthy cartilage, the collagen matrix traps and immobilizes

water molecules. When this structured matrix breaks down, the extra space is filled with free, unbound

water, and leads to elevated T2 relaxation times. The correlation between T2 relaxation time mapping

[23],[24]

and the collagen content has been validated, both in vitro and in vivo . The T2 value of cartilage is

a dipolar interaction due to the slow anisotropic motion of water molecules in the collagen matrix and

[14],[25]

varies as a function of the collagen arrangement in the static magnetic field , the strength of this

interaction is orientation-dependent and reaches its minimum at an angle of 54,7 (between the static

field and the axis of interacting protons, the so-called “magic angle”. Consequently, T2 changes along

cartilage thickness are reported to follow the orientational changes in the collagen fibril network.

Using appropriate arrangement of the articular surface with respect to the B0 field the resulting

laminated appearance in T2 maps approximately corresponds to the histological collagenous zones: the

superficial zone (orientation of collagen fibrils parallel to the articular surface), the transitional zone

(random fibril orientation) and the deep or radial zone (fibrils perpendicular to the articular surface

and perpendicular to the bone), which reveals the spatial collagen architecture in articular cartilage.

This spatial variation is a marker for hyaline-like matrix organization after cartilage repair.

MACI/MACT uses biomaterial scaffolds (natural or synthetic materials) as a carrier and seeds cells of

autologous chondrocytes. The repaired tissue can develop an organized collagen network, which is the

[1-3],[26],[27]

basis for histological characterization of normal hyaline articular cartilage over time . It is

possible to longitudinally evaluate the water content, the GAG concentration, and the concentration and

orientation of collagen fibres in regenerative cartilage after MACI/MACT by using the dGEMRIC and T2

mapping techniques.

In this document, T2 mapping and dGEMRIC data obtained from subjects who received MACI using

different MRI equipment are included Annex A.
5 T2 mapping evaluation in human knee articular cartilage
5.1 Characterization parameters and methods

The 1,5 T or 3,0 T magnetic resonance imaging equipment and multichannel phased-array knee coil

are recommended for T2 mapping examination of knee cartilage. It is recommended to use the same

field strength equipment for longitudinal evaluation to avoid the influence of static magnetic field B0

on the relaxation time of the tissue. Before MRI examinations, the subject should rest for more than

30 min to avoid mechanical loading by exercise, which can influence the T2 value of knee cartilage. B0

and B1 shimming is highly recommended before scanning the T2-mapping sequence for every patient.

Sagittal proton density-weighted images with fat saturation (FS-PDWI) and three-dimensional gradient

recalled echo (3D-GRE) pulse sequences are recommended for morphological evaluation of cartilage.

3D-GRE pulse sequences with spoiled gradient (such as SPGR, FLASH, and VIBE) or steady-state free

precession (such as DESS) can be chosen in different MR manufactures. The pixel size in plane of the

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3D-GRE pulse sequence should be consistent with pixel size in plane of the T2 mapping sequence, which

can ensure the accuracy of the image fusion registration.

A regularly repeated phantom test is recommended to ensure the status and stability of the MR system.

Phantom-based quality control is required after any change in the MR system hardware and software.

The protocol of T2 mapping consists of a sagittal, multi-echo spin echo pulse sequence for T2

measurement. Table 1 lists the recommended imaging parameters of T2 mapping in 1,5 T and 3,0 T MR

equipment, as a reference.
Table 1 — Recommended Magnetic resonance parameters of T2 mapping evaluation
T2 mapping
Parameters
1,5 T 3,0 T
FOV (mm x mm) 160 × 160 160 × 160
TR (ms) range 1 200 to 2 000 range 1 200 to 2 000

multiple TE (no less than 4 echo times), more multiple TE (no less than 4 echo times), more

echo times corresponds to more accurate echo times corresponds to more accurate
TE (ms)

T2 calculation, and the maximum echo time T2 calculation, and the maximum echo time

should be shorter than 80 ms should be shorter than 80 ms

Parallel acquisi- the acceleration factor should be no larger the acceleration factor should be no larger

tion than 2 than 2
Matrix no less than 256 × 256 no less than 320 × 320
Pixel size in plane
no larger than 0,6 × 0,6 no larger than 0,5 × 0,5
(mm )
Number of aver-
1 or 2 1 or 2
ages (NA)
Slice thickness
3 is recommended (ranging 3,0 to 4,0) 3 is recommended (ranging 3,0 to 4,0)
(mm)
Image plane sagittal plane sagittal plane
Number of slices no more than 30 slices no more than 30 slices

NOTE The parameters were suggested to be adjusted with different MR equipment and different signal-receiving coil.

MR examination of PDWI and T1-weighted 3D-GRE pulse sequences should achieve the following

standards:

a) the field of view (FOV) should be no larger than 160 mm × 160 mm and no smaller than 140 mm ×

140 mm;

b) the pixel size in plane of the PDWI pulse sequence should not be larger than 0,5 mm × 0,5 mm in 3,0

Tesla MRI equipment and should not be larger than 0,6 mm x 0,6 mm in 1,5 Tesla MRI equipment;

c) a 3,0-4,0 mm slice thickness is suggested in the PDWI pulse sequence;

d) for image matching, some parameters, such as FOV, the scanning centre and slice thickness, are

suggested to be kept the same for both PDWI and T2 mapping;

e) the voxel size of the 3D-GRE pulse sequence should be isotropic and not larger than 0,5 mm ×

0,5 mm × 0,5 mm in 3,0 Tesla MRI equipment and should not be larger than 0,6 mm × 0,6 mm ×

0,6 mm in 1,5 Tesla MRI equipment;

f) the fat-saturation technique is suggested in PDWI and 3D-GRE pulse sequences, such as water-

excitation or fat water separation methods;

g) imaging with high resolution can require multiple signal averages in 1,5 Tesla MR equipment for a

higher signal-to-noise ratio (SNR);
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h) if images are acquired with fat suppression, lowering the imaging bandwidth improves the overall

SNR.
5.2 T2 value measurement process
5.2.1 Post-processing of imaging

Post-processing of the multiple images generated by the T2 mapping sequences can be performed

online on the scanner or offline using algorithms written in separate programs, such as MATLAB (the

MathworksInc, Natick, MA). Automated processing on the scanner typically generates a pixel-by-pixel

map of T2 relaxation times, and the T2 maps can be overlain on anatomical images through image

registration. Generally, sagittal PDW images and 3D-GRE images are recommended for morphological

evaluation of regenerative cartilage and native cartilage. PDW images are sensitive to the signal

abnormality of regenerative tissue, and 3D-GRE pulse sequence is used to obtain anatomical images for

its high resolution. T2 map images can be registered to 3D GRE images for verification of regenerative

cartilage and native cartilage (see Figure 1).
5.2.2 Measurement method

T2 relaxation time is obtained by pixel-wise mono-exponential fitting of signal decay at different echo

times, and discarding the first echo for curve fitting is recommended in post-processing to minimize

[28]

the error in T2 . If the regenerative cartilage showed longer T2 component not covered by the entire

ETL, bi-exponential curves including the offset as an additional parameter should be applied and the

corresponding model can be manually selected in the MATLAB software for imaging processing.

The SE pulse sequence signal intensity (S) shall be calculated by Formula (1).
SM=×()11−−expT()RT//×−expT()ET2 (1)
where
S is the SE pulse sequence signal intensity;
M is equilibrium longitudinal magnetization;
TR is the repetition time;
T1 is the longitudinal relaxation time;
TE is the echo time;
T2 is the transverse relaxation time.
When TR>>T1, (1-exp(-TR/T1)) approaches 1. When TR is not much longer than T1(mo
...