ASTM F2079-02(2008)
(Test Method)Standard Test Method for Measuring Intrinsic Elastic Recoil of Balloon-Expandable Stents
Standard Test Method for Measuring Intrinsic Elastic Recoil of Balloon-Expandable Stents
SIGNIFICANCE AND USE
Minimal stent recoil is a desirable feature of a stent because it minimizes the maximum diameter to which a stent must be expanded to achieve its final relaxed diameter. A stent having a high recoil must be expanded to a greater diameter to achieve its final relaxed diameter than a stent having low recoil. Practically, excessive expansion of the vessel into which the stent is to be implanted may cause tissue damage resulting in a poor immediate result or poor long-term outcome. Stent recoil is affected by intrinsic properties of the material used to construct the stent and the specific geometric design of the stent; therefore, measuring stent recoil is an essential part of evaluating the design.
SCOPE
1.1 The purpose of this test method is to quantify the percentage by which the diameter of a stent decreases from its expanded diameter while still on the delivery balloon to its relaxed diameter after deflating the balloon. This test method is appropriate for stents manufactured from a material that is plastically deformed when the stent's diameter is increased from its predeployed size to its postdeployed size by mechanical means. This test method may be performed in air at room temperature unless there is a known temperature dependence of the material, in which case, the temperature at which the test is conducted shall be stated in the report.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:F2079–02 (Reapproved 2008)
Standard Test Method for
Measuring Intrinsic Elastic Recoil of Balloon-Expandable
Stents
This standard is issued under the fixed designation F 2079; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope the inflated delivery balloon. The balloon is deflated and the
outer diameter of the stent is remeasured in the same positions
1.1 The purpose of this test method is to quantify the
at approximately the same location.
percentage by which the diameter of a stent decreases from its
expanded diameter while still on the delivery balloon to its
4. Significance and Use
relaxed diameter after deflating the balloon.This test method is
4.1 Minimal stent recoil is a desirable feature of a stent
appropriate for stents manufactured from a material that is
because it minimizes the maximum diameter to which a stent
plastically deformed when the stent’s diameter is increased
must be expanded to achieve its final relaxed diameter.Astent
from its predeployed size to its postdeployed size by mechani-
having a high recoil must be expanded to a greater diameter to
cal means. This test method may be performed in air at room
achieve its final relaxed diameter than a stent having low
temperatureunlessthereisaknowntemperaturedependenceof
recoil.Practically,excessiveexpansionofthevesselintowhich
the material, in which case, the temperature at which the test is
the stent is to be implanted may cause tissue damage resulting
conducted shall be stated in the report.
in a poor immediate result or poor long-term outcome. Stent
1.2 The values stated in SI units are to be regarded as
recoil is affected by intrinsic properties of the material used to
standard. No other units of measurement are included in this
construct the stent and the specific geometric design of the
standard.
stent; therefore, measuring stent recoil is an essential part of
1.3 This standard does not purport to address all of the
evaluating the design.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5. Apparatus
priate safety and health practices and determine the applica-
5.1 Ameans to inflate with noncompressible fluid, typically
bility of regulatory limitations prior to use.
water, the delivery balloon on which the stent is mounted. The
2. Terminology means used must be capable of achieving the pressure required
to maintain the expanded diameter of the stent until it can be
2.1 Definitions:
measured and may include a device to monitor pressure.
2.1.1 labeled diameter, n—the nominal deployed size of a
5.2 A means to measure the outer diameter of the stent
stent as indicated on its manufacturer’s label.
without deforming the stent. Typically, a calibrated optical
2.1.2 stent recoil, n—theamount,expressedasapercentage,
system, which does not require contact with the stent, is used.
by which the diameter of a stent changes from the expanded
The resolution of the measurement system shall be 0.01 mm or
diameter measured with the stent on the inflated delivery
better. The accuracy of the system shall be 2 % of reading or
balloon to the final value measured after deflating the balloon.
better.
3. Summary of Test Method
6. Sampling, Test Specimens, and Test Units
3.1 A sample device representative of product that will be
6.1 Unless otherwise justified, all samples selected for
marketed is either premounted or mounted on the delivery
testing should be taken from fully processed, clinical quality
balloon at the time of use. The delivery balloon is inflated to
product. It is not required that these devices undergo terminal
the nominal expansion pressure indicated for the labeled stent.
sterilization.Cosmeticrejectsorothernonclinicalsamplesmay
The outer diameter of the stent is measured in two approxi-
be used if the cause for rejection has been shown not to affect
mately orthogonal rotational positions while the stent is still on
stent recoil.
6.2 The number of specimens tested for each unique stent
This test method is under the jurisdiction ofASTM Committee F04 on Medical
geometry should be sufficient to meet sampling requirements
andSurgicalMaterialsandDevices andisthedirectresponsibilityofSubcommittee
for desired specification limits. In general, a minimum of ten
F04.30 on Cardiovascular Standards.
specimens is recommended. If a single stent geometry is
Current edition approved May 1, 2008. Published June 2008. Originally
approved in 2001. Last previous edition approved in 2002 as F 2079 – 02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F2079–02 (2008)
intended to be used for more than one labeled diameter, recoil 8. Calculation
shall be evaluated for test specimens expanded to the smallest
8.1 Calculate the stent recoil for the location(s) measured in
and largest diameters intended for that geometry.
7.4 for each stent using the following equation:
6.3 Most stents are comprised of a repetitious continuous
Diameter
final
Stent Recoil ~%!5 1– * 100 (1)
S S DD
pattern or of repeating subunits. If stents are made longer by
Diameter
inflated
additional repetition of the bas
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:F2079–01 Designation: F 2079 – 02 (Reapproved 2008)
Standard Test Method for
Measuring Intrinsic Elastic Recoil of Balloon-Expandable
Stents
This standard is issued under the fixed designation F 2079; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 The purpose of this test method is to quantify the percentage by which the diameter of a stent decreases from its expanded
diameter while still on the delivery balloon to its relaxed diameter after deflating the balloon. This test method is appropriate for
stents manufactured from a material that is plastically deformed when the stent’s diameter is increased from its predeployed size
to its postdeployed size by mechanical means. This test method may be performed in air at room temperature unless there is a
known temperature dependence of the material, in which case, the temperature at which the test is conducted shall be stated in the
report.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Terminology
2.1 Definitions:
2.1.1 labeled diameter, n—desired final stent (inner/outer) diameter after deflation of the delivery balloon. —the nominal
deployed size of a stent as indicated on its manufacturer’s label.
2.1.2 stent recoil, n—the amount, expressed as a percentage, by which the diameter of a stent changes from the expanded
diameter measured with the stent on the inflated delivery balloon to the final value measured after deflating the balloon.
3. Summary of Test Method
3.1The delivery balloon bearing a 3.1 Asample device representative of product that will be marketed is either premounted, or
mounted on the delivery balloon at the time of use, use. The delivery balloon is inflated to expand the stent to slightly greater than
itsnominal expansion pressure indicated for the labeled diameter.stent. The outer diameter of the stent is measured in a minimum
oftwoapproximatelyorthogonalprojectionsrotationalpositionswhilethestentisstillontheinflateddeliveryballoon.Theballoon
is deflated and the outer diameter of the stent is remeasured in the same projectionspositions at approximately the same location.
4. Significance and Use
4.1 Minimal stent recoil is a desirable feature of a stent because it minimizes the maximum diameter to which a stent must be
expanded to achieve its final relaxed diameter. A stent having a high recoil must be expanded to a greater diameter to achieve its
final relaxed diameter than a stent having low recoil. Practically, excessive expansion of the vessel into which the stent is to be
implanted may cause tissue damage resulting in a poor immediate result or poor long-term outcome. Stent recoil is affected by
intrinsic properties of the material used to construct the stent and the specific geometric design of the stent; therefore, measuring
stent recoil is an essential part of evaluating the design.
5. Apparatus
5.1 A means to inflate with noncompressible fluid, typically water, the delivery balloon on which the stent is mounted. The
means used must be capable of achieving the pressure required to maintain the expanded diameter of the stent until it can be
measured and may include a device to monitor pressure.
This test method is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.30 on Cardiovascular Standards.
Current edition approved Jan. 10, 2001. Published March 2001.
This test method is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.30 on Cardiovascular Standards.
Current edition approved May 1, 2008. Published June 2008. Originally approved in 2001. Last previous edition approved in 2002 as F 2079 – 02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F 2079 – 02 (2008)
5.2 Ameans to measure the outer diameter of the stent without deforming the stent.Typically, a calibrated optical system, which
does not require contact with the stent, is used.The resolution of the measurement system shall be 0.01 mm or better.The accuracy
of the system shall be 2 % of reading or better.
6. Sampling, Test Specimens, and Test Units
6.1 Unless otherwise justified, all samples selected for testing should be taken from fully processed, clinical quality product.
It is not required that these devices undergo terminal sterilization. Cosmetic rejects or other nonclinical samples may be used if
the cause for rejection has been shown not to affect stent recoil.
6.2 The number of specimens tested for each unique stent geometry should be sufficient to meet sampling requirements for
desired specification limits. In general, a minimum of ten specimens is recommended. If a single stent geometry is intended to be
used for more than one labeled diameter, recoil shall be evaluated for test specimens expanded to the smallest and largest diameters
intended for that geometry.
6.3 Moststentsarecomprisedofarepetitiouscontinuouspatternorofrepeatingsubunits.Ifstentsaremadelongerbyadditional
repetition of the basic geometric pattern or by adding identical subunits, then recoil need be measured on only a single length
...
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