Radiotherapy equipment - Coordinates, movements and scales

Applies to equipment and data related to the process of teleradiotherapy, including patient image data used in relation with radiotherapy treatment planning systems, radiotherapy simulators, isocentric gamma beam therapy equipment, isocentric medical electron accelerators, and non-isocentric equipment when relevant. The object of this standard is to define a consistent set of coordinate systems for use throughout the process of teleradiotherapy, to define the marking of scales (where provided), to define the movements of equipment used in this process, and to facilitate computer control when used.

Strahlentherapie-Einrichtungen - Koordinaten, Bewegungen und Skalen

Appareils utilisés en radiothérapie - Coordonnées, mouvements et échelles

Est applicable aux appareils et aux données ayant trait aux opérations de téléradiothérapie, ce qui comprend les images numérisées du patient utilisées dans les systèmes de planification des traitements de radiothérapie, les simulateurs de radiothérapie, les appareils de gamma-thérapie isocentriques, les accélérateurs médicaux d'électrons isocentriques et, quand cela est applicable, les appareils non isocentriques. L'objet de cette norme est de définir des systèmes de coordonnées cohérents qui sont à utiliser tout au long des opérations de téléradiothérapie, de définir les graduations des échelles de mesure (là où elles sont prévues), de définir les mouvements des appareils utilisés dans ces opérations et de faciliter les contrôles informatiques lorsqu'ils sont utilisés.

Oprema za radioterapijo - Koordinate, gibanje in skale (IEC 61217:1996)

General Information

Status
Withdrawn
Publication Date
04-Sep-1996
Current Stage
6060 - Document made available
Start Date
05-Sep-1996
Completion Date
05-Sep-1996

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SLOVENSKI STANDARD
SIST EN 61217:1998
01-september-1998
Oprema za radioterapijo - Koordinate, gibanje in skale (IEC 61217:1996)
Radiotherapy equipment - Coordinates, movements and scales
Strahlentherapie-Einrichtungen - Koordinaten, Bewegungen und Skalen
Appareils utilisés en radiothérapie - Coordonnées, mouvements et échelles
Ta slovenski standard je istoveten z: EN 61217:1996
ICS:
11.040.50 Radiografska oprema Radiographic equipment
13.280 Varstvo pred sevanjem Radiation protection
SIST EN 61217:1998 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 61217:1998
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SIST EN 61217:1998
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SIST EN 61217:1998
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SIST EN 61217:1998
NORME
CEI
INTERNATIONALE
IEC
1217
INTERNATIONAL
Première
édition
STANDARD
First edition
1996-08
Appareils utilisés en radiothérapie —
Coordonnées, mouvements et échelles
Radiotherapy equipment —
Coordinates, movements and scales
© CEI 1996 Droits de reproduction réservés —
Copyright - all rights reserved

Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized

utilisée sous quelque forme que ce soit et par aucun procédé, in any form or by any means, electronic or mechanical,

électronique ou mécanique, y compris la photocopie les
et including photocopying and microfilm, without permission
microfilms, sans l'accord écrit de l'éditeur. in writing from the publisher
Bureau central de la Commission Electrotechnique Inte
rnationale 3, rue de Varembé Genève, Suisse
Commission Electrotechnique Internationale CODE PRIX
International Electrotechnical Commission PRICE CODE J^[^
IEC
McnUtyHaponuaa 3neurporexHNVecKaa KoMKCCwn
• • Pour prix, voir catalogue en vigueur
For price, see current catalogue
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SIST EN 61217:1998
1217 ©IEC:1996 — 3 —
CONTENTS
Page
FOREWORD 11
INTRODUCTION 13
Clause
1 Scope and object 17
2 Coordinate systems 17
2.1 General rules 17
2.2 Fixed reference system ("f") (figure la) 21
2.3 GANTRY coordinate system ("g") (figure 4) 21
2.4 BEAM LIMITING DEVICE or DELINEATOR coordinate system ("b") (figure 5) 21
2.5 WEDGE FILTER coordinate system ("w") (figure 7) 23
-RAY IMAGE RECEPTOR coordinate system ("r") (figures 6 and 8) 2.6 X 23
2.7 PATIENT SUPPORT coordinate system ("s") (figure 9) 25
2.8 Table top eccentric rotation coordinate system ("e") (figures 10 and 11) 25
2.9 Table top coordinate system ("t") (figures 10 and 11) 27
3 Identification of scales and digital DISPLAYS 29
4 Designation of EQUIPMENT movements 31
5 EQUIPMENT zero positions 33
6 List of scales, graduations, directions and DISPLAYS 33
6.1 Rotation of the GANTRY (figures 14a and 14b) 33
6.2 Rotation of the BEAM LIMITING DEVICE or DELINEATOR (figures 15a and15b) 33
6.3 Rotation of the WEDGE FILTER (figures 7 and 14a) 35
6.4 RADIATION FIELD Or DELINEATED RADIATION FIELD 35
6.5 PATIENT SUPPORT ISOCENTRIC rotation 41
6.6 Table top eccentric rotation 41
6.7 Table top linear movements 41
6.8 X-RAY IMAGE RECEPTOR movements 41
6.9 Other scales 43
Tables
1 EQUIPMENT movements and designations 31
2 Individual coordinate systems 45
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SIST EN 61217:1998
1217© IEC:1996 – 5 --
Figures Page
1 a Coordinate systems (see 2.1.2) with all angular positions set to zero 47

1 b Translation of origin Id along Xm, Ym, Zm and rotation around axis Zd parallel

to Zm (see 2.1.4) 49

1c Translation of origin Id along Xm, Ym, Zm and rotation around axis Yd parallel

to Ym (see 2.1.4) 49

2 X Y Z right-hand coordinate mother system (isometric drawing), showing yr, cp, 0

directions of positive rotation for daughter system (see 2.2) 51
3 Hierarchical structure among coordinate systems (see 2.1.3 and 2.1.5) 53
4 Rotation (cpg = 15°) of GANTRY
coordinate system Xg, Yg, Zg in fixed coordinate
system Xf, Yf, Zf (see 2.3) 55
5 Rotation (Ob = 15°) of BEAM LIMITING DEVICE
or DELINEATOR coordinate system
Xb, Yb, Zb in GANTRY coordinate system Xg, Yg, Zg and resultant rotation of

RADIATION FIELD or DELINEATED RADIATION FIELD Of dimensions FX and FY (see 2.4).... 57

6 Displacement of image intensifier type X-RAY IMAGE RECEPTOR coordinate system

origin, Ir, in GANTRY coordinate system, by Rx = –8, Ry = +10, Rz = –40 (see 2.6) 59

7 Rotation (Ow = 270°) and translation of WEDGE FILTER
coordinate system Xw, Yw, Zw
in BEAM LIMITING DEVICE coordinate system Xb, Yb, Zb, the BEAM LIMITING DEVICE
coordinate system having a rotation (Ob) of 345° (see 2.5) 61
8 Rotation (Or= 90°) and displacement of RADIOGRAPHIC CASSETTE type X-RAY IMAGE
RECEPTOR coordinate system Xr, Yr, Zr in GANTRY coordinate system Xg, Yg, Zg
(see 2.6) 63
9 Rotation (Os = 345°) of PATIENT SUPPORT coordinate system Xs, Ys, Zs in fixed
coordinate system Xf, Yf, Zf (see 2.7) 65

10 Table top eccentric coordinate system rotation 0e in PATIENT SUPPORT coordinate

system which has been rotated by Os in the fixed coordinate system with
0e = 360° – Os (see 2.8 and 2.9) 67
11 a Table top displaced below ISOCENTRE by Tz = -20 cm (see 2.8 and 2.9) 69
11 b Table top coordinate system displacement Tx = +5, Ty = Le + 10 in
PATIENT SUPPORT
coordinate system Xs, Ys, Zs rotation (Os = 330°) in fixed coordinate
system Xf, Yf, Zf (see 2.8 and 2.9) 69

11c Table top coordinate system rotation (0e = 30°) about table top eccentric system.

PATIENT SUPPORT
rotation (Os = 330°) in fixed coordinate system Tx = 0, Ty = Le
(see 2.8 and 2.9) 69

12a Example of BEAM LIMITING DEVICE scale, pointer on mother system (GANTRY), scale on

daughter system (BEAM LIMITING DEVICE), viewed from ISOCENTRE (see 2.1.6.2 and
clause 3) 71
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SIST EN 61217:1998
1217©IEC:1996 – 7 –
Figures
Page
12b Example of BEAM LIMITING DEVICE
scale, pointer on daughter system (BEAM LIMITING
DEVICE), on mother system
scale (GANTRY), viewed from ISOCENTRE (see 2.1.6.2
and clause 3) 73
12c Examples of scales (see clause 3) 75
13a Rotary GANTRY
(adapted from !EC 601-2-1) with identification of axes 1 to 8,
directions 9 to 13 and dimensions 14 and 15 (see clause 4) 77
13b ISOCENTRIC RADIOTHERAPY SIMULATOR
or TELERADIOTHERAPY EQUIPMENT, with

identification of axes 1; 4 to 6; 19, of directions 9 to 12; 16 to 18 and of dimen-

sions 14; 15; 20 to 23 (see clause 4) 79
13c View from RADIATION SOURCE Of TELERADIOTHERAPY RADIATION FIELD
or RADIOTHERAPY
SIMULATOR DELINEATED RADIATION FIELD (see clause 4) 81
14a Example of 1SOCENTRIC TELERADIOTHERAPY EQUIPMENT (see 6.1 and 6.3) 83
14b Example of ISOCENTRIC RADIOTHERAPY SIMULATOR EQUIPMENT (see 6.1) 85
15a Rotated (8b = 30°) symmetrical rectangular
RADIATION FIELD (FX x FY) at NORMAL
TREATMENT DISTANCE, viewed from beyond ISOCENTRE looking toward RADIATION
SOURCE (see 6.2) 87
15b Same rotated (Ob = 30°) symmetrical rectangular RADIATION FIELD (FX x FY)
NORMAL TREATMENT DISTANCE, viewed from RADIATION SOURCE (see 6.2) 87
16a Rectangular and symmetrical
RADIATION FIELD or DELINEATED RADIATION FIELD,
viewed from RADIATION SOURCE (see 6.4) 89
16b Rectangular and asymmetrical in
Yb RADIATION FIELD or DELINEATED RADIATION FIELD,
viewed from RADIATION SOURCE (see 6.4) 91
16c Rectangular and asymmetrical in Xb RADIATION FIELD
or DELINEATED RADIATION FIELD,
viewed from RADIATION SOURCE (see 6.4) 93

16d Rectangular and asymmetrical in Xb and Yb RADIATION FIELD or DELINEATED RADIATION

FIELD, viewed from RADIATION SOURCE (see 6.4) 95
16e Rectangular and symmetrical RADIATION FIELD,
rotated by Ob = 30°, viewed
from RADIATION SOURCE (see 6.4) 97
16f Rectangular and asymmetrical in Yb RADIATION FIELD,
rotated by 9b = 30°, viewed
from RADIATION SOURCE (see 6.4) 99

16g Rectangular and asymmetrical in Xb RADIATION FIELD, rotated by 8b = 30°, viewed

from
RADIATION SOURCE (see 6.4) 101
16h Rectangular and asymmetrical in Xb and Yb RADIATION FIELD, rotated by Ob
= 30°,
viewed from RADIATION SOURCE (see 6.4) 103
16i Irregular multi-element (multileaf) contiguous RADIATION FIELD,
viewed from RADIATION
SOURCE, with element motion in Xb direction (see 6.4) 105
16j Irregular multi-element (multileaf) two-part RADIATION FIELD, viewed from
RADIATION
SOURCE, with element motion in Xb direction (see 6.4) 107
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SIST EN 61217:1998
1217 ©IEC:1996 – 9 –
Figure Page
16k Irregular multi-element (multileaf) contiguous RADIATION FIELD, viewed from
RADIATION SOURCE,
with element motion in Yb direction (see 6.4) 109
Annexes

A Examples of coordinate transformations between individual coordinate systems 111

B Bibliography 127
C Rationale for changes in IEC scales 129
D Summary of additions and changes to scale statements in IEC 601-2-1,
IEC 601-2-11, IEC 976 and IEC 977 135
Terminology 137
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SIST EN 61217:1998
1217 ©
IEC:1996 – 11 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
RADIOTHERAPY EQUIPMENT -
COORDINATES, MOVEMENTS AND SCALES
FOREWORD

1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization

comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to

promote international co-operation on all questions concerning standardization in the electrical and electronic

fields. To this end and in addition to other activities, the IEC publishes International Standards. Their

preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt

with may participate in this preparatory work. International, governmental and non-governmental organizations

liaising with the IEC also participate in this preparation. The IEC collaborates closely with the International

Organization for Standardization (ISO) in accordance with conditions determined by agreement between the

two organizations.

2) The formal decisions or agreements of the IEC on technical matters, express as nearly as possible, an

international consensus of opinion on the relevant subjects since each technical committee has representation

from all interested National Committees.

The documents produced have the form of recommendations for international use and are published in the

form of standards, technical reports or guides and they are accepted by the National Committees in that

sense.

4) In order to promote international unification, IEC National Committees undertake to apply IEC International

Standards transparently to the maximum extent possible in their national and regional standards. Any

divergence between the IEC Standard and the corresponding national or regional standard shall be clearly

indicated in the latter.

The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with one of its standards.

Attention is drawn to the possibility that some of the elements of this International Standard may be the

subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 1217 has been prepared by sub-committee 62C: Equipment for

radiotherapy, nuclear medicine and radiation dosimetry, of IEC technical committee 62:

Electrical equipment in medical practice.
The text of this standard is based on the following documents:
FDIS
Report on voting
62C/143/FDIS
62C/165/RVD

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.
Annexes A, B, C, D and E are for information only.
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SIST EN 61217:1998
1217 ©
IEC:1996 – 13 –
INTRODUCTION
RADIOTHERAPY is
performed in medical centres where a variety of
EQUIPMENT from different
MANUFACTURERS is
usually concentrated in the RADIOTHERAPY
department. In order to plan and
simulate the treatment, set up the
PATIENT and direct the RADIATION BEAM, such EQUIPMENT
can be
put in different angular and linear positions and, in the case of
MOVING BEAM RADIOTHERAPY,
can
be rotated and translated during the IRRADIATION of
the PATIENT. It is
essential that the position of
the PATIENT, and the dimensions, directions, and qualities of the
RADIATION BEAM
prescribed in
the treatment plan, be set up or varied by programmes on the
RADIOTHERAPY EQUIPMENT
with

accuracy and without misunderstanding. Standard identification and scaling of coordinates is

required for EQUIPMENT used in RADIOTHERAPY,
including RADIOTHERAPY SIMULATORS,
because

differences in the marking and scaling of similar movements on the various types of

EQUIPMENT

used in the same department may increase the probability of error. In addition, data from

EQUIPMENT used to evaluate the tumour region, such as ultrasound, X-ray, CT and MRI should

be presented to the treatment planning system in a form which is consistent with the

RADIOTHERAPY
coordinate system. Coordinate systems for individual geometrical parameters are

required in order to facilitate the mathematical transformation of points and vectors from one

coordinate system to another.

A goal of this standard is to avoid ambiguity, confusion, and errors which could be caused when

using different types of EQUIPMENT.
Hence, its scope applies to all types of
TELERADIOTHERAPY
EQUIPMENT, RADIOTHERAPY SIMULATORS,
information from diagnostic EQUIPMENT
when used for
RADIOTHERAPY, recording and verification
EQUIPMENT, and to data input for the treatment planning
process.

Movement nomenclature is to be classified as defined terms according to IEC 788 and

appendix AA of IEC 601-2-1 and IEC 601-2-29 (see annex E).

This standard is issued as a publication separate from the 601 series of safety standards. It is

not a safety code and does not contain pe
rformance requirements. Thus, the present

requirements will not appear in future editions of the IEC 601-2 series, which deals exclusively

with safety requirements.

IEC 601-2-1, IEC 601-2-11, IEC 601-2-29, IEC 976, IEC 977, IEC 1168 and IEC 1170 include

EQUIPMENT
movements and scale conventions. A number of changes and additions have been
made in this standard. These are summarized in annex D.
A major value of a standard coordinate system is its contribution to safety in
RADIOTHERAPY

treatment planning. The scales that are demonstrated in this standard are consistent with the

coordinate systems described herein. USERS may use other scale conventions. It is anticipated

that

MANUFACTURERS will normally employ the scale conventions of this standard for new

EQUIPMENT.
If MANUFACTURERS
provide other optional scale conventions when requested by
USERS, such as
to match existing

EQUIPMENT in a USER'S facility or to comply with local convention or regulations,

such EQUIPMENT
cannot be said to comply with this standard.
It is also anticipated that
MANUFACTURERS may provide, as options, scales to convert a
USER'S
existing EQUIPMENT
to the scale conventions of this standard.
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SIST EN 61217:1998
1217 ©IEC:1996 – 15 –

This standard does not address non-ISOCENTRIC EQUIPMENT and pitch or roll movements of the

RADIATION HEAD, due to limited clinical use.
It is anticipated that future amendments may address the following:
— PATIENT coordinate system;
– Three-dimensional RADIOTHERAPY SIMULATORS;
– CT type RADIOTHERAPY SIMULATORS;
— non-ISOCENTRIC EQUIPMENT.
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SIST EN 61217:1998
1217 ©IEC:1996 – 17 –
RADIOTHERAPY EQUIPMENT -
COORDINATES, MOVEMENTS AND SCALES
1 Scope and object
This International Standard applies to EQUIPMENT
and data related to the process of
TELERADIOTHERAPY, including PATIENT image data used in relation with
RADIOTHERAPY treatment

planning systems, RADIOTHERAPY SIMULATORS, ISOCENTRIC GAMMA BEAM THERAPY EQUIPMENT,

ISOCENTRIC MEDICAL ELECTRON ACCELERATORS, and non-ISOCENTRIC EQUIPMENT
when relevant.

The object of this standard is to define a consistent set of coordinate systems for use

throughout the process of TELERADIOTHERAPY, to define the marking of scales (where provided),

to define the movements of EQUIPMENT used in this process, and to facilitate computer control

when used.
2 Coordinate systems

An individual coordinate system is assigned to each major part of the EQUIPMENT which can

potentially be moved in relation to another part, as illustrated in figure la and summarized in

table 1. Furthermore a fixed reference system is defined. Each major pa rt (e.g. GANTRY,

RADIATION HEAD)
is always stationary with respect to its own coordinate system.
Perspective views of an ISOCENTRIC MEDICAL ELECTRON ACCELERATOR and a
RADIOTHERAPY
SIMULATOR

are shown in figures la, 14a and 14b. Isometric projection drawings of coordinate

systems are shown in several figures. In the figures, an elliptic (isometric projection) arrow

around an axis of a coordinate system always shows clockwise rotation of that coordinate

system about that axis when viewed from its origin and in the positive direction.

NOTE – In the following description of individual coordinate systems, counter-clockwise (ccw) rotations are

sometimes described in which the axis of rotation is not viewed from the origin of the individual coordinate

system.

The definitions of coordinate systems, as stated in the following subclauses, allow mathe-

matical transformations (rotation and/or translation) for the transfer of a point or vector

coordinates in one system to any other coordinate system. See annex A for examples of

coordinate transformations.
2.1
General rules

2.1.1 All coordinate systems are Cartesian right-handed. The positive parameter directions of

linear and angular movements between systems are identified in figure 2. With all coordinate

system angles set to zero, all coordinate system Z axes are vertically upward.

2.1.2 Coordinate axes are identified by a capital letter followed by a lower-case letter,

representing coordinate system identification.

2.1.3 Coordinate systems have a hierarchical structure (mother-daughter relation) in the

sense that each system is derived from another system. The common mother system is the

fixed reference system. Figure 3 and table 2 show the hierarchical structure which is divided

into two sub-hierarchical structures, one in relation to the GANTRY, the second in relation to the

PATIENT SUPPORT.
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SIST EN 61217:1998
1217 © IEC:1996 - 19 -

2.1.4 The position and orientation of each daughter coordinate system (d) is derived from its

mother coordinate system (m) by translation of its origin Id along one, two or three axes of its

mother system and then by rotation of the daughter system about one of the daughter

translated system axes.
rts of the EQUIPMENT may follow a different sequence, as long as the
NOTE — The mechanical motions of pa

EQUIPMENT ends up in the same position and orientation as it would have done if the indicated sequence had

been followed.

Figures 1b and lc show examples of translation of the daughter system origin Id along the

mother system coordinate axes Xm, Ym, Zm.

Figure 1 b shows translation of origin Id along Xm, Ym, Zm and rotation about axis Zd which is

parallel to Zm.

Figure lc shows translation of origin Id along Xm, Ym, Zm and rotation about axis Yd which is

parallel to Ym.
BEAM LIMITING DEVICE coordinate system is derived from the GANTRY system and
Example: The

er from the fixed system. Thus, a rotation of the GANTRY system causes an analogous

the latt

rotation of the coordinate axes of the BEAM LIMITING DEVICE coordinate system in the fixed system

BEAM LIMITING DEVICE system (position of the RADIATION SOURCE) is displaced
and the origin of the
in the fixed system (in space).

2.1.5 A point defined in one system can be defined in the coordinates of the next higher

system (its mother) or the next lower system (its daughter) by applying a coordinate

transformation, see figure 3 and annex A. Thus, it is possible to calculate, for a point defined in

BEAM LIMITING DEVICE system, its coordinates in the table top system by application of

the

successive coordinate transformations (rotations and translations of the origin, as defined

in 2.1.4), going first from the BEAM LIMITING DEVICE system upwards to the fixed system (i.e. BEAM

LIMITING DEVICE system to GANTRY system to fixed system) and from this downwards to the table

top system (i.e. fixed system to PATIENT SUPPORT system to table top eccentric rotation system, if

available, to table top system). Such a coordinate transformation may considerably facilitate the

solution of complex geometrical problems encountered in treatment planning, as well as

minimize errors in the positioning of EQUIPMENT.
2.1.6 Notations

2.1.6.1 Capital letters are used for coordinate axis identification and lower-case letters are

used for coordinate system identification.
Example: Yg means y axis of the GANTRY system.

2.1.6.2 The rotation of one coordinate system with respect to its mother system about one

particular axis of its own system is designated by the rotation angle which identifies the axis

about which it rotates (yr about X, cp about Y, and 6 about Z), and by a lower-case letter

identifying the system involved.

Example: 9b = 30° means rotation of the "b" system with respect to the "g" system by an angle

of 30° (clockwise as viewed from ISOCENTRE) around axis Zb of the "b" system (see figures 12a,

12b and also figure 5, where Ob= 15°).

2.1.6.3 The linear position of the origin of a coordinate system within its mother system is

designated by capital letters identifying the daughter coordinate system and by the designation

of the coordinate axis of the mother system along which it is translated.
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SIST EN 61217:1998
1217 © IEC:1996 – 21 –

Example: Ry = (numerical value) means position of the origin of the X-RAY IMAGE RECEPTOR

coordinate system along coordinate axis Yg (of its mother system).
2.1.6.4 For a movable component pa
rt which does not have its own coordinate system, its

position within the system in which it moves is designated by a capital letter identifying the

device in movement and a lower-case letter identifying the coordinate axis of the coordinate

system along which it moves.
Example: X1 [Xb] = (numerical value) means position of
RADIATION FIELD or DELINEATED RADIATION
FIELD edge X1 along axis Xb of the
BEAM LIMITING DEVICE system.
NOTE — When a component pa rt
position can be displaced along only one coordinate axis, then the designation

of this coordinate axis can be omitted. Thus, for the above example, X1 = (numerical value) is sufficient.

2.1.6.5 The position of a point within a coordinate system is given by the numerical values of

its coordinates in that system.
Example: Coordinate values of a point in the X-RAY IMAGE RECEPTOR
system
xr = +20 cm
yr = –10 cm
zr = 0 cm
2.2 Fixed reference system ("f") (figure la)

The fixed coordinate system "f" is stationary in space. It is defined by a horizontal coordinate

axis Yf directed from the ISOCENTRE toward the GANTRY,
by a coordinate axis Zf directed

vertically upward and by a coordinate axis Xf, normal to Yf and Zf and directed to the viewer's

right when facing the GANTRY. For ISOCENTRIC EQUIPMENT the origin If is the
ISOCENTRE to and,
therefore, Yf is the rotation axis of the GANTRY.
2.3 GANTRY coordinate system ("g") (figure 4)

The "g" coordinate system is stationary with respect to the GANTRY and its mother system is the

"f" system. Its origin Ig is the IsocENTRE. Its coordinate axis Zg passes through and is directed

towards the RADIATION SOURCE. Coordinate axes Yg and Yf coincide.

The "g" system is in the zero angular position when it coincides with the "f" system.

The rotation of the "g" system is defined by the rotation of coordinate axes Xg, Zg by an angle

cpg about axis Yg (therefore about Yf of the "f" system).
An increase in the value of cpg corresponds to a clockwise rotation of the
GANTRY as viewed
along the horizontal axis Yf from the ISOCENTRE towards the GANTRY.
2.4 BEAM LIMITING DEVICE Or DELINEATOR coordinate system ("b") (figure 5)

The "b" coordinate system is stationary with respect to the BEAM LIMITING DEVICE or

DELINEATOR

system and its mother system is the "g" system. Its origin lb is the RADIATION SOURCE.

Its

coordinate axis Zb coincides with and points in the same direction as axis Zg. The coordinate

axes Xb and Yb are perpendicular to the corresponding edges X1, X2, Y1 and Y2 of the

RADIATION FIELD Or DELINEATED RADIATION FIELD (see 6.4).

NOTE — The positions of the RADIATION FIELD edges are defined by the coordinate system. The coordinate system

edges.
is not defined by the RADIATION FIELD
---------------------- Page: 15 ----------------------
SIST EN 61217:1998
1217 ©
IEC:1996 – 23 –
For
EQUIPMENT capable of variation of the distance from the ISOCENTRE
to the RADIATION SOURCE
(e.g.

some RADIOTHERAPY SIMULATORS), this SAD-movement corresponds to a linear displacement

of the "b" coordinate system along the Zg axis of its mother system ("g" system).

The "b" system is in the zero angular position when the coordinate axes Xb,
Yb are parallel to
and in the same directions as the corresponding axes Xg, Yg.

The rotation of the "b" system is defined by the rotation of the coordinate axes Xb,

Yb about
axis Zb (therefore about axis Zg of the "g" system) by an angle Ob.

An increase in the value of angle Ob corresponds to the clockwise rotation of the

RADIATION
FIELD or DELINEATED RADIATION FIELD as viewed from the ISOCENTRE
towards the RADIATION
SOURCE (see figures 15a, 15b).
2.5 WEDGE FILTER coordinate system ("w") (figure 7)
The "w" coordinate system is stationary with respect to the WEDGE FILTER
and its mother system

is the "b" system. Its origin, Iw, is a defined point such that the coordinate axis Yw is directed

towards the thin edge of the WEDGE FILTER and in its zero position axis Zw passes through the

RADIATION SOURCE, coincides with axis Zb and points in the same direction as Zb.
NOTE 1 – The MANUFACTURER or USER
may choose the location of Iw to suit the design of the WEDGE FILTER
DEVICE.

For example it is possible to define Iw as the point of intersection of axis Zw with a particular su

rface of
the WEDGE FILTER.

In the zero angular position of the "w" system (Ow 0) and of the "b" system (8b = 0) the thin

edge of the WEDGE FILTER (end, along Yw, with highest transmission) is toward the

GANTRY and
the coordinate axes Xw, Yw are parallel to the corresponding axes Xb, Yb.

The rotation of the "w" system is defined by the rotation of coordinate axes Xw, Yw about axis

Zw (parallel to axis Zb of the "b" system) by an angle Ow.

An increase in the value of angle Ow corresponds to the counter-clockwise rotation of the

WEDGE FILTER
about Zw (parallel to axis Zb) as viewed from the RADIATION SOURCE.

At the zero angular position of the "w", "b" and "g" coordinate systems, a positive longitudinal

displacement of the origin Iw corresponds to the movement of the WEDGE FILTER
thin edge
toward the
GANTRY, along Yb and a positive lateral displacement corresponds to the movement
along Xb to the viewer's right when facing the
GANTRY.
NOTE 2 – For convenience of access, mechanical
WEDGE FILTERS may be inserted transversely. In such cases,
WEDGE FILTER

orientation angles also apply. If, for example, with the "b" and "g" systems in zero angular

positions (9b = 0 and (pg = 0), the WEDGE FILTER
is inserted with the thin edge directed to the viewer's left when
facing the GANTRY,

the angle 9w corresponds to 90°. In the same conditions, when the WEDGE FILTER is inserted

with the thin edge directed to the viewer's right when facing the GANTRY, the angle Ow corresponds to 270°.

2.6
X-RAY IMAGE RECEPTOR coordinate system ("r") (figures 6 and 8)

The "r" coordinate system is stationary with respect to the X-RAY IMAGE RECEPTOR (e.g.

image
intensifier, RADIOGRAPHIC FILM
in RADIOGRAPHIC CASSETTE HOLDER, RADIATION
sensitive
foil/plate) and its mother system is the "g" system. Its origin
Ir is at the centre of the
IMAGE
RECEPTION AREA.
In the zero angular position of the "r" system, the coordinate axes Xr, Yr,
Zr are parallel to the
corresponding axes Xg, Yg, Zg of the "g" system.
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SIST EN 61217:1998
1217 © IEC:1996 - 25 -

The rotation of the "r" system is defined by the rotation of the coordinate axes Xr, Yr about

(parallel to axis Zg) by an angle Or.

An increase in the value of angle Or corresponds to a counter-clockwise rotation of the

X-RAY
IMAGE RECEPTOR
as viewed from the RADIATION SOURCE.
In the zero position of the "r" system, its origin Ir is at the
ISOCENTRE. This may not be

mechanically achievable, but it defines the origin of the displacement of the "r" system along

Zg.
NOTE 1 - The distance (SID) from the
RADIATION SOURCE to the X-RAY IMAGE RECEPTOR PLANE
may also be DISPLAYED
for use in determining the geometric magnification of the image.

The values of Rx, Ry and Rz are the lateral, longitudinal and vertical displacements of the

origin Ir of the
IMAGE RECEPTION AREA along Xg, Yg and Zg respectively.
NOTE 2 — When there are several different devices (such as
RADIOGRAPHIC FILM or IMAGE INTENSIFIER),
used as X-
RAY IMAGE RECEPTORS on a given EQUIPMENT,
each device may have its own origin, Ir.
2.7
PATIENT SUPPORT coordinate system ("s") (figure 9)
The "s" coordinate system is stationary with respect to that pa
rt of the PATIENT SUPPORT which
rotates about the ve rtical axis Zs. This rotation is achieved
...

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