EN 61217:1996
(Main)Radiotherapy equipment - Coordinates, movements and scales
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
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Standards Content (Sample)
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
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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
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Commission Electrotechnique Internationale CODE PRIX
International Electrotechnical Commission PRICE CODE J^[^
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• • 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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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)
at
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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1217 ©IEC:1996 – 9 –
Figure Page
9
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
E
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.
3)
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.
5)
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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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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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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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
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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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1217 © IEC:1996 - 25 -
The rotation of the "r" system is defined by the rotation of the coordinate axes Xr, Yr about
Zr
(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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