IEC 61675-2:1998

INTERNATIONAL IEC
STANDARD 61675-2
Edition 1.1
2005-02
Edition 1:1998 consolidated with amendment 1:2004
Radionuclide imaging devices –
Characteristics and test conditions –
Part 2:
Single photon emission computed tomographs

Reference number
Publication numbering
As from 1 January 1997 all IEC publications are issued with a designation in the
60000 series. For example, IEC 34-1 is now referred to as IEC 60034-1.
Consolidated editions
The IEC is now publishing consolidated versions of its publications. For example,
edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the base publication, the
base publication incorporating amendment 1 and the base publication incorporating
amendments 1 and 2.
Further information on IEC publications
The technical content of IEC publications is kept under constant review by the IEC,
thus ensuring that the content reflects current technology. Information relating to
this publication, including its validity, is available in the IEC Catalogue of
publications (see below) in addition to new editions, amendments and corrigenda.
Information on the subjects under consideration and work in progress undertaken
by the technical committee which has prepared this publication, as well as the list
of publications issued, is also available from the following:
• IEC Web Site (www.iec.ch)
• Catalogue of IEC publications
The on-line catalogue on the IEC web site (www.iec.ch/searchpub) enables you to
search by a variety of criteria including text searches, technical committees
and date of publication. On-line information is also available on recently issued
publications, withdrawn and replaced publications, as well as corrigenda.
• IEC Just Published
This summary of recently issued publications (www.iec.ch/online_news/ justpub)
is also available by email. Please contact the Customer Service Centre (see
below) for further information.
• Customer Service Centre
If you have any questions regarding this publication or need further assistance,
please contact the Customer Service Centre:

Email: custserv@iec.ch
Tel: +41 22 919 02 11
Fax: +41 22 919 03 00
INTERNATIONAL IEC
STANDARD 61675-2
Edition 1.1
2005-02
Edition 1:1998 consolidated with amendment 1:2004
Radionuclide imaging devices –
Characteristics and test conditions –
Part 2:
Single photon emission computed tomographs

 IEC 2005  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
PRICE CODE
CQ
Commission Electrotechnique Internationale
International Electrotechnical Commission
Международная Электротехническая Комиссия
For price, see current catalogue

– 2 – 61675-2 © IEC:1998+A1:2004(E)
CONTENTS
FOREWORD .3

1 General.5
1.1 Scope and object.5
1.2 Normative references .5
2 Terminology and definitions.6
3 Test methods .12
3.1 Calibration measurements .13
3.2 Measurement of COLLIMATOR hole misalignment .14
3.3 Measurement of SPECT system SENSITIVITY.14
3.4 Scatter .16
3.5 Measurement of SPECT non-uniformity of response.18
3.6 SPECT system SPATIAL RESOLUTION.18
3.7 Test methods for single photon computer tomographs
operated in coincidence detection mode .19
4 ACCOMPANYING DOCUMENTS.32

Annex A Index of defined terms .46

Figure 1 – Geometry of PROJECTIONS.35
Figure 2 – Cylindrical head phantom .36
Figure 3 – Phantom insert with holders for the scatter source.37
Figure 4 – Evaluation of SCATTER FRACTION .38
Figure 5 – Reporting TRANSVERSE RESOLUTION .39
Figure 6 – Evaluation of FWHM .40
Figure 7 – Evaluation of EQUIVALENT WIDTH (EW) .41
Figure 8 – Phantom insert with hollow spheres.42
Figure 9 – Cross-section of body phantom .43
Figure 10 – Arm phantom .43
Figure 11 – Phantom configuration for COUNT RATE measurements according to 3.7.5.3.1.2 .44
Figure 12 – Scheme of the evaluation of COUNT LOSS correction .44
Figure 13 – Phantom insert for the evaluation of ATTENUATION correction .45

61675-2 © IEC:1998+A1:2004(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RADIONUCLIDE IMAGING DEVICES –
CHARACTERISTICS AND TEST CONDITIONS –

Part 2: Single photon emission computed tomographs

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of 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, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). 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. 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 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 IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61675-2 has been prepared by subcommittee 62C: Equipment for
radiotherapy, nuclear medicine and radiation dosimetry, of IEC technical committee 62:
Electrical equipment in medical practice.
This consolidated version of IEC 61675-2 consists of the first edition (1998) [documents
62C/206/FDIS and 62C/215/RVD] and its amendment 1 (2004) [documents 62C/378/FDIS and
62C/379/RVD].
The technical content is therefore identical to the base edition and its amendment and has
been prepared for user convenience.
It bears the edition number 1.1.
A vertical line in the margin shows where the base publication has been modified by
amendment 1.
– 4 – 61675-2 © IEC:1998+A1:2004(E)
In this standard, the following print types are used:
– TERMS DEFINED IN CLAUSE 2 OF THIS STANDARD OR LISTED IN ANNEX A: SMALL CAPITALS.
The requirements are followed by specifications for the relevant tests.
Annex A is for information only.
A bilingual version of this standard may be issued at a later date.
The committee has decided that the contents of the base publication and its amendments will
remain unchanged until the maintenance result date indicated on the IEC web site under
"http://webstore.iec.ch" in the data related to the specific publication. At this date, the
publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
61675-2 © IEC:1998+A1:2004(E) – 5 –
RADIONUCLIDE IMAGING DEVICES –
CHARACTERISTICS AND TEST CONDITIONS –

Part 2: Single photon emission computed tomographs

1 General
1.1 Scope and object
This part of IEC 61675 specifies terminology and test methods for describing the character-
istics of Anger type rotational GAMMA CAMERA SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHS
(SPECT), equipped with parallel hole collimators. As these systems are based on Anger type
GAMMA CAMERAS this part of IEC 61675 shall be used in conjunction with IEC 60789. These
systems consist of a gantry system, single or multiple DETECTOR HEADS and a computer
system together with acquisition, recording, and display devices.
This part of IEC 61675-2 also specifies test conditions for declaring the characteristics of
single photon computer tomographs operated in coincidence mode as well as in single
photon mode.
The test methods specified for coincidence mode are based on the test methods for
dedicated PET tomographs as described in IEC 61675-1 to reflect as well as possible the
clinical use of coincidence detection. Tests have been modified to reflect the limited
sensitivity and COUNT RATE CHARACTERISTICS of the single photon computer tomographs
operated in coincidence detection mode only when needed.
The test methods specified in this part of IEC 61675 have been selected to reflect as much
as possible the clinical use of Anger type rotational GAMMA CAMERA SINGLE PHOTON EMISSION
COMPUTED TOMOGRAPHS (SPECT). It is intended that the test methods be carried out by
manufacturers thereby enabling them to describe the characteristics of SPECT systems on a
common basis.
No test has been specified to characterize the uniformity of reconstructed images because all
methods known so far will mostly reflect the noise of the image.
1.2 Normative references
The following referenced documents are indispensable for the application 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.
IEC 60788:1984, Medical radiology – Terminology
IEC 60789:1992, Characteristics and test conditions of radionuclide imaging devices – Anger
type gamma cameras
IEC 61675-1,  Radionuclide imaging devices – Characteristics and test conditions – Part 1:
Positron emission tomographs
– 6 – 61675-2 © IEC:1998+A1:2004(E)
2 Terminology and definitions
For the purposes of this part of IEC 61675 the definitions given in IEC 60788, IEC 60789 and
IEC 61675-1 (some of which are repeated in this clause), and the following definitions apply.
Defined terms are printed in small capital letters.
2.1
SYSTEM AXIS
Axis of symmetry characterized by geometrical and physical properties of the arrangement of
the system
NOTE The SYSTEM AXIS of a GAMMA CAMERA with rotating detectors is the axis of rotation.
2.1.1
COORDINATE SYSTEMS
2.1.2
FIXED COORDINATE SYSTEM
Cartesian system with axes X, Y, and Z, Z being the SYSTEM AXIS. The origin of the FIXED
COORDINATE SYSTEM is defined by the centre of the TOMOGRAPHIC VOLUME (see Figure 1). The
SYSTEM AXIS is orthogonal to all TRANSVERSE SLICES.
2.1.3
COORDINATE SYSTEM OF PROJECTION
Cartesian system of the IMAGE MATRIX of each two-dimensional projection with axes X and Y
p p
(defined by the axes of the IMAGE MATRIX). The Y axis and the projection of the system axis
p
onto the detector front face have to be in parallel. The origin of the COORDINATE SYSTEM OF
PROJECTION is the centre of the IMAGE MATRIX (see Figure 1).
2.1.4
CENTRE OF ROTATION (COR)
Origin of that COORDINATE SYSTEM, which describes the PROJECTIONS of a TRANSVERSE SLICE with
respect to their orientation in space
NOTE The CENTRE OF ROTATION of a TRANSVERSE SLICE is given by the intersection of the SYSTEM AXIS with the
mid-plane of the corresponding OBJECT SLICE.
2.1.5
OFFSET
Deviation of the position of the PROJECTION of the COR (X' ) from X = 0. (See Figure 1)

p p
2.2
TOMOGRAPHY (see annex A)
2.2.1
TRANSVERSE TOMOGRAPHY
In TRANSVERSE TOMOGRAPHY the three-dimensional object is sliced by physical methods, e.g.
collimation, into a stack of OBJECT SLICES, which are considered as being two-dimensional
and independent from each other. The transverse image planes are perpendicular to the
SYSTEM AXIS.
2.2.2
EMISSION COMPUTED TOMOGRAPHY (ECT)
Imaging method for the representation of the spatial distribution of incorporated
RADIONUCLIDES in selected two-dimensional SLICES through the object

61675-2 © IEC:1998+A1:2004(E) – 7 –
2.2.2.1
PROJECTION
Transformation of a three-dimensional object into its two-dimensional image or of a two-
dimensional object into its one-dimensional image, by integrating the physical property which
determines the image along the direction of the PROJECTION BEAM
NOTE This process is mathematically described by line integrals in the direction of projection and called the
Radon-transform.
2.2.2.2
PROJECTION BEAM
Determines the smallest possible volume in which the physical property which determines the
image is integrated during the measurement process. Its shape is limited by the SPATIAL
RESOLUTION in all three dimensions.
NOTE In SPECT the PROJECTION BEAM usually has the shape of a long thin diverging cone.
2.2.2.3
PROJECTION ANGLE
Angle at which the PROJECTION is measured or acquired
NOTE For illustration see Figure 1.
2.2.2.4
SINOGRAM
Two-dimensional display of all one-dimensional PROJECTIONS of an object slice, as a function
of the PROJECTION ANGLE
The PROJECTION ANGLE is displayed on the ordinate. The linear PROJECTION coordinate is
displayed on the abscissa.
2.2.2.5
OBJECT SLICE
A slice in the object. The physical property of this slice that determines the measured
information is displayed in the tomographic image.
2.2.2.6
IMAGE PLANE
A plane assigned to a plane in the OBJECT SLICE
NOTE Usually the IMAGE PLANE is the mid-plane of the corresponding OBJECT SLICE.
2.2.2.7
TOMOGRAPHIC VOLUME
Ensemble of all volume elements which contribute to the measured PROJECTIONS for all
PROJECTION ANGLES
NOTE For a rotating GAMMA CAMERA with a circular field of view the TOMOGRAPHIC VOLUME is a sphere provided
that the radius of rotation is larger than the radius of the field of view. For a rectangular field of view, the
TOMOGRAPHIC VOLUME is a cylinder.
2.2.2.7.1
TRANSVERSE FIELD OF VIEW
Dimensions of a slice through the TOMOGRAPHIC VOLUME, perpendicular to the SYSTEM AXIS.
For a circular TRANSVERSE FIELD OF VIEW it is described by its diameter.
NOTE For non-cylindrical TOMOGRAPHIC VOLUMES the TRANSVERSE FIELD OF VIEW may depend on the axial position
of the slice.
– 8 – 61675-2 © IEC:1998+A1:2004(E)
2.2.2.7.2
AXIAL FIELD OF VIEW
Dimensions of a slice through the TOMOGRAPHIC VOLUME parallel to and including the SYSTEM
AXIS. In practice it is specified only by its axial dimension given by the distance between the
centres of the outermost defined IMAGE PLANES plus the average of the measured AXIAL SLICE
WIDTH measured as EQUIVALENT WIDTH (EW).
2.2.2.7.3
TOTAL FIELD OF VIEW
Dimensions (three-dimensional) of the TOMOGRAPHIC VOLUME
2.3
IMAGE MATRIX
Arrangement of MATRIX ELEMENTS in a preferentially cartesian coordinate system
2.3.1
MATRIX ELEMENT
Smallest unit of an IMAGE MATRIX, which is assigned in location and size to a certain volume
element of the object (VOXEL)
2.3.1.1
PIXEL
MATRIX ELEMENT in a two-dimensional IMAGE MATRIX
2.3.1.2
TRIXEL
MATRIX ELEMENT in a three-dimensional IMAGE MATRIX
2.3.2
VOXEL
Volume element in the object which is assigned to a MATRIX ELEMENT in the IMAGE MATRIX
(two-dimensional or three-dimensional). The dimensions of the VOXEL are determined by the
dimensions of the corresponding MATRIX ELEMENT via the appropriate scale factors and by
the system's SPATIAL RESOLUTION in all three dimensions.
2.4
POINT SPREAD FUNCTION (PSF)
Scintigraphic image of a POINT SOURCE
2.4.1
PHYSICAL POINT SPREAD FUNCTION
For tomographs, a two-dimensional POINT SPREAD FUNCTION in planes perpendicular to the
PROJECTION BEAM at specified distances from the detector
NOTE The PHYSICAL POINT SPREAD FUNCTION characterizes the purely physical imaging performance of the
tomographic device independent from, e.g. sampling, image reconstruction and image processing, but dependent
on the COLLIMATOR. A PROJECTION BEAM is characterized by the entirety of all PHYSICAL POINT SPREAD FUNCTIONS as
a function of distance along its axis.
2.4.2
AXIAL POINT SPREAD FUNCTION
Profile passing through the peak of the PHYSICAL POINT SPREAD FUNCTION in a plane parallel to
the SYSTEM AXIS
61675-2 © IEC:1998+A1:2004(E) – 9 –
2.4.3
TRANSVERSE POINT SPREAD FUNCTION
Reconstructed two-dimensional POINT SPREAD FUNCTION in a tomographic IMAGE PLANE
NOTE In TOMOGRAPHY, the TRANSVERSE POINT SPREAD FUNCTION can also be obtained from a line source located
parallel to the SYSTEM AXIS.
2.5
SPATIAL RESOLUTION
Ability to concentrate the count density distribution in the image of a POINT SOURCE to a point
2.5.1
TRANSVERSE RESOLUTION
SPATIAL RESOLUTION in a reconstructed plane perpendicular to the SYSTEM AXIS
2.5.1.1
RADIAL RESOLUTION
TRANSVERSE RESOLUTION along a line passing through the position of the source and the
SYSTEM AXIS
2.5.1.2
TANGENTIAL RESOLUTION
TRANSVERSE RESOLUTION in the direction orthogonal to the direction of RADIAL RESOLUTION
2.5.2
AXIAL RESOLUTION
For tomographs with sufficiently fine axial sampling fulfilling the sampling theorem, SPATIAL
RESOLUTION along a line parallel to the SYSTEM AXIS
2.5.3
EQUIVALENT WIDTH (EW)
Width of that rectangle having the same area and the same height as the response function,
e.g. the POINT SPREAD FUNCTION
2.6 Tomographic sensitivity
2.6.1
SLICE SENSITIVITY
Ratio of COUNT RATE as measured on the SINOGRAM to the ACTIVITY concentration in the
phantom
NOTE In SPECT the measured counts are not numerically corrected for scatter by subtracting the SCATTER
FRACTION.
2.6.2
VOLUME SENSITIVITY
Sum of the individual SLICE SENSITIVITIES
2.6.3
NORMALIZED VOLUME SENSITIVITY
VOLUME SENSITIVITY divided by the AXIAL FIELD OF VIEW of the tomograph or the phantom
length, whichever is the smaller
2.7
SCATTER FRACTION (SF)
Ratio between the number of scattered photons and the sum of scattered plus unscattered
photons for a given experimental set-up

– 10 – 61675-2 © IEC:1998+A1:2004(E)
2.8
SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY (SPECT)
EMISSION COMPUTED TOMOGRAPHY utilizing single photon detection of gamma-ray emitting
RADIONUCLIDES
2.8.1
DETECTOR POSITIONING TIME
Fraction of the total time spent on an acquisition which is not used in collecting data
2.8.2
DETECTOR HEAD TILT
Deviation of the COLLIMATOR axis from orthogonality with the SYSTEM AXIS
2.8.3
RADIUS OF ROTATION
Distance between the SYSTEM AXIS and the COLLIMATOR front face
2.9
RADIOACTIVE SOURCE
See rm-20-02 of IEC 60788
2.9.1
POINT SOURCE
RADIOACTIVE SOURCE approximating a δ-function in all three dimensions
2.9.2
LINE SOURCE
Straight RADIOACTIVE SOURCE approximating a δ-function in two dimensions and being
constant (uniform) in the third dimension
2.10
POSITRON EMISSION TOMOGRAPHY
PET
emission computed tomography utilizing the annihilation radiation of positron emitting
radionuclides by coincidence detection
[IEC 61675-1, definition 2.1.3]
2.10.1
POSITRON EMISSION TOMOGRAPH
tomographic device, which detects the annihilation radiation of positron emitting
radionuclides by coincidence detection
[IEC 61675-1, definition 2.1.3.1]
2.10.2
ANNIHILATION RADIATION
IONIZING RADIATION that is produced when a particle and its antiparticle interact and cease to
exist
[IEC 61675-1, definition 2.1.3.2]

61675-2 © IEC:1998+A1:2004(E) – 11 –
2.10.3
LINE OF RESPONSE
LOR
axis of the PROJECTION BEAM
NOTE In PET, it is the line connecting the centres of two opposing detector elements operated in coincidence
[IEC 61675-1, definition 2.1.3.5]
2.10.4
TOTAL COINCIDENCES
sum of all coincidences detected
[IEC 61675-1, definition 2.1.3.6]
2.10.4.1
TRUE COINCIDENCE
result of COINCIDENCE DETECTION of two gamma events originating from the same positron
annihilation
[IEC 61675-1, definition 2.1.3.6.1]
2.10.4.2
SCATTERED TRUE COINCIDENCE
TRUE COINCIDENCE where at least one participating PHOTON was scattered before the
COINCIDENCE DETECTION
[IEC 61675-1, definition 2.1.3.6.2]
2.10.4.3
UNSCATTERED TRUE COINCIDENCES
difference between true coincidences and scattered true coincidences
[IEC 61675-1, definition 2.1.3.6.3]
2.10.4.4
RANDOM COINCIDENCE
result of COINCIDENCE DETECTION in which both participating PHOTONS emerge from different
positron annihilations
[IEC 61675-1, definition 2.1.3.6.4]
2.10.5
SINGLES RATE
COUNT RATE measured without COINCIDENCE DETECTION, but with energy discrimination
[IEC 61675-1, definition 2.1.3.7]
2.10.6
TWO-DIMENSIONAL RECONSTRUCTION
in TWO-DIMENSIONAL RECONSTRUCTION, the data are rebinned prior to reconstruction into
sinograms, which are the PROJECTION data of transverse slices, which are considered being
independent of each other and being perpendicular to the SYSTEM AXIS. So, each event will be
assigned, in the axial direction, to that transverse slice passing the midpoint of the
corresponding LINE OF RESPONSE. Any deviation from perpendicular to the SYSTEM AXIS is
neglected. The data are then reconstructed by two-dimensional methods, i.e. each slice is
reconstructed from its associated sinogram, independent of the rest of the data set
NOTE This is the STANDARD method of reconstruction for POSITRON EMISSION TOMOGRAPHS using small axial
acceptance angles, i.e. utilizing septa. For POSITRON EMISSION TOMOGRAPHS using large axial acceptance angles,
i.e. without septa, this method is also called “single slice rebinning”.
[IEC 61675-1, definition 2.1.4.1]

– 12 – 61675-2 © IEC:1998+A1:2004(E)
2.10.7
THREE-DIMENSIONAL RECONSTRUCTION
in THREE-DIMENSIONAL RECONSTRUCTION, the LINES OF RESPONSE are not restricted to being
perpendicular to the SYSTEM AXIS. So, a LINE OF RESPONSE may pass several transverse slices.
Consequently, transverse slices cannot be reconstructed independent of each other. Each
slice has to be reconstructed utilizing the full three-dimensional data set
[IEC 61675-1, definition 2.1.4.2]
2.11
RECOVERY COEFFICIENT
measured (image) ACTIVITY concentration of an active volume divided by the true ACTIVITY
concentration of that volume, neglecting ACTIVITY CALIBRATION FACTORS
NOTE For the actual measurement, the true ACTIVITY concentration is replaced by the measured ACTIVITY
concentration in a large volume.
[IEC 61675-1, definition 2.5]
2.12
NORMALIZED SLICE SENSITIVITY
slice sensitivity divided by the axial slice width (EW) for that slice
[IEC 61675-1, definition 2.6.1.1]
2.12.1
COUNT RATE CHARACTERISTIC
function giving the relationship between observed COUNT RATE and TRUE COUNT RATE
[IEC 60788, definition rm-34-21]
2.12.2
COUNT LOSS
difference between measured COUNT RATE and TRUE COUNT RATE, which is caused by the finite
RESOLVING TIME of the instrument
[IEC 61675-1, definition 2.7.1]
2.12.3
ADDRESS PILE UP
false address calculation of an artificial event which passes the ENERGY
WINDOW, but is formed from two or more events by the PILE UP EFFECT
[IEC 61675-1, definition 2.7.4, modified]
2.12.4
RADIOACTIVE SOURCE
quantity of radioactive material having both an ACTIVITY and a specific ACTIVITY above specific
levels
[IEC 60788, definition rm-20-02]
3 Test methods
All measurements shall be performed with the PULSE AMPLITUDE ANALYZER WINDOW as specified
in Table 1 of IEC 60789. Additional measurements with other settings as specified by the
manufacturer can be performed. Before the measurements are performed, the tomographic
system shall be adjusted by the procedure normally used by the manufacturer for an installed
unit and shall not be adjusted specially for the measurement of specific parameters. If any test
cannot be carried out exactly as specified in the standard, the reason for the deviation and the
exact conditions under which the test was performed shall be stated clearly.

61675-2 © IEC:1998+A1:2004(E) – 13 –
Unless otherwise specified, each DETECTOR HEAD in the system shall be characterized by a
full data set covering an angular range of 360°. For multiheaded systems, characterization
shall also be provided for an acquisition covering the minimal rotation required to obtain a
complete set of data (e.g. 120° for a three-headed system). If the tomograph is specified to
operate in a non-circular orbiting mode influencing the performance parameters, test results
shall be reported in addition.
Unless otherwise specified, measurements shall be carried out at COUNT RATES not exceeding
20 000 counts per second.
Measurements of performance parameters in the planar mode of operation are a prerequisite.
A complete set of performance parameters shall be measured as specified in IEC 60789.
3.1 Calibration measurements
3.1.1 Measurement of the CENTRE OF ROTATION (COR)
An error-free reconstruction requires the knowledge of the position of the PROJECTION of the
COR into the coordinate system X , Y for each PROJECTION (i.e. for each PROJECTION angle)
p p
of that slice. For a circular rotation of the DETECTOR and for an ideal system, the PROJECTION
of a POINT SOURCE at the COR will be at the same position X' in the projection matrix for all
p
angles of PROJECTION (see Figure 1).
To determine the CENTRE OF ROTATION, the OFFSET X' has to be measured. POINT SOURCE(S)
p
are used. A minimum of 32 projections equally spaced over 360° are acquired and displayed
as a SINOGRAM. The RADIUS OF ROTATION shall be set to 20 cm. The source(s) shall be
positioned radially at least 5 cm from the system axis to get SINOGRAMS with a discernible
shape of a sine function. The OFFSET shall be determined for a minimum of three slices with
axial positions, (Z direction), one at the centre of the FIELD OF VIEW and the other two, ±1/3 of
the AXIAL FIELD OF VIEW from the centre.
At least 10 000 counts per view shall be acquired. The length of PIXEL side shall be less than
4 mm. For the calculation of the centroid (centre of gravity) X (θ) of the source in the X
p p
direction, 50 mm wide strips in the Y direction centred around the Y position of each source
p
shall be used. This shall be done for each projection angle θ. Then the OFFSET is determined
by fitting a sine function to the X (θ) values of each source, where
p
X (θ) = A sin(θ + ϕ) + X'
p
where
θ is the angle of projection;
A is the amplitude;
ϕ is the phase shift of the sine function;
X' is the average OFFSET to be reported for the three different axial positions.
NOTE If there is a DETECTOR HEAD TILT the position of the image of the POINT SOURCE will move not only in the x
p
direction, but also in the Y direction. To determine the X movement not influenced by the Y movement (for a
p p p
reasonable amount of head tilt), the centroid is calculated using the 50 mm wide strip. The subscript p refers to the
projection space (see Figure 1).
NOTE If a system uses an automatic OFFSET correction which cannot be switched off, then X' shall be zero.
In addition, the difference between fit and data shall be plotted (showing the error) as a
function of θ. The maximum difference for each axial position shall be reported. The values
are valid only for the COLLIMATOR used and shall be stated in millimetres.
NOTE Systematic deviations (trends) are indicative of varying OFFSET during rotation of the detector.

– 14 – 61675-2 © IEC:1998+A1:2004(E)
3.1.2 DETECTOR HEAD TILT
An error-free reconstruction requires that the direction of the COLLIMATOR holes is orthogonal
to the SYSTEM AXIS for each angle of projection. Deviations from this requirement are called
DETECTOR HEAD TILT.
Using the measurements according to 3.1.1 the DETECTOR HEAD TILT can be determined by
calculating the centroid Y (θ) of the image of the POINT SOURCE in the Y direction, using
p p
strips over the full field-of-view in the X direction. This calculation shall be done for each
p
angle of projection. A sine function is fitted to all those values,
Y (θ)= B sin(θ + ϕ) + D
p
where
θ is the angle of projection;
B is the amplitude;
ϕ is the phase shift of the sine function.
Report the head tilt angle value a = arcsin B/A, where A is the amplitude resulting from the
COR measurement (3.1.1).
NOTE If there is no DETECTOR HEAD TILT, B must be zero and D must be the Y position of the source.
p
In addition the difference between fit and data shall be plotted (showing the error) as a
function of θ.
3.2 Measurement of COLLIMATOR hole misalignment
COLLIMATOR are parallel, the OFFSET is constant for all source
If all holes of a parallel hole
positions within the measuring volume, assuming linearity of the positioning electronics. To
detect possible misalignments of the collimator holes, the OFFSET shall be determined using a
point source placed at all intersections of an orthogonal positioning grid, lying in the X, Z
plane, covering the field of view. The grid lines shall be 10 cm apart. The radius of rotation
shall be at least 20 cm. The mean value of all measured OFFSETs shall be calculated and the
maximum deviation from that value stated.
3.3 Measurement of SPECT system SENSITIVITY
3.3.1 DETECTOR POSITIONING TIME
In combination with the acquisition time chosen, the DETECTOR POSITIONING TIME determines
that fraction of the total time spent on an acquisition which is not useful in collecting data.
Therefore it will influence the sensitivity of a tomographic device. This is especially true for a
rotating detector working in "step and shoot" mode.
99m
A POINT SOURCE of Tc shall be placed at the CENTRE OF ROTATION in air. The COUNT RATE
shall be greater than 1 000 cps. Two 360° tomographic acquisitions of a stated number, P
,
j
PROJECTIONS (one with at least 60, the other with at least 120 PROJECTIONS) shall be
performed using an acquisition time ΔT per PROJECTION of 10 s. The subscript j is either
acq
"low" or "high" corresponding to the range of approximately 60 or 120 projections. The time T
j
from the start of acquisition of the first projection to the end of the acquisition of the last
projection shall be measured. A corresponding static acquisition of duration T shall also be
j
performed directly after the tomographic acquisition. The data shall be decay corrected for
the different starting times.
61675-2 © IEC:1998+A1:2004(E) – 15 –
The total DETECTOR POSITIONING TIME T shall be calculated according to:
pos
NN− T
()static,jjtotal,j
T =
pos,j
N
static,j
where
N is the sum of the counts in all PROJECTIONS;
total
N is the number of counts in the static acquisition.

static
The mean positioning time per PROJECTION ΔT is then calculated by dividing T by the
pos pos
number of transitions between PROJECTION steps actually used.
T
pos,j
ΔT =
pos,j
P −1
()
j
The correction factor c for the calculation of the VOLUME SENSITIVITY is then given by
j
ΔT
acq, j
c =
j
ΔΔTT+
acq,jjpos,
The correction factor c shall be calculated and reported for the subscript j with corresponding
j
acquisition times per PROJECTION ΔT , of 30 s (low) and 15 s (high), respectively. This
acq j
corresponds to a typical clinical situation of total acquisition time of 30 min.
3.3.2 NORMALIZED VOLUME SENSITIVITY
The measurement shall be carried out using a cylindrical phantom of 200 mm ± 3 mm outside
diameter, of wall thickness 3 mm ± 1 mm, and 190 mm ±3 mm inside length (see Figure 2),
99m
filled homogeneously with a water solution of Tc.
The ACTIVITY concentration a (kBq/cm ) shall be accurately determined by counting at least
ave
two samples from that solution in a calibrated well counter and correcting the result for
radioactive decay to the time of measurement (midpoint of acquisition interval).
NOTE The test is critically dependent upon accurate assays of radioactivity as measured in a dose calibrator or
well counter. It is difficult to maintain an absolute calibration with such devices to accuracies better than 10 %.
Absolute reference standards using appropriate (γ-emitters should be considered if higher degrees of accuracy are
required.
The phantom shall be positioned so that its long axis coincides with the SYSTEM AXIS (parallel
to and as close as possible to the SYSTEM AXIS). The radius of rotation R shall be 20 cm. For
each COLLIMATOR used routinely for SPECT imaging at least one million counts shall be
acquired in static imaging mode and the acquisition time T [sec] recorded. For a rectangular

a
region of interest (ROI) centred on the image of the phantom the number of counts N shall
ROI
be determined. The width of the ROI shall be at most 240 mm to cover the cylinder diameter,
and the length l shall be at least 150 mm in the axial direction and centred to the phantom.
The NORMALIZED VOLUME SENSITIVITY S is then calculated by dividing the number of counts
norm
N registered from the ROI by the activity concentration a , the acquisition time T , the
ROI ave a
axial length l of the ROI, and by multiplying by the correction factor c (see 3.3.1) according to
j
the following equation:
N
ROI  
S = c cps / kBq / cm
()
norm j  
 
aTl
ave a
– 16 – 61675-2 © IEC:1998+A1:2004(E)
The values shall be specified and stated for the subscript j of low and high respectively.
NOTE For a given phantom set-up and parallel hole COLLIMATOR, the NORMALIZED VOLUME SENSITIVITY and the
SYSTEM SENSITIVITY measured according to 3.1 of IEC 60789 are related by a fixed ratio and the correction factor c

j
3.4 Scatter
The scattering of primary gamma rays results in events with false information for radiation
source localization. Variations in design and implementation cause emission tomographs to
have different sensitivities to scattered radiation. The purpose of this procedure is to
measure the relative system sensitivity to scattered radiation, expressed by the SCATTER
FRACTION (SF), as well as the values of the SCATTER FRACTION in each slice(SFI).
3.4.1 Scatter measurement
The measurements shall be performed by imaging a single line source at three different
radial positions within a water-filled test phantom, using the COLLIMATOR used for SPECT
imaging, a circular orbit and a 20 cm radius of rotation.
Unscattered events are assumed to lie within a 2 × FWHM wide strip centred on the image of
the line source in each SINOGRAM. This width region is chosen because the scatter value is
insensitive to the exact width of the region, and a negligible number of unscattered events lie
more than one FWHM from the line image.
The width of the scatter response function allows a simplified analysis method. A linear
interpolation across the strip from the points of intersection of the scatter tails and the edges
of the 2 × FWHM wide strip is used to estimate the amount of scatter present in the strip. The
area under the line of interpolation plus the contributions outside the strip constitute the
estimated scatter.
Estimates of the SCATTER FRACTION for uniform source distributions are made under the
assumption of slow radial dependence. In this assumption, the measure of SCATTER FRACTION

for a line source on-axis is applied to a cross-sectional area out to a radius of 22,5 mm. The
SCATTER FRACTION for a line source of 45 mm off-axis is applied to an annulus between
22,5 mm and 67,5 mm. Likewise, the SCATTER FRACTION for a line source 90 mm off-axis is
applied to an annulus between 67,5 mm and 100 mm (see Figure 3). The three values for
SCATTER FRACTION are weighted by the areas to which they are applied, yielding a weighted
average. The annular areas are in the ratios of 1:8:10,75 respectively.
3.4.1.1 RADIONUCLIDE
99m
The RADIONUCLIDE for the measurement shall be Tc, with an ACTIVITY less than that at
which the percent dead-time losses exceed 5 % (see IEC 60789).
3.4.1.2 Source distribution
The test phantom shall be filled with non-radioactive water as a scatter medium. The test
phantom line source shall be inserted, parallel to the axis of the cylinder, sequentially at radii
of 0 mm, 45 mm, and 90 mm. The phantom shall be centred axially. For tomographs with an
AXIAL FIELD OF VIEW greater than 165 mm, the phantom shall be centred within the AXIAL FIELD
OF VIEW.
61675-2 © IEC:1998+A1:2004(E) – 17 –
3.4.1.3 Data collection
Data shall be taken with the source at the specified radii from the long axis of the tomograph.
SINOGRAM data shall be acquired for each of the radial locations of the line source. At least
200 000 counts per slice shall be acquired for each slice within:
a) the AXIAL FIELD OF VIEW;
b) the central 165 mm;
where the phantom was placed, whichever is the smaller.
3.4.1.4 Data processing
Data shall not be corrected for scatter or ATTENUATION.
3.4.2 Analysis
All SINOGRAMS corresponding to slices at least 1 cm from either end of the phantom shall be
processed. Thus for tomographs with an AXIAL FIELD OF VIEW less than 165 mm, all slices shall
be processed.
All PIXELS in each SINOGRAM which correspond to points which are located further than 12 cm
from the centre shall be set to zero. For each projection angle within the SINOGRAM, the
location of the centre of the line source shall be determined by finding the PIXEL with the
largest value. Each PROJECTION shall be shifted so that the PIXEL containing the maximum
value aligns with the central PIXEL row of the SINOGRAM. After realignment, a sum projection
shall be produced. The counts in the PIXELS at the left and right edges of the 2 × FWHM wide
strip C and C , respectively shall be obtained from the sum projection (see Figure 4).
L,i,k R,i,k
Linear interpolation shall be used to find the count levels at ±1 × FWHM from the central PIXEL
of the projection. The average of the two count levels C and C shall be multiplied by

L,i,k R,i,k
the fractional number of PIXELS between the edges of the 2 × FWHM wide strip, with the
product added to the counts in the PIXELS outside the strip, to yield the number of scattered
counts C , for the slice i and the source position k. The total counts (scattered plus
s,i,k
unscattered) C is the sum of the counts in all PIXELS in the sum projection.
tot,i,k
The average ACTIVITY A during data acquisition over the time interval T for the line
ave,k acq,k
source at position k, shall be calculated by correcting for decay (each midpoint of the time
intervals T is related to a common starting time).
acq,k
The SCATTER FRACTION SF for each slice, i, due to a uniform source distribution shall be
i
calculated as follows:
     
C C C
s,ii,1 s, ,2 s,i,3
+ 8 +10,75
     
A A A
 ave,1  ave,2  ave,3
     
SF =
i
     
C C C
tot,ii,1 tot, ,2 tot,i,3
+81+0,75
     
A A A
     
ave,1 ave,2 ave,3
     
where the subscripts 1, 2 and 3 refer to line sources at radii 0 mm, 45 mm and 90 mm,
respectively.
3.4.3 Report
For each slice, i, that was processed, the value of SF shall be tabulated. The average SF of
i
the set of values of SF shall also be reported as the system SCATTER FRACTION for uniform
i
sources.
– 18 – 61675-2 © IEC:1998+A1:2004(E)
3.5 Measurement of SPECT non-uniformity of response
At this time there is no suitable method to measure reconstructed non-uniformity of response.
3.6 SPECT system SPATIAL RESOLUTION
3.6.1 Phantom
The IEC phantom shall be adopted (see Figures 2 and 3).
3.6.2 Source
Three POINT SOURCES, prepared from a RADIONUCLIDE selected from Table 1 of IEC 60789 and
stated, of dimensions not to exceed 2 mm in any direction, shall be placed within the water-
filled cylinder. The axis of the cylinder shall coincide with the SYSTEM AXIS. The first POINT
SOURCE shall be placed on the axis of the cylinder (see Figure 3) and at the central plane in
the Z direction (see Figure 1).
The second POINT SOURCE shall be placed at the radial position of 45 mm and –50 mm from
the central plane in the Z direction. The third POINT SOURCE shall be placed at the radial
position of 90 mm and +50 mm from the central plane in the Z direction.
3.6.3 Measurements
To measure the SPECT system SPATIAL RESOLUTION the axis of the phantom shall be aligned
with the SYSTEM AXIS and oriented such that the two off-centre POINT SOURCES will intercept
either the X or Y axis of
...

IEC 61675-2 ®
Edition 1.0 1998-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Radionuclide imaging devices – Characteristics and test conditions –
Part 2: Single photon emission computed tomographs

Dispositifs d’imagerie par radionucléides – Caractéristiques et conditions
d’essai –
Partie 2: Systèmes de tomographie d'émission à photon unique
Copyright © 1998 IEC, Geneva, Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé Fax: +41 22 919 03 00
CH-1211 Geneva 20 info@iec.ch
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing more than 30 000 terms and
Technical Specifications, Technical Reports and other definitions in English and French, with equivalent terms in 14
documents. Available for PC, Mac OS, Android Tablets and additional languages. Also known as the International
iPad. Electrotechnical Vocabulary (IEV) online.

IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a More than 55 000 electrotechnical terminology entries in
variety of criteria (reference number, text, technical English and French extracted from the Terms and Definitions
committee,…). It also gives information on projects, replaced clause of IEC publications issued since 2002. Some entries
and withdrawn publications. have been collected from earlier publications of IEC TC 37,

77, 86 and CISPR.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: csc@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Catalogue IEC - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
Application autonome pour consulter tous les renseignements
Le premier dictionnaire en ligne de termes électroniques et
bibliographiques sur les Normes internationales,
électriques. Il contient plus de 30 000 termes et définitions en
Spécifications techniques, Rapports techniques et autres
anglais et en français, ainsi que les termes équivalents dans
documents de l'IEC. Disponible pour PC, Mac OS, tablettes
14 langues additionnelles. Egalement appelé Vocabulaire
Android et iPad.
Electrotechnique International (IEV) en ligne.

Recherche de publications IEC - www.iec.ch/searchpub
Glossaire IEC - std.iec.ch/glossary
Plus de 55 000 entrées terminologiques électrotechniques, en
La recherche avancée permet de trouver des publications IEC
en utilisant différents critères (numéro de référence, texte, anglais et en français, extraites des articles Termes et
comité d’études,…). Elle donne aussi des informations sur les Définitions des publications IEC parues depuis 2002. Plus
projets et les publications remplacées ou retirées. certaines entrées antérieures extraites des publications des

CE 37, 77, 86 et CISPR de l'IEC.
IEC Just Published - webstore.iec.ch/justpublished

Service Clients - webstore.iec.ch/csc
Restez informé sur les nouvelles publications IEC. Just
Published détaille les nouvelles publications parues. Si vous désirez nous donner des commentaires sur cette
Disponible en ligne et aussi une fois par mois par email. publication ou si vous avez des questions contactez-nous:
csc@iec.ch.
IEC 61675-2 ®
Edition 1.0 1998-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Radionuclide imaging devices – Characteristics and test conditions –

Part 2: Single photon emission computed tomographs

Dispositifs d’imagerie par radionucléides – Caractéristiques et conditions

d’essai –
Partie 2: Systèmes de tomographie d'émission à photon unique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX T
ICS 11.040.50 ISBN 978-2-8322-1974-4

– 2 – IEC 61675-2:1998 © IEC 1998
CONTENTS
Page
FOREWORD . . 3

Clause
1 General . 4
1.1 Scope and object . .  4
1.2 Normative references . 4
2 Terminology and definitions . 4
3 Test methods . 9
3.1 Calibration measurements . 9
3.2 Measurement of COLLIMATOR hole misalignment . 10
3.3 Measurement of SPECT system SENSITIVITY . 11
3.4 Scatter . 12
3.5 Measurement of SPECT non-uniformity of response . 14
3.6 SPECT system SPATIAL RESOLUTION . 14
4 ACCOMPANYING DOCUMENTS . 15

Figures
1 Geometry of PROJECTIONS. 16
2 Cylindrical head phantom . 17
3 Phantom insert with holders for the scatter source . 18
4 Evaluation of SCATTER FRACTION . 19
5 Reporting TRANSVERSE RESOLUTION . 20
6 Evaluation of FWHM. 21
7 Evaluation of EQUIVALENT WIDTH (EW) . 22

Annex A – Index of defined terms . 23

INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
RADIONUCLIDE IMAGING DEVICES –
CHARACTERISTICS AND TEST CONDITIONS –

Part 2: Single photon emission computed tomographs

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.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 61675-2 has been prepared by subcommittee 62C: Equipment for
radiotherapy, nuclear medicine and radiation dosimetry, of IEC technical committee 62:
Electrical equipment in medical practice.
This bilingual version (2014-12) corresponds to the English version, published in 1998-01.
The text of this standard is based on the following documents:
FDIS Report on voting
62C/206/FDIS 62C/215/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.
The French version of this standard has not been voted upon.
In this standard, the following print types are used:
– TERMS DEFINED IN CLAUSE 2 OF THIS STANDARD OR LISTED IN ANNEX A: SMALL CAPITALS.
The requirements are followed by specifications for the relevant tests.
Annex A is for information only.

– 4 – IEC 61675-2:1998 © IEC 1998
RADIONUCLIDE IMAGING DEVICES –
CHARACTERISTICS AND TEST CONDITIONS –

Part 2: Single photon emission computed tomographs

1 General
1.1 Scope and object
This part of IEC 61675 specifies terminology and test methods for describing the character-
istics of Anger type rotational GAMMA CAMERA SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHS
(SPECT), equipped with parallel hole collimators. As these systems are based on Anger type
GAMMA CAMERAS this part of IEC 61675 shall be used in conjunction with IEC 60789. These
systems consist of a gantry system, single or multiple DETECTOR HEADS and a computer system
together with acquisition, recording, and display devices.
The test methods specified in this part of IEC 61675 have been selected to reflect as much as
possible the clinical use of Anger type rotational GAMMA CAMERA SINGLE PHOTON EMISSION
COMPUTED TOMOGRAPHS (SPECT). It is intended that the test methods be carried out by
manufacturers thereby enabling them to describe the characteristics of SPECT systems on a
common basis.
No test has been specified to characterize the uniformity of reconstructed images because all
methods known so far will mostly reflect the noise of the image.
1.2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this part of IEC 61675. At the time of publication, the editions indicated
were valid. All normative documents are subject to revision, and parties to agreements based
on this part of IEC 61675 are encouraged to investigate the possibility of applying the most
recent editions of the normative documents indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
IEC 60788:1984, Medical radiology – Terminology
IEC 60789:1992, Characteristics and test conditions of radionuclide imaging devices; Anger
type gamma cameras
IEC 61675-1,  Radionuclide imaging devices – Characteristics and test conditions – Part 1:
Positron emission tomographs
2 Terminology and definitions
For the purpose of this part of IEC 61675 the definitions given in IEC 60788, IEC 60789 and
IEC 61675-1 (see annex A), and the following definitions apply.
Defined terms are printed in small capital letters.

2.1
SYSTEM AXIS
Axis of symmetry characterized by geometrical and physical properties of the arrangement of
the system
NOTE – The SYSTEM AXIS of a GAMMA CAMERA with rotating detectors is the axis of rotation.
2.1.1
COORDINATE SYSTEMS
2.1.2
FIXED COORDINATE SYSTEM
Cartesian system with axes X, Y, and Z, Z being the SYSTEM AXIS. The origin of the FIXED
COORDINATE SYSTEM is defined by the centre of the TOMOGRAPHIC VOLUME (see figure 1). The
SYSTEM AXIS is orthogonal to all TRANSVERSE SLICES.
2.1.3
COORDINATE SYSTEM OF PROJECTION
Cartesian system of the IMAGE MATRIX of each two-dimensional projection with axes X and Y
p p
(defined by the axes of the IMAGE MATRIX). The Y axis and the projection of the system axis
p
onto the detector front face have to be in parallel. The origin of the COORDINATE SYSTEM OF
PROJECTION is the centre of the IMAGE MATRIX (see figure 1).
2.1.4
CENTRE OF ROTATION (COR)
Origin of that COORDINATE SYSTEM, which describes the PROJECTIONS of a TRANSVERSE SLICE with
respect to their orientation in space
NOTE – The CENTRE OF ROTATION of a TRANSVERSE SLICE is given by the intersection of the SYSTEM AXIS with the
mid-plane of the corresponding OBJECT SLICE.
2.1.5
OFFSET
Deviation of the position of the PROJECTION of the COR (X' ) from X = 0. (See figure 1)

p p
2.2
TOMOGRAPHY (see annex A)
2.2.1
TRANSVERSE TOMOGRAPHY
In TRANSVERSE TOMOGRAPHY the three-dimensional object is sliced by physical methods, e.g.
collimation, into a stack of OBJECT SLICES, which are considered as being two-dimensional and
independent from each other. The transverse image planes are perpendicular to the SYSTEM
AXIS.
2.2.2
EMISSION COMPUTED TOMOGRAPHY (ECT)
Imaging method for the representation of the spatial distribution of incorporated RADIONUCLIDES
in selected two-dimensional SLICES through the object
2.2.2.1
PROJECTION
Transformation of a three-dimensional object into its two-dimensional image or of a two-
dimensional object into its one-dimensional image, by integrating the physical property which
determines the image along the direction of the PROJECTION BEAM
NOTE – This process is mathematically described by line integrals in the direction of projection and called the
Radon-transform.
– 6 – IEC 61675-2:1998 © IEC 1998
2.2.2.2
PROJECTION BEAM
Determines the smallest possible volume in which the physical property which determines the
image is integrated during the measurement process. Its shape is limited by the SPATIAL
RESOLUTION in all three dimensions.
NOTE – In SPECT the PROJECTION BEAM usually has the shape of a long thin diverging cone.
2.2.2.3
PROJECTION ANGLE
Angle at which the PROJECTION is measured or acquired
NOTE – For illustration see figure 1.
2.2.2.4
SINOGRAM
Two-dimensional display of all one-dimensional PROJECTIONS of an object slice, as a function of
the PROJECTION ANGLE
The PROJECTION ANGLE is displayed on the ordinate. The linear PROJECTION coordinate is
displayed on the abscissa.
2.2.2.5
OBJECT SLICE
A slice in the object. The physical property of this slice that determines the measured
information is displayed in the tomographic image.
2.2.2.6
IMAGE PLANE
A plane assigned to a plane in the OBJECT SLICE
NOTE – Usually the IMAGE PLANE is the mid-plane of the corresponding OBJECT SLICE.
2.2.2.7
TOMOGRAPHIC VOLUME
Ensemble of all volume elements which contribute to the measured PROJECTIONS for all
PROJECTION ANGLES
NOTE – For a rotating GAMMA CAMERA with a circular field of view the TOMOGRAPHIC VOLUME is a sphere provided
that the radius of rotation is larger than the radius of the field of view. For a rectangular field of view, the
TOMOGRAPHIC VOLUME is a cylinder.
2.2.2.7.1
TRANSVERSE FIELD OF VIEW
Dimensions of a slice through the TOMOGRAPHIC VOLUME, perpendicular to the SYSTEM AXIS. For
a circular TRANSVERSE FIELD OF VIEW it is described by its diameter.
NOTE – For non-cylindrical TOMOGRAPHIC VOLUMES the TRANSVERSE FIELD OF VIEW may depend on the axial position
of the slice.
2.2.2.7.2
AXIAL FIELD OF VIEW
Dimensions of a slice through the TOMOGRAPHIC VOLUME parallel to and including the SYSTEM
AXIS. In practice it is specified only by its axial dimension given by the distance between the
IMAGE PLANES plus the average of the measured AXIAL SLICE
centres of the outermost defined
WIDTH measured as EQUIVALENT WIDTH (EW).
2.2.2.7.3
TOTAL FIELD OF VIEW
Dimensions (three-dimensional) of the TOMOGRAPHIC VOLUME

2.3
IMAGE MATRIX
MATRIX ELEMENTS in a preferentially cartesian coordinate system
Arrangement of
2.3.1
MATRIX ELEMENT
Smallest unit of an IMAGE MATRIX, which is assigned in location and size to a certain volume
element of the object (VOXEL)
2.3.1.1
PIXEL
MATRIX ELEMENT in a two-dimensional IMAGE MATRIX
2.3.1.2
TRIXEL
MATRIX ELEMENT in a three-dimensional IMAGE MATRIX
2.3.2
VOXEL
Volume element in the object which is assigned to a MATRIX ELEMENT in the IMAGE MATRIX (two-
dimensional or three-dimensional). The dimensions of the VOXEL are determined by the
dimensions of the corresponding MATRIX ELEMENT via the appropriate scale factors and by
the system's SPATIAL RESOLUTION in all three dimensions.
2.4
POINT SPREAD FUNCTION (PSF)
Scintigraphic image of a POINT SOURCE
2.4.1
PHYSICAL POINT SPREAD FUNCTION
For tomographs, a two-dimensional POINT SPREAD FUNCTION in planes perpendicular to the
PROJECTION BEAM at specified distances from the detector
NOTE – The PHYSICAL POINT SPREAD FUNCTION characterizes the purely physical imaging performance of the
tomographic device independent from, e.g. sampling, image reconstruction and image processing, but dependent
on the COLLIMATOR. A PROJECTION BEAM is characterized by the entirety of all PHYSICAL POINT SPREAD FUNCTIONS as a
function of distance along its axis.
2.4.2
AXIAL POINT SPREAD FUNCTION
Profile passing through the peak of the PHYSICAL POINT SPREAD FUNCTION in a plane parallel to
the SYSTEM AXIS
2.4.3
TRANSVERSE POINT SPREAD FUNCTION
Reconstructed two-dimensional POINT SPREAD FUNCTION in a tomographic IMAGE PLANE
NOTE – In TOMOGRAPHY, the TRANSVERSE POINT SPREAD FUNCTION can also be obtained from a line source located
parallel to the SYSTEM AXIS.
2.5
SPATIAL RESOLUTION
Ability to concentrate the count density distribution in the image of a POINT SOURCE to a point
2.5.1
TRANSVERSE RESOLUTION
SPATIAL RESOLUTION in a reconstructed plane perpendicular to the SYSTEM AXIS

– 8 – IEC 61675-2:1998 © IEC 1998
2.5.1.1
RADIAL RESOLUTION
TRANSVERSE RESOLUTION along a line passing through the position of the source and the
SYSTEM AXIS
2.5.1.2
TANGENTIAL RESOLUTION
TRANSVERSE RESOLUTION in the direction orthogonal to the direction of RADIAL RESOLUTION
2.5.2
AXIAL RESOLUTION
For tomographs with sufficiently fine axial sampling fulfilling the sampling theorem, SPATIAL
RESOLUTION along a line parallel to the SYSTEM AXIS
2.5.3
EQUIVALENT WIDTH (EW)
Width of that rectangle having the same area and the same height as the response function,
e.g. the POINT SPREAD FUNCTION
2.6 Tomographic sensitivity
2.6.1
SLICE SENSITIVITY
Ratio of COUNT RATE as measured on the SINOGRAM to the ACTIVITY concentration in the
phantom
NOTE – In SPECT the measured counts are not numerically corrected for scatter by subtracting the SCATTER
.
FRACTION
2.6.2
VOLUME SENSITIVITY
Sum of the individual SLICE SENSITIVITIES
2.6.3
NORMALIZED VOLUME SENSITIVITY
VOLUME SENSITIVITY divided by the AXIAL FIELD OF VIEW of the tomograph or the phantom length,
whichever is the smaller
2.7
SCATTER FRACTION (SF)
Ratio between the number of scattered photons and the sum of scattered plus unscattered
photons for a given experimental set-up
2.8
SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY (SPECT)
EMISSION COMPUTED TOMOGRAPHY utilizing single photon detection of gamma-ray emitting
RADIONUCLIDES
2.8.1
DETECTOR POSITIONING TIME
Fraction of the total time spent on an acquisition which is not used in collecting data
2.8.2
DETECTOR HEAD TILT
Deviation of the COLLIMATOR axis from orthogonality with the SYSTEM AXIS

2.8.3
RADIUS OF ROTATION
Distance between the SYSTEM AXIS and the COLLIMATOR front face
2.9
RADIOACTIVE SOURCE
See rm-20-02 of IEC 60788
2.9.1
POINT SOURCE
RADIOACTIVE SOURCE approximating a δ-function in all three dimensions
2.9.2
LINE SOURCE
Straight RADIOACTIVE SOURCE approximating a δ-function in two dimensions and being constant
(uniform) in the third dimension
3 Test methods
All measurements shall be performed with the PULSE AMPLITUDE ANALYZER WINDOW as specified
in table 1 of IEC 60789. Additional measurements with other settings as specified by the
manufacturer can be performed. Before the measurements are performed, the tomographic
system shall be adjusted by the procedure normally used by the manufacturer for an installed
unit and shall not be adjusted specially for the measurement of specific parameters. If any test
cannot be carried out exactly as specified in the standard, the reason for the deviation and the
exact conditions under which the test was performed shall be stated clearly.
Unless otherwise specified, each DETECTOR HEAD in the system shall be characterized by a full
data set covering an angular range of 360°. For multiheaded systems, characterization shall
also be provided for an acquisition covering the minimal rotation required to obtain a complete
set of data (e.g. 120° for a three-headed system). If the tomograph is specified to operate in a
non-circular orbiting mode influencing the performance parameters, test results shall be
reported in addition.
Unless otherwise specified, measurements shall be carried out at COUNT RATES not exceeding
20 000 counts per second.
Measurements of performance parameters in the planar mode of operation are a prerequisite.
A complete set of performance parameters shall be measured as specified in IEC 60789.
3.1 Calibration measurements
3.1.1 Measurement of the CENTRE OF ROTATION (COR)
An error-free reconstruction requires the knowledge of the position of the PROJECTION of the
COR into the coordinate system X , Y for each PROJECTION (i.e. for each PROJECTION angle) of
p p
that slice. For a circular rotation of the DETECTOR and for an ideal system, the PROJECTION of a
POINT SOURCE at the COR will be at the same position X' in the projection matrix for all angles
p
of PROJECTION (see figure 1).
To determine the CENTRE OF ROTATION, the OFFSET X' has to be measured. POINT SOURCE(S)
p
are used. A minimum of 32 projections equally spaced over 360° are acquired and displayed as
a SINOGRAM. The RADIUS OF ROTATION shall be set to 20 cm. The source(s) shall be positioned
radially at least 5 cm from the system axis to get SINOGRAMS with a discernible shape of a sine
function. The OFFSET shall be determined for a minimum of three slices with axial positions,
(Z direction), one at the centre of the FIELD OF VIEW and the other two, ±1/3 of the AXIAL FIELD
OF VIEW from the centre.
– 10 – IEC 61675-2:1998 © IEC 1998
At least 10 000 counts per view shall be acquired. The length of PIXEL side shall be less than
4 mm. For the calculation of the centroid (centre of gravity) X (θ) of the source in the X
p p
direction, 50 mm wide strips in the Y direction centred around the Y position of each source
p
shall be used. This shall be done for each projection angle θ. Then the OFFSET is determined
by fitting a sine function to the X (θ) values of each source, where
p
X (θ) = A sin(θ + ϕ) + X'
p
where
θ is the angle of projection;
A is the amplitude;
ϕ is the phase shift of the sine function;
X' is the average OFFSET to be reported for the three different axial positions.
NOTE – If there is a DETECTOR HEAD TILT the position of the image of the POINT SOURCE will move not only in the x
p
direction, but also in the Y direction. To determine the X movement not influenced by the Y movement (for a
p p p
reasonable amount of head tilt), the centroid is calculated using the 50 mm wide strip. The subscript p refers to the
projection space (see figure 1).
NOTE – If a system uses an automatic OFFSET correction which cannot be switched off, then X' shall be zero.
In addition, the difference between fit and data shall be plotted (showing the error) as a
function of θ. The maximum difference for each axial position shall be reported. The values are
valid only for the COLLIMATOR used and shall be stated in millimetres.
NOTE – Systematic deviations (trends) are indicative of varying OFFSET during rotation of the detector.
3.1.2 DETECTOR HEAD TILT
An error-free reconstruction requires that the direction of the COLLIMATOR holes is orthogonal to
the SYSTEM AXIS for each angle of projection. Deviations from this requirement are called
DETECTOR HEAD TILT.
Using the measurements according to 3.1.1 the DETECTOR HEAD TILT can be determined by
calculating the centroid Y (θ) of the image of the POINT SOURCE in the Y direction, using strips
p p
over the full field-of-view in the X direction. This calculation shall be done for each angle of
p
projection. A sine function is fitted to all those values,
Y (θ)= B sin(θ + ϕ) + D
p
where
θ is the angle of projection;
B is the amplitude;
ϕ is the phase shift of the sine function.
Report the head tilt angle value a = arcsin B/A, where A is the amplitude resulting from the COR
measurement (3.1.1).
NOTE – If there is no DETECTOR HEAD TILT, B must be zero and D must be the Y position of the source.
p
In addition the difference between fit and data shall be plotted (showing the error) as a function
of θ.
3.2 Measurement of COLLIMATOR hole misalignment
If all holes of a parallel hole COLLIMATOR are parallel, the OFFSET is constant for all source
positions within the measuring volume, assuming linearity of the positioning electronics. To
detect possible misalignments of the collimator holes, the OFFSET shall be determined using a

point source placed at all intersections of an orthogonal positioning grid, lying in the X, Z plane,
covering the field of view. The grid lines shall be 10 cm apart. The radius of rotation shall be at
least 20 cm. The mean value of all measured OFFSETs shall be calculated and the maximum
deviation from that value stated.
3.3 Measurement of SPECT system SENSITIVITY
3.3.1 DETECTOR POSITIONING TIME
In combination with the acquisition time chosen, the DETECTOR POSITIONING TIME determines
that fraction of the total time spent on an acquisition which is not useful in collecting data.
Therefore it will influence the sensitivity of a tomographic device. This is especially true for a
rotating detector working in "step and shoot" mode.
99m
A POINT SOURCE of Tc shall be placed at the CENTRE OF ROTATION in air. The COUNT RATE
shall be greater than 1 000 cps. Two 360° tomographic acquisitions of a stated number, P
,
j
PROJECTIONS (one with at least 60, the other with at least 120 PROJECTIONS) shall be performed
using an acquisition time ∆T per PROJECTION of 10 s. The subscript j is either "low" or "high"
acq
corresponding to the range of approximately 60 or 120 projections. The time T from the start of
j
acquisition of the first projection to the end of the acquisition of the last projection shall be
shall also be performed directly
measured. A corresponding static acquisition of duration T
j
after the tomographic acquisition. The data shall be decay corrected for the different starting
times.
The total DETECTOR POSITIONING TIME T shall be calculated according to:
pos
N − N T
( )
static,j total,j j
T =
pos,j
N
static,j
where
N is the sum of the counts in all PROJECTIONS;
total
N is the number of counts in the static acquisition.

static
The mean positioning time per PROJECTION ∆T is then calculated by dividing T by the
pos pos
number of transitions between PROJECTION steps actually used.
T
pos,j
∆T =
pos,j
P −1
( )
j
The correction factor c for the calculation of the VOLUME SENSITIVITY is then given by
j
∆T
acq, j
c =
j
∆T +∆T
acq, j pos, j
The correction factor c shall be calculated and reported for the subscript j with corresponding
j
acquisition times per PROJECTION ∆T , of 30 s (low) and 15 s (high), respectively. This
acq j
corresponds to a typical clinical situation of total acquisition time of 30 min.
3.3.2 NORMALIZED VOLUME SENSITIVITY
The measurement shall be carried out using a cylindrical phantom of 200 mm ± 3 mm outside
diameter, of wall thickness 3 mm ± 1 mm, and 190 mm ±3 mm inside length (see figure 2),
99m
filled homogeneously with a water solution of Tc.

– 12 – IEC 61675-2:1998 © IEC 1998
The ACTIVITY concentration a (kBq/cm ) shall be accurately determined by counting at least
ave
two samples from that solution in a calibrated well counter and correcting the result for
radioactive decay to the time of measurement (midpoint of acquisition interval).
NOTE – The test is critically dependent upon accurate assays of radioactivity as measured in a dose calibrator or
well counter. It is difficult to maintain an absolute calibration with such devices to accuracies better than 10 %.
Absolute reference standards using appropriate (γ-emitters should be considered if higher degrees of accuracy are
required.
The phantom shall be positioned so that its long axis coincides with the SYSTEM AXIS (parallel to
and as close as possible to the SYSTEM AXIS). The radius of rotation R shall be 20 cm. For each
COLLIMATOR used routinely for SPECT imaging at least one million counts shall be acquired in
static imaging mode and the acquisition time T [sec] recorded. For a rectangular region of

a
interest (ROI) centred on the image of the phantom the number of counts N shall be
ROI
determined. The width of the ROI shall be at most 240 mm to cover the cylinder diameter, and
the length l shall be at least 150 mm in the axial direction and centred to the phantom. The
NORMALIZED VOLUME SENSITIVITY S is then calculated by dividing the number of counts N
norm ROI
, the acquisition time T , the axial
registered from the ROI by the activity concentration a
ave a
length l of the ROI, and by multiplying by the correction factor c (see 3.3.1) according to the
j
following equation:
N
ROI  
S = c cps / kBq / cm
( )
norm j  
 
a T l
ave a
The values shall be specified and stated for the subscript j of low and high respectively.
NOTE – For a given phantom set-up and parallel hole COLLIMATOR, the NORMALIZED VOLUME SENSITIVITY and the
SYSTEM SENSITIVITY measured according to 3.1 of IEC 60789 are related by a fixed ratio and the correction factor c
.
j
3.4 Scatter
The scattering of primary gamma rays results in events with false information for radiation
source localization. Variations in design and implementation cause emission tomographs to
have different sensitivities to scattered radiation. The purpose of this procedure is to measure
the relative system sensitivity to scattered radiation, expressed by the SCATTER FRACTION (SF),
as well as the values of the SCATTER FRACTION in each slice(SFI).
3.4.1 Scatter measurement
The measurements shall be performed by imaging a single line source at three different radial
positions within a water-filled test phantom, using the COLLIMATOR used for SPECT imaging, a
circular orbit and a 20 cm radius of rotation.
Unscattered events are assumed to lie within a 2 × FWHM wide strip centred on the image of the
line source in each SINOGRAM. This width region is chosen because the scatter value is
insensitive to the exact width of the region, and a negligible number of unscattered events lie
more than one FWHM from the line image.
The width of the scatter response function allows a simplified analysis method. A linear
interpolation across the strip from the points of intersection of the scatter tails and the edges of
the 2 × FWHM wide strip is used to estimate the amount of scatter present in the strip. The area
under the line of interpolation plus the contributions outside the strip constitute the estimated
scatter.
Estimates of the SCATTER FRACTION for uniform source distributions are made under the
assumption of slow radial dependence. In this assumption, the measure of SCATTER FRACTION
for a line source on-axis is applied to a cross-sectional area out to a radius of 22,5 mm. The
SCATTER FRACTION for a line source of 45 mm off-axis is applied to an annulus between
22,5 mm and 67,5 mm. Likewise, the SCATTER FRACTION for a line source 90 mm off-axis is

applied to an annulus between 67,5 mm and 100 mm (see figure 3). The three values for
SCATTER FRACTION are weighted by the areas to which they are applied, yielding a weighted
average. The annular areas are in the ratios of 1:8:10,75 respectively.
3.4.1.1 RADIONUCLIDE
99m
The RADIONUCLIDE for the measurement shall be Tc, with an ACTIVITY less than that at which
the percent dead-time losses exceed 5 % (see IEC 60789).
3.4.1.2 Source distribution
The test phantom shall be filled with non-radioactive water as a scatter medium. The test
phantom line source shall be inserted, parallel to the axis of the cylinder, sequentially at radii of
AXIAL
0 mm, 45 mm, and 90 mm. The phantom shall be centred axially. For tomographs with an
FIELD OF VIEW greater than 165 mm, the phantom shall be centred within the AXIAL FIELD OF
VIEW.
3.4.1.3 Data collection
Data shall be taken with the source at the specified radii from the long axis of the tomograph.
SINOGRAM data shall be acquired for each of the radial locations of the line source. At least
200 000 counts per slice shall be acquired for each slice within:
a) the AXIAL FIELD OF VIEW;
b) the central 165 mm;
where the phantom was placed, whichever is the smaller.
3.4.1.4 Data processing
Data shall not be corrected for scatter or ATTENUATION.
3.4.2 Analysis
All SINOGRAMS corresponding to slices at least 1 cm from either end of the phantom shall be
processed. Thus for tomographs with an AXIAL FIELD OF VIEW less than 165 mm, all slices shall
be processed.
All PIXELS in each SINOGRAM which correspond to points which are located further than 12 cm
from the centre shall be set to zero. For each projection angle within the SINOGRAM, the location
of the centre of the line source shall be determined by finding the PIXEL with the largest value.
Each PROJECTION shall be shifted so that the PIXEL containing the maximum value aligns with
the central PIXEL row of the SINOGRAM. After realignment, a sum projection shall be produced.
The counts in the PIXELS at the left and right edges of the 2 × FWHM wide strip C and C ,
L,i,k R,i,k
respectively shall be obtained from the sum projection (see figure 4). Linear interpolation shall
be used to find the count levels at ±1 × FWHM from the central PIXEL of the projection. The
average of the two count levels C and C shall be multiplied by the fractional number of

L,i,k R,i,k
PIXELS between the edges of the 2 × FWHM wide strip, with the product added to the counts in
the PIXELS outside the strip, to yield the number of scattered counts C , for the slice i and the
s,i,k
source position k. The total counts (scattered plus unscattered) C is the sum of the counts
tot,i,k
in all PIXELS in the sum projection.
ACTIVITY A during data acquisition over the time interval T for the line
The average
ave,k acq,k
source at position k, shall be calculated by correcting for decay (each midpoint of the time
intervals T is related to a common starting time).
acq,k
The SCATTER FRACTION SF for each slice, i, due to a uniform source distribution shall be
i
calculated as follows:
– 14 – IEC 61675-2:1998 © IEC 1998
     
C C C
s,i,1 s,i,2 s,i,3
+ 8 + 10,75
     
A A A
 ave,1  ave,2  ave,3
     
SF=
i
     
C C C
tot,i,1 tot,i,2 tot,i,3
+ 8 + 10,75
     
A A A
     
ave,1 ave,2 ave,3
     
where the subscripts 1, 2 and 3 refer to line sources at radii 0 mm, 45 mm and 90 mm,
respectively.
3.4.3 Report
shall be tabulated. The average SF of
For each slice, i, that was processed, the value of SF
i
the set of values of SF shall also be reported as the system SCATTER FRACTION for uniform
i
sources.
3.5 Measurement of SPECT non-uniformity of response
At this time there is no suitable method to measure reconstructed non-uniformity of response.
3.6 SPECT system SPATIAL RESOLUTION
3.6.1 Phantom
The IEC phantom shall be adopted (see figures 2 and 3).
3.6.2 Source
Three POINT SOURCES, prepared from a RADIONUCLIDE selected from table 1 of IEC 60789 and
stated, of dimensions not to exceed 2 mm in any direction, shall be placed within the water-
filled cylinder. The axis of the cylinder shall coincide with the SYSTEM AXIS. The first POINT
SOURCE shall be placed on the axis of the cylinder (see figure 3) and at the central plane in the
Z direction (see figure 1).
The second POINT SOURCE shall be placed at the radial position of 45 mm and –50 mm from the
central plane in the Z direction. The third POINT SOURCE shall be placed at the radial position of
90 mm and +50 mm from the central plane in the Z direction.
3.6.3 Measurements
To measure the SPECT system SPATIAL RESOLUTION the axis of the phantom shall be aligned with
SYSTEM AXIS and oriented such that the two off-centre POINT SOURCES will intercept either
the
the X or Y axis of the reconstructed transverse slice. Measurements shall be carried out with
a 200 mm radius of rotation unless otherwise specified. For those systems that cannot achieve
200 mm, the maximum possible radius of rotation shall be set and stated. Data shall
be acquired with a PIXEL size equal to or less than 30 % of the system FWHM at 200 mm
from the face of the COLLIMATOR using at least 120 equally spaced projection angles over
360° acquisition. The PIXEL size and the number of projections shall be stated. Three
transverse slices, 10 mm ± 3 mm thick shall be reconstructed using a ramp filter with a cut-off
at the Nyquist frequency as determined by the acquisition PIXEL size. A minimum of
250 000 counts shall be acquired into each reconstructed slice.
The three slices to be analysed shall be positioned so as to include the centre of the phantom,
and the points ±50 mm distant along the axis of the phantom. Profiles of the TRANSVERSE POINT
SPREAD FUNCTIONS of each reconstructed transverse slice shall be obtained both in the X and Y
direction (see figure 5) to yield PIXEL size, RADIAL and TANGENTIAL RESOLUTION. From the
coronal or sagittal slice containing the three POINT SOURCES, profiles of the POINT SPREAD
FUNCTIONS shall be obtained in the Z direction to yield PIXEL size and AXIAL RESOLUTION.

3.6.4 Evaluation and report
From the measured POINT SPREAD FUNCTIONS (see 3.6.3), the following data shall be obtained
and reported:
RADIAL RESOLUTION (FWHM and EW) for each position in the radial direction from the
a) the
measurements described in 3.6.3 (see figures 3, 5, 6 and 7);
b) the TANGENTIAL RESOLUTION (FWHM and EW) in the tangential direction from the measurements
for each position described in 3.6.3 (see figures 3, 5, 6 and 7);
c) the AXIAL RESOLUTION (FWHM and EW) in the axial direction from the measurements for each
position described in 3.6.3 (see figures 3, 6 and 7).
4 ACCOMPANYING DOCUMENTS
A document shall accompany each SINGLE PHOTON EMISSION COMPUTED TOMOGRAPH and shall
include the following information.
4.1 All items specified in
– Clause 4 of IEC 60789
– Calibration measurements of COR as specified in 3.1.1
– Measurement of head tilt as specified in 3.1.2
– Measurement of COLLIMATOR head misalignment as specified in 3.2
4.2 SPECT system SPATIAL RESOLUTION
– TRANSVERSE RESOLUTION (RADIAL and TANGENTIAL) as specified in 3.6.4
– AXIAL RESOLUTION as specified in 3.6.4
PIXEL size as specified in 3.6.3
– axial
– transaxial PIXEL size as specified in 3.6.3
4.3 SENSITIVITY
– DETECTOR POSITIONING TIME as specified in 3.3.1
– NORMALIZED VOLUME SENSITIVITY as specified in 3.3.2
4.4 SCATTER FRACTION
– SCATTER FRACTIONS SF and SF as specified in 3.4.3
i
– 16 – IEC 61675-2:1998 © IEC 1998

IEC  151/98
NOTE – The fixed coordinate system X, Y, Z has its origin at the centre of the TOMOGRAPHIC VOLUME (shown as a
cylinder), the Z-axis being the SYSTEM AXIS. The coordinate system of projection X Y is shown for a PROJECTION
p p
ANGLE θ. For each θ, the one-dimensional PROJECTION of the marked OBJECT SLICE has the address range shown
(hatched). Within this range the CENTRE OF ROTATION is projected onto the address X (offset).
p
Figure 1 – Geometry of PROJECTIONS

± 1
3 ± 1
± 3
190 ± 3
± 3
∅ 200 ± 3
φ 200
IEC  152/98
Di
...