IEC 61675-2:1998/AMD1:2004

INTERNATIONAL IEC
STANDARD
61675-2
AMENDMENT 1
2004-12
Amendment 1
Radionuclide imaging devices –
Characteristics and test conditions –
Part 2:
Single photon emission computed tomographs

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– 2 – 61675-2 Amend. 1  IEC:2004(E)
FOREWORD
This amendment has been prepared by subcommittee 62C: Equipment for radiotherapy,
nuclear medicine and radiation dosimetry, of IEC technical committee 62: Electrical
equipment in medical practice.
The text of this amendment is based on the following documents:
FDIS Report on voting
62C/378/FDIS 62C/379/RVD
Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication 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• withdrawn,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.
_____________
Introduction to this amendment
Since this International Standard was first published in 1998, further developments of single
photon computer tomographs allow some of the tomographs to be operated in coincidence
detection mode as well. To comply with this trend, this amendment describes test conditions
in concordance with the test methods established for dedicated PET systems.
_____________
Page 2
CONTENTS
Add the title of new subclause 3.7 as follows:
3.7 Test methods for single photon computer tomographs operated in coincidence detection
mode
Add the titles of new Figures 8 to 13 as follows:
8 Phantom insert with hollow spheres
9 Cross-section of body phantom
10 Arm phantom
11 Phantom configuration for COUNT RATE measurements according to 3.7.5.3.1.2
COUNT LOSS correction
12 Scheme of the evaluation of
13 Phantom insert for the evaluation of ATTENUATION correction

61675-2 Amend. 1  IEC:2004(E) – 3 –
Page 4
1.1 Scope and object
Add, after the first paragraph, the following new text:
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.
2 Terminology and definitions
Replace the first sentence by the following:
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.
Add, at the end of this clause, on page 9, the following new definitions:
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]
2.10.3
LINE OF RESPONSE
LOR
PROJECTION BEAM
axis of the
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]

– 4 – 61675-2 Amend. 1  IEC:2004(E)
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]

61675-2 Amend. 1  IEC:2004(E) – 5 –
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]

– 6 – 61675-2 Amend. 1  IEC:2004(E)
Page 9
3 Test methods
Add, on page 15, the following subclauses:
3.7 Test methods for single photon computer tomographs operated in coincidence
detection mode
For all measurements, the tomograph shall be set up according to its normal mode of
operation, i.e. it shall not be adjusted specially for the measurement of specific parameters.
If the tomograph is specified to operate in different modes influencing the performance
parameters, for example with different energy windows, different axial acceptance angles,
with and without septa, with TWO-DIMENSIONAL RECONSTRUCTION and THREE-DIMENSIONAL
RECONSTRUCTION, the test results shall be reported in addition. The tomographic configuration
(e.g. energy thresholds, axial acceptance angle, reconstruction algorithm, radius of rotation,
configuration of heads) shall be chosen according to the manufacturer's recommendation and
clearly stated.
If any test cannot be carried out exactly as specified in this standard, the reason for the
deviation and the exact conditions under which the test was performed shall be stated clearly.
The test phantoms shall be centred within the tomograph’s AXIAL FIELD OF VIEW, if not specified
otherwise.
Single photon computer tomographs operated in coincidence mode must also conform to all
planar and SPECT tests (e.g. 3.1 to 3.6).
NOTE For tomographs with an AXIAL FIELD OF VIEW greater than 16,5 cm, this centring will only produce
performance estimates for the central part. However, if the phantoms were displaced axially in order to cover the
entire AXIAL FIELD OF VIEW, false results could be obtained for the central planes, if the axial acceptance angle of
the detectors was not fully covered with ACTIVITY.
3.7.1 SPATIAL RESOLUTION
3.7.1.1 General
SPATIAL RESOLUTION measurements are used to estimate the ability of a tomograph to
reproduce the spatial distribution of a tracer in an object in a reconstructed image. The
measurement is performed by imaging POINT (or LINE) SOURCES in air and reconstructing
images using a sharp reconstruction filter. Although this does not represent the condition of
imaging a patient, where tissue scatter is present and limited statistics require the use of a
smooth reconstruction filter, the measured SPATIAL RESOLUTION provides a best-case
comparison between tomographs, indicating the highest achievable performance.
3.7.1.2 Purpose
The purpose of this measurement is to characterize the ability of the tomograph to recover
small objects by characterizing the width of the reconstructed TRANSVERSE POINT SPREAD
FUNCTIONS of radioactive POINT SOURCES or of extended LINE SOURCES placed perpendicular to
the direction of measurement. The width of the spread function is measured by the FULL WIDTH
AT HALF MAXIMUM (FWHM) and the EQUIVALENT WIDTH (EW).
To define how well objects can be reproduced in the axial direction, the AXIAL SLICE WIDTH
(commonly referred to as the slice thickness) is used. It is measured with a POINT SOURCE,
which is stepped through the tomograph’s TRANSVERSE FIELD OF VIEW axially in small
increments and is characterized by the EW and the FWHM of the AXIAL POINT SPREAD
FUNCTION for each individual slice.

61675-2 Amend. 1  IEC:2004(E) – 7 –
The AXIAL RESOLUTION is defined for tomographs with sufficiently fine axial sampling (volume
detectors) and could be measured with a stationary POINT SOURCE. For these systems the
AXIAL RESOLUTION (EW and FWHM) is equivalent to the AXIAL SLICE WIDTH. These systems
(fulfilling the sampling theorem in the axial direction) are characterized by the fact that the
AXIAL POINT SPREAD FUNCTION of a stationary POINT SOURCE would not vary if the position of the
source were varied in the axial direction for half the axial sampling distance.
3.7.1.3 Method
3.7.1.3.1 General
For all systems, the SPATIAL RESOLUTION shall be measured in the transverse IMAGE PLANE in
two directions (i.e. radially and tangentially). In addition, for those systems having sufficiently
fine axial sampling, an AXIAL RESOLUTION also shall be measured.
The TRANSVERSE FIELD OF VIEW and the IMAGE MATRIX size determine the PIXEL size in the
transverse IMAGE PLANE. In order to measure accurately the width of the spread function, its
FWHM should span at least ten PIXELS. A typical imaging study of a brain, however, requires a
260 mm TRANSVERSE FIELD OF VIEW, which together with a 128 x 128 IMAGE MATRIX and 6 mm
SPATIAL RESOLUTION, results in a FWHM of only three PIXELS. The width of the response may
be incorrect if there are fewer than ten PIXELS in the FWHM. Therefore, if possible, the PIXEL
size should be made close to one-tenth of the expected FWHM during reconstruction and
should be indicated as ancillary data for the TRANSVERSE RESOLUTION measurement. For
volume imaging systems, the TRIXEL size, in both the transverse and axial dimensions, should
be made close to one-tenth the expected FWHM, and should be indicated as ancillary data for
the SPATIAL RESOLUTION measurement. For all systems, the AXIAL SLICE WIDTH is measured by
moving the source in fine steps to sample the response function adequately. For the AXIAL
SLICE WIDTH measurement, the step size should be close to one-tenth the expected EW. It is
assumed that a computer-controlled bed will be used for accurate positioning of the
RADIOACTIVE SOURCE.
3.7.1.3.2 RADIONUCLIDE
The RADIONUCLIDE for the measurement shall be F, with an ACTIVITY such that the percent
COUNT LOSS is less than 5 % and the RANDOM COINCIDENCE rate is less than 5 % of the TOTAL
COINCIDENCE rate.
3.7.1.3.3 RADIOACTIVE SOURCE distribution
3.7.1.3.3.1 General
POINT SOURCES or LINE SOURCES, respectively, shall be used as described in 3.7.1.3.3.2 to
3.7.1.3.3.4.
3.7.1.3.3.2 TRANSVERSE RESOLUTION
Tomographs shall use LINE SOURCES, suspended in air to minimize scatter, for measurements
of TRANSVERSE RESOLUTION. The sources shall be kept parallel to the long axis of the
tomograph and shall be positioned radially at 100 mm intervals along Cartesian axes in a
plane perpendicular to the long axis of the tomograph i.e. r = 10 mm, 100 mm, 200 mm . up
to the edge of the TRANSVERSE FIELD OF VIEW. The last position shall be not more than 20 mm
from the edge and shall be stated. Each of these positions yields two measurements of
TRANSVERSE RESOLUTION, which shall be distinguished by being in the radial or tangential
direction.
NOTE The SPATIAL RESOLUTION at r = 0 mm may yield artificial values due to sampling, so this measurement is
done at the position r = 10 mm.

– 8 – 61675-2 Amend. 1  IEC:2004(E)
3.7.1.3.3.3 AXIAL SLICE W
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