IEC 61675-1:2022

IEC 61675-1 ®
Edition 3.0 2022-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Radionuclide imaging devices – Characteristics and test conditions –
Part 1: Positron emission tomographs

Dispositifs d'imagerie par radionucléides – Caractéristiques et conditions
d'essai –
Partie 1: Tomographes à émission de positrons

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IEC 61675-1 ®
Edition 3.0 2022-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Radionuclide imaging devices – Characteristics and test conditions –

Part 1: Positron emission tomographs

Dispositifs d'imagerie par radionucléides – Caractéristiques et conditions

d'essai –
Partie 1: Tomographes à émission de positrons

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 11.040.50 ISBN 978-2-8322-1089-5

– 2 – IEC 61675-1:2022 © IEC 2022
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Test methods . 13
4.1 General . 13
4.2 SPATIAL RESOLUTION . 13
4.2.1 General . 13
4.2.2 Purpose . 14
4.2.3 Method . 14
4.2.4 Analysis . 15
4.2.5 Report . 17
4.3 Tomographic sensitivity . 18
4.3.1 General . 18
4.3.2 Purpose . 18
4.3.3 Method . 18
4.3.4 Analysis . 20
4.3.5 Report . 20
4.4 Scatter measurement . 20
4.4.1 General . 20
4.4.2 Purpose . 20
4.4.3 Method . 20
4.4.4 Analysis . 21
4.4.5 Report . 23
4.5 PET COUNT RATE PERFORMANCE . 23
4.5.1 General . 23
4.5.2 Purpose . 23
4.5.3 Method . 23
4.5.4 Analysis . 24
4.5.5 Report . 26
4.6 Time-of-flight resolution . 26
4.6.1 General . 26
4.6.2 Purpose . 27
4.6.3 Method . 27
4.6.4 Radionuclide, source distribution and data collection . 27
4.6.5 Data processing . 27
4.6.6 Analysis . 28
4.6.7 Scatter and random removal . 29
4.6.8 FWHM analysis. 29
4.6.9 Report . 29
4.7 Image quality and quantification accuracy of source ACTIVITY concentrations
and PET/CT registration accuracy . 30
4.7.1 General . 30
4.7.2 Purpose . 30
4.7.3 Method . 30

4.7.4 Data analysis . 35
4.7.5 Report . 38
5 ACCOMPANYING DOCUMENTS . 39
5.1 General . 39
5.2 Design parameters and configuration . 39
5.3 SPATIAL RESOLUTION . 40
5.4 Sensitivity . 40
5.5 SCATTER FRACTION . 40
5.6 COUNT RATE performance . 40
5.7 TIME-OF-FLIGHT resolution . 40
5.8 Image quality and quantification accuracy of source ACTIVITY concentrations . 40
Bibliography . 41
Index of defined terms . 42

Figure 1 – Evaluation of FWHM . 16
Figure 2 – Evaluation of EQUIVALENT WIDTH (EW) . 17
Figure 3 – Scatter phantom configuration and position on the imaging bed . 19
Figure 4 – Evaluation of SCATTER FRACTION . 22
Figure 5 – Determination of LOR distance from line source . 27
Figure 6 – Cross-section of body phantom . 31
Figure 7 – Phantom insert with hollow spheres . 32
Figure 8 – Image quality phantom and scatter phantom position for whole body scan
acquisition . 33
Figure 9 – Placement of ROIs in the phantom background . 36

– 4 – IEC 61675-1:2022 © IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RADIONUCLIDE IMAGING DEVICES –
CHARACTERISTICS AND TEST CONDITIONS –

Part 1: Positron emission tomographs

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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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.
IEC 61675-1 has been prepared by subcommittee 62C: Equipment for radiotherapy, nuclear
medicine and radiation dosimetry, of IEC technical committee 62: Electrical equipment in
medical practice. It is an International Standard.
This third edition cancels and replaces the second edition published in 2013. This edition
constitutes a technical revision.
This edition includes the following significant technical change with respect to the previous
edition: requirements have been changed or newly created regarding the technical aspects of
SPATIAL RESOLUTION, sensitivity measurement, SCATTER FRACTION, COUNT RATE performance,
image quality, PET/CT registration accuracy and time-of-flight resolution.

The text of this International Standard is based on the following documents:
Draft Report on voting
62C/811/CDV 62C/828/RVC
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
In this document, the following print types are used: terms defined in Clause 3 of this document
or as noted: small capitals.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
A list of all parts in the IEC 61675 series, published under the general title Radionuclide imaging
devices – Characteristics and test conditions, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates that it
contains colours which are considered to be useful for the correct understanding of its
contents. Users should therefore print this document using a colour printer.

– 6 – IEC 61675-1:2022 © IEC 2022
INTRODUCTION
Further developments of POSITRON EMISSION TOMOGRAPHS allow most of the tomographs to be
operated in fully 3D acquisition mode. To comply with this trend, this document describes test
conditions in accordance with this acquisition characteristic. In addition, today a POSITRON
EMISSION TOMOGRAPH often includes X-RAY EQUIPMENT for COMPUTED TOMOGRAPHY (CT). For this
document, PET-CT hybrid devices are considered to be state of the art, dedicated POSITRON
EMISSION TOMOGRAPHS not including the X-ray component being special cases only.
While the test methods specified herein are optimized for the PET component of PET-CT hybrid
devices, they may also be used for the PET component of PET-MR hybrid devices.
The test methods specified in this document have been selected to reflect as much as possible
the clinical use of POSITRON EMISSION TOMOGRAPHS. It is intended that the tests be carried out
by MANUFACTURERS, thereby enabling them to declare the characteristics of POSITRON EMISSION
TOMOGRAPHS in the ACCOMPANYING DOCUMENTS. This document does not indicate which tests
will be performed by the MANUFACTURER on an individual tomograph or which class-standards
may be used to characterize the performance of POSITRON EMISSION TOMOGRAPHS by the
MANUFACTURER.
RADIONUCLIDE IMAGING DEVICES –
CHARACTERISTICS AND TEST CONDITIONS –

Part 1: Positron emission tomographs

1 Scope
This part of IEC 61675 specifies terminology and test methods for declaring the characteristics
of POSITRON EMISSION TOMOGRAPHS. POSITRON EMISSION TOMOGRAPHS detect the ANNIHILATION
RADIATION of positron emitting RADIONUCLIDES by COINCIDENCE DETECTION.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 TR 60788:2004, Medical electrical equipment – Glossary of defined terms
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC TR 60788:2004 and
the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
tomography
radiography of one or more layers within an object
[SOURCE: IEC TR 60788:2004, rm-41-15]
3.1.1
emission computed tomography
ECT
imaging method for the representation of the spatial distribution of incorporated RADIONUCLIDES
in selected two-dimensional slices through the object
3.1.1.1
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 1 to entry: This process is mathematically described by line integrals in the direction of PROJECTION (along the
LINE OF RESPONSE) and called "Radon transform".

– 8 – IEC 61675-1:2022 © IEC 2022
3.1.1.2
projection beam
beam that determines the smallest possible volume in which the physical property which
determines the image is integrated during the measurement process
Note 1 to entry: The PROJECTION BEAM's shape is limited by SPATIAL RESOLUTION in all three dimensions.
Note 2 to entry: The PROJECTION BEAM mostly has the shape of a long thin cylinder or cone. In POSITRON EMISSION
TOMOGRAPHY, it is the sensitive volume between two detector elements operated in coincidence.
3.1.1.3
projection angle
angle at which the PROJECTION is measured or acquired
3.1.1.4
sinogram
two-dimensional display of all one-dimensional PROJECTIONS of an OBJECT SLICE, as a function
of the PROJECTION ANGLE
Note 1 to entry: The PROJECTION ANGLE is displayed on the ordinate, and the linear projection coordinate is
displayed on the abscissa.
3.1.1.5
object slice
physical property that corresponds to a slice in the object and that determines the measured
information and which is displayed in the tomographic image
3.1.1.6
image plane
plane assigned to a plane in the OBJECT SLICE
Note 1 to entry: Usually, the IMAGE PLANE is the midplane of the corresponding OBJECT SLICE.
3.1.1.7
system axis
axis of symmetry, characterized by geometrical and physical properties of the arrangement of
the system
Note 1 to entry: For a circular POSITRON EMISSION TOMOGRAPH, the SYSTEM AXIS is the axis through the centre of the
detector ring. For tomographs with rotating detectors, it is the axis of rotation.
3.1.1.8
tomographic volume
PROJECTIONS for all
juxtaposition of all volume elements which contribute to the measured
PROJECTION ANGLES
3.1.1.8.1
transverse field of view
dimensions of a slice through the TOMOGRAPHIC VOLUME, perpendicular to the SYSTEM AXIS
Note 1 to entry: For a circular TRANSVERSE FIELD OF VIEW, it is described by its diameter.
Note 2 to entry: For non-cylindrical TOMOGRAPHIC VOLUMES, the TRANSVERSE FIELD OF VIEW may depend on the axial
position of the slice.
3.1.1.8.2
axial field of view
AFOV
field which is characterized by dimensions of a slice through the TOMOGRAPHIC VOLUME, parallel
to and including the SYSTEM AXIS

Note 1 to entry: In practice, the AXIAL FIELD OF VIEW is specified only by its axial dimension, given by the distance
between the centre of the outmost defined IMAGE PLANEs plus the average of the measured AXIAL RESOLUTION.
3.1.1.8.3
total field of view
field which is characterized by dimensions (three-dimensional) of the TOMOGRAPHIC VOLUME
3.1.2
positron emission tomography
PET
EMISSION COMPUTED TOMOGRAPHY utilizing the ANNIHILATION RADIATION of positron emitting
RADIONUCLIDES by COINCIDENCE DETECTION
3.1.2.1
positron emission tomograph
tomographic device, which detects the ANNIHILATION RADIATION of positron emitting
RADIONUCLIDES by COINCIDENCE DETECTION
3.1.2.2
annihilation radiation
ionizing radiation that is produced when a particle and its antiparticle interact and cease to exist
3.1.2.3
coincidence detection
method which checks whether two opposing detectors have detected one photon each
simultaneously
Note 1 to entry: By this method, the two photons are concatenated into one event.
Note 2 to entry: The COINCIDENCE DETECTION between two opposing detector elements serves as an electronic
collimation to define the corresponding PROJECTION BEAM or LINE OF RESPONSE (LOR), respectively.
3.1.2.4
coincidence window
time interval during which two detected photons are considered being simultaneous
3.1.2.5
line of response
LOR
PROJECTION BEAM
axis of the
Note 1 to entry: In PET, the LINE OF RESPONSE is the line connecting the centres of two opposing detector elements
operated in coincidence.
3.1.2.6
total coincidences
sum of all coincidences detected
3.1.2.6.1
true coincidence
result of COINCIDENCE DETECTION of two gamma events originating from the same positron
annihilation
3.1.2.6.2
scattered true coincidence
TRUE COINCIDENCE where at least one participating photon was scattered before the COINCIDENCE
DETECTION
– 10 – IEC 61675-1:2022 © IEC 2022
3.1.2.6.3
unscattered true coincidence
the difference between TRUE COINCIDENCES and SCATTERED TRUE COINCIDENCES
3.1.2.6.4
random coincidence
COINCIDENCE DETECTION in which participating photons do not originate from the same
result of a
positron annihilation.
3.1.2.7
singles rate
COUNT RATE measured without COINCIDENCE DETECTION, but with energy discrimination
3.1.3
two-dimensional reconstruction
image reconstruction at which 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
3.1.4
three-dimensional reconstruction
LINES OF RESPONSE are not restricted to being perpendicular
image reconstruction at which the
to the SYSTEM AXIS so that a LINE OF RESPONSE may pass several transverse slices
3.2
image matrix
matrix in which each element corresponds to the measured or calculated
physical property of the object at the location described by the coordinates of this MATRIX

ELEMENT
3.2.1
matrix element
smallest unit of an IMAGE MATRIX, which is assigned in location and size to a certain volume
element of the object (VOXEL)
3.2.2
pixel
MATRIX ELEMENT in a two-dimensional IMAGE MATRIX
3.2.3
voxel
volume element in the object which is assigned to a MATRIX ELEMENT in a two- or three-
dimensional IMAGE MATRIX
Note 1 to entry: The dimensions of the VOXEL are determined by the dimensions of the corresponding MATRIX
ELEMENT via the appropriate scale factors and by the systems SPATIAL RESOLUTION in all three dimensions.
3.3
point spread function
PSF
scintigraphic image of a POINT SOURCE
3.3.1
physical point spread function
two-dimensional POINT SPREAD FUNCTION in planes perpendicular to the
PROJECTION BEAM at specified distances from the detector
Note 1 to entry: The PHYSICAL POINT SPREAD FUNCTION characterizes the purely physical (intrinsic) imaging
performance of the tomographic device and is independent of for example sampling, image reconstruction and image

processing. A PROJECTION BEAM is characterized by the entirety of all PHYSICAL POINT SPREAD FUNCTIONs as a function
of distance along its axis.
3.3.2
axial point spread function
profile passing through the peak of the PHYSICAL POINT SPREAD FUNCTION in a plane parallel to
the sYSTEM AXIS
3.3.3
transverse point spread function
reconstructed two-dimensional POINT SPREAD FUNCTION in a tomographic IMAGE PLANE
Note 1 to entry: In TOMOGRAPHY, the TRANSVERSE POINT SPREAD FUNCTION can also be obtained from a LINE SOURCE
located parallel to the SYSTEM AXIS.
3.4
spatial resolution
ability to concentrate the count density distribution in the image of a POINT
SOURCE to a point
3.4.1
transverse resolution
SPATIAL RESOLUTION in a reconstructed plane perpendicular to the SYSTEM AXIS
3.4.1.1
radial resolution
TRANSVERSE RESOLUTION along a line passing through the position of the source and the SYSTEM
AXIS
3.4.1.2
tangential resolution
TRANSVERSE RESOLUTION in the direction orthogonal to the direction of RADIAL RESOLUTION
3.4.2
axial resolution
SPATIAL RESOLUTION along a line parallel to the SYSTEM AXIS
Note 1 to entry: AXIAL RESOLUTION only applies for tomographs with sufficiently fine axial sampling fulfilling the
sampling theorem.
3.4.3
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
Note 1 to entry: EW better reflects scatter tails of the response function than FWHM or FWTM.
[SOURCE: IEC TR 60788:2004, rm-34-45, modified – Note to entry added.]
3.4.4
full width at half maximum
FWHM
for a bell-shaped curve, distance parallel to the abscissa axis between the points where the
ordinate has half of its maximum value
[SOURCE: IEC TR 60788:2004, rm-73-02]

– 12 – IEC 61675-1:2022 © IEC 2022
3.5
recovery coefficient
measured (image) ACTIVITY concentration of an active volume divided by the true ACTIVITY
concentration of that volume, neglecting ACTIVITY calibration factors
Note 1 to entry: For the actual measurement, the true ACTIVITY concentration is replaced by the measured ACTIVITY
concentration in a large volume.
3.6
slice sensitivity
ratio of COUNT RATE as measured on the SINOGRAM to the ACTIVITY concentration in the phantom
Note 1 to entry: In PET, the measured counts are numerically corrected for scatter by subtracting the SCATTER
FRACTION.
3.7
volume sensitivity
sum of the individual SLICE SENSITIVITIES
3.8
count rate characteristic
function giving the relationship between observed COUNT RATE and TRUE COUNT RATE
[SOURCE: IEC TR 60788:2004, rm-34-21]
3.8.1
count loss
difference between measured COUNT RATE and TRUE COUNT RATE, which is caused by the finite
RESOLVING TIME of the instrument
3.8.2
count rate
number of counts per unit of time
3.8.3
true count rate
COUNT RATE that would be observed if the RESOLVING TIME of the device were zero
[SOURCE: IEC TR 60788:2004, rm-34-20]
3.9
scatter fraction
SF
ratio between SCATTERED TRUE COINCIDENCES and the sum of SCATTERED plus UNSCATTERED TRUE
COINCIDENCES for a given experimental set-up
3.10
point source
RADIOACTIVE SOURCE approximating a δ-function in all three dimensions
3.11
line source
straight RADIOACTIVE SOURCE approximating a δ-function in two dimensions and being constant
(uniform) in the third dimension

3.12
calibration
process to establish the relation between COUNT RATE per
volume element locally in the image and the corresponding ACTIVITY concentration in the object
for object sizes not requiring RECOVERY CORRECTION
Note 1 to entry: In order to have this CALIBRATION fairly independent of the object under study, the application of
proper corrections to the data, e.g., ATTENUATION, scatter, COUNT LOSS, radioactive decay, detector normalization,
RANDOM COINCIDENCES (PET), and branching ratio (PET) is mandatory. The independency of the object is required to
scale clinical images in terms of kBq/ml or standardized uptake values (SUV).
3.13
PET count rate performance
relationship between the measured COUNT RATE of TRUE COINCIDENCES, RANDOM COINCIDENCES,
TOTAL COINCIDENCES, and noise equivalent count rate versus ACTIVITY
3.14
time-of-flight resolution
TOF resolution
uncertainty of the measurement of the difference of the arrival time of the two photons from the
same annihilation event
4 Test methods
4.1 General
For all measurements, the acquisition parameters of the tomograph shall be set up according
to its normal mode of operation, i.e., it is not 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 axial acceptance angles, with TWO-
DIMENSIONAL RECONSTRUCTION and THREE-DIMENSIONAL RECONSTRUCTION, the test results shall
be reported for every mode of operation. The tomograph configuration (e.g. energy thresholds,
axial acceptance angle, reconstruction algorithm) shall be chosen according to the MANUFACTU-
RER’s recommendation and clearly stated. If any test cannot be carried out exactly as specified
in this document, the reason for the deviation and the exact conditions under which the test
was performed shall be stated clearly.
It is postulated that a POSITRON EMISSION TOMOGRAPH is capable to estimate RANDOM
COINCIDENCES and to perform the appropriate correction. In addition, a POSITRON EMISSION
TOMOGRAPH provides corrections for scatter, ATTENUATION, COUNT LOSS, branching ratio,
radioactive decay, and CALIBRATION.
The test phantoms shall be centred within the tomograph’s AXIAL FIELD OF VIEW, if not specified
otherwise.
4.2 SPATIAL RESOLUTION
4.2.1 General
SPATIAL RESOLUTION measurements describe partly the ability of a tomograph to reproduce the
spatial distribution of a tracer in an object in a reconstructed image. The measurement shall be
performed by imaging POINT 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
and/or iterative reconstruction methods, the measured SPATIAL RESOLUTION provides an
objective comparison between tomographs.

– 14 – IEC 61675-1:2022 © IEC 2022
4.2.2 Purpose
The purpose of this measurement is to characterize the ability of the tomograph to recover small
objects.
The SPATIAL RESOLUTION shall be characterized by the width of the reconstructed TRANSVERSE
POINT SPREAD FUNCTIONS of radioactive POINT SOURCES. The width of the point spread function
shall be measured by the FULL WIDTH AT HALF MAXIMUM (FWHM) and the EQUIVALENT WIDTH (EW).
4.2.3 Method
4.2.3.1 General
For all systems, the SPATIAL RESOLUTION shall be measured in the transverse IMAGE PLANE in
two directions (i.e., radially and tangentially) and in the axial direction.
4.2.3.2 RADIONUCLIDE
18 22
The RADIONUCLIDE for the measurement shall be F or Na, with an ACTIVITY such that the
percent COUNT LOSS is less than 5 % or the RANDOM COINCIDENCE rate is less than 5 % of the
TOTAL COINCIDENCE rate.
4.2.3.3 RADIOACTIVE SOURCE distribution
4.2.3.3.1 General
POINT SOURCES shall be used with the largest dimension less than or equal to 1 mm.
4.2.3.3.2 Source positioning
POINT SOURCES, suspended in air, shall be used to minimize scatter, for measurements of
TRANSVERSE RESOLUTION. Resolution measurements shall be made on two planes perpendicular
to the LONG AXIS of the tomograph, one at the centre of the AXIAL FIELD OF VIEW and the second
on a plane offset from the central plane by 3/8 of the AXIAL FIELD OF VIEW (i.e., one-eighth of the
AXIAL FIELD OF VIEW from the end of the tomograph). On each plane, sources shall be positioned
at 1 cm, 10 cm, and 20 cm from the SYSTEM AXIS (the 20 cm location may be omitted if it is not
covered by the TRANSVERSE FIELD OF VIEW). The sources shall be positioned on either the
horizontal or vertical line intersecting the SYSTEM AXIS, so that the radial and tangential
directions are aligned with the image grid.
4.2.3.4 Data collection
Data shall be collected for all sources in each of the six positions specified in 4.2.3.3.2, either
singly or in groups of multiple sources, to minimize the data acquisition time. At least
100 000 counts for each POINT SOURCE shall be acquired.
4.2.3.5 Data processing
Filtered backprojection reconstruction using a ramp filter with the cutoff at the Nyquist frequency
of the PROJECTION data or its 3D equivalent shall be employed for all SPATIAL RESOLUTION data.
No resolution enhancement methods shall be used. The pixel size in the transverse plane shall
be chosen to allow at least 3 pixels per FWHM.
Results obtained using alternate reconstruction algorithms may be reported in addition to the
filtered backprojection results, provided that the alternate reconstruction methods and their
parameters are described in sufficient detail to reproduce the study results.

4.2.4 Analysis
The RADIAL RESOLUTION and the TANGENTIAL RESOLUTION shall be determined by forming one-
dimensional response functions. These response functions shall be created by taking profiles
from the TRANSVERSE POINT SPREAD FUNCTION through the reconstructed 3D-image of each POINT
SOURCE in radial and tangential directions passing through the peak of the distribution. The
width of each profile shall be two times the expected FWHM in both directions perpendicular to
the direction of the analysis.
The AXIAL RESOLUTION of the POINT SOURCE measurements shall be determined by forming one-
dimensional response functions (AXIAL POINT SPREAD FUNCTIONS), which result from taking
profiles through the reconstructed 3D-image in the axial direction passing through the peak of
the distribution. The width of each profile shall be two times the expected FWHM in both
directions perpendicular to the direction of the analysis.
Each FWHM shall be determined by linear interpolation between adjacent PIXELS at half the
PIXEL value, which is the peak of the response function (see Figure 1). The maximum
maximum
PIXEL value C shall be determined by a parabolic fit using the peak point and its two nearest
m
neighbours. Values shall be converted to millimetre units by multiplication with the appropriate
PIXEL width.
– 16 – IEC 61675-1:2022 © IEC 2022

NOTE C is the maximum value of the interpolation curve, A and B are the points where the interpolation count
m
curve cuts the line of half-maximum value. Then FWHM = X – X .
B A
Figure 1 – Evaluation of FWHM
Each EQUIVALENT WIDTH (EW) shall be measured from the corresponding response function. EW
shall be calculated from Formula (1):
PW
EW = C (1)
∑ i
i
C
m
where
is the sum of the counts in the profile between the limits defined by 1/20 C on either
C m
∑
i
i
side of the peak;
C is the maximum PIXEL value of the profile as determined in the FWHM calculation above,
m
as opposed to the maximum pixel value among the pixel locations;
PW is the PIXEL width in millimetres (see Figure 2).

NOTE EW is given by the width of that rectangle having the area of the LINE SPREAD FUNCTION and its maximum
value C .
m
EW ∑(C× PW ) C
i m
The PIXEL width PW is x – x .
i+1 i
The areas shaded differently are equal.
Figure 2 – Evaluation of EQUIVALENT WIDTH (EW)
4.2.5 Report
RADIAL RESOLUTION, TANGENTIAL RESOLUTION, and AXIAL RESOLUTION (FWHM and EW) for each
POINT SOURCE position shall be calculated and reported. Transverse and axial PIXEL dimensions
shall be reported.
If special reconstruction methods were used, the results of the tests shall be reported together
with the exact description of the methodology.
=
– 18 – IEC 61675-1:2022 © IEC 2022
4.3 Tomographic sensitivity
4.3.1 General
Tomographic sensitivity is a parameter that characterizes the rate at which coincidence events
RADIOACTIVE SOURCE in the limit of low ACTIVITY where COUNT
are detected in the presence of a
LOSSES and RANDOM COINCIDENCES are negligible. The measured rate of TRUE COINCIDENCES for
a given distribution of the RADIOACTIVE SOURCE depends upon many factors, including the
detector material, size, and packing fraction, tomograph ring diameter, axial acceptance window
and septa geometry, ATTENUATION, scatter, dead-time, and energy thresholds.
4.3.2 Purpose
The purpose of this measurement is to determine the detected rate of UNSCATTERED TRUE
COINCIDENCES per unit of ACTIVITY concentration for a standard volume source, i.e., a cylindrical
phantom of given dimensions.
4.3.3 Method
4.3.3.1 General
The tomographic sensitivity test places a specified volume of radioactive solution of known
ACTIVITY in the TOTAL FIELD OF VIEW of the POSITRON EMISSION TOMOGRAPH and observes the
resulting COUNT RATE. The system’s sensitivity shall be calculated from these values. The test
is critically dependent upon accurate assays of ACTIVITY as measured in a dose calibrator or
well counter. It is difficult to maintain an absolute CALIBRATION with such devices to accuracies
finer than 10 %. Absolute reference standards using positron emitters should be considered if
higher degrees of accuracy are required.
One of the later frames of the PET COUNT RATE PERFORMANCE test (4.5) can be used to determine
the SLICE SENSITIVITY and VOLUME SENSITIVITY if the RADIONUCLIDE used for these measurements
is F.
4.3.3.2 RADIONUCLIDE
The RADIONUCLIDE used for these measurements shall be F. The amount of ACTIVITY at the
time of the tomographic sensitivity measurement shall be such that the percentage of COUNT
LOSSES is less than 2 %.
4.3.3.3 RADIOACTIVE SOURCE distribution
The test phantom shall be a solid right circular cylinder composed of polyethylene with a specif
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