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PET/CT Quality Control
Department of Radiology
The University of Chicago
Clinical Physicist for the Nuclear Medicine Section
Bill C. O’Brien-Penney
Associate Professor of Radiology
Disclosures and Conflicts of Interest
• None
Bill O’Brien-Penney
Operator’s
Guide,
biograph 16
HI-REZ,
Siemens
Medical,
2004
CT QC
phantom
Operator’s
Guide,
biograph 16
HI-REZ,
Siemens
Medical,
2004
PET Ge-68
QC tub
phantom
Outline
• Motivation and overall guidelines
• PET QC
• CT QC
• CT Dosimetry
• PET/CT QC
Reference
• IMAGING GUIDELINES FOR NUCLEAR
CARDIOLOGY PROCEDURES, E. Gordon DePuey
EG, Ed., pp 1-186, ASNC Imaging Guidelines, ASNC,
2006.
Motivation
• “Agencies that accredit facilities for medical use take Quality Assurance programs seriously.”
• “Over the past few years there has been a growing trend among medical insurance companies to require that a facility be accredited by an external agency as a prerequisite for reimbursement of medical imaging procedures.”
DePuey GE, 2006, pp. 4
Motivation
• “The ACR equipment guidelines require proof of both a
Quality Assurance program specific to … PET
cameras… including the submission of images of …
multipurpose Plexiglas PET phantoms, and equipment
acceptance testing reports.”
• “The ICANL equipment guidelines also require proof via
written documentation of ongoing camera and non-
imaging equipment QC that is reviewed during the site
visit.”DePuey GE, 2006, pp. 5
Quality Control
“A detailed description of the quality control procedures
for all instruments. This should include the testing
frequency, imaging or data format, and data analysis and
action levels.”
Society of Nuclear Medicine Procedure
Guideline for General Imaging, SNM, 2004
Site for SNM guidelines
http://interactive.snm.org/index.cfm?PageID=772
Quality Control Records
Society of Nuclear Medicine Procedure
Guideline for General Imaging, SNM, 2004
Records of all quality control procedures should be
maintained for the time specified by regulatory agencies.
A log of all instrument problems should be maintained,
and all problems should be reported to the chief
technologist or supervisor.
ICANL requirements: Equipment Quality Control
Essentials and Standards, ICANL, 2003
“The facility must have written protocols for and
maintain records of all routine quality control of
imaging and non-imaging equipment. There must also
be records of service and maintenance.”
• Principlesa. Regular performance
b. Prompt interpretation of results
c. Accurate and timely record keeping
QC principles - ASRT
PET-CT Curriculum, ASRT, pp.15, 2006
FOLLOW-UP PROCEDURES AND
WRITTEN SURVEY REPORT
The medical physicist … shall report the findings to the
physician(s), to the responsible professional(s) in charge of
obtaining or providing necessary service to the equipment,
… and, if appropriate, initiate the required service. Action
should be taken immediately by direct verbal communica-
tion if there is imminent danger to patients or staff using the
equipment due to unsafe conditions. Written survey reports
shall be provided in a timely manner consistent with the
importance of any adverse findings.
ACR Tech. STD for Med. Nuc. Phys. … of PET-CT …, 2006
http://www.crcpd.org/Pubs/PET-CT-Fusion/
02-16-04_1000_Fairobent.pdf(Note: 2004)
Reference
REGULATION: QUALITY ASSURANCE PROGRAMS
FOR MEDICAL DIAGNOSTIC X-RAY
INSTALLATIONS N.J.A.C. 7:28-22, New Jersey
Department of Environmental Protection
Bureau of Radiological Health, 2001
Website: http://www.state.nj.us/dep/rpp
7:28-22.4 QUALITY ASSURANCE PROGRAM MANUAL
(a) The registrant of any diagnostic medical x-ray equipment
used in the healing arts shall develop and continuously
implement a quality assurance program that includes a
quality assurance program manual that contains the following
elements:
1. A list of clearly identified individuals and assigned
responsibilities for maintaining the quality assurance program
and for performing the quality control tests.
New Jersey Regs, 7:28-22, 2001
7:28-22.4 QUALITY ASSURANCE PROGRAM MANUAL
2. Quality Control (QC) measures which shall include:
i. QC Tests to be performed and the frequency of each test;
ii. List of equipment to be tested;
iii. Acceptability limits for each test performed;
iv. Description of each QC test procedure;
v. Sample forms for each QC test performed;
vi. Processor and solutions maintenance; and
vii. Annual Medical Physicist’s QC Survey.
New Jersey Regs, 7:28-22, 2001
PET QC
Reference
• Positron Emission Tomography (PET) – Computed
Tomography (CT) Curriculum, American Society of
Radiologic Technologists, 15000 Central Ave. SE,
Albuquerque, NM, 2004.
PET QC mentioned by ASRT
•Quality Controla) Normalization
b) Blank scan (rotating rod source)
c) Gains (singles)
d) Cross-calibration
PET-CT Curriculum, ASRT, pp.6, 2006
• System performancea) Scatter fraction
b) Noise equivalent count rate
c) NEMA standards and testing
70cm long NEMA 2001 scatter and rate phantom
Placement of
scatter phantom
Area under scatter curve (1994 NEMA)
Area under Scatter curve Noise Equivalent Count rate
NEMA 2001 sensitivity phantom
NEMA body phantom reconstruction
Reference
• ACR TECHNICAL STANDARD FOR
MEDICAL NUCLEAR PHYSICS
PERFORMANCE MONITORING OF PET-CT
IMAGING EQUIPMENT, ACR, 2006
ACR PET QC Standards - ANNUAL
1. Spatial resolution (radial, tangential, and axial)
2. Count rate performance, including count loss
correction factor.
– a. System dead time
– b. Count rate versus activity
• i. Prompt coincidences
• ii. Random coincidences
• iii. Background coincidences
• iv. Net true coincidences
ACR Tech. STD for Med. Nuc. Phys. … of PET-CT …, 2006
ACR PET QC Standards - ANNUAL
3. Sensitivity (cps/MBq/ml) 2D and 3D modes as
applicable.
4. Uniformity (plane-by-plane in 2D and 3D modes
as applicable).
5. Attenuation-correction calibration accuracy
(quantification).
6. Linearity of bed motion.
ACR Tech. STD for Med. Nuc. Phys. … of PET-CT …, 2006
ACR PET QC Standards - ANNUAL
7. Reproducibility of transmission rod motion (extension and retraction) as applicable.
8. Reproducibility of lead septa motion (extension and retraction) as applicable.
9. Image contrast and full system test (phantom scan).
10. Reproducibility and accuracy of standardized uptake value (SUV) as applicable.
ACR Tech. STD for Med. Nuc. Phys. … of PET-CT …, 2006
Reference
PET Phantom Instructions for Evaluation of PET
Image Quality, ACR, 2006 American College of Radiology
1891 Preston White Dr., Reston, VA 20191
ACR PET phantom
PET Phantom Instr. for Eval. of PET Image Qual., ACR, 2006
ACR PET phantom
PET Phantom Instr. for Eval. of PET Image Qual., ACR, 2006
ACR PET phantom
PET Phantom Instr. for Eval. of PET Image Qual., ACR, 2006
Large “background”
ROI and small ROI
just inside largest
“hot” cylinder
ACR PET phantom
PET Phantom Instr. for Eval. of PET Image Qual., ACR, 2006
Apply small ROI to
the “hot” and “cold”
cylinders. Determine
max for hot cylinder
ROIs and min and
mean for cold and
background cylinders.
ICANL requirements
Essentials and Standards, ICANL, 2003
ASNC recommended QC
ACCEPTANCE TESTING
For 3D whole body imaging, use the methods described in
the recent NEMA standards (NU 2-2001) for acceptance
testing.
Using the older NEMA standard (NU 2-1994) may be more
appropriate for brain imaging and pediatric imaging. If you
are using 2D whole body imaging, these methods may be
easier and more relevant.
DePuey EG, ASNC imaging guidelines, 2006
ASNC recommended PET QC
• Sensitivity
• Transverse Resolution
• Scatter Fraction
• Accuracy of attenuation correction
and overall clinical image quality
(body phantom)
DePuey EG, ASNC imaging guidelines, 2006
ASNC suggested QC Procedures:
Dedicated PET imaging devices
annualTransverse Resolution
daily
(or at least weekly)
Sensitivity and overall
system performance
Once upon delivery and
upon major hardware
upgrades
Acceptance testing as per
NEMA NU 2-2001
FrequencyProcedure
DePuey GE, 2006, pp. 5
ASNC suggested QC Procedures:
Dedicated PET imaging devices
DePuey GE, 2006, pp. 5
annualAccuracy of Attenuation
correction
annualScatter Fraction
annualAccuracy
(corrections for count losses
and randoms)
FrequencyProcedure
ASNC suggested QC Procedures:
Dedicated PET imaging devices
As per the manufacturerMeasurements Specified by
the Manufacturer
annualImage Quality
FrequencyProcedure
DePuey GE, 2006, pp. 5
Schelbert HR, et al., Society of Nuclear Medicine Procedure
Guideline for Tumor Imaging Using F-18 FDG,
(http://www.snm.org/guidelines), 1999
“For semiquantitative or quantitive studies, accurate
calibration of scanner counts to well counter counts is
needed; therefore, a cylindrical type calibration should be
performed on that day or at regular intervals, typically
once or twice a week. The dose injected into the patient
should also be recorded as accurately as possible.”
1999 SNM FDG imaging guidelines
Delbeke1 D, et al., Procedure Guideline for Tumor Imaging with
18F-FDG PET/CT 1.0, (http://www.snm.org/guidelines), 2006
2006 SNM FDB imaging guidelines
The quality control procedures for PET should include a
calibration measurement of activity in a phantom containing
a known concentration, generally as a function of axial
position within the scanner field of view. A daily check on
the stability of the individual detectors also should be
performed to identify detector failures and drifts
PET QC a CNMT might do
Society of Nuclear Medicine Performance and
Responsibility Guidelines for NMT, SNM, 2003
(a) Sinogram acquisition and evaluation;
(b) Well counter standard uptake value calibration;
(c) PET/CT system alignment calibration;
(d) CT system quality assurance;
(e) Glucometer quality assurance…; and
(f) Rubidium generator quality assurance to include
dose calibrator/generator calibration and
parent/daughter breakthrough.
Sinogram of a Tub phantom
CT QC
CT Scanner QC
David E. Hintenlang, Ph.D., DABRMedical Physics Program Director
Department of Nuclear and Radiological Engineering Department of Biomedical Engineering
Presented by:
American College of Medical Physics 2004 Annual MeetingScottsdale Arizona
RADIATION PROTECTION IN
DIAGNOSTIC AND
INTERVENTIONAL RADIOLOGY
Part 18: Optimization of protection in CT scanner
Practical exercise - Quality Control
IAEA Training Material on Radiation Protection in
Diagnostic and Interventional Radiology
Compliance Guidance for COMPUTED TOMOGRAPHY
QUALITY CONTROL, New Jersey Department of
Environmental Protection, Bureau of Radiological Health,
2001.
Website: http://www.state.nj.us/dep/rpp
New Jersey BRH, 2001Mutic, S, et. al., .. Simulator QC… Med. Phys. 30: 2762-92, 2003
Mutic, S, et. al., Med. Phys. 30: 2762-92, 2003Mutic, S, et. al., Med. Phys. 30: 2762-92, 2003
AAPM REPORT NO. 74: QUALITY CONTROL
IN DIAGNOSTIC RADIOLOGY, AAPM, 2002
DailyCT Number Accuracy of Water,
Image Noise,
Image Uniformity
Artifacts.
AAPM REPORT NO. 74: QUALITY CONTROL
IN DIAGNOSTIC RADIOLOGY, AAPM, 2002
SemiannuallyImaged Slice Thickness (Slice Sensitivity Profile, SSP)
Dose Profile Width
Slice Positioning Accuracy
CT Number Scale Accuracy and Stability
Spatial Resolution (Image Sharpness)
Low-Contrast Detectability
Dosimetry of Axial Scans
Dosimetry of the Digital Survey Radiograph
Resolution, Gray Scale, Image Distortion, and Artifacts
in the Video Monitor and the Hard Copy
Annual Medical Physicist Survey
• Alignment light accuracy
• Alignment of Table to gantry
• Table/gantry tilt
• Slice localization from scanned projection radiograph
(localization image)
• Table incrementation accuracy
• Slice thickness
• CT number accuracy and linearity
ACR - CT Accreditation Program Requirements, ‘07
Slice Thickness
The slice thickness is determined in the center
of the field of view as the distance between
the two points on the sensitivity profile along
the axis of rotation at which response has
fallen to 50%.
IAEA, Part 18
Measurement of Measurement of
irradiated slice irradiated slice
widths for a range widths for a range
of nominal slice of nominal slice
width settingswidth settings
Dose Profiles (Irradiated slice width)
IAEA, Part 18
Dose Profiles (Irradiated slice width)
• Measurement of irradiated slice widths, for all nominal slice width settings, provides a direct test of pre-patient beam collimation functionality and allows geometric efficiencies to be calculated for the scanner
• Geometric efficiency (GE) is defined as:
GE = width slice irradiated x 100 %
width slice imaged
• It is recommended that GE value is displayed on the console if it is less than 70%
IAEA, Part 18
Annual Medical Physicist Survey
• Image quality
– 1. High-contrast (spatial) resolution
– 2. Low-contrast resolution
– 3. Image uniformity
– 4. Noise
– 5. Artifact evaluation
• Other tests as required by state or local regulations
ACR - CT Accreditation Program Requirements, ‘07
Annual Medical Physicist Survey
• Display devices
– 1. Video display
– 2. Hard-copy display
• Dosimetry
– 1. Computed tomography
• dosimetry index (CTDI)
– 2. Patient radiation dose for representative
examinations
ACR - CT Accreditation Program Requirements, ‘07
Continuous Quality Control
• Frequency – per physicist, at least manufacturer’s
recommendations
• Done according to written protocols
• Physicist reviews at least annually
• Deficiencies found are corrected, actions documented
• Preventative maintenance on schedule, documented, and
done by qualified personnel.
• Service log maintained
ACR - CT Accreditation Program Requirements, ‘07
Reference
McCollough CH, et al., “The phantom portion of the
American College of Radiology .ACR. Computed
Tomography .CT. accreditation program: Practical tips,
artifact examples, and pitfalls to avoid”, Med. Phys., 31:
2423-2442, 2004
ACR phantom (Gammex 464)
McCollough CH, et al., 2004
ACR phantom (Gammex 464)
McCollough CH,
et al., 2004
ACR phantom (Gammex 464)
McCollough CH, et al., 2004
ACR phantom (Gammex 464)
McCollough CH, et al., 2004
Alignment
Accuracy
(good)
ACR phantom (Gammex 464)
McCollough CH, et al., 2004
Slice thickness
Hintenlang DE, CT Scanner QC, ACMP 2004
Slice thickness estimation
ACR phantom (Gammex 464)
McCollough CH, et al., 2004
CT # accuracy
CT Number Calibration
• ROIs must be placed within the cylinders
• Polyethylene mean CT number must be between
–107 and –87 HU
• Water mean CT number must be between
–7 and +7 HU (± 5 HU preferred)
ACR - Phantom Testing Criteria., ‘03
CT Number Calibration
• Acrylic mean CT number must be between +110 and +130 HU
• Bone mean CT number must be between +850 and +970 HU
• Air mean CT number must be between –1005 and –970 HU
• The adult abdomen protocol from Table 1 must be used
ACR - Phantom Testing Criteria., ‘03
Standards for Quality Control at Canadian Radiation Treatment
Centres: CT-Simulators, Canadian Association of Provincial
Cancer Agencies, 2005
Reference
Electron
Density
phantom
RMI
ACR phantom (Gammex 464)
McCollough CH, et al., 2004
Slice thickness
ACR phantom (Gammex 464)
McCollough CH, et al., 2004
Slice thickness
Slice Thickness
• Image data required for HRC, ~ 3, ~ 5, and ~ 7 mm slice
thicknesses
• Water mean CT number must be between –7 and +7 HU
(± 5 HU preferred)
• The slice width must be within 1.5 mm of the prescribed
width
ACR - Phantom Testing Criteria., ‘03
ACR phantom (Gammex 464)
McCollough CH, et al., 2004
Low contrast
section
ACR phantom (Gammex 464)
McCollough CH, et al., 2004
Low contrast
section
ACR phantom (Gammex 464)
McCollough CH, et al., 2004
Uniformity and noise
section
ACR phantom (Gammex 464)
McCollough CH, et al., 2004
Uniformity and noise
section
T h e P h a n t o m L a b o r a t o r y,
C a t p h a n ® 500 and 600 M a n u a l, 2006
T h e P h a n t o m L a b o r a t o r y,
C a t p h a n ® 500 and 600 M a n u a l, 2006
Water vs. kVp
• Image data are required for all selectable kVp
settings
• Water mean CT number must be between
–7 and +7 HU (± 5 HU preferred)
ACR - Phantom Testing Criteria., ‘03
ACR phantom (Gammex 464)
McCollough CH,
et al., 2004
High contrast
section
(Numbers
Indicate
Line-pairs / cm)
ACR phantom (Gammex 464)
McCollough CH,
et al., 2004
high contrast
section
Philips’ CT head and body phantom
Gemini GXL manual, Philips, 2005
Display and film QC
• SMPTE or other video test pattern must be present in
the first box of each film sheet
• The 95% square must be visible (whites must not be
saturated)
• The 5% square must be visible (blacks must not be
saturated)
• No aliasing of bar patterns or other artifacts
ACR - Phantom Testing Criteria., ‘03
SMPTE pattern for display testing
McCollough CH, et al., 2004
SMPTE pattern for display testing
McCollough CH, et al., 2004
CT
Dosimetry
RADIATION SAFETY IN IMAGING
Radiologists, radiologic technologists, and all supervising
physicians have a responsibility to minimize radiation
dose to individual patients, to staff, and to society as a
whole, while maintaining the necessary diagnostic image
quality. This is the concept “As Low As Reasonably
Achievable (ALARA).”
ACR Tech. STD for Med. Nuc. Phys. … of PET …, 2006
RADIATION SAFETY IN IMAGING
Facilities, in consultation with the medical physicist,
should have in place and should adhere to policies and
procedures, in accordance with ALARA, to vary
examination protocols to take into account patient body
habitus, such as height and/or weight, body mass index or
lateral width.
ACR Tech. STD for Med. Nuc. Phys. … of PET …, 2006 Capintec website, 2003
CT “head” dose phantom, with “body” ring
CIRS, model 007,
CIRS website,
2005
Dosimetry
Note other holes
are filled,
Ionization chamber
Is in center hole
Abdominal
dosimetry
Note other holes
are filled,
Ionization chamber
Is in center hole
Dosimetry - CTDI in Perspex Phantoms
• The body phantom placed on the patient table and the
head phantom is supported in the head rest
• Phantoms are aligned centered at the scan isocentre
• The ion chamber is inserted into either the central or one
of the peripheral cavities of the phantom (all other
cavities being filled with Perspex rods)
IAEA, Part 18
Dosimetry - CTDI in Perspex Phantoms
• Dose measurements at the center are used to calculate the
central CTDI
• Peripheral CTDI is measured in at least four positions
around the phantom, so as to achieve a true average
Note: if gantry rotation is initiated from different angular
positions for successive scans it may be necessary to take
a number of measurements at each position in order to
get a representative mean dose
IAEA, Part 18
Head phantomHead phantomBody phantom Body phantom (or annulus (or annulus
to fit over head phantom)to fit over head phantom)
Insert to plug holesInsert to plug holes
Dosimetry - CTDI in Perspex Phantoms
IAEA, Part 18
• Central and peripheral CTDI’s are used to
calculate weighted CTDI, CTDIw:
• CTDIws can be compared against diagnostic
reference levels for standard scan examinations
Dosimetry - CTDI in Perspex Phantoms
IAEA, Part 18
)( CTDI3
2+CTDI
3
1
C
1=CTDI p100,c100,wn
ACR recommended maximum doses
ACR - CT Accreditation Program Requirements, ‘07
PET/CT QC
Reference
• ACR TECHNICAL STANDARD FOR
MEDICAL NUCLEAR PHYSICS
PERFORMANCE MONITORING OF PET-CT
IMAGING EQUIPMENT, ACR, 2006
ACR PET-CT QC Standards
The results of the QC program shall be monitored
annually by the medical physicist. If measured values of
QC parameters fall outside the control limits, the physicist
should initiate appropriate investigative or corrective
actions. A medical physicist should be available to assist
in prescribing corrective actions for unresolved problems.
ACR Tech. STD for Med. Nuc. Phys. … of PET-CT …, 2006
ACR PET-CT QC Standards
Specific Tests for PET-CT
“The performance of either the PET or CT system can affect the overall performance of dual-modality imaging. Each system should be tested individually, as listed previously, and together to examine coregistration. For this purpose, specially designed phantoms shall be scanned on both PET and CT systems. Accuracy of coregistration shall be determined by established procedure.”
ACR Tech. STD for Med. Nuc. Phys. … of PET-CT …, 2006
Delbeke1 D, et al., Procedure Guideline for Tumor Imaging with
18F-FDG PET/CT 1.0, (http://www.snm.org/guidelines), 2006
“In addition, for PET/CT, a check on the alignment
between the CT and the PET scanners should be
performed periodically. Such a gantry alignment check
should determine any offset between the CT and the
PET scanners to be incorporated into the fused image
display to ensure accurate image alignment.”
PET/CT image alignment accuracy
Lubberink M:
Quality control
of PET and
PET/CT
scanners
Crossed
rod source
PET/CT
registration
Phantom
Used by
Siemens
GEMINI GXL –
Instructions
for Use,
Philips
Medical
Systems, 2005
Image
alignment
calibration
holder
ASNC recommended PET-CT QC
• Registration accuracy
• Accuracy of attenuation correction
– Compare to rotating-rod-source based correction
if possible.
– Use phantom with non-uniform attenuation and “hot” and “cold” spots
– Also use a uniform activity and attenuation tub
DePuey EG, ASNC imaging guidelines, 2006
Combined PET/CT QC Procedures:
DePuey GE, 2006, pp. 17
MandatoryAttenuation Correction
Accuracy
MandatoryRegistration
RequirementTest
Inspect Clinical Images for Artifacts
“Streak artifacts result from problems with CT
transmission images, such as insufficient X-ray tube
intensity in obese individuals, breathing mismatch,
truncation, and beam hardening resulting from bone
(arms down) or metal adjacent to the heart
(pacemakers and internal defibrillators) “
DePuey EG, ASNC imaging guidelines, pp.141, 2006