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  • 1. 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.
  • 2. 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.” • Principles a. Regular performance b. Prompt interpretation of results c. Accurate and timely record keeping QC principles - ASRT PET-CT Curriculum, ASRT, pp.15, 2006
  • 3. 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
  • 4. 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 Control a) Normalization b) Blank scan (rotating rod source) c) Gains (singles) d) Cross-calibration PET-CT Curriculum, ASRT, pp.6, 2006 • System performance a) 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)
  • 5. Area under Scatter curve Noise Equivalent Count rate NEMA 2001 sensitivity phantom NEMA body phantom reconstruction
  • 6. 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
  • 7. 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
  • 8. 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
  • 9. 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., DABR Medical Physics Program Director Department of Nuclear and Radiological Engineering Department of Biomedical Engineering Presented by: American College of Medical Physics 2004 Annual Meeting Scottsdale 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
  • 10. New Jersey BRH, 2001 Mutic, S, et. al., .. Simulator QC… Med. Phys. 30: 2762-92, 2003 Mutic, S, et. al., Med. Phys. 30: 2762-92, 2003 Mutic, S, et. al., Med. Phys. 30: 2762-92, 2003 AAPM REPORT NO. 74: QUALITY CONTROL IN DIAGNOSTIC RADIOLOGY, AAPM, 2002 Daily CT Number Accuracy of Water, Image Noise, Image Uniformity Artifacts. AAPM REPORT NO. 74: QUALITY CONTROL IN DIAGNOSTIC RADIOLOGY, AAPM, 2002 Semiannually Imaged 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
  • 11. 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 ofMeasurement of irradiated sliceirradiated slice widths for a rangewidths for a range of nominal sliceof 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
  • 12. 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)
  • 13. 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
  • 14. 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
  • 15. 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
  • 16. 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
  • 17. 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
  • 18. 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 phantom Body phantomBody 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 )( CTDI 3 2 +CTDI 3 1 C 1 =CTDI p100,c100,wn ACR recommended maximum doses ACR - CT Accreditation Program Requirements, ‘07
  • 19. 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
  • 20. 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