ACMP Talk: Isotope
Imaging/Accreditation
MT Madsen, PhD, FAAPM, FACR
Department of Radiology
University of Iowa
Background & Disclaimer
Information
• I am a member of the ACR physics
subcommittee for nuclear medicine
accreditation.
• The University of Iowa Nuclear Medicine and
PET clinics are not accredited beyond the Joint
Commission.
• Although I have tried to present current
information, please contact the accreditation
agencies for the latest requirements.
MIPPA: The Medicare Improvements for
Patients and Providers Act (2008)
• Providers of advanced diagnostic imaging services that
bill under Part B of the Medicare Physician Fee
Schedule must be accredited by Jan. 1, 2012 to receive
payment for the technical component of these services.
– The accreditation requirements do not affect
hospitals .
– Those facilities that fall under MIPPA will not receive
payment unless fully accredited.
– Facilities that already have accreditation must keep
renewals current.
Advanced Imaging
Accreditation Agencies
• American College of Radiology
– Nuclear Medicine and PET modules
– Requires the submission of quality control
imaging studies.
• Intersocietal Accreditation Commission
– Intersocietal Commission for the Accreditation
of Nuclear Medicine Laboratories (ICANL)
• Joint Commission
ACR Nuclear Medicine/PET Modules
Facilities will be able to choose from one or more of
three modules for each accreditation:
• Nuclear medicine accreditation
– Module 1 – General nuclear medicine (planar imaging)
– Module 2 – SPECT
– Module 3 – Nuclear cardiology imaging
• PET accreditation
– Module 1 – Oncology
– Module 2 – Brain
– Module 3 – Cardiac
QC Phantom Image
Evaluation Parameters
• Planar:
– Uniformity
– Spatial resolution
• SPECT:
– Uniformity
– Contrast
– Spatial resolution
• PET:
– Uniformity
– Noise
– Contrast
– Spatial resolution
Planar QC Evaluation
• Uniformity
– Intrinsic
– Extrinsic
• Spatial Resolution
– Intrinsic (Bar Phantom)
– Extrinsic (Bar Phantom)
– Extrinsic (SPECT Phantom)
ACR Planar Instructions
• Uniformity: Set the energy window for the appropriate
radionuclide (Tc-99m, Co-57, Tl-201, Ga-67 or In-111) and
acquire an intrinsic or system flood field image using a 256
x 256 matrix. For LFOV cameras (longest dimension > 32
cm), acquire 10 million counts. For SFOV field cameras
(longest dimension < 32 cm), 5 million counts are
satisfactory. Use the clinical analyzer window(s) settings.
• Spatial Resolution: Set the energy window and acquire an
intrinsic or system resolution pattern image using a 512 x
512 matrix (or the finest matrix that is available). For LFOV
cameras, acquire 5 million counts. For SFOV cameras, 3
million counts are satisfactory. Use the clinical analyzer
window(s) settings.
Planar Uniformity Pitfalls
• Poor detector uniformity
– Unacceptable detectors
– Images without current correction
• Source geometry
– Inverse square law effects
• Display windows
– Failure to use entire display range
Poor Detector Uniformity
Poor Uniformity: Corrections Bypassed
• On some systems, the uniformity calibration
flood is displayed without uniformity corrections.
• Best results will be obtained by acquiring a
routine flood image AFTER (i.e. within a short
time) of the uniformity calibration.
Source Geometry
• Intrinsic floods on some systems are difficult.
– Detector geometry may preclude sufficient source
distance.
• However, do NOT submit images that cannot be
interpreted.
– Collect flood image in an acceptable geometry OR
– Apply inverse square law (curvature correction).
Display Windows
Use linear mapping of the display with the lower threshold set
at 0% (or ≤ 5% of the maximum upper level) and the upper
threshold set to the maximum count.
Planar Spatial Resolution Pitfalls
• Improper phantom setup
– Source location
– Failure to reposition SPECT phantom for 2nd detector
• Wrong bar pattern
– Too fine or too coarse to display resolution.
– Minimum bars should be between 2 – 3 mm.
• Ga-67 Imaging
– Use appropriate collimation
– Select energy windows carefully
SPECT QC Evaluation
• SPECT Uniformity
– Artifact-free through out volume
• SPECT Contrast
– Smallest sphere
• SPECT Spatial Resolution
– Smallest rod pattern
ACR SPECT Instructions
• If you use 3 or more isotopes for SPECT imaging, you
are required to submit SPECT phantom studies for only
2 of the isotopes.
• The recommended activities for the ACR approved
phantoms are 10- 20 mCi Tc-99m, 4- 8 mCi of Tl-201,
and 5-10 mCi Ga-67/In-111.
• Carefully position the phantom aligning the central ais of
the phantom with the axis of rotation.
• Use appropriate collimation.
• Acquire in 128 x 128 over 360 degrees with 120 views (if
possible). Collect a total of 32 million counts.
ACR SPECT Instructions
• Reconstruction: Sites should use the clinical technique
optimized for the ACR Phantom. However, sites may
alternatively substitute the Butterworth filter.
• Apply (Chang) attenuation correction. For most cameras,
the linear attenuation coefficient for Tc-99m is 0.11 to
0.12/cm.
• Display: For Tc-99m, display axial slices through the
phantom with 0.6 – 0.9 cm thickness (add 2 slices). For
other isotopes, display axial slices with 0.9 cm thickness
(add 3 slices). Additionally, submit a composite
of up to 12 summed axial slices through the
rod section.
SPECT Uniformity Pitfalls
• Poor planar uniformity
– Non-uniformities especial near the midline of the FOV will cause
SPECT artifacts.
– If uniformity artifacts are present, perform uniformity correction &
rescan.
• Display settings
– Size the images appropriately.
– Under-exposure and especially over-exposure can make
artifacts appear worse.
– Use full display range (thresholding amplifies problems).
• Attenuation correction
– Attenuation correction should be applied to 360o data.
– May not be necessary or desirable for 180o data.
Example of Uniformity Artifacts
Display Thresholds/Gray Scale
Use linear mapping of the display with the lower
threshold set at 0% (or ≤ 5% of the maximum upper
level) and the upper threshold set to the maximum count.
Image Size
• Individual images should be between 3 - 6 cm in diameter.
Images that are difficult to read and may be returned to the
facility without review.
Attenuation Correction
SPECT Spatial Resolution &
Contrast Pitfalls (360o Acquisition)
• Keep close to the phantom
– Position table to optimal height
– Use auto-contouring
• Use appropriate collimation
– High resolution collimators for Tc-99m
– Medium energy collimators for In-111 or Ga-67
• Use appropriate energy windows
• Use appropriate reconstruction
Auto-contouring vs Circular Orbit
Radius of rotation should be as close as possible to 20 cm and
the center of the phantom must be close to the axis-of-rotation
but auto-contouring is permitted (and should be used).
SPECT Spatial Resolution &
Contrast Pitfalls (180o Acquisition)
• Assemble the SPECT phantom properly
• Position the SPECT phantom properly
• Use appropriate collimation
– High resolution collimators for Tc-99m
– Medium energy collimators for In-111 or Ga-67
• Use appropriate energy windows
• Use appropriate reconstruction
SPECT Feature Alignment
Good Alignment
Bad Alignment
SPECT Phantom at different starting angles
Full 360o
What’s Wrong With This Picture?
Sphere Orientation
The location of the spheres with respect to the rods
is crucial for 180o SPECT imaging.
Rods
Spheres
Things To Avoid …
• Images on multiple CDs
– All phantom images can easily fit on 1 CD.
– Multiple CDs are confusing & take too much time to review.
– Solution: Put all phantom images on 1 CD
• DICOM viewer software
–
–
–
–
Often takes an inordinate time to load
Vague instructions & non-intuitive operation
System hangups
Solution: Submit images as jpegs.
• Images that can’t be interpreted
– Too small
– Over or under exposed
– Solution: Follow instructions
Other Physics Related
Accreditation Issues
• Quality Control Performance Testing
– Acceptance Testing
– Annual Tests
– Routine Quality Control
Quality Control Requirements
Gamma Camera
Tests
Energy Peaking
Uniformity
Spatial Resolution
Energy Resolution
Count Rate
Performance
ACR
Frequency
ICANL
Frequency
Daily
Weekly
Daily
Daily
Weekly
Annually
Annually
Collimator integrity
Annually
Preventive Maintenance
Biannually
Quality Control Requirements
SPECT
Tests
Relative Sensitivity
Uniformity
Correction
Center of Rotation
Overall
Performance
ACR
Frequency
Annually
Physicist
Recommendation
Monthly
Biannual for Tc-99m
Alternate quarters for
other radionuclides
ICANL
Frequency
Manufacturer
Recommendation
Monthly
Annually
AAPM Task Group 177
• Task Group No. 177 Gamma Camera, SPECT, and
SPECT/CT Acceptance Testing and Annual Physics
Surveys
• Members: Jim Halama (Chair), Michael Dennis, Daryl
Graham, Beth Harkness, Srinivas Cheenu Kappadath,
Fady Kassem, Mark Madsen, Richard Massoth, Mathew
Palmer, James Patton, Nicole Ranger, Gary Sayed,
Sharon White, Laurence Williams, Wesley Wooten.
• Completion: end of 2011.
Summary
• Accreditation is required by MIPPA for
non-hospital based clinics by January
2012.
• ACR, ICANL and the Joint Commission
are accreditation agencies.
• All require a comprehensive quality
assurance program.
• Phantom studies for accreditation require
care in the acquisition and presentation.