Unit 4 Pharmaceutical Organic Chemisty 3 Quinoline
Quality assurance in pet
1. Quality assurance in PET/CT
Dr.Vishnukumar R, MD Nuclear Medicine
Jawaharlal Institute of Post graduate Medical Education and Research (JIPMER),
Puducherry, India.
2.
3.
4. • Quality Assurance- General concept of taking actions
to ensure that delivered products or services meet
performance requirements.
• QMS- Defines steps has to be taken to ensure that
the desired level of care.
• Quality control- Specific set of measurements
focused on monitoring the performance of installed
imaging equipment relative to image quality and
dose on a periodic basis, for example, monthly or
daily.
8. • Defined actions regarding quality assurance (QA).
• Documents illustrating correct use of the imaging
equipment, test objects, phantoms and sources.
• Detailing test modalities and procedures to follow in
the case of abnormal results.
• Records of all tests, calibrations and corrective
actions performed.
• Proper training of all the staff involved in handling
PET, QC and QA.
12. • Acceptance testing:
– Done at the time of installation, end of warranty
period and post service.
– Serves to set reference values.
– Sets optimal operating parameters.
– Ensures buyer and regulatory bodies to meet their
specifications.
• Quality control:
– Routine procedures done at different frequencies.
– To ensure there is no deviation from the reference
values.
14. Spatial resolution
• Purpose:
– PMT and other components age over a period of
time.
• Materials:
– 3 point sources 1mm in diameter.
– 1MBq F18
– Source holder
15. • Data acquisition:
– 1cm represents centre of
the axial FOV.
– 20 cm: edge effects.
• Pixel size- 1.5mm/pixel
• 1,00,000 cpm
• Filtered back-projection
with a ramp filter and no
further smoothing should
be applied
16. • Data analysis:
– FWHM and FWTM will be calculated for all 3
positions (Radial, sagittal and transaxial).
– Values should meet specifications quoted by
vendor.
– Ratio of FWHM to FWTM-1.8 (1.8-2.0)
– Tolerance level
17. Sensitivity
• Aim:
– To determine the rate of detected true coincidence
events per unit of radioactivity concentration for a
standard source configuration.
• Materials:
– Line source required (700±5mm)
– 700 mm long Aluminum sleeves (5 sleeves).
– 5 MBq F18
18. • Data acquisition:
– Centre of transaxial FOV and 10 cm from centre FOV.
– 10000 true events per slice should be recorded.
– After each recording increase wall thickness by adding next
sleeve and complete all measurement associated with all 5
sleeves.
• Data analysis:
– Single slice rebinning should be used.
– Count rate of each slice associated with each sleeve
measurement has to be noted.
– Measured count rate has to be decay corrected and
attenuation corrected.
20. Scatter fraction
• To estimate count
losses due to random
and scatter events.
• However due to
improvement in PET
systems random event
loss is negligible.
• The scatter fraction (SF)
is a measure of scatter
coincidence data in the
overall counts recorded.
22. • Data acquisition and
processing:
– Tomographic images are
acquired.
– Summed projection data of
all projections within
central 24 cm FOV will be
considered.
– Before summing, LOR in
each projection will be
normalized to central pixel.
– SF will be obtained from
Trapezoidal area and
counts beyond 24 cm from
central FOV
24. Image quality
• Different parameters like scanner sensitivity,
uniformity, contrast and spatial resolution, etc,..
Determines image quality.
• To provide an overall assessment of the imaging
capabilities of the system under similar
conditions as a clinical whole body scan.
• To compare different systems, to check the
reproducibility.
• NEMA recommends to use a phantom mimicking
patient chest.
25. Materials
• Body compartment- 18cm in
length.
• Six hollow spheres with internal
diameters of 1.0, 1.3, 1.7, 2.2,
2.8 and 3.7 cm with wall
thickness of not more that 1
mm.
• Cylindrical insert to mimic lung-
5 cm in diameter, filled with
low atomic number material.
• It contains styroform beads and
water.
• For out of field radioactivity,
another phantom similar to
scatter phantom is used
26. • Body compartment:
– Fill with an F18 solution of 5.3 ± 0.27 kBq/mL radioactivity
concentration.
• Spheres:
– 2.8 cm and 3.7 cm spheres are filled with water to mimic cold
lesions.
– 1.0, 1.3, 1.7 and 2.2 cm spheres are to be filled with an F18
solution that has either 4 or 8 times higher radioactivity
concentration than the background.
• Line source:
– Filled with 116 MBq of F18 to mimic an out-of-field radioactivity
with an effective concentration equal to the background
radioactivity concentration.
27.
28. • Data acquisition:
– Should mimic whole body protocol.
– Scan speed- 100cm in 60 min
• Analysis:
– Choose a centre slice in which the hot and cold spheres are visualized with the
highest contrast.
– Circular ROI’s are drawn over hot and cold sphere areas.
– ROI size should equal to size of the respective spheres.
– 12 background ROI if 3.7 cm should be drawn 15 mm away from spheres.
– ROIs of the same sizes as the smaller spheres (10, 13, 17, 22 and 28 mm)
should be drawn concentric to each of the 37 mm ROIs on the background
region.
– 3 cm ROI is drawn over lung insert.
– Similar set of ROI are drawn over 4 slices surrounding center slice.
30. Image contrast:
– Contrast for hot sphere:
– Contrast for cold sphere:
Accuracy of attenuation and scatter correction:
– Check accuracy in uniform medium.
– Analysed in lung insert, if accurate values should
be as close to 0.
31. • Accuracy of radioactivity quantification:
– Measure in background area.
– Calculate true concentration after decay
correction.
– Calculate concentration from 12 background ROI.
32. Summary
• Quality assurance- process related; Quality
control- product related.
• Acceptance testing- done at installation, end
of warranty period and post service.
• Quality control- to ensure product works
according to the set standards.
• Acceptance testing- Spatial resolution,
sensitivity, scatter correction and image
quality.
