Radiation dosimetry of 18F-FDG PET/CT: incorporating exam-specific parameters in dose estimates.
Whole body fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) is the standard of care in oncologic diagnosis and staging, and patient radiation dose must be well understood to balance exam benefits with the risk from radiation exposure. Although reference PET/CT patient doses are available, the potential for widely varying total dose prompts evaluation of clinic-specific patient dose. The aims of this study were to use exam-specific information to characterize the radiation dosimetry of PET/CT exams that used two different CT techniques for adult oncology patients and evaluate the practicality of employing an exam-specific approach to dose estimation.



Whole body PET/CT scans from two sets of consecutive adult patients were retrospectively reviewed. One set received a PET scan with a standard registration CT and the other a PET scan with a diagnostic quality CT. PET dose was calculated by modifying the standard reference phantoms in OLINDA/EXM 1.1 with patient-specific organ mass. CT dose was calculated using patient-specific data in ImPACT. International Commission on Radiological Protection publication 103 tissue weighting coefficients were used for effective dose.



One hundred eighty three adult scans were evaluated (95 men, 88 women). The mean patient-specific effective dose from a mean injected 18F-FDG activity of 450 ± 32 MBq was 9.0 ± 1.6 mSv. For all standard PET/CT patients, mean effective mAs was 39 ± 11 mAs, mean CT effective dose was 5.0 ± 1.0 mSv and mean total effective dose was 14 ± 1.3 mSv. For all diagnostic PET/CT patients, mean effective mAs was 120 ± 51 mAs, mean CT effective dose was 15.4 ± 5.0 mSv and mean total effective dose was 24.4 ± 4.3 mSv. The five organs receiving the highest organ equivalent doses in all exams were bladder, heart, brain, liver and lungs.



Patient-specific parameters optimize the patient dosimetry utilized in the medical justification of whole body PET/CT referrals and optimization of PET and CT acquisition parameters. Incorporating patient-specific data into dose estimates is a worthwhile effort for characterizing patient dose, and the specific dosimetric information assists in the justification of risk and optimization of PET/CT.
Department of Medical Physics, Box 84, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY, 10065, USA. quinnb@mskcc.org.
Brian
B
Quinn
Department of Medical Physics, Box 84, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY, 10065, USA.
Zak
Z
Dauer
Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, USA.
Neeta
N
Pandit-Taskar
Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, USA.
Heiko
H
Schoder
Department of Medical Physics, Box 84, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY, 10065, USA.|Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, USA.
Lawrence T
LT
Dauer
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D008875:Middle Aged; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods*; D011829:Radiation Dosage; D011874:Radiometry; D012189:Retrospective Studies; D051598:Whole Body Imaging / Q000379:methods*; D055815:Young Adult
D019788:Fluorodeoxyglucose F18
18F-FDG; CT; Effective dose; PET/CT; Radiation exposure