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Patient surface radiation doses at two PET imaging facilities
L Gonzalez1, C A Cordeiro, E Vano
1Department of Radiology, School of Medicine, Complutense University, 28040 Madrid, Spain. luciano@med.ucm.es
Health Physics
|April 23, 2003
Summary
Patient radiation doses from 18FDG PET imaging are lower than expected, particularly at the breasts and gonads. Higher injected activity reduces the proportion of radiotracer used for imaging, impacting dose calculations.
Area of Science:
- Nuclear Medicine
- Medical Physics
- Radiological Dosimetry
Background:
- Positron Emission Tomography (PET) imaging utilizes radiotracers like 18F-fluorodeoxyglucose (18FDG).
- Accurate patient dosimetry is crucial for optimizing administered activity and ensuring radiation safety in PET procedures.
- Existing literature provides calculated radiation doses, but practical measurements are needed for validation.
Purpose of the Study:
- To measure patient surface radiation doses at breast and gonad locations following 18FDG administration for PET imaging.
- To audit current PET imaging procedures and optimize administered radionuclide activity.
- To compare measured doses with calculated values from literature and investigate discrepancies.
Main Methods:
- Patient dosimetry using LiF TLD-100 chips placed at breast and gonad locations for 2 hours post-injection.
- Measurement of patient surface radiation doses at two PET facilities.
- Investigation of Standard Uptake Values (SUVs) from image reconstruction to validate breast dosimetry.
Main Results:
- Mean skin doses ranged from 3.3-6.1 microGy/MBq at gonads and 3.9-6.4 microGy/MBq at breasts.
- Measured doses were consistently lower than literature-reported calculations, with increasing discrepancies at higher injected activities.
- The proportion of injected 18FDG contributing to image production decreased as injected activity increased.
- Right breast doses were higher than left, suggesting differential radiotracer uptake by the liver.
Conclusions:
- Measured patient doses from 18FDG PET are lower than previously calculated, indicating a need to re-evaluate dosimetry protocols.
- The relationship between injected activity and dose is not strictly proportional, with diminishing returns in image quality at higher activities.
- Observed dose variations highlight the importance of site-specific dosimetry audits and understanding radiotracer biodistribution for radiation safety.