TITLE:
Relationship between Patient-Dependent Parameters and Radiation Dose Rates Measured around Patients Undergoing PET/CT Imaging Using 18F-FDG
AUTHORS:
Khaled Soliman, Saad Al Qahtani, Ahmed Alenezi
KEYWORDS:
FDG, Measured Dose Rate, Patient Voiding Factor, Patient Attenuation Factor, Patient Size
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.7 No.3,
August
30,
2018
ABSTRACT: Objectives: Patients
undergoing 18F-FDG PET/CT imaging are considered external radiation
sources. Accurate dose rate estimates are important for conducting realistic risk assessments and performing dose
reconstruction in cases of accidental exposures. The patient radiation self-attenuation factor is assumed to be a function of
the patient’s body size metrics, but we
can use these metrics to predict the dose rate around the patients with
accuracy. The objective of this work was first
to measure the patient attenuation factor by performing direct dose rate
measurements from patients undergoing PET/CT imaging studies using 18F-FDG.
The second objective was to study the possible correlation between the measured
dose rate constant per unit activity from the patients and their body size metrics;
five metrics were tested in this work. The last objective was to measure the
patients’ voiding factor. Methods: We have measured dose rates at one
meter from 57 patients and noted the patient’s
height (H), weight (W) and calculated patient size metrics namely: Equivalent Cylindrical
Diameter (ECD), Equivalent Spherical Diameter (ESD) and the Body Mass Index
(BMI). Results: The measured average dose rate was 92.2 ± 14 μSv·h-1·GBq-1 measured at one meter. Therefore, the dose rate constant of 92 μSv·h-1·GBq-1 proposed by the AAPM, TG-108 report is adequate for radiation protection
purposes. There was no statistically significant correlation between the dose
rate constant per unit activity and the patient body size metrics. We have
measured a patient voiding factor of 0.89 ± 0.06 in comparison with 0.85
recommended by the AAPM. Conclusions: The presented data can be used by
medical physicist working in nuclear medicine in formulating more accurate risk
estimations resulting from radiation exposure from patients undergoing 18F-FDG
PET/CT imaging.