Comparative analysis of physical doses and biomarker changes in subjects underwent Computed Tomography, Positron Emission Tomography-Computed Tomography, and interventional procedures.

Even though the medical uses of ionizing radiation are well-acknowledged globally as vital tools for the improvement of human health, they also symbolize the major man-made sources of radiation exposure to the population. Estimation of absorbed dose and biological changes after radiation-based imaging might help to better understand the effects of low dose radiation. Because of this, we measured the Entrance Surface Dose (ESD) at different anatomical locations using Lithium tetraborate doped with manganese (Li2B4O7: Mn), recorded Dose Length Product (DLP) and Dose Area Product (DAP), analyzed Chromosomal Aberration (CA), Micronucleus (MN), gamma-H2AX (γ-H2AX), and p53ser15 proteins in the blood lymphocytes of patients (n = 267) underwent Computed Tomography (CT), Positron Emission Tomography-CT (PET/CT), and interventional procedures and healthy volunteers (n = 19). The DLP and effective doses obtained from PET/CT procedures were significantly higher (p < 0.05) when compared to CT. Fluoroscopic time and DAP were significantly higher (p < 0.05) in therapeutic compared to diagnostic interventional procedures. All the anatomical locations registered a significant amount of ESD, the ESD obtained from CT and interventional procedures were significantly (p < 0.05) higher when compared to PET/CT. Fluoroscopic time did not correlate with the ESD (eye, head, thyroid, and shoulder; R2 = 0.03). CA frequency after PET/CT was significantly higher (p < 0.001) when compared to CT and interventional procedures. MN frequency was significantly higher in 24-hs (p < 0.001) post-interventional procedure compared to 2-hs. The mean ± SD of mean fluorescence intensity of γ-H2AX and p53ser15 obtained from all subjects underwent PET/CT and interventional procedures did not show a significant difference (p > 0.05) between pre- and post-procedure. However, the relative fluorescence intensity of γ-H2AX and p53ser15 was >1 in 58.5 % and 65.8 % of subjects respectively. Large inter-individual variation and lack of correlation between physical dose and biomarkers suggest the need for robust dosimetry with a large sample size to understand the health effects of low dose radiation.

18F-FDG PET/CT scanning: Biological effects on patients: Entrance surface dose, DNA damage, and chromosome aberrations in lymphocytes.

Positron Emission Tomography/Computed Tomography (PET/CT), a combination of PET and CT, is used in tumor staging, therapy planning, and treatment response monitoring. During PET imaging, patients receive low doses of radiation, which can induce an adaptive response and necessitate higher doses for therapeutic efficacy. Higher doses may augment toxicity to normal cells. We are examining the effects of short-term, low-dose exposures to ionizing radiation. Entrance Surface Dose (ESD) to head, shoulders, and pelvis regions were measured using Li2B4O7: Mn thermoluminescent dosimeters. Induced DNA damage in lymphocytes was measured using γ-H2AX, p53Ser-15, chromosome aberrations, and micronucleus formation in subjects (n = 25) who underwent 18F-FDG PET/CT. The mean ESD ± SD value obtained were 32.40 ± 16.86, 32.58 ± 14.22, 32.02 ± 15.42, 43.55 ± 18.25 and 42.80 ± 24.67 mGy for the head, right shoulder, left shoulder, right pelvic, and left pelvic regions, respectively. The effective doses of PET and CT ranged from 4.01 to 6.61 and 16.40-72.18 mSv, respectively, and the obtained Dose Length Product (DLP) varied from 1093 to 4812 mGy*cm. There was no correlation between DLP and ESD (r2 = 0.1). The chromosome aberration assay showed a significant increase (p < 0.05), post-scanning vs. pre-scanning; the γ-H2AX, p53Ser-15, and micronucleus assays did not show significant increases. Induced DNA damage showed inter-individual variation among the study subjects. Our results imply that the patients received a biologically significant dose during 18F-PET/CT scanning and precautions may be needed to reduce any long-term risk of exposure.