Evaluation of an X-Ray Dose Profile Derived from an Optically Stimulated Luminescent Dosimeter during Computed Tomographic Fluoroscopy.

Hiroaki Hasegawa,Hiroshi Tanaka,Masanori Sato

doi:10.1371/journal.pone.0132154

Hiroaki Hasegawa, Hiroshi Tanaka + Show 1 more

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https://doi.org/10.1371/journal.pone.0132154

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Abstract

The purpose of this study was to evaluate scatter radiation dose to the subject surface during X-ray computed tomography (CT) fluoroscopy using the integrated dose ratio (IDR) of an X-ray dose profile derived from an optically stimulated luminescent (OSL) dosimeter. We aimed to obtain quantitative evidence supporting the radiation protection methods used during previous CT fluoroscopy. A multislice CT scanner was used to perform this study. OSL dosimeters were placed on the top and the lateral side of the chest phantom so that the longitudinal direction of dosimeters was parallel to the orthogonal axis-to-slice plane for measurement of dose profiles in CT fluoroscopy. Measurement of fluoroscopic conditions was performed at 120 kVp and 80 kVp. Scatter radiation dose was evaluated by calculating the integrated dose determined by OSL dosimetry. The overall percent difference of the integrated doses between OSL dosimeters and ionization chamber was 5.92%. The ratio of the integrated dose of a 100-mm length area to its tails (−50 to −6 mm, 50 to 6 mm) was the lowest on the lateral side at 80 kVp and the highest on the top at 120 kVp. The IDRs for different measurement positions were larger at 120 kVp than at 80 kVp. Similarly, the IDRs for the tube voltage between the primary X-ray beam and scatter radiation was larger on the lateral side than on the top of the phantom. IDR evaluation suggested that the scatter radiation dose has a high dependence on the position and a low dependence on tube voltage relative to the primary X-ray beam for constant dose rate fluoroscopic conditions. These results provided quantitative evidence supporting the radiation protection methods used during CT fluoroscopy in previous studies.

Highlights

Because of increasing use of X-ray computed tomography (CT), the percentage of the total radiation dose to patients has become larger for CT than for other X-ray imaging procedures [1]
Yukihara et al [19] reported that the CTDI100 values based on the optically stimulated luminescent (OSL) dose profile agreed within ± 5% with the CTDI100 values based on a 100-mm long pencil ionization chamber
Under a measurement condition used in clinical practice, the accuracy of the integrated dose from OSL dosimetry was equal to that from using an ionization chamber

Summary

Introduction

Because of increasing use of X-ray computed tomography (CT), the percentage of the total radiation dose to patients has become larger for CT than for other X-ray imaging procedures [1]. With respect to CT procedures, the X-ray exposure time in CT fluoroscopy has become a major concern [2, 3] because the examination time is longer for CT-guided interventional radiology (e.g., percutaneous needle biopsy and drainage) than for other CT diagnostic imaging procedures [4,5,6]. In contrast with CT fluoroscopy, a conventional method uses a single-shot scan shows biopsy needle displacement caused by respiration (quick-check techniques [4]). Personnel exposure cannot be avoided because the physician is required to operate devices by the side of the patient even during the CT fluoroscopic procedure. The personnel exposure is mainly caused by scatter of the primary X-ray beam irradiation intended for the patient

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