TLD environmental monitoring of new scanner facilities at the Nuclear Medicine Department of the Taiwan Medical University Hospital

Abstract

OBJECTIVE: Single-photon emission computed tomography (SPECT) as well as dual energy X-ray absorptiometry (DXA) scanners were designed in July 2018 at the Nuclear Medicine Department (NM), of the Taiwan Medical University Hospital. These scanners emit substantial X-rays from the target, which are tungsten, iron. Therefore, patients undergoing SPECT and DXA diagnosis, in addition to medical personnel, are exposed to undesirable photon leakage. METHODS: Following administration of radiopharmaceuticals, patients become radioactive sources; thus, it is necessary to evaluate a possible increase in the environmental gamma exposure rates in the NM as a result of the operation of the new scanners. A three month evaluation of environmental radiation in the NM was performed using the accurate and sensitive TLD-100H approach, which gives an error rate less than 10%. RESULTS: Detected exposure radiation rates in the NM ranged from 0.12 ± 0.02 to 1.00 ± 0.15 mSv per month, indicating that the imaging room had significantly different radiation rates. The results were compared with previous results, and no significant contribution to the enhancement of environmental gamma radiation was detected, which remained far below the occupational dose recommended by ICRP 60. The minimum detectable dose (MDD) for environmental radiation is also discussed herein to demonstrate the reliability of TLD-100H. CONCLUSION: Recommendations were sent to the authorities of AEC-ROC to implement actions that could reduce doses at these high-dose locations to meet the ALARA principle.

Evaluating environmental radiations of the tomotherapy facility by optimizing full factorial design of the TLD technique

“…This was because the 45-cm-thick Fe could effectively attenuate extra photons. Reasonably, the measured radiations were in agreement with published studies [5,7].…”

“…The TLD-100 has been used for calculating environmental radiations for the last three decades because TLD indicates long time accumulation of radiations [3][4][5][6][7][8][9]. To find the optimum group for environmental radiations using TLD-100H, one must find the optimum levels for the factors of Harshaw 3500 reader using FFD.…”

“…Automatically, the Harshaw 3500 reader was used to read irradiated TLD chips after the 1-month monitor as described in previous studies [2][3][4][5][6][7][8][9]. Moreover, Tseng et al used highly sensitive TLDs to evaluate leakage photon doses around the linac providing Volumetric Modukated Arc Therapy [3].…”

“…Analysis of X-ray leakage and scattering from the linac of the medical university has been reported in several previous studies [3][4][5][6][7][8][9]. The dose calibration line of group 1 (130 • C initial temperature, 11 • C/s, and maximum temperature 230 • C) was plotted as a function of TLD measurement, as shown in Fig.…”

“…A detailed survey is important to evaluate the extra radiations spread within this facility. Many published studies consider the thermoluminescent dosimeter (TLD) as one of the most effective approaches in dramatic radiations [3][4][5][6][7][8][9].…”