This retrospective study provides an insight into the levels of radiation exposure of six nuclear medicine (NM) staff (four technologists and two nurses) performing routine diagnostic 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET/CT) at the University Clinical Centre of the Republic of Srpska, Department of Nuclear Medicine and Thyroid Disorders, Banja Luka, Bosnia and Herzegovina. Data analysis included monthly staff exposure measured with personal thermoluminescent dosimeters (TLD) between June and December 2018, quantified in terms of normalised dose for the whole body [Hp(10)] and dominant hand [Hp(0.07)] and their comparison between each staff member and between the two groups (technologists and nurses). The study goal was to establish how our Department compared with reports from other PET/CT centres worldwide in terms of annual number of procedures and exposure limits and whether there could be room for further improvements in radiation protection. The number of procedures rose considerably from 208 in 2016 to 876 in 2019 and was 423 in the observed seven-month period. Mean individual whole-body exposure dose per GBq of injected 18F-FDG activity, [Hp(10)/A] was 18.55 μSv/GBq for the four technologists and 15.61 μSv/GBq for the two nurses. Mean dominant-hand exposure dose per GBq of injected 18F-FDG activity [Hp(0.07)/A] was 16.99 μSv/GBq and 25.44 μSv/GBq for the two groups, respectively. The average annual cumulative dose for all staff was (1.06±0.29) mSv for Hp(10) and (1.15±0.32) mSv for Hp(0.07). These results are comparable with those of similar studies. Staff doses were well below the annual limits. Nurses received slightly higher extremity doses than technologists. In view of the increasing trends in the number of PET/CT procedures, dose monitoring should be continued to identify exposure hotspots and maintain doses as low as possible.
Introduction: Using computed tomography (CT) and treatment planning systems (TPS) in radiotherapy, due to the difference in photon beam energy on CT and linear accelerator, it is necessary to convert Hounsfield units (HU) to relative electron density (RED) values. The aim of this dosimetric study was to determine whether there is a significant effect of potential in the CT tube, field of view size (FOV), and phantom dimensions on the CT conversion curve CT-RED. The second aim is whether there are significant differences between the CT-RED obtained by the Computerized Imaging Reference Systems (CIRS) Thorax 002LFC phantom and the “reference” curve in the TPS, obtained by the CIRS 062M pelvis phantom, at the same CT conditions.Methods: Heterogeneous CIRS 062M and CIRS Thorax 002LFC phantoms were used, which anatomically and dimensionally represent the human pelvis, head, and thorax, with a set of known RED inserts. They were scanned on a CT LightSpeed GE simulator and obtained CT-RED.Results: The high voltage in the CT tube had a significant effect on the HU (t = 10.72, p < 0.001) for RED values >1.1, while FOV as a parameter did not show statistical significance for the 062M pelvis phantom. Comparing the slopes (062M pelvis and head) of the CT-RED for RED ≥ 1.1, the obtained value is t = 1.404 (p = 0.163). In the case of a 062M pelvis and a 002LFC phantom, we have seen a difference in RED values (for the same HU value) of 5 % in the RED region ≥ 1.1 (bone).Conclusion: Patients should be imaged on a CT simulator only at the potential of the CT tube on which the conversion curve was recorded. The influence of the FOV and scanned phantom dimensions is not statistically significant on the appearance of the calibration curve (RED ≥ 1.1).
Background/Aim. The aim of this epidemiological study was to investigate the impact of the Covid-19 pandemic on the weekly number of external beam radiotherapy (EBRT) fractions and monthly brachytherapy (BT) applications, without intentional hypofractionation. We also investigated how the pandemic affected the number of EBRT patients younger and older than 70 years. Methods. The Affidea Radiotherapy Center, Banja Luka (BL), provides radiotherapy (RT) to the population (1.15 million) of the Republic of Srpska (Bosnia and Herzegovina). We analyzed the period of 14 months before the onset and the same period during the Covid-19. Results. The average weekly number of EBRT fractions from January 2019 to the end of February 2020, was 680.5 (SD 67.4), and from March 2020 to the end of April 2021, it was 617.1 (SD 96.4). During April 2020, the weekly number of the EBRT decreased by 67.9 % compared to the same period in 2019, while in March 2021 it fell by 42.4 %. Paired samples T-test showed that the occurrence of the Covid-19 pandemic had a statistically significant effect t(60)=4.627, p<0.05, on the reduction in the number of weekly EBRT fractions in BL RT center. When comparing EBRT patients over 70 years old to those fewer than 70 years old, the decrease was 16.3 % vs. 1.6 %, respectively. The Wilcoxon signed-rank test revealed that the Covid-19 pandemic had a statistically significant effect (Z=-2.42, p=0.016) on reducing the number of monthly BT applications. Conclusion. A statistically significant decline in EBRT and BT was observed in BL RT Centre for the first fourteen months of the pandemic. The "waves" of the pandemic "closed" the medical wards needed for the diagnosis and therapy of oncology patients and converted them into Covid-19. Therefore, some oncology patients who would have had indication for RT never received it.
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