Evaluation of radiation dose in computed tomography simulator
Keywords:
computed tomography simulation, radiation dose, dose reference levelsAbstract
Background: Computed tomography (CT) simulator is the gold standard tool for radiotherapy treatment planning. In CT imaging the radiation dose must be as low as possible to minimize the patient’s risk but still sufficiently high to obtain a satisfying image quality for diagnostic and treatment.
Objectives: To evaluate the radiation dose of patients who underwent a CT simulation for radiotherapy treatment planning at Sakon Nakhon Hospital and to compare the radiation dose with diagnostic reference levels (DRLs) and dose reference levels for radiotherapy CT simulation (DRLs of RT CT).
Materials and methods: Computed tomography dose index in air (CTDIair) and volume computed tomography dose index (CTDIvol) were measured. The measured CTDIvol was then compared with the displayed CT scanner CTDIvol. After that, 1-year CTDIvol and dose length product (DLP) were retrospectively collected from patient records between October 1st, 2020 and September 30th, 2021. The data included patients of the head and neck (H&N), thorax, and pelvis simulation protocols. The CTDIvol and DLP values obtained with parameters were compared with the DRLs and DRLs of RT CT.
Results: The CT scanner output was 0.20 mGy/mAs. The displayed CT scanner CTDIvol was higher than the measured CTDIvol. The deviations between measured and reported CTDIvol of H&N, thorax, and pelvis protocols were 7.20%, 2.14% and 1.36%, respectively. The median values of CTDIvol and DLP were 15.97 mGy and 638.11 mGy.cm for the H&N protocol, 11.54 mGy and 487.64 mGy.cm for the thorax protocol, and 12.01 mGy and 541.25 mGy.cm for the pelvis protocol, respectively.
Conclusion: There were no CT simulation protocols in which the radiation doses exceeded the DRLs and dose reference levels for CT in radiation oncology. The radiation doses in computed tomography for radiotherapy treatment planning were properly optimized following the imaging guidelines.
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