Evaluasi dosis CT Simulator pada Radioterapi Head and Neck dan Pelvis
Main Article Content
Abstract
The CT Simulator is an imaging modality used in radiotherapy for target delineation and dose calculation in therapy planning. AAPM TG 204 provides conversion factors based on patient body size, specifically for CTDIvol correction, as it does not directly measure the patient's radiation dose. Despite its advantages, there is still limited attention given to dose-saving strategies in CT simulation. This study aims to evaluate the percentage of additional radiation dose by utilizing Size-Specific Dose Estimate (SSDE) per AAPM TG 204. Ten patients each undergoing head and neck (CT HNC) and pelvis CT scans were assessed. The CTDIvol values displayed on the console were verified using a dosimeter chamber on a CTDI body phantom. The results show an average verification value of 2.78% for CT HNC and 2.02% for CT Pelvis, within the acceptable threshold set by ACR and Bapeten (≤ 20%). The average SSDE values recorded were 83.02 mGy for CT HNC and 39.08 mGy for CT Pelvis. Additionally, the average percentage of dose contribution to the prescribed therapy dose was 1.6% for CT HNC and 0.43% for CT Pelvis, below the ICRU Report 50 recommendations. The CT HNC dose was higher due to using a larger tube current (mA), which results in higher X-ray intensity, and a slower rotation time, leading to longer radiation exposure. However, the CT Pelvic dose exceeded the I-DRL reference of 17 mGy, with an average of 27.31 mGy. Optimisation of scanning parameters remains essential, and, where feasible, substituting non-ionizing imaging modalities such as MRI, which offers several benefits, can be advantageous.
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