| Summary: | 碩士 === 元培科技大學 === 放射技術研究所 === 102 === This study aims to compare treatment plans using sliding window Intensity modulated radiation therapy (SW-IMRT) and Rapid-arc in NPC patients.
In this study, between 2008 and 2010, 33 patients with NPC were planned using both SW-IMRT and Rapid-arc techniques based on the patient’s CT images acquired at simulation. The volume ‘PGTV-70’ was prescribed 7000cGy in 35 fractions, ‘PCTV-63’ 6300cGy in 35 fractions, and ‘PCTV-50.4’ 5040cGy in 28 fractions. For each patient, SW-IMRT and Rapid-arc plans were evaluated in terms of target coverage and critical organ protection. Homogeneity and conformal indexes were compared for target coverage. Critical organs including the brain stem, spinal cord, both sides of the parotid gland, mouth and eyes were assessed using the maximum dose, mean dose, or V26Gy.
For the same target dose coverage, homogeneity index for Rapid-arc plans were worse than SW-IMRT plans by 0.02 or more. However, in parotid gland and oral cavity, V26Gy for Rapid-arc plans were less than SW-IMRT plans by 12%. In addition, the treatment delivery time for Rapid-arc plans were reduced by 296 seconds (61%), and the monitoring unit reduced by 1054MU (65%) compared to SW-IMRT plans.
Rapid-arc plans produced similar target coverage as SW-IMRT plans, but provided better protection for parotid gland and oral cavity. The delivery of Rapid-arc plans were more efficient as they require less delivery time and MU. Compared to SW-IMRT, Rapid-arc appears to be more suitable for NPC patient.
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