|Title:||Application of directional block for brainstem in tomotherapy treatment planning of nasopharyngeal carcinoma|
|Subject:||Hong Kong Polytechnic University -- Dissertations.|
Nasopharynx -- Cancer -- Treatment.
|Department:||Department of Health Technology and Informatics|
|Pages:||52 leaves : ill. (some col.) ; 30 cm.|
|Abstract:||Purpose: The main objective of the study is to investigate the geometric correlation between planning target volume (PTV) and brainstem in the patients with nasopharyngeal carcinoma (NPC), so as to identify the determining factors in the optimal application of directional block in tomotherapy treatment plans. Materials and Methods: Fourteen (14) NPC patients treated with helical tomotherapy were recruited. The geometric correlation of the nasopharyngeal planning target volume (NP-PTV) and the brainstem was quantified by measuring the reference beamlet direction lines in concentric mode. Different geometric correlations between the NP-PTV and the brainstem were recorded including the size of the brainstem, the mean and minimum separations between the NP-PTV and the brainstem, the size of NP-PTV, the depth of the NP-PTV inside the patient, and the NP-PTV concavity. They were tested statistically for the significant correlation between the maximum radiation doses received by the brainstem in their helical tomotherapy plans with directional block applied on the brainstem. All plans followed the same minimum dose requirement for the NP-PTV with 95% volume of the NP-PTV receiving not less than 70Gy. The maximum dose received by the brainstem (BS Dmax) in each plan was recorded for analysis. Results: The mean separation between the NP-PTV and the brainstem demonstrated the most significant correlation with the maximum radiation dose received by the brainstem (rs=-0.656, p=0.011). Conclusions: The mean separation between the NP-PTV and the brainstem was the most determining factors in the optimal application of directional block to the brainstem in helical tomotherapy treatment plans.|
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