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The effect of material assignment in nasal cavity on dose calculation for nasopharyngeal carcinoma (NPC) using Acuros XB
Author(s) -
Cheung Michael L. M.,
Chow Vivian U. Y.,
Kan Monica W. K.,
Chan Anthony T. C.
Publication year - 2022
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1002/acm2.13698
Subject(s) - nasal cavity , nasopharyngeal carcinoma , significant difference , lung , nuclear medicine , medicine , radiation therapy , surgery
Purpose To evaluate the effect of material assignment in nasal cavity on dose calculation for the volumetric modulated arc therapy (VMAT) of nasopharyngeal carcinoma (NPC) using Acuros XB (AXB) algorithm. Methods The VMAT plans of 30 patients with NPC were calculated using AXB with material auto‐assignment of nasal cavity to lung and reassignment to air respectively. The doses to the planning target volumes (PTVs) overlapping with nasal cavity with material auto‐assignment of lung (AXB_Lung) were compared to the values obtained when nasal cavity was reassigned to air (AXB_Air) under the dose‐to‐medium ( D m ) reporting mode of AXB. Results For dose calculated under AXB_Lung, the D 98% , D 2% , and D mean of the PTV 69.96 _Air Cavity (PTV of prescription dose 69.96 Gy overlapping with nasal cavity) were on average 16.1%, 1.6%, and 8.6% larger than that calculated under AXB_Air, respectively. Up to 19.5% difference in D 98% , 3% difference in D 2% , and 11.2% difference in D mean were observed in the worst cases for PTV 69.96 . Similar trend was observed for the PTV 5940 _Air Cavity, in which the D 98% , D 2% , and D mean calculated under AXB_Lung were on average 14.7%, 2.5%, and 10.2% larger than that calculated under AXB_Air, respectively. In the worst cases, the difference observed in D 98% , D 2% , and D mean could be up to 17.7%, 4.5%, and 12.7%, respectively. Conclusions Significant dose difference calculated by AXB between the material assignment of lung and air in nasal cavity for NPC cases might imply the possibility of underdosage to the PTVs that overlap with inhomogeneity. Therefore, attention should be put to ensure that accurate material assignment for dose calculation under AXB such that optimal dosage was given for tumor control.

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