Accuracy Evaluation of Collapsed Cone Convolution Superposition Algorithms for the Nasopharynx Interface in the Early Stage of Nasopharyngeal Carcinoma

• Published in: BioMed research international Vol. 2022; no. 1; p. 5227609
• Main Authors: Lai, Yuan-Chun, Hung, Li-Chung, Jeng, Chien-Chung, Feng, Chen-Ju, Chang, Tung-Hao, Hsu, Shih-Ming
• Format: Journal Article
• Language: English
• Published: United States Hindawi 2022; John Wiley & Sons, Inc
• Subjects: Accuracy; Algorithms; Anthropomorphism; Care and treatment; Complications and side effects; Convolution; Dosimetry; Energy; Evaluation; Humans; Interfaces; Irradiation; Mathematical analysis; Monte Carlo simulation; Nasopharyngeal cancer; Nasopharyngeal carcinoma; Nasopharyngeal Carcinoma - radiotherapy; Nasopharyngeal Neoplasms - radiotherapy; Nasopharynx; Patient outcomes; Patients; Phantoms, Imaging; Planning; Radiation; Radiation dosage; Radiation measurement; Radiation therapy; Radiometry - methods; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted - methods; Throat cancer; Tissues; Taiwan; United States > US
• ISSN: 2314-6133; 2314-6141; 2314-6141
• DOI: 10.1155/2022/5227609

This study combined the use of radiation dosimeteric measurements and a custom-made anthropomorphic phantom in order to evaluate the accuracy of therapeutic dose calculations at the nasopharyngeal air-tissue interface. The doses at the nasopharyngeal air-tissue interface obtained utilizing the Pinnacle and TomoTherapy TPS, which are based on collapsed cone convolution superposition (CCCS) algorithms, were evaluated and measured under single 10×10 cm2, 2×2 cm2, two parallel opposed 2×2 cm2 and clinical fields for early stage of nasopharyngeal carcinoma by using EBT3, GR-200F, and TLD 100. At the air-tissue interface under a 10×10 cm2 field, the TPS dose calculation values were in good agreement with the dosimeter measurement with all differences within 3.5%. When measured the single field 2×2 cm2, the differences between the average dose were measured at the distal interface for EBT3, GR-200F, and TLD-100 and the calculation values were -15.8%, -16.4%, and -4.9%, respectively. When using the clinical techniques such as IMRT, VMAT, and tomotherapy, the measurement results at the interface for all three techniques did not imply under dose. Small-field sizes will lead to dose overestimation at the nasopharyngeal air-tissue interface due to electronic disequilibrium when using CCCS algorithms. However, under clinical applications of multiangle irradiation, the dose errors caused by this effect were not significant.