A comparative evaluation of two head and neck immobilization devices using verification film for head and neck cancer patients receiving radiation therapy at Ocean Road Cancer Institute (ORCI) aero-digestive tract

Dukho AJ* and Nazima Dharsee

Background: Accurate and reproducible patient positioning is fundamental to the success of fractionated radiotherapy. To achieve accurate daily treatment delivery, various immobilization devices are used in radiotherapy departments. At ORCI the mostly used immobilization devices for radiotherapy treatment of head and neck cancer patients are thermoplastic mask and LS-2000. However, the effectiveness and accuracy of these immobilization devices in daily set-up is not known. This study was performed to evaluate accuracy and reproducibility of patient setup for both thermoplastic mask and LS-2000 devices, during irradiation of head and neck tumors. 

Methods: 30 head and neck cancer patients treated at ORCI between May 2017 and July 2017 were enrolled. 16 patients were immobilized with LS-2000, while 14 patients were immobilized with thermoplastic mask. All patients attended planning session which was done using Tera-Six simulator, and treatment was done using a CO-60 machine. Portal films were taken on the initial treatment day and once per week for three weeks of treatment. 90 portal images were analyzed to assess patient displacement in antero-posterior and supero-inferior directions by measuring distance from center of treatment field to clearly visible bony landmark using a ruler. 

Results: The ranges of set up deviation for both thermoplastic mask and LS-2000 immobilization devices were (-0.53cm to +0.67cm) and (-0.8 to +1.42cm) in AP direction, and (-0.53cm to +1.07cm) and (-0.47cm to 2.23cm) in SI direction. Seventy eight point six percent (78.6%) and seventy five percent (75%) of setup deviations were within ±0.4cm in AP direction for both thermoplastic mask and LS-2000 immobilization devices respectively. In SI direction fifty seven (57.1%) and fifty percent (50%) of setup deviation were within ±0.4cm, for both thermoplastic mask and LS-2000 devices respectively. The random errors for the thermoplastic mask and LS-2000 devices were ±0.34cm and ±0.62cm in AP direction and± 0.48cm and ±0.64cm in SI direction respectively. The systematic deviations were ±0.35cm and ±0.62cm in AP direction and± 0.5cm and ±0.64cm in SI direction for the thermoplastic mask and LS-2000 devices respectively. 

Conclusion: Thermoplastic mask for immobilization of HNC treatment provides a field placement reproducibility that was better than LS-2000 as it demonstrated smaller translational set up displacements in both AP and SI directions.

Keywords: Head and neck cancer; Comparative evaluation; Immobilization devices; Thermoplastic mask; LS -2000; ORCI

Published on: Aug 23, 2018 Pages: 21-26

Full Text PDF Full Text HTML DOI: 10.17352/ijrro.000031
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