EFFECTIVENESS WITH THE USE OF A CUSTOM-MADE NECK SUPPORT CUSHION IN IMAGE GUIDED RADIATION THERAPY FOR HEAD AND NECK PATIENTS

Objectives: To evaluate the reproducibility of the use of a personalized neck support cushion for Head and Neck patients under Image Guided (EPID) Intensity Modulated Radiation Therapy. Methods and Materials: Positioning variations of 64 Head and Neck patients were acquired from comparison between Digitally Reconstructed Radiographs (DRR) and Portal images. Position uncertainty was accessed and analyzed using Van Herks formula, so that 99% of patients would receive minimum coverage of the 95% isodose. An average of seven pairs of Portal images (Anterior and Lateral) per patient were acquired. Uncertainty in positioning in the Lateral, vertical and longitudinal directions were compared with and without the use of the personalized neck support, which is positioned between the neck and standard Head pillows. Results: For a total of 32 patients evaluated without the use of the custom-made neck support cushion, PTV population margins of 0.27, 0.44 and 0.38-cm in the lateral, vertical and longitudinal directions, respectively. For the other 32 patients using the personalized neck support cushion, results for PTV margin were 0.27, 0.35 and 0.31- cm in the same directions. The comparison of the results show a reduction in positioning uncertainty in the lateral and longitudinal directions of 18% and 18,5%, respectively. There was no difference in the lateral direction. Conclusion: The study demonstrates that thermoplastic mask immobilization complemented with the use of a personalized neck support cushion presents better results in terms of positioning reproducibility. Considering that the current Head and Neck PTV institutional margin is 0.5- cm, reductions on the order of 0.1-cm were considered statistically significant. Therefore, there is better agreement between planned and delivered radiation doses with better treatment accuracy and potential toxicity reduction.