Comparison of Radiotherapy Positioning Deviations in Head and Neck Cancer Patients With and Without the Use of Dental Impression Fixation Devices

Abstract

At present, the use of advanced 3D techniques to fix head and neck cancer patients undergoing radiation therapy treatment (Volumetric Modulated Arc Therapy:  VMAT) is very important for the accuracy and precision of the radiation location both during the radiation treatment and every day until the prescribed treatment plan is complete. Objectives of the study for choosing to use of fixation device is an important factor. Therefore, a comparison of the positioning errors of head and neck cancer patients from the use of 2 groups of fixation devices: Group 1 (Tooth impression device + standard headrest) and Group 2 (Standard headrest). Study of patients irradiated with the VMAT technique by examining the location of the irradiation using 3D X-Ray cone beam computed tomography (CBCT). This study had a sample groups of head and cancer patients 15 patients per group, with a total of 112 and 119 CBCT images, respectively, for compare with reference image (Digital Reconstructed Radiography: DRR) from the treatment plan. The horizontal plane (X, Y, and Z) and rotational plane (sagittal, coronal, and transverse) tolerance and the number of repeated irradiation setup was assessed. All data for the two fixation groups were compared. The results of the study found that the rates of re-irradiation setup in patients in group 1 was 25.9 percent and group 2 was 48.7 percent, which were significantly different (P<0.001) and the rates of re-irradiation patient setup in the sagittal direction were 5.4 percent and 25.2 percent (P<0.001) and the ratio of re-irradiation setup comparing the two groups was 0.5 (P=0.023). Summary of the use of fixation devices for head and neck cancer patients undergoing radiation therapy using the VMAT technique with a dental impression set together with standard fixation devices help to reduce re-irradiation patient setup with statistical significance, especially in the head-foot direction can reduce the rate of re-irradiation positions up to 5 times and reduce the total time spent on radiation treatment each day. Importantly, it reduces the patient's exposure to unnecessary radiation doses for repeat CBCT procedures and reduces the cost of purchasing fixation equipment.