Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada.
Department of Radiation Oncology, Juravinski Cancer Centre, Hamilton, ON, Canada.
J Appl Clin Med Phys. 2020 Jun;21(6):26-32. doi: 10.1002/acm2.12862. Epub 2020 May 6.
The tracheostomy site and adjacent skin is at risk for recurrence in head/neck squamous cell cancer patients. The tracheostomy tube is an in situ device located directly over the tracheostomy site and may have clinical implications on the radiation dose delivered to the peristomal region. This study aimed to investigate this effect by comparing the prescribed treatment planning dose with the actual dose in vivo to the peristomal clinical target region. A retrospective, dosimetric study was performed with approval of the institutional research ethics board.
Fifteen patients who had received high-dose radiotherapy to the tracheostomy region with in vivo dose measurements were included. The radiation dose at the skin surface underneath the tracheostomy device was measured using an optically stimulated luminescent dosimeter (OSLD) and was compared with the prescribed dose from the radiation planning system. The effect of the tracheostomy flange and/or soft tissue equivalent bolus on the peristomal dose was calculated.
Patients with tracheostomy equipment in situ were found to have a 3.7% difference between their prescribed and actual dose. With a tissue equivalent bolus there was a 2.0% difference between predicted and actual. The mean prescribed single fraction dose (mean = 191.8 cGy, SD = 40.18) and OSLD measured dose (mean = 194.02 cGy, SD = 44.3) were found to have no significant difference. However, with the flange excluded from the planning simulation (density = air) target skin dose deviated from predicted by an average of 55.3% (range = 12.4-72.9, SD = 22.5) and volume coverage was not achieved.
In summary, the tracheostomy flange acts like bolus with a twofold increase in the skin surface dose. Changes in the peristomal apparatus from simulation to treatment needs to be considered to ensure that the simulated dose and coverage is achieved.
气管造口部位及邻近皮肤是头颈部鳞状细胞癌患者复发的高危区域。气管造口管是一种位于气管造口部位正上方的原位设备，可能对造口周围区域的辐射剂量有临床影响。本研究旨在通过比较计划靶区（PTV）的规定治疗计划剂量与体内实际剂量，来探讨这种影响。这项回顾性、剂量学研究获得了机构研究伦理委员会的批准。
共纳入 15 例接受气管造口区域高剂量放疗并进行体内剂量测量的患者。使用光激励发光剂量计（OSLD）测量气管造口设备下方皮肤表面的辐射剂量，并与放射治疗计划系统的规定剂量进行比较。计算气管造口法兰和/或软组织等效体模对造口周围剂量的影响。
发现有气管造口设备的患者，其规定剂量与实际剂量相差 3.7%。使用组织等效体模，预测剂量与实际剂量相差 2.0%。单次规定剂量（平均值=191.8 cGy，标准差=40.18）和 OSLD 测量剂量（平均值=194.02 cGy，标准差=44.3）之间无显著差异。然而，当将法兰从计划模拟中排除（密度=空气）时，目标皮肤剂量平均偏离预测值 55.3%（范围=12.4-72.9，标准差=22.5），且体积覆盖率未达到。
总之，气管造口法兰的作用类似于体模，使皮肤表面剂量增加两倍。从模拟到治疗，需要考虑造口周围设备的变化，以确保模拟剂量和覆盖范围得以实现。
