Clinical Implementation of Jaw Tracking for 3D-CRT: Dosimetric Evaluation and Patient-Specific QA Requirement
Abstract
Purpose
Jaw-tracking is a standard feature for IMRT and VMAT on TrueBeam accelerators, but its application in 3D-conformal radiotherapy (3D-CRT) is less common. Benefits may exist when utilizing electronic compensation. This study evaluates the dosimetric impact, delivery accuracy, and multi-machine reliability of dynamic-jaw (DJ) for 3D-CRT plans to determine if it can be safely implemented without routine PSQA.
Methods
Ten previously treated 3D-CRT cases (breast, spine, and liver) with field sizes > 3x3cm2 were recalculated using fixed-jaw (FJ) and DJ tracking. Comparative metrics included total MU, target mean dose, OAR maximum dose (parotids, contralateral breast, lung, and spine), Conformity Index (CI), and Gradient Measure (GM). PSQA was performed using EPID and ArcCheck, compared against TPS predicted fluence (2%/2mm gamma criteria). To minimize output variation, FJ and DJ QA plans were measured consecutively. Secondary dose verification was performed via ClearCalc. Finally, cross-machine deliverability was verified by delivering same plan across eight machines and comparing results via gamma analysis. Statistical significance was assessed using Welch’s t-test (p 3x3cm2 jaw-tracking can be safely implemented without routine PSQA on accelerators adhering to TG-142 recommended standards.