Feasibility of target current pulse counting method for output dose measurement on the trilogy accelerator: dose...

This study aims to assess the feasibility of the target current pulse counting method for accurate output dose measurement on the Trilogy accelerator, and explore the potential of dose quasi-quantization and real-time monitoring to enhance dose accuracy and reliability.

Data acquisition card was employed to capture target current pulse signals from the Trilogy accelerator. The feasibility of the pulse counting method for dose monitoring was evaluated. The method was then used to analyze dose distribution discrepancies in six Dynamic Multi-leaf Collimator (DMLC) wedge fields (MU range: 2 to 100) at varying dose densities. Pulse signals from 37 VMAT fields were combined with control point data to generate a time-dose curve. The Mean Squared Error (MSE) was used to quantify their similarity. Finally, the MU of the VMAT fields were halved, and the same procedure was applied to calculate the MSE and compare it with the original MU field.

Target current pulse counts showed a linear correlation with MU (R² > 0.999) and high repeatability (< 0.5 %). The method enabled output dose quasi-quantization (RapidArc: 3.318 cMU, non-RapidArc: 2.782 cMU). The time-dose curve provided an explanation for the stepped dose distribution in low MU (≤ 20 MU) DMLC fields, and original MU had a lower MSE in VMAT tests (3.33 × 10^-5 vs 4.72 × 10^-5, p < 0.001).

The method allows precise output dose detection by integrating dose quantization and time attributes, establishing a time-dose curve for millisecond-level monitoring, which is valuable for low-dose analysis.