Commissioning and Clinical Implementation of Total Skin Electron Irradiation Using a Standard Truebeam Linear Accelerator
Abstract
Purpose
To commission and clinically implement a modified Stanford technique for Total Skin Electron Irradiation (TSEI) using a standard TrueBeam linac, achieving consistent and high-quality skin dose coverage.
Methods
Commissioning was performed on a TrueBeam linac using a 6 MeV electron beam at a dose rate of 1000 MU/min. A field size of 34 × 34 cm² was used with a phantom (solid water or Rando) positioned at a source-to-surface distance (SSD) of 400 cm behind a 4-mm beam degrader. Optimal dual-gantry angles and field uniformity were determined using Farmer chamber measurements along vertical and horizontal axes at SSD = 400 cm and verified with film dosimetry. Percent depth dose (PDD) curves were measured in solid water using a parallel-plate chamber at gantry angle=270° and at the optimized dual-gantry angles. Absolute dose calibration was performed using both parallel-plate and cylindrical chambers. Total treatment dose was determined using MOSFET dosimeters and a cylindrical phantom, accounting for dose contributions from adjacent dual fields. The B-factor was defined as the ratio of total treatment dose to calibration point dose. An end-to-end test was conducted to validate overall dosimetric accuracy.
Results
Optimal dual-gantry angles were identified as 254° and 286°, achieving dose uniformity within ±10% over vertical distances from −100cm to 80cm and horizontal distances from −35cm to 35cm. PDD measurements yielded a reference depth (d_ref) of 0.9cm and a depth of maximum dose (d_max) of 0.6cm for both gantry configurations. The calibration point dose for a single dual-fields was 0.0487 cGy/MU at d_max, while the total treatment dose was 0.136 cGy/MU, resulting in a B-factor of 2.79. End-to-end testing with MOSFETs and TLDs confirmed dosimetric accuracy.
Conclusion
The commissioned modified Stanford technique achieved clinically acceptable dose uniformity and provides a practical and effective TSEI option using a standard TrueBeam linac.