2923 - A Novel "Lying-on-Couch" Total Skin Electron Beam Therapy (TSEBT) to Improve Access, Reproducibility, and Ergonomics for Frail and Non-Ambulatory Patients

Purpose/Objective(s): Total skin electron beam therapy (TSEBT) is traditionally delivered with patients standing for prolonged periods at extended treatment distance, limiting feasibility for frail, elderly, or non-ambulatory individuals. Existing recumbent approaches often rely on floor-level positioning that is difficult to reproduce and physically demanding for therapists. We developed a “lying-on-couch” TSEBT technique to improve patient comfort, setup reproducibility, and workflow safety while maintaining clinically acceptable dose uniformity.

Materials/Methods: The technique employs 9 MeV high-dose-rate electron beams with patient positioned on an in-house rotational overlay platform (Spinning Manny) securely indexed to the couch. The platform enables transitions between head-first and feet-first orientations without patient repositioning, standardizing setup and reducing therapist ergonomic burden. A custom degrader made of tungsten, PLA, and PMMA was used to improve field uniformity. The treatment consisted of 8 paired AP/PA fields: four paired fields at gantry 0° with longitudinal offsets of ±22 cm and ±80 cm, and four paired fields at each oblique gantry angle (60° and 300°) using same longitudinal offsets. For the oblique beams, lateral offsets were –24.5 cm at 60° and +24.5 cm at 300° to enhance lateral coverage. All fields were delivered with couch at 0° and lowered to –57 cm. The longitudinal direction was controlled through rotation of the overlay platform. Optimal uniform dose profiles were established by empirically adjusting field shifts and weights based on ion chamber measurements. End-to-end validation was performed using OSLDs on an anthropomorphic Rando phantom.

Results: The combination of a customized beam degrader and empirically optimized beam arrangement achieved an overall dose uniformity within ±10% over 74 cm lateral width and 190 cm longitudinal length. End-to-end OSLD measurements demonstrated homogeneous surface doses ranging from 94% to 110% of prescription, matching the dosimetric quality of the standard standing technique.

Conclusion: This couch-based TSEBT technique achieves dosimetric uniformity comparable to conventional standing approaches while significantly improving patient comfort, setup consistency, and staff ergonomics using a couch-based workflow. By enabling safe and reproducible treatment for frail or non-ambulatory patients previously unable to tolerate standard TSEBT, this technique expands access to definitive cutaneous radiotherapy and establishes a practical, clinically deployable paradigm for modern TSEBT delivery.