VMAT-based total body irradiation on a conventional LINAC: workflow, procedure and preliminary results

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Total body irradiation (TBI) is a critical component of hematopoietic stem cell transplantation.
• Conventional TBI techniques often face challenges in dose homogeneity and organ sparing.

Purpose of the Study:

• To evaluate the feasibility of implementing volumetric modulated arc therapy (VMAT)-based techniques for TBI.
• To assess the utility of extended cone-beam computed tomography (CBCT) image guidance with VMAT for TBI using a conventional linear accelerator.

Main Methods:

• Retrospective analysis of 27 patients undergoing TBI between November 2016 and December 2024.
• Dosimetric planning using a multi-isocenter VMAT approach with Eclipse™ treatment planning system.
• Treatment delivery on Varian linear accelerators with extended-field CBCT for image guidance and setup verification.

Main Results:

• All 148 scheduled treatment fractions were completed successfully.
• Mean lung dose was 10.12 Gy, with achieved dose homogeneity of 1.24.
• Average session duration was 87 minutes, with precise setup corrections using CBCT.

Conclusions:

• VMAT-based TBI is a feasible and promising alternative to conventional 2D-TBI.
• VMAT offers improved dose homogeneity and enhanced organ sparing, with reproducibility comparable to helical tomotherapy (HT) systems.
• Further prospective studies are warranted to confirm long-term clinical benefits of VMAT for TBI.