Early clinical experience with a total body irradiation technique using field-in-field beams and on-line image guidance

• Published in: Physics and imaging in radiation oncology Vol. 16; pp. 12 - 17
• Main Authors: van Leeuwen, Ruud G.H., Verwegen, Drean, van Kollenburg, Peter G.M., Swinkels, Marc, van der Maazen, Richard W.M.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.10.2020; Elsevier
• Subjects: Original
• ISSN: 2405-6316; 2405-6316
• DOI: 10.1016/j.phro.2020.09.004

Total body irradiation (TBI) is a treatment used in the conditioning of patients prior to hematopoietic stem cell transplantation. We developed an extended-distance TBI technique using a conventional linac with multi-leaf collimator to deliver a homogeneous dose, and spare critical organs. Patients were treated either in lateral recumbent or in supine position depending on the dose level. A conventional linac was used with the patient midline at 350 cm from the beam source. A series of beams was prepared manually using a 3D treatment planning system (TPS) aiming to improve dose homogeneity, spare the organs at risk and facilitate accurate patient positioning. An optimized dose calculation model for extended-distance treatments was developed using phantom measurements. During treatment, in-vivo dosimetry was performed using electronic dosimeters, and accurate positioning was verified using a mobile megavoltage imager. We analyzed dose volume histogram parameters for 19 patients, and in-vivo measurements for 46 delivered treatment fractions. Optimization of the dose calculation model for TBI improved dose calculation by 2.1% at the beam axis, and 17% at the field edge. Treatment planning dose objectives and constraints were met for 16 of 19 patients. Results of in-vivo dosimetry were within the set limitations (±10%) with mean deviations of 3.7% posterior of the lungs and 0.6% for the abdomen. We developed a TBI treatment technique using a conventional linac and TPS that can reliably be used in the conditioning regimen of patients prior to stem cell transplantation.