Linear Accelerator-Based Intensity-Modulated Total Marrow Irradiation Technique for Treatment of Hematologic Malignancies: A Dosimetric Feasibility Study

Purpose: To investigate the dosimetric feasibility of linear accelerator-based intensity-modulated total marrow irradiation (IM-TMI) in patients with hematologic malignancies. Methods and Materials: Linear accelerator-based IM-TMI treatment planning was performed for 9 patients using the Eclipse treatment planning system. The planning target volume (PTV) consisted of all the bones in the body from the head to the mid-femur, except for the forearms and hands. Organs at risk (OAR) to be spared included the lungs, heart, liver, kidneys, brain, eyes, oral cavity, and bowel and were contoured by a physician on the axial computed tomography images. The three-isocenter technique previously developed by our group was used for treatment planning. We developed and used a common dose-volume objective method to reduce the planning time and planner subjectivity in the treatment planning process. Results: A 95% PTV coverage with the 99% of the prescribed dose of 12 Gy was achieved for all nine patients. The average dose reduction in OAR ranged from 19% for the lungs to 68% for the lenses. The common dose-volume objective method decreased the planning time by an average of 35% and reduced the inter- and intra- planner subjectivity. Conclusion: The results from the present study suggest that the linear accelerator-based IM-TMI technique is clinically feasible. We have demonstrated that linear accelerator-based IM-TMI plans with good PTV coverage and improved OAR sparing can be obtained within a clinically reasonable time using the common dose-volume objective method proposed in the present study.