Abstract
In this work, we develop a total body irradiation technique that utilizes arc delivery, a buildup spoiler, and inverse optimized multileaf collimator (MLC) motion to shield organs at risk. The current treatment beam model is verified to confirm its applicability at extended source‐to‐surface distance (SSD). The delivery involves 7–8 volumetric modulated arc therapy arcs delivered to the patient in the supine and prone positions. The patient is positioned at a 90° couch angle on a custom bed with a 1 cm acrylic spoiler to increase surface dose. Single‐step optimization using a patient CT scan provides enhanced dose homogeneity and limits organ at risk dose. Dosimetric data of 109 TBI patients treated with this technique is presented along with the clinical workflow. Treatment planning system (TPS) verification measurements were performed at an extended SSD of 175 cm. Measurements included: a 4‐point absolute depth‐dose curve, profiles at 1.5, 5, and 10 cm depth, absolute point‐dose measurements of an treatment field, 2D Gafchromic® films at four locations, and measurements of surface dose at multiple locations of a Alderson phantom. The results of the patient DVH parameters were: Body‐5 mm D98 95.3 ± 1.5%, Body‐5 mm D2 114.0 ± 3.6%, MLD 102.8 ± 2.1%. Differences between measured and calculated absolute depth‐dose values were all <2%. Profiles at extended SSD had a maximum point difference of 1.3%. Gamma pass rates of 2D films were greater than 90% at 5%/1 mm. Surface dose measurements with film confirmed surface dose values of >90% of the prescription dose. In conclusion, the inverse optimized delivery method presented in the paper has been used to deliver homogenous dose to over 100 patients. The method provides superior patient comfort utilizing a commercial TPS. In addition, the ability to easily shield organs at risk is available through the use of MLCs.
Highlights
Total body irradiation (TBI) is an essential part of bone marrow transplant conditioning as it has been shown to eliminate residual chemotherapy‐resistant cancer cells and it provides additional immunosuppression to enhance engraftment.[1]
We report on our patient experience and the measurements made to verify the accuracy of our Treatment planning system (TPS)'s beam model at extended source‐to‐surface distance (SSD)
Two dose profiles are shown, one down the midline and one across the lungs (Fig. 6). These profiles illustrate a homogenous dose within ±10% of the prescription coverage of the Body‐ 5 mm structure, and the mean lung dose (MLD) was recorded from the plan sum of the supine and prone plans for all 109 patients
Summary
Total body irradiation (TBI) is an essential part of bone marrow transplant conditioning as it has been shown to eliminate residual chemotherapy‐resistant cancer cells and it provides additional immunosuppression to enhance engraftment.[1]. A variety of TBI delivery techniques have been developed Most of these techniques involve opposing beams that are either lateral or anterior‐posterior (AP/PA) and are performed with the patient at an extended distance to limit the need for junctioning fields.[7,8] An example of a lateral technique is lateral parallel opposed pair (POP) beams with the patient under full bolus, which provides good dose homogeneity and utilizes simple dose calculation algorithms.[9,10] Drawbacks to this approach include reduced patient comfort and the limited ability to shield organs at risk without compromising dose to bones. Multiple field techniques require accurate matching of field junctions in order to limit hot and cold regions during delivery to the patient
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
