Quality of Intensity Modulated Radiation Therapy Treatment Plans Using a60 Co Magnetic Resonance Image Guidance Radiation Therapy System

• Published in: International journal of radiation oncology, biology, physics Vol. 92; no. 4; pp. 771 - 778
• Main Authors: Wooten, H. Omar, PhD, Green, Olga, PhD, Yang, Min, PhD, DeWees, Todd, PhD, Kashani, Rojano, PhD, Olsen, Jeff, MD, Michalski, Jeff, MD, Yang, Deshan, PhD, Tanderup, Kari, PhD, Hu, Yanle, PhD, Li, H. Harold, PhD, Mutic, Sasa, PhD
• Format: Journal Article
• Language: English
• Published: 2015
• Subjects: Hematology, Oncology and Palliative Medicine; Radiology
• ISSN: 0360-3016
• DOI: 10.1016/j.ijrobp.2015.02.057

Purpose This work describes a commercial treatment planning system, its technical features, and its capabilities for creating60 Co intensity modulated radiation therapy (IMRT) treatment plans for a magnetic resonance image guidance radiation therapy (MR-IGRT) system. Methods and Materials The ViewRay treatment planning system (Oakwood Village, OH) was used to create60 Co IMRT treatment plans for 33 cancer patients with disease in the abdominal, pelvic, thorax, and head and neck regions using physician-specified patient-specific target coverage and organ at risk (OAR) objectives. Backup plans using a third-party linear accelerator (linac)-based planning system were also created. Plans were evaluated by attending physicians and approved for treatment. The60 Co and linac plans were compared by evaluating conformity numbers (CN) with 100% and 95% of prescription reference doses and heterogeneity indices (HI) for planning target volumes (PTVs) and maximum, mean, and dose-volume histogram (DVH) values for OARs. Results All60 Co IMRT plans achieved PTV coverage and OAR sparing that were similar to linac plans. PTV conformity for60 Co was within <1% and 3% of linac plans for 100% and 95% prescription reference isodoses, respectively, and heterogeneity was on average 4% greater. Comparisons of OAR mean dose showed generally better sparing with linac plans in the low-dose range <20 Gy, but comparable sparing for organs with mean doses >20 Gy. The mean doses for all60 Co plan OARs were within clinical tolerances. Conclusions A commercial60 Co MR-IGRT device can produce highly conformal IMRT treatment plans similar in quality to linac IMRT for a variety of disease sites. Additional work is in progress to evaluate the clinical benefit of other novel features of this MR-IGRT system.