Integrated IMRT and IGRT: a complex helical tomotherapy treatment of cranial-spinal lesions with daily CT image guidance

Chuan Wu, Janice Ryu, William Hall, Fanqing Guo and Tianxiao Liu

University of California – Davis, Sacramento, CA 95817 USA

Helical tomotherapy is a novel technology that is designed as an integrated intensity modulated radiation therapy (IMRT) and image-guided radiation therapy (IGRT) platform. Its unique fan beam rotating geometry and simultaneous couch movement gives it the capability of delivering highly conformal doses to targets while sparing surrounding normal structures, further enhanced by onboard CT guidance during treatment. In this work, we present a complex clinical case of using helical tomotherapy to treat a pediatric patient with M3 medulloblastoma. The optimized helical tomotherapy plan shows a highly conformal dose to both brain and spinal cord tumor lesions, compared to the plan on the same patient by conventional 3D CRT technique. The sparing of critical structures is excellent. The patient specific quality assurance using both ion chambers and film measurement in phantom shows that the calculated dose agrees with the measurement within 3%. In subsequent treatment, image guidance was used through out the course to minimize patient inter-fractional motion and setup errors. During his daily treatment, after the patient skin tattoos were aligned with room lasers, a mega-voltage CT (MVCT) scan was made. The acquired images were fused to the planning CT images on tomotherapy workstation. Based on fusion result, further patient position adjustments (translations plus roll) were made and then treatment initiated. In conclusion, we present the comprehensive process of a complex integrated IMRT and IGRT case at University of California – Davis cancer center. We believe it very valuable to share this experience with institutions and colleagues in China.