Department of Radiation Medicine   

Arnab Chakravarti, MD

Radiation Medicine’s mission is to: provide radiation therapy for every cancer patient through applied medical research, advanced radiation technologies and treatment techniques for personalized radiation medicine; advance medical knowledge through innovative research; and educate highly skilled medical specialists. The Department has six attending physicians, five medical physicists, four radiation oncology residents, two physician assistants, two radiation physics residents, two radiation physics postdoctoral fellows and a support staff of radiation oncology dosimetrists, radiation therapists, radiation oncology nurses and radiation therapy students. Technologies acquired in 2007 include image-guided radiation therapy (IGRT), consisting of a new linear accelerator with image-guided radiation therapy and integrated cone beam computed tomography (CT) imaging, and a dedicated 40-slice CT scanner with four-dimensional planning capability that allows imaging of moving tumor targets. This enables high-precision stereotactic radiation therapy of moving tumor targets. A novel image-guided brachytherapy program also was developed in 2007.

• The Department’s program of integrated anatomical and functional tumor imaging in radiation therapy and response monitoring has expanded to include imaging and nonimaging parameters into response monitoring and outcome prediction.
• The development of tumor-response models has further advanced to developing multimodality response prediction model integrating imaging-based and non-imaging parameters. Radiobiological models to guide radiation-dose prescription and treatment delivery schedules have been developed. A generalized Linear-Quadratic (gLQ) model has been proposed for the treatment schedule design of radiosurgery and high-dose-rate brachytherapy.
• Hypo-fractionation Stereotactic Radiotherapy (HFSRT), the treatment of tumors with larger high-precision doses and fewer treatment sessions and shorter treatment courses, requires a new understanding of dose/time in radiation therapy. Such treatment approaches and schedules have been developed for large tumors based on radiobiological modeling.
• Work on tumor targeting and delineation in radiation therapy has expanded to address fundamental questions in radiation oncology that affect radiation-therapy planning, particularly in stereotactic radiosurgery and imaging-based brachytherapy.
• Novel instrumentation for advanced radiation therapy planning and delivery methods in stereotactic therapy are a new area of research for the Department.

• Integrated Anatomical and Functional Tumor Imaging in Radiation Therapy Planning and Response Monitoring – Based on prior National Institutes of Health (NIH)-funded research on functional imaging in cervical cancer (Nina Mayr, MD, principal investigator), the predictive value of tumor perfusion and early tumor volumetric response had been established in the prior year. In 2007 this work expanded to incorporate non-imaging patient- and tumor-specific parameters in an effort to achieve an in-vivo multimodality predictor of ultimate therapy outcome that would be available early during cytotoxic cancer treatment. The interplay between the microenvironment within the tumor region (oxygenation/perfusion early during therapy) and beyond the tumor region (systemic oxygenation) has been identified as a factor influencing tumor control to cytotoxic therapy and cancer survival.
• Tumor Response Modeling and Multimodality Response Prediction Models – This research has focused on developing predictive tumor-response models based on the above results. Development of such predictive assays will bring scientists closer to devising individualized multimodality algorithms for personalized radiation medicine.
• The research focus on response modeling by Jian Wang, PhD, which builds on his pioneer work on theoretical radiobiological modeling studies of prostate cancer response, has expanded to explore kinetics of volumetric tumor response in cervical cancer and has been applied to radiosurgical concepts. In 2007, Wang presented a landmark concept of the Generalized Linear-Quadratic Formula for High-Dose- Rate Brachytherapy and Radiosurgery, which generalizes the model to various high dose-fraction modalities and guides principles of dose/fractionation for novel radiation therapy regimens, at the 2007 annual meeting of the American Society of Therapeutic Radiology and Oncology.
• Regimens of Hypo-Fractionation Stereotactic Radiation Therapy (HSRT) for Large Brain Tumor – With the Department’s adopted tomotherapy technique, HSRT for brain tumors has entered clinical practice. There is an urgent need for better understanding of effective and safe regimens for these new hypo-fractionation techniques, and published data on this approach is scarce. Based on clinical experience of gamma-knife stereotactic surgery for brain tumors and whole-brain radiation, Jian Wang, PhD, and colleagues developed HSRT regimens for large brain tumors using radiobiological models and presented their results at the 2007 annual meeting of the American Society of Therapeutic Radiology and Oncology.
• New results and concepts on tumor targeting and delineation in radiation therapy have addressed imaging-based brachytherapy, which has a direct impact on patient care by improving precision, decreasing therapy-related side effects and holding the potential to improve outcome in gynecologic cancer patients. Updated results on the optimal use of tumor imaging in radiation therapy for cervical cancer were presented at the 2007 annual meeting of the American Brachytherapy Society. The use of high-field strength MRI for improved radiation therapy planning has also been explored, and two presentations on 7 Tesla MRI in brain lesions were made at the 2007 annual meeting of the American Society of Therapeutic Radiology and Oncology.
• Novel instrumentation for advanced radiation therapy planning strategies and delivery methods developed in 2007 involve expanded computational methods of radiation therapy optimization, including design of more effective dose planning methods in stereotactic radiosurgery and radiotherapy.
• The Department made the largest number of scientific presentations from one institution in radiation oncology at the 2007 Annual Meeting of the Radiological Society of North America, which was attended by more than 60,000 people from around the world.