Medical Physics Seminar – Monday, February 11, 2013
Opportunities in Proton Therapy and Brachytherapy
Ryan Flynn, Ph.D.
Clinical Assistant Professor, Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, IA
In the last several years, the size and cost of intensity modulated proton therapy (IMPT) systems has dropped substantially, enabling the acquisition of such technology in single-room, non-academic settings. Given the progress in intensity modulated x-ray therapy delivery techniques over the last couple of decades, IMPT techniques, as opposed to conventional proton therapy techniques, are required in order for proton therapy dose distributions to be competitive with those of intensity modulated x-ray therapy. In this presentation, state-of-the-art proton therapy systems capable of delivering IMPT are reviewed, as are challenges associated with effective IMPT delivery. Such challenges include managing uncertainties associated with Bragg peak location inside the patient, image guidance, and minimizing the lateral penumbra of IMPT dose distributions.
The second part of the talk will focus on novel methods for intensity modulated brachytherapy. Electronic brachytherapy sources such as the Xoft AxxentTM can be partially shielded, enabling the delivery of dose distributions that are deliberately not radially symmetric about the source catheter. Such systems can be used to deliver dose distributions that are superior to conventional intracavitary brachytherapy, specifically for cervical and colorectal cancer. An interstitial rotating shield brachytherapy technique based on partially-shielded gadolinium-153 radiation sources is also introduced, which can substantially reduce doses to organs at risk for prostate cancer patients.