Medical Physics Seminar – Monday, December 13, 2010
Confidence-Weighted Treatment Planning and Delivery: A New Paradigm in Radiotherapy
Jatinder R. Palta, Ph.D., FAAPM (guest of Dr. Larry DeWerd)
Professor & Physics Residency, Program Director, University of Florida, College of Medicine, Gainesville, FL USA
The uncertainties in dose delivered to a patient arise from each step of the overall process of radiation therapy, which starts with image acquisition and ends with the dose delivery. The enhanced capabilities and functionalities of 3D RTP systems present a challenge for radiation therapy staff to maintain the quality, safety, and reliability of radiotherapy without resorting to extensive efforts in quality assurance (QA). Increased complexity of advanced technologies is inevitably associated with larger possible uncertainties, which can potentially result in unfavorable clinical consequences. This has been addressed by the development of patient specific QA; a process that is onerous, resource intensive, and not comprehensive. There are well documented clinical cases in which even a detailed QA procedure is unable to resolve large discrepancies between measured and calculated dose distributions. This observation can only be attributed to a complex interplay of uncertainties in the treatment planning and delivery process that are not accounted for in the RT process. We have developed an analytical model that incorporates all clinically significant dosimetric and spatial uncertainties in IMRT and a priori predicts overall uncertainty associated with any IMRT treatment plan. The ability to accurately predict these discrepancies at the time of the planning allows clinicians to objectively evaluate each IMRT plan and discard plans that have potentially large uncertainties. Furthermore, the minimization of overall uncertainty in treatment planning can be used as a critical element of IMRT multi-criteria optimization in the future. In summary, this analytical model has the potential to increase the safety and efficacy of IMRT, while at the same time, minimize the effort expended in time-consuming and onerous patient specific QA measurements.
Learning Objectives:
• Understand the sources of uncertainties in IMRT planning and delivery
• Learn to evaluate the impact of spatial and dosimetric uncertainties in the IMRT process.