Uncertainties in Adaptive Radiation Therapy

Date(s) - 04/12/2012
12:30 pm - 2:30 pm

Jason Pukala, BME Medical Physics PhD Student

Adaptive radiation therapy (ART) may be defined as “a radiation treatment process where the treatment plan can be modified using a systematic feedback of measurements.”  Currently, treatment planning for radiotherapy assumes that the treatment parameters, including patient anatomy and positioning, will not vary over therapy course.  However, many of the parameters do change resulting in a delivered dose that does not equal the planned dose.  Adequate assessment of the delivered dose and the adaptation of a treatment plan to mitigate negative dosimetric variations is the goal of ART as described in this document.  The assessment of the delivered dose is required to make sound treatment decisions and acts as a set of measurements that are “fed-back” into the radiotherapy process.  One common way to obtain these measurements is through the use of repeated volumetric patient imaging and deformable image registration (DIR).  Repeated volumetric imaging provides a database of images that may be used for dose recalculations based on the changing patient anatomy.  DIR provides a means to auto-segment subsequent images according to the contours defined on the planning image set as well as accumulate the delivered dose over a treatment course.  As with other techniques used in radiation therapy, those listed above have inherent limitations that lead to imperfect results.  Therefore, to evaluate the delivered dose with confidence, the uncertainties of these tools must be understood and quantified.  This investigation proposes to use dose recalculation software and novel deformation analysis approaches to quantify the dosimetric uncertainties of these tools and create clinically-useful applications.