Fifty-sixth annual meeting of the American association of physicists in medicine
SU-E-J-148: Evaluating Tumor Response with a Commercially Available Deformable Registration System
The purpose of this study is to present a method for evaluating the response to treatment using a commercially available deformable image registration software package (Velocity Medical Systems) and repeat PET/CT imaging. This technique can be used to identify volumes that are risk for tumor recurrence.
Response to treatment was evaluated using PET/CT images acquired prior-to and post-treatment for radiation therapy patients treated with concurrent chemotherapy. Velocity (Version 3.0.1) was used to deform the initial PET/CT to the post treatment PET/CT. The post-treatment PET images were then subtracted from the pre-treatment PET images. The resulting re-sampled image is a three-dimensional SUV difference map that shows pixels with increasing SUV values. SUV values increases greater than 2.5 in the post treatment images were identified for additional follow-up.
A total of 5 Lung patients were analyzed as part of this study. One lung patient in the cohort had an SUV increase of +3.28 that was identified using the SUV difference map. This volume of increased uptake was located outside the treatment field and adjacent to the 35 Gy isodose line. The remaining four patients all had SUV decreases inside the planning target volume, and no unexpected areas of increase outside the irradiated volumes. All five patients were analyzed using standard tools inside the Velocity application.
The response to treatment can easily be measured using serial PET/CT images and a commercially available deformable image registration. This provides both the radiation oncologists and medical oncologists with a quantitative assessment of their treatment to use in patient follow-up.