SU‐E‐J‐168: Proton Radiography for Pediatric, T‐Spine and Lung Malignancies; Development and Enhancement of a Proton Imaging Technique

Purpose: Proton radiography (PR) was investigated for daily set up prior to proton radiation treatment, which would provide improved imaging capabilities along with reduced radiation dose to pediatric, lung and T‐spine tumors. Pediatric patients are more susceptible to radiation induced malignancies and toxicities from therapeutic and diagnostic radiation. While, in the case of T‐spine and lung tumors, motion and lung heterogeneities can significantly reduce the benefit of using proton beam therapy. Methods: A group of 5 pediatric patients with 1) neuroblastoma, 2) spinal malignancy, or 3) thoracic tumor were used to evaluate proton radiography. In addition, 7 lung/T‐spine tumors were also used to evaluate the ability of proton radiography to allow real‐time tumor tracking, while the tumor is moving within the lung with the patient respiration. Proton radiographic images were generated using a Monte Carlo imaging tool, PR‐Imaging, developed at MGH. Results: Radiographic images of the lung tumors were generated with simulated PR‐Imaging using a scanned proton pencil beam (PBS) at 230MeV, 330MeV and 490MeV, and compared to diagnostic X‐ray digitally reconstructed radiographs (DRR). In addition, whole body PR‐Images of pediatrics was compared to conventional X‐ray radiographs. PR images with high resolution comparable to that of a diagnostic x‐ray were generated. The X‐ray portal images and the X‐ray radiographs present better edge detection, while lung tissue to soft tissue boundaries of the tumor were better distinguished in PR images. The PR‐imaging allows the oncologist and radiologist to change windowing level and tumor contrast level relative to soft tissue background. Conclusions: PR‐Imaging prior to therapy allows for high quality images that can provide information on range degradation of the proton therapy beam. PR‐Imaging during therapy allows for daily quality assurance and tumor tracking during radiation to guarantee that it has been appropriately treated with radiation.