Radiation therapy uses high energy, penetrating radiation to destroy or stop development of cancer cells, a process which also causes damage to surrounding healthy tissue. Conventional radiation treatment is created using a planning software that generates a plan based on the patient’s internal geometry (position of the target cancer cells and surrounding organs), and this plan remains unchanged for the whole treatment process. The ability to more closely and uniformly target the cancer cells, which includes the ability to map and adjust to changes in the internal geometry between and during treatments, would help to minimize impact to surrounding healthy tissue. A new form of radiation therapy known as adaptive radiation therapy (ART) may hold the answer. This modality allows for modifications of the original treatment plan before each treatment fraction, while the patient is in the treatment room. However, due to time constraints, only a selected set of treatment parameters of the original plan can be modified, which limits the full potential of this technique. Ante Mestrovic is exploring the development of a method for rapid, complete treatment plan modification that characterizes the patient’s internal geometry using three-dimensional ray tracing. His goal is to develop a time-efficient way of adapting treatment plans immediately before each treatment session. This would provide for more precise targeting of cancer cells, helping to reduce radiation exposure to healthy tissue and surrounding organs and contributing to a better outcome for patients undergoing radiation therapy.