Medical Physics Seminar – Monday, April 13, 2020
Split-filter dual-energy CT: investigation of tumor visibility, spectral separation, and dose allocation
Lianna DiMaso (student of Larry DeWerd and Jessica Miller)
Pancreatic and liver cancer are the fourth and fifth causes of cancer-related deaths in the United States. Unfortunately, delineating pancreas and liver tumors using conventional single-energy CT can be a challenge because these tumors have poor innate contrast with surrounding healthy tissue, which makes it hard to accurately treat the tumor while sparing healthy tissue during radiation therapy. This work investigates the benefits of a novel split-filter dual-energy CT (DECT) system to improve tumor segmentation in patients with pancreatic and liver cancer for radiation therapy applications. Split-filter DECT is a single source DECT modality that has recently been implemented for clinical use as a cost-effective additive feature to the Siemens SOMATOM Definition Edge CT Scanner and is referred to as TwinBeam. TwinBeam is operated with a 120 kVp x-ray source and a split filter made of gold and tin. Some other DECT modalities include dual-source, sequential scan, and fast kVp-switching, which instead are operated with high tube potential of 140 kVp. This work also investigates the impact of peak tube voltage on split-filter DECT through the quantification of spectral separation and dose allocation, as the accuracy and quality of virtual DECT images depend on these two parameters.
Ultrasound, Atherosclerosis, and Stroke Risk: A Quantitative Approach
Catherine Steffel (student of Tomy Varghese and Carol Mitchell)
Stroke is the fifth leading cause of death in the United States and the second leading cause of death worldwide. Throughout my PhD, I have worked to improve the ways that we can noninvasively and inexpensively see the atherosclerotic plaques that cause some of these strokes and other harmful health events. My ultimate goal is to give physicians an inside look at which plaques are vulnerable, helping them identify individuals who are more likely to have a stroke years before an adverse health event occurs. During this talk, I will discuss the results of our in-vivo and ex-vivo ultrasound imaging studies and my path through the Medical Physics PhD at UW-Madison.