Seminar

Medical Physics Seminar – Monday, April 1, 2019

Application of NIST-traceable Dosimetry Methods in Radiobiology

speaker

Natalie Viscariello (student of Dr. Larry DeWerd)
Research Assistant, Department of Medical Physics, UW-School of Medicine & Public Health, Madison, WI - USA

In the past decade, the reproducibility of preclinical radiobiology research has been called into question. One major limitation for consistency across institutions is the lack of defined dose measurement techniques for biology researchers, leading to limited dosimetry details and reporting. With the advent of irradiators that aim to mimic human treatments (e.g. the Small Animal Radiation Research Platform –SARRP), investigation into the accuracy of machine’s output is crucial. Measurement of dose in this energy range and in these irradiators is complicated, as kilovoltage dosimetry protocols are based on air-kerma standards, not dose to water. In addition, detectors can exhibit large changes in response with energy. Using both measurement and Monte Carlo methods, the application of currently existing kilovoltage dosimetry protocols was investigated for an XRad 320 x-ray irradiator and the SARRP. Modifications for non-reference conditions, including mouse phantom dose verification measurements, were determined.


Development of an Optical Device that Measures Hemoglobin Oxygen Saturation in Tissue and its Application to Improve Radiotherapy

speaker

Leonard Che Fru (student of Dr. Larry DeWerd)
Research Assistant, Department of Medical Physics, UW-School of Medicine & Public Health, Madison, WI - USA

Understanding the dynamic nature of tumor hypoxia is vital for cancer therapy. The presence of oxygen within a tumor during radiation therapy increases the likelihood of local control. We developed a novel interstitial diffuse optical probe to make real-time measurements of blood volume fraction and hemoglobin oxygen saturation within a tumor at high temporal resolution. This device was initially characterized and benchmarked using a custom vessel designed to control hemoglobin oxygen saturation and blood volume in a solution of blood with different concentrations of an oxygen scavenger, tetrakis (hydroxymethyl) phosphonium chloride. The optical device was found to consistently monitor the changes in oxygen saturation and these changes correlated to the concentration of the oxygen scavenger added. In near-simultaneous measurements of blood volume and oxygen saturation in tumor-bearing mice, the changes in blood volume and oxygen saturation measured with the interstitial diffuse optical probe were benchmarked against photoacoustic imaging system to track and compare temporal dynamics of oxygen saturation and blood volume in a patient-derived xenograft model of hypopharyngeal carcinoma. Positive correlations between our device and photoacoustic imaging in measuring blood volume and oxygen saturation were seen.


Location: 1325 HSLC (Health Sciences Learning Center), 750 Highland Ave., Madison, WI 53705 - USA

Time: 4:00pm-5:00pm