Session Y06: Medical Physics and Radiation

Live

Precise knowledge of the radiation emitted by unstable nuclei is needed in both the production and use of medical isotopes. The decay of many isotopes which now find use in nuclear medicine were last studied more than 30 years ago using very primitive detection setups and without a particular function in mind. Since then, the field of gamma-ray spectroscopy has made tremendous advances, now often using multiple high-purity germanium (HPGe) detectors employing Compton-suppression technology and high efficiency gamma-gamma coincidence spectroscopy. In the present work, we make use of these new techniques to significantly improve the knowledge of decay schemes of several isotopes with applied uses. Sources of isotopes were produced and purified at the University of Wisconsin then shipped to Argonne National Laboratory where high-precision, gamma-ray measurements were performed using the state-of-the-art gamma-ray spectrometer, Gammasphere, consisting of 100 Compton-suppressed HPGe detectors. An overview of results on a number of isotopes will be presented including studies of emerging PET imaging isotopes, 72As and 61Cu. New decay schemes will be presented and their impact on the use of isotope discussed.   

Live

This talk continues the presentation at APS March Meeting 2019 and APS April Meeting 2019. In this part of the project the first submodel is presented; The information processing from teeth to the nerves. Information processing is modeled via p-waves passing through the tooth layers enamel and dentin. Odontoblasts located in the liquid in the tubules of the tooth dentin layer perform finally the transformation into electrical information (an electrical signal) that passes along nerves.   

Live

Radium-224 decays by alpha emission with a half-life of 3.631(2) d, approaching secular equilibrium with its progeny approximately 6 d after separation from its $^{\mathrm{228}}$Th parent. Like some other alpha-emitting nuclides, $^{\mathrm{224}}$Ra is currently being investigated for applications in molecular radiotherapy of various forms of cancer. In such applications, understanding dose-response relationships requires accurate activity assays. We address some challenges in assaying a nuclide approaching or at equilibrium with short-lived progeny, with focus on nuclear data considerations. Half-lives govern the relative abundances of the progeny, while the gamma-ray emission probabilities underlie common clinical activity measurements. We treat the $\gamma_{\mathrm{1,0}}$(Rn) (241 keV) emission as both a point of reference for a bilateral intercomparison and, then, as a measurand. We assess equivalence between the USA and UK standards for $^{\mathrm{224}}$Ra activity and report new values for the $^{\mathrm{224}}$Ra half-life and $\gamma_{\mathrm{1,0}}$(Rn) emission probability.   

Live

Radiation therapy is one of the most convenient techniques used for cancer treatment. Radiation therapy can harm both healthy and cancerous cells. The main aim of radiation therapy is to enhance the radiation effect on cancer cells while minimizing effects on near healthy cells. Gold nanoparticles are versatile materials for biomedical applications because they are relatively inert, stable and easily synthesized, which lead to the high absorption coefficient. The objective of this experiment is to investigate how the size of gold nanoparticles in radiation therapy affects cancer cell survival. This experiment used JC mouse breast cancer cells for an in vitro experiment, which were treated with gold nanoparticles and X-rays of varying sizes. The cells were treated with the same mass concentrations (0.167 µg/mL) of the different sizes of the gold nanoparticles (5, 15, 30, 50 and 100 nm) with multiple radiation energies (100, 250 and 350 kVp). The survival assays showed the radiation effect on cancer cell survival comparing the treatment sizes of gold nanoparticles. The results indicated that each size treatment of gold nanoparticles except for 5 nm showed significant decreases in cancer cell survival. The 50 nm of gold nanoparticles treatment had the strongest radio-sensitization   

On Demand

The calculations of permanent Whole Person Impairment (WPI) Ratings for patients who have sustained injuries or illness are crucial for determining benefits and liability. WPI Ratings vary from 0{\%} (normal) to 100{\%} (totally nonfunctional). WPI Ratings are difficult to calculate and require specialized knowledge and an exhaustively detailed patient medical exam. This research investigates the validity of replacing this time-consuming, costly medical exam (the classical method) with an algorithm that requires relatively fewer data points during the exam (the faster method). We found that, for a large sample of patients, the WPI Ratings generated by the faster method were surprisingly similar to the slower classical method. The average of the difference between the two calculated WPI Ratings was 0.1{\%}, and the standard deviation of the difference was less than 3{\%}. This is far less than that allowed by administrative rulesets used to adjudicate injury claims. These results may have major consequences for the calculation of WPI Ratings, medical providers, insurance carriers, patients, and other stakeholders in distributing and receiving injury benefits. This work results from an interdisciplinary medical and physics collaboration.   

On Demand

Very high energy electrons (VHEEs) is one of the promising modalities proposed for next generation of medical accelerators. Here, we study dosimetric properties of these electron beams using Geant4 Monte Carlo simulation. VHEE beams were simulated at the mean energies of 50-100MeV with 15{\%} deviation. A water phantom was irradiated with single and pair orthogonal fields using square planar beams at different SSDs. Calculation was performed with grid spacing resolution of 1mm for 10$^{\mathrm{7}}$ particles. Our results show that VHEE beams can deliver adequate dose to both shallow and deep-seated targets with acceptable lateral dose spread. Increase in penumbra at SSDs up to 50cm is small, while it is considerable at 100cm SSD. Beam obliquity effects are negligible for VHEE beams. At 100MeV, the majority of bremsstrahlung photons (83{\%}) has energies less than 6MeV. This alleviates concern for room shielding. Dosimetry properties of VHEE beams suggest similar dose coverage of both shallow and deep-seated targets with fewer orthogonal beams and lower dose to normal tissue compared to photon beams. The limited range of the electron dose deposition reduces the need of surrounding-beam orientations and entices consideration of alternate delivery arrangements.   

Imaging and Localization of Radiological Sources by Luminescence Dosimetry

Luminescence dosimetry has long been a mainstay in the realms of personnel and accident dosimetry, however recent advances have demonstrated these new techniques may also have a place in nuclear nonproliferation and treaty verification. Previous research has shown that using a combination of optically stimulated luminescence (OSL) and thermoluminescence (TL) allows for the assay of nuclear material with surprising resolution. Likewise, doses to surface mount resistors (SMRs), like those found in common personal electronics, have been measured down to background levels using OSL. In the present work, a two-dimensional array of commercially available optically stimulated luminescence dosimetry was used to image and localize the position of a weapons grade plutonium (WGPu) source after removal of the source material. This work illustrates how luminescence dosimetry may be able to reconstruct events, involving radiological source material, occurring arbitrarily far in the past.