Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session A15: Physics in Medicine: Innovations in Modeling and TherapyLive
|
Hide Abstracts |
Sponsoring Units: GMED Chair: Matija Milanic |
Monday, March 15, 2021 8:00AM - 8:12AM Live |
A15.00001: Acoustically detonated microbubbles using low frequency insonation: mechanism for low energy mechanical ablation Tali Ilovitsh, Mike Bismuth Noninvasive ultrasound surgery can be achieved using focused ultrasound to locally affect the targeted site without damaging intervening tissues. Histotripsy uses short and intense acoustic pulses to destroy the tissue via a purely mechanical effect. Here we show that coupled with low-frequency excitation, targeted microbubbles serve as mechanical therapeutic warheads that trigger potent mechanical effects at specific locations under the direction of focused ultrasound. Upon low frequency excitation (below 500 kHz), high amplitude microbubbles oscillations occur at substantially lower pressures as compared to higher MHz ultrasonic frequencies. Here, we used these enhanced oscillations to achieve cells and tissue fractionation at low pressures of hundreds of kilopascals (an order of magnitude less than the pressures used in standard histotripsy). We demonstrate these capabilities using two low frequencies of 250 kHz and 80 kHz in vitro, in cell cultures, and in ex vivo tissue. Specifically, we compare the oscillations of free vs. targeted microbubbles and show that cell-targeted microbubbles can effectively destroy cancer cells at low ultrasonic pressures. This technology provides a unique theranostic ultrasound-based technology for low energy mechanical ablation of tissues. |
Monday, March 15, 2021 8:12AM - 8:24AM Live |
A15.00002: Efficient N95 Mask Disinfection Method with Photon Up-and-Down Conversion Materials Emma Xu, Changhwan Lee, Stefanie Pritzl, Theobald Lohmueller, Bruce Cohen, Emory Chan, P. James Schuck The covid-19 pandemic poses many challenging problems to physicists. For example, what are the best virus disinfection methods? Recent research has shown that under a 254nm UVC lamp, N95 masks can be disinfected and reused. However, 254 nm irradiation is not very efficient as UV photons bounce inside the mask and cause unnecessary photodegradation to the mask polymers. As an alternative approach, we propose embedding upconverting nanoparticles (UCNPs) and photon down-conversion materials inside the mask. By illuminating the mask with near infrared (NIR) light that can more efficiently penetrate deep into the mask layers, the UCNPs will convert NIR light into UV at the mask fiber surfaces for virus disinfection, while the photon down-conversion material within the fibers will convert the UV back to NIR before it has a chance to cause irreversible damages. One further advantage of this method is that we have now shown that certain UCNPs can emit in the far UVC region (200nm). Unlike 254nm UV light, which is detrimental to human skin and eyes, the shorter wavelength of far UVC is unable to penetrate through even the top layer of skin cells. Our disinfection method thus holds potential for active disinfection, that is, disinfecting the surfaces of objects during human presence. |
Monday, March 15, 2021 8:24AM - 8:36AM Live |
A15.00003: Disassembling Blood Clots and Improving Blood Oxygenation With Magnetic Field To Save Covid-19 Patients Rongjia Tao With the fight against coronavirus pandemic, we have learned that the blood clotting caused by Covid-19 is the main issue making this disease much more server than other flu or pneumonia. An alarming number of COVID-19 patients developed blood clots that trigger heart attack, stroke or other disasters. Autopsies found blood clots in every organ of coronavirus victims. Currently blood thinner medicines are used to reduce the blood clot formation in the sickest Covid-19 patients. Unfortunately, all blood thinners increase the risk of bleeding, serious, or even life threatening for these patients. Many of them were not saved by these medicines. Here we propose a new method to treat Covid-19 patients with thrombosis: applying a strong magnetic field along the patients’ arm. When the blood clots come to the magnetic field with blood circulation, the red blood cells are polarized. The magnetic dipolar interaction will force them to break the biding. The blood clots are thus disassembled and the blood oxygen function is improved. In addition, the blood viscosity along the flow direction is reduced, turbulence in blood circulation will be suppressed, and the incidence of blood clots causing heart attack and stroke can be prevented. Most coronavirus patients with thrombosis can be saved. |
Monday, March 15, 2021 8:36AM - 8:48AM Live |
A15.00004: A semi-empirical approach for independent dose calculations for complex teletherapy treatments Luciano Rivetti, Dario Sanz The need for high accuracy of physical simulations in radiation therapy has put aside more simplistic methods for dose calculation. However, the complexity and the computation times make simulations less practical for an independent verification of dose calculation. In this work we describe a novel algorithm which allows assessment of the dose in a specific point of the treatment plan. We developed a relationship that models the contribution to the final dose from two components: dose delivered by charge particles which are the result of the first interaction of radiation with the environment, and dose delivered by charge particles which are the result of scattered radiation. To validate our algorithm, we compared it with a highly-accurate computerized treatment planning system (TPS) and with dose measurements of 45 challenging treatment plans. We found that the relative differences against both, TPS and measurements, were less than 4% except for breast cancer plans, where differences were higher than 10% due to the irregularity of radiation fields. In conclusion, we developed a novel and robust method for dose calculation which has easy application and provide sufficient accuracy and dose interpretability for independent verification of dose calculation in radiation therapy. |
Monday, March 15, 2021 8:48AM - 9:00AM Live |
A15.00005: Evaluation of probabilistic radiotherapy planning in prostate cancer Peter Ferjancic, Uulke A. v.d. Heide, Robert Jeraj External beam radiation therapy (RT) is one of the leading modalities for treating cancer. Current clinical RT planning guidelines were established in 1993 and account for uncertainties using target volume expansion by geometric margins. This approach is simple to use but has several limitations and oversimplifies complex processes that are not linear in nature. |
Monday, March 15, 2021 9:00AM - 9:12AM Live |
A15.00006: An Ising/Potts Model Approach to Predicting Pathogen Case Fatality Rate and Vaccine Efficacy Based on Structural Motifs Robert A. Makin III, Steven Durbin Dating to the work of Bragg and Williams in the 1930s, characterizing system disorder with a single numerical value has proven to be an effective approach to predicting key properties. We demonstrate that it is possible to extend the concept of a Bragg-Williams order parameter (S) to pathogenic systems such as viruses and bacteria by examining the protein arrangement on the particle's outer surface. Underlying the methodology is the concept of structural motifs, which describe the nearest neighbor environment of each protein. For a fully ordered surface (S=1), the number of distinct motifs is limited and purely a function of the number of different proteins. Towards the other extreme (S=0), additional motifs become allowed, with the type and number of each dictated by S. A linear relationship between Case Fatality Rate and S2 is obtained through Ising/Potts type models where each protein is represented by a distinct spin, and confirmed with experimental data across multiple viral families. Additionally, there is a robust correlation between vaccine efficacy and the order parameter difference between vaccine and corresponding pathogen. |
Monday, March 15, 2021 9:12AM - 9:24AM Live |
A15.00007: A Monte Carlo Dose Verification Model for the Small Fields with 6FFF and 10FFF Energy Beams of the Varian True Beam (EDGE) Radiosurgery System Taindra Neupane, Ryan Stevens, Dr. Charles Shang, Dr. Wazir Muhammad, Theodora Leventouri The measured dosimetry uncertainties in our clinical cases treated with diminutive static MLC fields of 10MV FFF arc beams in Stereotactic Radiosurgery have suggested a possible cause of MLC geometric uncertainties. To further investigate this with various MLC displacements, we created a Monte Carlo (MC) dose model for both 6FFF and 10FFF beams of Varian EDGE Clinac system using the EGSnrc MC program. 10-30 million incident particles were simulated to validate the MC model w/o MLC by using the phase space files provided by the Varian systems. The input parameters varied during the MC simulations were the number of incident particles, directional Bremsstrahlung splitting, range rejection, particle splitting and voxel size to reduce the dose uncertainty and optimize the efficiency. Preliminary MC dose simulations resulted dose uncertainties < 5% for 10x10, 5x5 cm2 open fields with 6FFF and 10FFF energy beams at 100cm SSD, d=dmax as well as 95cm SSD, d=5cm water phantom set ups. Dose uncertainty of <4% was obtained for the reference MLC field 5.0x5.0 cm2 and the test smallest field 0.5x0.5cm2 at 95 cm SSD, d=5cm water phantom set up. Comparison of the MC dose model against the Eclipse TPS as well as the measurements by SRS Mapcheck have shown a satisfactory initial validation score. |
Monday, March 15, 2021 9:24AM - 9:36AM Live |
A15.00008: Mathematical Models for Living Forms in Medical Physics
Submodel 2: Information Coding and Information Processing through Nerves Christina Pospisil This talk continues the presentations Mathematical Models for Living Forms in Medical Physics and Mathematical Models for Living Forms in Medical Physics Submodel 1: The information processing from teeth to Nerves from the APS March Meetings 2019, 2020 (the APS March Meeting 2020 got canceled because of Covid-19), the second presentation was given at the APS April Meeting 2020 Conference. The first two presentations were dedicated to the project survey and 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. The third part of the project: Submodel 2: Information Coding and Information Processing through Nerves models the information coding and the information processing through the nerves. The information of an entity hitting/touching a tooth is coded as electrical information unit, which is further processed in the living system. |
Monday, March 15, 2021 9:36AM - 9:48AM Live |
A15.00009: PG production yield enhancement for facilitating in-vivo proton beam range verification Panagiota Galanakou, Theodora Leventouri, Dr. Wazir Muhammad Regardless of the Prompt Gamma (PG) technique being used to monitor the range of proton beam in vivo, the low PG statistics detected entangle the efficiency of their clinical implementation. We propose a new technique for PG production yield enhancement by inducing a non-radioactive element in the tumor area. This would potentially optimize the detection of the PG characteristic peaks of 4.44 MeV and 6.13 MeV resulting from 12C* and 16O* de-excitations respectively, and help in proton range verification in-vivo. The elements tested were19F, 17O,12C, and 1H. We simulated via the Tool for Particle Simulations (TOPAS) Monte Carlo (MC) package, the interaction of 75 MeV incident proton beam in a concentric cylindrical geometry; the outer cylinder was filled with water and the inner cylinder was filled with water and 0.01%-25% fraction in weight of the candidate elements. We identified the PG characteristic peaks in the spectrum, and then we assessed the PG enhancement for the different material concentrations. All tested elements led to a PG production yield enhancement by 15-16% and up to 4% for the 4.44 MeV and 6.15 MeV PG peak accordingly. Simulations with different materials and assessment of probable toxicity induced from the enhancers to the organ at risks are in progress. |
Monday, March 15, 2021 9:48AM - 10:00AM On Demand |
A15.00010: Operating Procedures for COVID-19 in a Nuclear Medicine Department María Margarita López Titla, Rafael Jesús Martínez Portillo, Carlos Salvador Quiroz Navarro, Ernesto Ramirez Nieto The COVID-19 is a highly transmittable viral disease. It has placed significant challenges on health-care systems whether in the preparation, response, or recovery phase of the pandemic. Nuclear Medicine facilities had to rapidly adjust their standard operating procedures to cope with the pandemic cases and deliver their services. This was done with local guidance, resources available and following the International Atomic Energy Agency (IAEA) recommendations. We implemented contingency procedures that included: the use of personal protective equipment, effective patient flow (screening triage and targeted referral), apply all standard radiation protection and optimization principles. In case the hybrid study involves a CT of the chest, it was imperative to look for incidental COVID-19, if incidental findings were detected it was reported to the clinician to triaged the patient correctly. All non-urgent nuclear cardiology studies were postponed because COVID-19 is associated with increased risks in patients with cardiovascular disease. Myocardial perfusion studies for ischemic heart disease were triaged as “must be performed using precautions”. The number of our nuclear medicine studies decreased in 50% in April 2020. We could detect incidentally one case of COVID-19. |
Monday, March 15, 2021 10:00AM - 10:12AM On Demand |
A15.00011: Cold atmospheric plasma is a novel modality to combat chemoresistance in cancer cells Milad Rasouli, Elaheh Amini, Kostya (Ken) Ostrikov The current standard therapy of ovarian cancer is the combination of surgery and multiagent chemotherapy. Cancer drug resistance, in particular, acquired resistance, leading to therapeutic failure in the treatment of ovarian cancer treatment. Today, Cold atmospheric plasmas and plasma stimulated liquid are currently gaining increasing attention for oncotheraphy. Plasma contains chemical and physical agents and plasma treatment is transferring these agents to the target. Here, we report the effect of plasma as a novel technology alone and in combination with carboplatin for cisplatin resistance ovarian cells. To this end, the human ovarian cancer cell line (SKOV-3) cell line was cultured in physiological conditions and was seeded in a microplate. SKOV-3 cell lines were exposed to different plasma treatment conditions. Also, the combination treatment of plasma and carboplatin were conducted. Cell viability assay was performed to analyze cell death. Our result indicates plasma can destroy carboplatin resistance. Besides, plasma resensitized cisplatin resistance ovarian cells to chemotherapeutic agents. Our findings revealed plasma therapy could be important for future ovarian cancer treatment. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700