Health and Medical Physics Commons^™

Resilience And Reality: Exploring The Lived Experiences Of People Living With Hiv In Texas During The Covid-19 Pandemic – A Qualitative Study., Ahmed F. Alanazi

Social Work Dissertations - Archive

This study investigated the lived experiences of individuals living with HIV (PLWH) in the Dallas-Fort Worth (DFW) area of Texas during the COVID-19 pandemic, using an Interpretative Phenomenological Analysis (IPA) framework. The research examined the intersection of health, social dynamics, and psychological resilience among PLWH, who faced compounded vulnerabilities due to systemic inequities and the dual public health crises of HIV and COVID-19. Through semi-structured interviews with ten participants from diverse backgrounds, the study captured the profound impacts of disrupted healthcare systems, heightened stigma, and social isolation on this marginalized population. The findings reveal that the pandemic exacerbated existing inequities …

A Multiple X-Ray-Source Array (Mxa) System With A Planar Two-Dimensional Source Distribution For Digital Breast Tomosynthesis, Alejandro Sisniega, Andrew M Hernandez, Shadi A Shakeri, Elizabeth A Morris, John M Boone, Jeffrey H Siewerdsen, Paul R Schwoebel

Faculty, Staff and Student Publications

Background: Digital breast tomosynthesis (DBT) has outpaced digital mammography in clinical adoption in the United States; however, substantial technological limitations remain to image quality in DBT, including undersampling from a one-dimensional (1D) scan geometry, x-ray source motion during acquisition, and patient motion artifacts from long exam times.

Purpose: A thermionic cathode x-ray system employing two-dimensional (2D, planar) multiple x-ray-source arrays (MXA) is proposed to improve DBT image quality.

Methods: A 1D MXA, consisting of a linear array of thermionic cathodes was used to simulate a 2D MXA. The 1D MXA included 11 focal spots separated by a distance of Δd …

Promotion And Tenure For Medical Physicists Should Be Based On Article Specific Measures And Not On Journal Impact Factor, Samantha Hedrick, Jinzhong Yang, Yi Rong

Faculty, Staff and Student Publications

No abstract provided.

Interpreting The Biological Effects Of Protons As A Function Of Physical Quantity: Linear Energy Transfer Or Microdosimetric Lineal Energy Spectrum?, Fada Guan, Lawrence Bronk, Matthew Kerr, Yuting Li, Leslie A Braby, Mary Sobieski, Xiaochun Wang, Xiaodong Zhang, Clifford Stephan, David R Grosshans, Radhe Mohan

Faculty, Staff and Student Publications

The choice of appropriate physical quantities to characterize the biological effects of ionizing radiation has evolved over time coupled with advances in scientific understanding. The basic hypothesis in radiation dosimetry is that the energy deposited by ionizing radiation initiates all the consequences of exposure in a biological sample (e.g., DNA damage, reproductive cell death). Physical quantities defined to characterize energy deposition have included dose, a measure of the mean energy imparted per unit mass of the target, and linear energy transfer (LET), a measure of the mean energy deposition per unit distance that charged particles traverse in a medium. The …

Nanoscale Gold Nanoparticle (Gnp)-Laden Tumor Cell Model And Its Use For Estimation Of Intracellular Dose From Gnp-Induced Secondary Electrons, Sandun Jayarathna, Amrit Kaphle, Sunil Krishnan, Sang Hyun Cho

Faculty, Staff and Student Publications

Background: Gold nanoparticles (GNPs) accumulated within tumor cells have been shown to sensitize tumors to radiotherapy. From a physics point of view, the observed GNP-mediated radiosensitization is due to various downstream effects of the secondary electron (SE) production from internalized GNPs such as GNP-mediated dose enhancement. Over the years, numerous computational investigations on GNP-mediated dose enhancement/radiosensitization have been conducted. However, such investigations have relied mostly on simple cellular geometry models and/or artificial GNP distributions. Thus, it is at least desirable, if not necessary, to conduct further investigations using cellular geometry models that properly reflect realistic cell morphology as well as …

Automatic Vessel Attenuation Measurement For Quality Control Of Contrast-Enhanced Ct: Validation On The Portal Vein, Kevin Mccoy, Sujay Marisetty, Dominique Tan, Corey T Jensen, Jeffrey H Siewerdsen, Christine B Peterson, Moiz Ahmad

Faculty, Staff and Student Publications

Background: Adequate image enhancement of organs and blood vessels of interest is an important aspect of image quality in contrast-enhanced computed tomography (CT). There is a need for an objective method for evaluation of vessel contrast that can be automatically and systematically applied to large sets of CT exams.

Purpose: The purpose of this work was to develop a method to automatically segment and measure attenuation Hounsfield Unit (HU) in the portal vein (PV) in contrast-enhanced abdomen CT examinations.

Methods: Input CT images were processed by a vessel enhancing filter to determine candidate PV segmentations. Multiple machine learning (ML) classifiers …

Quantitative Evaluation Of 90y-Pet/Ct And 90y-Spect/Ct-Based Dosimetry Following Yttrium-90 Radioembolization, Srinivas Cheenu Kappadath, Eric Courtney Henry, Benjamin P Lopez, Armeen Mahvash

Faculty, Staff and Student Publications

Background: Following yttrium-90 radioembolization (90Y-RE), 90Y-PET/CT and 90Y-SPECT/CT imaging provide the means to calculate the voxelized absorbed dose distribution. Given the widespread use of the two imaging modalities and lack of well-established standardized dosimetry protocols for 90Y-RE, there is a clinical need to systematically investigate and evaluate differences in the performance of voxel-based dosimetry between 90Y-PET/CT and 90Y-SPECT/CT.

Purpose: To quantitatively analyze and compare 90Y-PET/CT and 90Y-SPECT/CT-based dosimetry following 90Y-RE.

Methods: 90Y-PET/CT and 90Y-SPECT/CT imaging was acquired for 35 patients following 90Y-RE with TheraSphere for the treatment of unresectable hepatocellular carcinoma. Dosimetry was performed using the local deposition method with …

Landmark-Based Auto-Contouring Of Clinical Target Volumes For Radiotherapy Of Nasopharyngeal Cancer, Carlos Sjogreen, Tucker J Netherton, Anna Lee, Moaaz Soliman, Skylar S Gay, Callistus Nguyen, Raymond Mumme, Ivan Vazquez, Dong Joo Rhee, Carlos E Cardenas, Mary K Martel, Beth M Beadle, Laurence Edward Court

Faculty, Staff and Student Publications

Background: The delineation of clinical target volumes (CTVs) for radiotherapy for nasopharyngeal cancer is complex and varies based on the location and extent of disease.

Purpose: The current study aimed to develop an auto-contouring solution following one protocol guidelines (NRG-HN001) that can be adjusted to meet other guidelines, such as RTOG-0225 and the 2018 International guidelines.

Methods: The study used 2-channel 3-dimensional U-Net and nnU-Net framework to auto-contour 27 normal structures in the head and neck (H&N) region that are used to define CTVs in the protocol. To define the CTV-Expansion (CTV1 and CTV2) and CTV-Overall (the outer envelope of …

Evaluating The Relationship Between Magnetic Resonance Image Quality Metrics And Deep Learning-Based Segmentation Accuracy Of Brain Tumors, Rajarajeswari Muthusivarajan, Adrian Celaya, Joshua P Yung, James P Long, Satish E Viswanath, Daniel S Marcus, Caroline Chung, David Fuentes

Faculty, Staff and Student Publications

Background: Magnetic resonance imaging (MRI) scans are known to suffer from a variety of acquisition artifacts as well as equipment-based variations that impact image appearance and segmentation performance. It is still unclear whether a direct relationship exists between magnetic resonance (MR) image quality metrics (IQMs) (e.g., signal-to-noise, contrast-to-noise) and segmentation accuracy.

Purpose: Deep learning (DL) approaches have shown significant promise for automated segmentation of brain tumors on MRI but depend on the quality of input training images. We sought to evaluate the relationship between IQMs of input training images and DL-based brain tumor segmentation accuracy toward developing more generalizable models …

Evaluating Automatically Generated Normal Tissue Contours For Safe Use In Head And Neck And Cervical Cancer Treatment Planning, Raphael Douglas, Adenike Olanrewaju, Raymond Mumme, Lifei Zhang, Beth M Beadle, Laurence Edward Court

Faculty, Staff and Student Publications

Purpose: Volumetric-modulated arc therapy (VMAT) is a widely accepted treatment method for head and neck (HN) and cervical cancers; however, creating contours and plan optimization for VMAT plans is a time-consuming process. Our group has created an automated treatment planning tool, the Radiation Planning Assistant (RPA), that uses deep learning models to generate organs at risk (OARs), planning structures and automates plan optimization. This study quantitatively evaluates the quality of contours generated by the RPA tool.

Methods: For patients with HN (54) and cervical (39) cancers, we retrospectively generated autoplans using the RPA. Autoplans were generated using deep-learning and RapidPlan …

Thyroid Cartilage Metastases From Prostate Cancer On 18f Psma Pet Ct: A Case Series, Poonamjeet Loyal, Samuel Gitau, Khalid Makhdomi

Imaging & Diagnostic Radiology, East Africa

Prostate cancer metastases to the thyroid cartilage is an extremely rare phenomenon. We report three cases of advanced prostate carcinoma with metastases to the thyroid cartilage identified on 18F prostate-specific membrane antigen-1007 (PSMA-1007) positron emission tomography (PET)/computed tomography (CT). The pathophysiology and possibility for under-reporting are also discussed. Prostate cancer metastases to the larynx should be considered in the differential diagnosis of thyroid cartilage lesions in patients with advanced prostate cancer and is associated with poor prognosis.

A Radiotherapy Community Data-Driven Approach To Determine Which Complexity Metrics Best Predict The Impact Of Atypical Tps Beam Modeling On Clinical Dose Calculation Accuracy, Fre'etta Mae Dayo Brooks, Mallory Carson Glenn, Victor Hernandez, Jordi Saez, Hunter Mehrens, Julianne Marie Pollard-Larkin, Rebecca Maureen Howell, Christine Burns Peterson, Christopher Lee Nelson, Catharine Helen Clark, Stephen Frasier Kry

Faculty, Staff and Student Publications

PURPOSE: To quantify the impact of treatment planning system beam model parameters, based on the actual spread in radiotherapy community data, on clinical treatment plans and determine which complexity metrics best describe the impact beam modeling errors have on dose accuracy.

METHODS: Ten beam modeling parameters for a Varian accelerator were modified in RayStation to match radiotherapy community data at the 2.5, 25, 50, 75, and 97.5 percentile levels. These modifications were evaluated on 25 patient cases, including prostate, non-small cell lung, H&N, brain, and mesothelioma, generating 1,000 plan perturbations. Differences in the mean planned dose to clinical target volumes …

Optimized Scoring Of End-To-End Dosimetry Audits For Passive Motion Management – A Simulation Study Using The Iroc Thorax Phantom, Alex Burton, Mathieu Gaudreault, Nicholas Hardcastle, Jessica Lye, Sabeena Beveridge, Stephen F Kry, Rick Franich

Faculty, Staff and Student Publications

Dosimetry audits for passive motion management require dynamically-acquired measurements in a moving phantom to be compared to statically calculated planned doses. This study aimed to characterise the relationship between planning and delivery errors, and the measured dose in the Imaging and Radiation Oncology Core (IROC) thorax phantom, to assess different audit scoring approaches. Treatment plans were created using a 4DCT scan of the IROC phantom, equipped with film and thermoluminescent dosimeters (TLDs). Plans were created on the average intensity projection from all bins. Three levels of aperture complexity were explored: dynamic conformal arcs (DCAT), low-, and high-complexity volumetric modulated arcs …

Post-Modeling Adjustments And Delivered Dose Verification Of The 6fff Beam Model Commissioned For The Monaco Treatment Planning System, Grant C. Debevec

LSU Master's Theses

External beam radiation therapy has been shown to be an effective treatment method for tumors and abnormalities of the spine and vertebral region. Treating the spine using a stereotactic body radiation therapy (SBRT) technique can reduce toxicity to the spinal cord. The 6 MV flattening filter free (6FFF) beam model is currently used to plan and calculate dose for SBRT treatment plans, and the treatment plans are delivered using a linear accelerator (LINAC).

The commissioned beam model represents an invariant component of a LINAC. For volumetric modulated arc therapy (VMAT) treatment plans, the multileaf collimator (MLC) positions are changing throughout …

The Theory Of X-Ray And Neutron Interferometry Using A Modulated Phase Grating, Hunter C. Meyer

LSU Master's Theses

Grating interferometry exploits wave interference to simultaneously image multiple physical properties of an object and can be performed using X-rays or neutrons. The modulated phase grating interferometer (MPGI) is a recently developed interferometry system that allows for the simultaneous acquisition of attenuation, differential-phase contrast, and dark-field images, which highlight X-ray or neutron absorption, refraction, and small angle scatter, respectively. This interferometry system uses a single grating, with a relatively high period envelope function, to produce interference fringes that can be directly resolved by standard high resolution detectors. The grating is sampled at a relatively low pitch, to meet coherence requirements …

The Role Of Sport For Adolescents: The Effect Of Sport Participation As A Unique Form Of Physical Activity On Mental Health And Overall Subjective Well-Being During Adolescence, Caleb M. Rogers

Senior Theses

Well-being is an extremely multifaceted domain, as there are numerous factors that contribute to one’s way of life. Objective well-being focuses primarily on material factors such as access to food, housing, and a steady household income. Although these factors play a large role, it is important to analyze well-being from the perspective of the individual. Subjective well-being focuses on how one perceives one's own well-being. Physical activity has been well established as one factor associated with improvements within this domain for adolescents. This project investigates the role of one specific form of physical activity during adolescence: sport. The general assumption …

Automatic End-To-End Vmat Treatment Planning For Rectal Cancers, Kai Huang, Christine Chung, Ethan B Ludmir, Lifei Zhang, Constance A Owens, Jean Gumma-De La Vega, Jack Duryea, Yao Zhao, Xinru Chen, David Fuentes, Carlos E Cardenas, Tina Marie Briere, Sam Beddar, Laurence E Court, Prajnan Das

Faculty, Staff and Student Publications

BACKGROUND: The treatment planning process from segmentation to producing a deliverable plan is time-consuming and labor-intensive. Existing solutions automate the segmentation and planning processes individually. The feasibility of combining auto-segmentation and auto-planning for volumetric modulated arc therapy (VMAT) for rectal cancers in an end-to-end process is not clear.

PURPOSE: To create and clinically evaluate a complete end-to-end process for auto-segmentation and auto-planning of VMAT for rectal cancer requiring only the gross tumor volume contour and a CT scan as inputs.

METHODS: Patient scans and data were retrospectively selected from our institutional records for patients treated for malignant neoplasm of the …

The Value Of Global Collaborations, Chris Trauernicht, Laurence Court

Faculty, Staff and Student Publications

No abstract provided.

Correcting Ct Misregistration In Data-Driven Gated (Ddg) Pet With Pet Self-Gating And Deformable Image Registration, Peng Sun, M Allan Thomas, Dershan Luo, Tinsu Pan

Faculty, Staff and Student Publications

Background: Misregistration between CT and PET data can result in mis-localization and inaccurate quantification of functional uptake in whole body PET/CT imaging. This problem is exacerbated when an abnormal inspiration occurs during the free-breathing helical CT (FB CT) used for attenuation correction of PET data. In data-driven gated (DDG) PET, the data selected for reconstruction is typically derived from the end-expiration (EE) phase of the breathing cycle, making this potential issue worse.

Purpose: The objective of this study is to develop a deformable image registration (DIR)-based respiratory motion model to improve the registration and quantification between misregistered FB CT and …

Girth-Based Administered Activity For Pediatric 99mtc-Dmsa Spect, Ye Li, Justin L Brown, Jingyan Xu, Junyu Chen, Michael Ghaly, Monet Dugan, Xinhua Cao, Yong Du, Frederic H Fahey, Wesley Bolch, George Sgouros, Eric C Frey

Faculty, Staff and Student Publications

Background: Pediatric molecular imaging requires a balance between administering an activity that will yield sufficient diagnostic image quality while maintaining patient radiation exposure at acceptable levels. In current clinical practice, this balance is arrived at by the current North American Consensus Guidelines in which patient weight is used to recommend the administered activity (AA).

Purpose: We have previously demonstrated that girth (waist circumference at the level of the kidneys) is better at equalizing image quality than patient weight for pediatric Tc-99m DMSA renal function imaging. However, the correlation between image quality (IQ), AA, and patient girth has not been rigorously …