Other Medical Sciences Commons^™

Hepatocellular Carcinoma Image-Guided Intervention: Quantitative Characterization Of Reagents For Thermochemical Ablation, Emily A. Thompson

Dissertations & Theses (Open Access)

Thermochemical ablation (TCA) is a minimally invasive therapy under development for hepatocellular carcinoma, a leading cause of cancer death worldwide. TCA utilizes acid-base chemistry delivered simultaneously to induce local ablation when administered. When delivered via a mixing catheter placed directly into the tumor, acid (e.g., AcOH) and base (e.g., NaOH) react to completion at the catheter tip, producing the acetate salt, water, and releasing heat (Δ>50°C) in sufficient quantities to induce lethal osmotic and thermal stress in tumor cells. However, these two reagents are not distinguishable from tissues with noninvasive imaging modalities, which makes monitoring the delivery of TCA …

Advancement Of A 3d Computational Phantom And Its Age Scaling Methodologies For Retrospective Dose Reconstruction Studies, Aashish Gupta

Dissertations & Theses (Open Access)

We have used a 3D age-scalable computational phantom for over two decades for retrospective dose reconstruction studies of childhood cancer survivors (CCS) treated with 2D historic radiotherapy (RT). However, our phantom and its age scaling functions (ASF) must be updated so that it can be used in studies that include survivors treated with contemporary RT. We aimed to implement our phantom and its age scaling functions in DICOM format and determine the feasibility of applying our ASFs to accurately scale the whole-body CT-based anatomies.

In the implementation study, we developed Python scripts that model the phantom and ASFs in a …

Quantitative Magnetic Resonance Imaging For The Early Prediction Of Treatment Response In Triple Negative Breast Cancer, Benjamin C. Musall

Dissertations & Theses (Open Access)

Triple Negative Breast Cancer (TNBC) is an aggressive subtype of breast cancer which lacks upregulated hormone receptors. Because of this, it is not vulnerable to clinically available targeted therapies. When treated with standard of care neoadjuvant systemic therapy (NAST), TNBC only shows approximately a 40% rate of pathologic complete response (pCR). A biomarker which could predict TNBC response to NAST early during treatment would be useful, as it would allow for non-responders to be triaged to alternative therapies and potentially allow for the treatment of responders to be de-escalated.

Quantitative Magnetic Resonance Imaging (MRI) may be used to probe and …

Nuclear-Targeted Gold Nanoparticles Enhance The Effects Of Radiation Therapy With And Without Liposomal Delivery, Maureen Aliru

Dissertations & Theses (Open Access)

Less that 10% of pancreatic cancer patients are eligible for curative resection, and clinical trials evaluating chemoradiation in locally advanced patients with unresectable disease have been largely disappointing. New and creative therapeutic approaches are needed to address the unment need for treatment options. The objective of this thesis is to advance radiosensitization of treatment-resistant densely desmoplastic pancreatic cancer using nanoparticles to surmount biological barriers to effective particle distribution for DNA-targeting.

Clinical translation of radiosensitizing nanoparticles has stalled owing to technical challenges. Current strategies to use AuNPs for radiosensitization require large quantities of gold, kilovoltage x-rays, immediate irradiation after intravenous administration, …

Modeling Anatomic Changes For Adaptive Radiotherapy In Locally Advanced Lung Cancer Patient Population, James Alexander Kavanaugh

LSU Doctoral Dissertations

Anatomic changes occurring mid-treatment for patients undergoing radiation therapy for locally advanced lung cancer can degrade the quality of the intended treatment plan. These changes include tumor regression, geometric misalignment, and lung density changes (atelectasis and pleural effusion), and are visible on the daily 3D cone beam CT (CBCT). To maintain the intended treatment quality, adaptive radiotherapy (ART) can be employed to modify the treatment plan to account for these anatomic changes. However, the evaluation on when to adapt is currently completed manually by the treating clinicians, resulting in a subjective and inconsistent application. To address these limitations, a series …

Modeling Proton Relative Biological Effectiveness Using Monte Carlo Simulations Of Microdosimetry, Mark A. Newpower

Dissertations & Theses (Open Access)

Proton therapy is a radiotherapy modality that can offer a better physical dose distribution when compared to photon radiotherapy by taking advantage of the Bragg peak, a narrow region of rapid energy loss. Proton therapy is also known to offer an enhanced relative biological effectiveness (RBE) compared to photons. In the current clinical standard, RBE is fixed at 1.1 at all points along the proton beam, meaning protons are assumed to require 10% less dose than photons to achieve target coverage and organ at risk (OAR) sparing. However, there is mounting clinical evidence, and a significant number of in vitro …

Improved Target Coverage Of Spinal Metastases Through The Use Of Flattening Filter Free Beams, Laura Bennett

Dissertations & Theses (Open Access)

Of the patients that are diagnosed with metastatic disease, up to 40% will develop vertebral osseous metastases. These metastases tend to be located in close proximity to the spinal cord itself, making it difficult to achieve the recommended minimum dose of 14 Gy for single fraction SBRT or 21 Gy¹ for three fraction SBRT while maintaining acceptable doses to the cord and cauda equina. This proximity of the target to critical structures has the potential to compromise the efficacy of the radiation treatment plan in favor of reducing normal tissue dose, resulting in poor local control and tumor recurrence …

Investigation Of Stereotactic Body Radiation Therapy Delivery Accuracy On An Elekta Linear Accelerator, Addie Barron

LSU Master's Theses

Purpose: This work investigated the delivery accuracy of high-dose lung and spine stereotactic treatments delivered with the Elekta Infinity and Versa HD platforms. The accuracy of these platforms will be used for consideration in implementing a spine stereotactic radiosurgery (SSRS) program at Mary Bird Perkins Cancer Center.

Methods: A geometric phantom was used to perform Winston-Lutz type tests that assessed the relevant degrees of freedom (gantry, collimator, and couch) of the delivery system. A lung stereotactic body radiation therapy (SBRT) and spine SRS treatment plan were generated for use in end-to-end testing. Delivery accuracy was tested using a novel diode …

Benefit Of Intensity Modulated Bolus Electron Conformal Therapy For Post Mastectomy Chest Wall Irradiation, John Doiron

LSU Master's Theses

Purpose: The delivery of post-mastectomy radiotherapy (PMRT) with bolus electron conformal therapy (BECT) for patients with left-sided breast cancer can reduce second cancer complication probability (SCCP) compared to modern rotational intensity modulated x-ray (IMXT) techniques such as volumetric modulated arc therapy (VMAT) or Tomotherapy. However, rotational IMXT yields superior levels of dose homogeneity compared to BECT. This study investigates the use of intensity modulated (IM) BECT (IM-BECT) to improve dose homogeneity in the chest wall (CW) region of the PMRT planning target volume (PTV) abutted to parallel opposed IMXT tangents for the remaining PTV for a clinically-representative set of patients, …

Proposed Method For Measuring The Let Of Radiotherapeutic Particle Beams, Stephen D. Bello

Physics & Astronomy ETDs

The Bragg peak geometry of the depth dose distributions for hadrons allows for precise and effective dose delivery to tumors while sparing neighboring healthy tissue. Further, compared against other forms of radiotherapeutic treatments, such as electron beam therapy (EBT) or photons (x and \(\gamma\)-rays), hadrons create denser ionization events along the particle track, which induces irreparable damage to DNA, and thus are more effective at inactivating cancerous cells. The measurement of radiation's ability to inactivate cellular reproduction is the relative biological effectiveness (RBE). A quality related to the RBE that is a measurable physical property is the linear energy transfer …

Impact Testing Of Youth-Level Helmets Versus College-Level Helmets, Nicole Hermann

Industrial Technology and Packaging

With so many studies being conducted on professional football players regarding concussions and other related brain injuries, it’s amazing that such an important demographic has been missed. While NFL players are just as subjected to serious injuries as anyone else or even more so, it is important to remember that these players are outfitted, in most cases, with top-of-the-line equipment -- especially their helmets. If the focus is shifted to a younger demographic, youth football players in middle school and high school, the equipment is far less advanced and in a vast majority of cases, has been previously used by …

An Investigation Of Nurbs-Based Deformable Image Registration, Travis J. Jacobson

Theses and Dissertations

Deformable image registration (DIR) is an essential tool in medical image processing. It provides a means to combine image datasets, allowing for intra-subject, inter-subject, multi-modality, and multi-instance analysis, as well as motion detection and compensation. One of the most popular DIR algorithms models the displacement vector field (DVF) as B-splines, a sum of piecewise polynomials with coefficients that enable local shape control. B-splines have many advantageous properties in the context of DIR, but they often struggle to adequately model steep local gradients and discontinuities. This dissertation addresses that limitation by proposing the replacement of conventional B-splines with a generalized formulation …

Evaluation Of Polymer Gel Dosimeters For Measurements Of Dose And Let In Proton Beams, Kevin M. Vredevoogd

Dissertations & Theses (Open Access)

This project assessed the effectiveness of polymer gel dosimeters as tools for measuring the dose deposited by and LET of a proton beam. A total of three BANG® dosimeter formulations were evaluated: BANG®-3-Pro-2 BANGkits™ for dose measurement and two BANG®-3 variants, the LET-Baseline and LET-Meter dosimeters, for LET measurement. All dosimeters were read out using an OCT scanner. The basic characteristics of the BANGkits™ were assessed in a series of photon and electron irradiations. The dose-response relationship was found to be sigmoidal with a threshold for response of approximately 15 cGy. The active region of the dosimeter, the volume in …

Development And Implementation Of The Use Of Optically Stimulated Luminescent Detectors In The Radiological Physics Center Anthropomorphic Quality Assurance Phantoms, Jennelle Bergene

Dissertations & Theses (Open Access)

The Radiological Physics Center (RPC) uses both on-site and remote reviews to credential institutions for participation in clinical trials. Anthropomorphic quality assurance (QA) phantoms are one tool the RPC uses to remotely audit institutions, which include thermoluminescent dosimeters (TLDs) and radiochromic film. The RPC desires to switch from TLD as the absolute dosimeter in the phantoms, to optically stimulated luminescent dosimeters (OSLDs), but a problem lies in the angular dependence exhibited by the OSLD. The purpose of this study was to characterize the angular dependence of OSLD and establish a correction factor if necessary, to provide accurate dosimetric measurements as …

Development And Implementation Of A Remote Audit Tool For High Dose Rate (Hdr) 192ir Brachytherapy Using Optically Stimulated Luminescence Dosimetry, Kevin Casey

Dissertations & Theses (Open Access)

This work aimed to create a mailable and OSLD-based phantom with accuracy suitable for RPC audits of HDR brachytherapy sources at institutions participating in NCI-funded cooperative clinical trials. An 8 × 8 × 10 cm³ prototype with two slots capable of holding nanoDot Al₂O₃:C OSL dosimeters (Landauer, Glenwood, IL) was designed and built. The phantom has a single channel capable of accepting all ¹⁹²Ir HDR brachytherapy sources in current clinical use in the United States. Irradiations were performed with an ¹⁹²Ir HDR source to determine correction factors for linearity with dose, dose rate, …

Clinical Impact Of Couch Top And Rails On Imrt And Arc Therapy, Kiley B. Pulliam

Dissertations & Theses (Open Access)

Purpose: To evaluate the clinical impact of the Varian Exact Couch on dose and volume coverage to targets and critical structures and tumor control probability (TCP) for 6-MV IMRT and Arc Therapy.

Methods: Five clinical prostate patients were planned with both, 6-MV 8-field IMRT and 6-MV 2-field RapidArc using the Eclipse treatment planning system (TPS). These plans neglected treatment couch attenuation, as is standard clinical practice. Dose distributions were then recalculated in Eclipse with the inclusion of the Varian Exact Couch (imaging couch top) and the rails in varying configurations. The changes in dose and coverage were evaluated using the …

Thoracic Target Volume Delineation Using Various Maximum-Intensity Projection Computed Tomography Image Sets For Stereotactic Body Radiation Therapy, David A. Zamora

Dissertations & Theses (Open Access)

The motion of lung tumors during respiration makes the accurate delivery of radiation therapy to the thorax difficult because it increases the uncertainty of target position. The adoption of four-dimensional computed tomography (4D-CT) has allowed us to determine how a tumor moves with respiration for each individual patient. Using information acquired during a 4D-CT scan, we can define the target, visualize motion, and calculate dose during the planning phase of the radiotherapy process. One image data set that can be created from the 4D-CT acquisition is the maximum-intensity projection (MIP). The MIP can be used as a starting point to …

An Implantable Mosfet Dosimeter Modified To Act As A Fiducial Marker, Joseph S. Dick

Dissertations & Theses (Open Access)

In external beam radiation therapy, it is imperative that the prescribed dose is administered to the correct location and in the correct amount. Though several ex vivo methods of quality assurance are currently employed to achieve this goal, verifying that the correct dose is received within the patient in situ is impossible without the capability of measuring dose inside the patient. Recently, a method of measuring dose delivered within the patient has been developed, an implantable MOSFET dosimeter. This dosimeter is implanted within the patient and records the dose received. Since the dosimeter is implanted in the patient, it could …