Physics Commons^™

Third Generation Gamma Camera Spect System, Narayan Bhusal

LSU Master's Theses

Single Photon Emission Computed Tomography (SPECT) is a non-invasive imaging modality, frequently used in myocardial perfusion imaging. The biggest challenges facing the majority of clinical SPECT systems are low sensitivity, poor resolution, and the relatively high radiation dose to the patient. New generation systems (GE Discovery, DSPECT) dedicated to cardiac imaging improve sensitivity by a factor of 5-8. The purpose of this work is to investigate a new gamma camera design with 21 hemi-ellipsoid detectors each with a pinhole collimator for Cardiac SPECT for further improvement in sensitivity, resolution, imaging time, and radiation dose.

To evaluate the resolution of our …

Analytical Models Of Neutron Spectral Fluence, Kerma And Absorbed-Dose For Proton Therapy, Suman Shrestha

LSU Master's Theses

Abstract

Purpose: The accurate prediction of stray neutron dose has become increasingly important as it increases the risk of second cancer development after proton therapy. Previously reported analytical models predicted the quantity dose equivalent, which includes physical and biological considerations but does not explicitly take into account material dependence and variation in the radiation quality. The purpose of this study was to investigate the feasibility of an analytical model of absorbed dose to water from stray neutrons in proton therapy.

Methods: To calculate neutron absorbed dose and kerma in water, the authors developed analytical models of neutron spectral fluence and …

Verification And Evaluation Of A Passive Intensity Modulation Device For Bolus Conformal Therapy, Elizabeth Noel Hilliard

LSU Master's Theses

Purpose: Bolus electron conformal therapy (BECT) provides effective radiation treatment for superficial cancers and other diseases close to the skin surface, but can have as great as a 30% planning target volume (PTV) dose heterogeneity due to scattering from the irregular proximal bolus surface. Intensity modulated (IM) BECT can improve PTV dose homogeneity, but is not currently available. This study fabricated patient-specific passive intensity modulators and validated their delivering planned dose distributions calculated by a modified pencil beam redefinition algorithm (PBRA).

Methods: Two test-patterns and four patient-specific intensity modulators were designed, fabricated, and tested. Dose plans were generated …

Development Of A Slab-Based Monte Carlo Proton Dose Algorithm With A Robust Material-Dependent Nuclear Halo Model, John Wesley Chapman Jr

LSU Doctoral Dissertations

Pencil beam algorithms (PBAs) are often utilized for dose calculation in proton therapy treatment planning because they are fast and accurate under most conditions. However, as discussed in Chapman et al (2017), the accuracy of a PBA can be limited under certain conditions because of two major assumptions: (1) the central-axis semi-infinite slab approximation; and, (2) the lack of material dependence in the nuclear halo model. To address these limitations, we transported individual protons using a class II condensed history Monte Carlo and added a novel energy loss method that scaled the nuclear halo equation in water to arbitrary geometry. …

Endorectal Digital Prostate Tomosynthesis, Joseph Robert Steiner

LSU Doctoral Dissertations

Several areas of prostate cancer (PCa) management, such as imaging permanent brachytherapy implants or small, aggressive lesions, benefit from high image resolution. Current PCa imaging methods can have inadequate resolution for imaging these areas. Endorectal digital prostate tomosynthesis (endoDPT), an imaging method that combines an external x-ray source and an endorectal x-ray sensor, can produce three-dimensional images of the prostate region that have high image resolution compared to typical methods. This high resolution may improve PCa management and increase positive outcomes in affected men.

This dissertation presents the initial development of endoDPT, including system design, image quality assessment, and examples …

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, …