Medicine and Health Sciences Commons^™

Evaluation Of Presage® As A 3d Dose Verification Tool In Proton Beams, Mitchell Carroll

Dissertations & Theses (Open Access)

Radiotherapy techniques have advanced and radiation dose plans have become much more complex over the last decade. This is especially true in proton therapy, which involves extremely steep dose gradients as a result of positioning the Bragg peak to cover the volumes to be treated. The Bragg peak can be shifted significantly in the patient as a result of nonuniformities in the tissue composition in its path, which can result in treatment complications. Some traditional dose verification tools used in proton beam commissioning and treatment plan verification are film, TLD, and ionization chambers. Such 0D and 2D dosimeters are incapable …

3d Scintillator Detector Quenching Characterization For Scanning Proton Beams, Fahed Alsanea

Dissertations & Theses (Open Access)

Proton pencil beam scanning is becoming the standard treatment delivery technique for proton therapy centers. Scanned proton pencil beams provide a highly conformal dose distribution. The complex dose distribution poses challenges for quality assurance measurements leading to sophisticated detector setups and time consuming measurements. Fast 3D measurements are therefore desirable to verify the complex dose distribution and to enable the utilization of the full potential of proton therapy. The overall objective of this project is to improve volumetric scintillators detectors to provide 3D measurements for applications for beam commissioning, quality assurance program, and patient-specific treatment delivery verification.

Detectors based on …

Identification Of Intracranial Lesions With Dual-Energy Computed Tomography And Magnetic Resonance Phase Imaging, Megan C. Jacobsen

Dissertations & Theses (Open Access)

On conventional Single-energy Computed Tomography (SECT), lesions with an attenuation greater than 100 Hounsfield Units (HU) can be definitively diagnosed as calcification. However, low-density calcifications and hemorrhage may have overlapping attenuation ranges between 40 and 100 HU and, therefore, cannot be differentiated with SECT alone. On T2*-weighted Gradient Recalled Echo (GRE) MRI, these lesions appear as “foci of susceptibility” in which their signal is hypointense due to the magnetic susceptibility of the lesions differing from that of the background tissue.

Dual-energy Computed Tomography (DECT) and Phase-Sensitive Magnetic Resonance Imaging (PS-MRI) represent two new imaging paradigms which both have the potential …

Development And Implementation Of A Homogeneous And A Heterogeneous Anthropomorphic End To End Quality Assurance Audit System Phantom For Magnetic Resonance Guided Radiotherapy Modalities Ranging From 0.35 T To 1.50 T, Angela Steinmann

Dissertations & Theses (Open Access)

Introduction: Magnetic resonance (MR) guided radiation therapy (MRgRT) is an emerging field that integrates an MR imager with either a linear accelerator or three radioactive cobalt-60 sources. Before institutions participate in multi-institutional NCI-sponsored clinical trials, they are required to perform a credentialing test provided by IROC-Houston. During the credentialing test, end-to-end phantoms are used to evaluate the institution’s ability to perform consistent and accurate radiation treatments. IROC-Houston’s conventional anthropomorphic phantoms are not visible in MR, thus they are insufficient for MRgRT systems. The purpose of this work was to create an anthropomorphic thorax and a head and neck (H&N) phantom …

Development And Commissioning Of An Independent Peer Review System For A Small Animal Irradiator, Mary Peters

Dissertations & Theses (Open Access)

Dosimetry for small animal irradiators lacks the standardization of clinical radiotherapy practice, yet plays a central translational role in human trial design. The purpose of this work was to improve the dosimetric accuracy and consistency of animal studies by developing an independent peer review system to verify dose delivery from animal irradiators. This study focused on the development of a mouse phantom and characterization of the thermoluminescent dosimetry system for a commonly used small animal irradiator.

First, a mouse model and irradiation stand were designed with the purpose of being used in a mailable audit. Two mouse phantoms were machined …

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 …

Development Of 3d-Printed Patient Specific Bolus For Clinical Use In Total Scalp Irradiation, Garrett Baltz

Dissertations & Theses (Open Access)

Total scalp irradiation (TSI) is a specialized radiation therapy technique that aims to deliver a uniform dose to the entire scalp. Original electron-based TSI techniques had limited homogeneity due to hot and cold spots created at field junctions due to the multiple matched fields that were required to treat the entire scalp. The transition to photon volumetric-modulated arc therapy based TSI techniques has improved homogeneity, to the point where non-conformal bolus is now a limiting factor. Bolus is required to build-up full dose to the scalp surface in total scalp irradiation. Creating bolus that is conformal to the scalp is …