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Articles 1 - 9 of 9
Full-Text Articles in Medicine and Health Sciences
New Tools For Monitoring Gamma Camera Uniformity, Brad K. Lofton
New Tools For Monitoring Gamma Camera Uniformity, Brad K. Lofton
Dissertations & Theses (Open Access)
Detector uniformity is a fundamental performance characteristic of all modern gamma camera systems, and ensuring a stable, uniform detector response is critical for maintaining clinical images that are free of artifact. For these reasons, the assessment of detector uniformity is one of the most common activities associated with a successful clinical quality assurance program in gamma camera imaging. The evaluation of this parameter, however, is often unclear because it is highly dependent upon acquisition conditions, reviewer expertise, and the application of somewhat arbitrary limits that do not characterize the spatial location of the non-uniformities. Furthermore, as the goal of any …
Thoracic Target Volume Delineation Using Various Maximum-Intensity Projection Computed Tomography Image Sets For Stereotactic Body Radiation Therapy, David A. Zamora
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 …
Characterization Of Optically Stimulated Luminescent Detectors In Photon & Proton Beams For Use In Anthropomorphic Phantoms, James R. Kerns
Characterization Of Optically Stimulated Luminescent Detectors In Photon & Proton Beams For Use In Anthropomorphic Phantoms, James R. Kerns
Dissertations & Theses (Open Access)
This study investigated characteristics of optically stimulated luminescent detectors (OSLDs) in protons, allowing comparison to thermoluminescent detectors, and to be implemented into the Radiological Physics Center’s (RPC) remote audit quality assurance program for protons, and for remote anthropomorphic phantom irradiations. The OSLDs used were aluminum oxide (Al2O3:C) nanoDots from Landauer, Inc. (Glenwood, Ill.) measuring 10x10x2 mm3. A square, 20(L)x20(W)x0.5(H) cm3 piece of solid water was fabricated with pockets to allow OSLDs and TLDs to be irradiated simultaneously and perpendicular to the beam. Irradiations were performed at 5cm depth in photons, and in the center of a 10 cm SOBP in …
Dynamic Chemical Shift Imaging For Image-Guided Thermal Therapy, Brian A. Taylor
Dynamic Chemical Shift Imaging For Image-Guided Thermal Therapy, Brian A. Taylor
Dissertations & Theses (Open Access)
Magnetic resonance temperature imaging (MRTI) is recognized as a noninvasive means to provide temperature imaging for guidance in thermal therapies. The most common method of estimating temperature changes in the body using MR is by measuring the water proton resonant frequency (PRF) shift. Calculation of the complex phase difference (CPD) is the method of choice for measuring the PRF indirectly since it facilitates temperature mapping with high spatiotemporal resolution. Chemical shift imaging (CSI) techniques can provide the PRF directly with high sensitivity to temperature changes while minimizing artifacts commonly seen in CPD techniques. However, CSI techniques are currently limited by …
An Implantable Mosfet Dosimeter Modified To Act As A Fiducial Marker, Joseph S. Dick
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 …
Benchmarking And Implementation Of A New Independent Monte Carlo Dose Calculation Quality Assurance Audit Tool For Clinical Trials, Scott E. Davidson
Benchmarking And Implementation Of A New Independent Monte Carlo Dose Calculation Quality Assurance Audit Tool For Clinical Trials, Scott E. Davidson
Dissertations & Theses (Open Access)
Introduction Commercial treatment planning systems employ a variety of dose calculation algorithms to plan and predict the dose distributions a patient receives during external beam radiation therapy. Traditionally, the Radiological Physics Center has relied on measurements to assure that institutions participating in the National Cancer Institute sponsored clinical trials administer radiation in doses that are clinically comparable to those of other participating institutions. To complement the effort of the RPC, an independent dose calculation tool needs to be developed that will enable a generic method to determine patient dose distributions in three dimensions and to perform retrospective analysis of radiation …
Thoracic Radiotherapy Treatment Planning With Cine Pet/Ct, Adam C. Riegel
Thoracic Radiotherapy Treatment Planning With Cine Pet/Ct, Adam C. Riegel
Dissertations & Theses (Open Access)
Purpose: Respiratory motion causes substantial uncertainty in radiotherapy treatment planning. Four-dimensional computed tomography (4D-CT) is a useful tool to image tumor motion during normal respiration. Treatment margins can be reduced by targeting the motion path of the tumor. The expense and complexity of 4D-CT, however, may be cost-prohibitive at some facilities. We developed an image processing technique to produce images from cine CT that contain significant motion information without 4D-CT. The purpose of this work was to compare cine CT and 4D-CT for the purposes of target delineation and dose calculation, and to explore the role of PET in target …
Implementation Of An Anthropomorphic Phantom For The Evaluation Of Proton Therapy Treatment Procedures, Ryan L. Grant
Implementation Of An Anthropomorphic Phantom For The Evaluation Of Proton Therapy Treatment Procedures, Ryan L. Grant
Dissertations & Theses (Open Access)
With an increasing number of institutions offering proton therapy, the number of multi-institutional clinical trials involving proton therapy will also increase in the coming years. The Radiological Physics Center monitors sites involved in clinical trials through the use of site visits and remote auditing with thermoluminescent dosimeters (TLD) and mailable anthropomorphic phantoms. Currently, there are no heterogeneous phantoms that have been commissioned to evaluate proton therapy. It was hypothesized that an anthropomorphic pelvis phantom can be designed to audit treatment procedures (patient simulation, treatment planning and treatment delivery) at proton facilities to confirm agreement between the measured dose and calculated …
Commissioning An Anthropomorphic Spine And Lung Phantom For Remote Dose Verification Of Institutions Participating In Rtog 0631, Douglas F. Caruthers
Commissioning An Anthropomorphic Spine And Lung Phantom For Remote Dose Verification Of Institutions Participating In Rtog 0631, Douglas F. Caruthers
Dissertations & Theses (Open Access)
The RPC developed a new phantom to ensure comparable and consistent radiation administration in spinal radiosurgery clinical trials. This study assessed the phantom’s dosimetric and anatomic utility. The ‘spine phantom’ is a water filled thorax with anatomy encountered in spinal radiosurgery: target volume, vertebral column, spinal canal, esophagus, heart, and lungs. The dose to the target volume was measured with axial and sagittal planes of radiochromic film and thermoluminescent dosimeters (TLD). The dose distributions were measured with the radiochromic film calibrated to the absolute dose measured by the TLD. Four irradiations were administered: a four angle box plan, a seven …