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Articles 91 - 108 of 108
Full-Text Articles in Other Physics
Evaluation Of Polymer Gel Dosimeters For Measurements Of Dose And Let In Proton Beams, Kevin M. Vredevoogd
Evaluation Of Polymer Gel Dosimeters For Measurements Of Dose And Let In Proton Beams, Kevin M. Vredevoogd
Dissertations and 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 and 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 To Ol For High Dose Rate (Hdr) 192ir Brachytherapy Using Optically Stimulated Luminescence Dosimetry, Kevin Casey
Dissertations and 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, …
Verification Of The Clinical Implementation Of The Respiratory Gated Beam Delivery Technique With Synchrotron-Based Proton Irradiation, Yoshikazu Tsunashima
Verification Of The Clinical Implementation Of The Respiratory Gated Beam Delivery Technique With Synchrotron-Based Proton Irradiation, Yoshikazu Tsunashima
Dissertations and Theses (Open Access)
The clinical advantage for protons over conventional high-energy x-rays stems from their unique depth-dose distribution, which delivers essentially no dose beyond the end of range. In order to achieve it, accurate localization of the tumor volume relative to the proton beam is necessary. For cases where the tumor moves with respiration, the resultant dose distribution is sensitive to such motion. One way to reduce uncertainty caused by respiratory motion is to use gated beam delivery. The main goal of this dissertation is to evaluate the respiratory gating technique in both passive scattering and scanning delivery mode. Our hypothesis for the …
Evaluation Of Deformable Image Registration For Improved 4d Ct-Derived Ventilation For Image Guided Radiotherapy, Richard Castillo
Evaluation Of Deformable Image Registration For Improved 4d Ct-Derived Ventilation For Image Guided Radiotherapy, Richard Castillo
Dissertations and Theses (Open Access)
Recent treatment planning studies have demonstrated the use of physiologic images in radiation therapy treatment planning to identify regions for functional avoidance. This image-guided radiotherapy (IGRT) strategy may reduce the injury and/or functional loss following thoracic radiotherapy. 4D computed tomography (CT), developed for radiotherapy treatment planning, is a relatively new imaging technique that allows the acquisition of a time-varying sequence of 3D CT images of the patient's lungs through the respiratory cycle. Guerrero et al. developed a method to calculate ventilation imaging from 4D CT, which is potentially better suited and more broadly available for IGRT than the current standard …
Improving The Accuracy Of Radiation Pneumonitis Dose Response Models, Yevgeniy Vinogradskiy
Improving The Accuracy Of Radiation Pneumonitis Dose Response Models, Yevgeniy Vinogradskiy
Dissertations and Theses (Open Access)
The prognosis for lung cancer patients remains poor. Five year survival rates have been reported to be 15%. Studies have shown that dose escalation to the tumor can lead to better local control and subsequently better overall survival. However, dose to lung tumor is limited by normal tissue toxicity. The most prevalent thoracic toxicity is radiation pneumonitis. In order to determine a safe dose that can be delivered to the healthy lung, researchers have turned to mathematical models predicting the rate of radiation pneumonitis. However, these models rely on simple metrics based on the dose-volume histogram and are not yet …
The Role Of Cell Sterilization In Population Based Studies Of Radiogenic Second Cancers Following Radiation Therapy, Annelise Giebeler
The Role Of Cell Sterilization In Population Based Studies Of Radiogenic Second Cancers Following Radiation Therapy, Annelise Giebeler
Dissertations and Theses (Open Access)
Advances in radiotherapy have generated increased interest in comparative studies of treatment techniques and their effectiveness. In this respect, pediatric patients are of specific interest because of their sensitivity to radiation induced second cancers. However, due to the rarity of childhood cancers and the long latency of second cancers, large sample sizes are unavailable for the epidemiological study of contemporary radiotherapy treatments. Additionally, when specific treatments are considered, such as proton therapy, sample sizes are further reduced due to the rareness of such treatments. We propose a method to improve statistical power in micro clinical trials. Specifically, we use a …
The Development And Implementation Of An Anthropomorphic Head Phantom For The Assessment Of Proton Therapy Treatment Procedures, Paige A. Summers
The Development And Implementation Of An Anthropomorphic Head Phantom For The Assessment Of Proton Therapy Treatment Procedures, Paige A. Summers
Dissertations and Theses (Open Access)
Proton therapy has become an increasingly more common method of radiation therapy, with the dose sparing to distal tissue making it an appealing option, particularly for treatment of brain tumors. This study sought to develop a head phantom for the Radiological Physics Center (RPC), the first to be used for credentialing of institutions wishing to participate in clinical trials involving brain tumor treatment of proton therapy. It was hypothesized that a head phantom could be created for the evaluation of proton therapy treatment procedures (treatment simulation, planning, and delivery) to assure agreement between the measured dose and calculated dose within …
Evaluation Of Intensity Modulated Radiation Therapy (Imrt) Delivery Error Due To Imrt Treatment Plan Complexity And Improperly Matched Dosimetry Data, Jacqueline R. Tonigan
Evaluation Of Intensity Modulated Radiation Therapy (Imrt) Delivery Error Due To Imrt Treatment Plan Complexity And Improperly Matched Dosimetry Data, Jacqueline R. Tonigan
Dissertations and Theses (Open Access)
Intensity modulated radiation therapy (IMRT) is a technique that delivers a highly conformal dose distribution to a target volume while attempting to maximally spare the surrounding normal tissues. IMRT is a common treatment modality used for treating head and neck (H&N) cancers, and the presence of many critical structures in this region requires accurate treatment delivery. The Radiological Physics Center (RPC) acts as both a remote and on-site quality assurance agency that credentials institutions participating in clinical trials. To date, about 30% of all IMRT participants have failed the RPC’s remote audit using the IMRT H&N phantom. The purpose …
Two-Photon-Excited Tryptophan Fluorescence Microscopy For Leukocytes And Cancer Cells Imaging, Jesus A. Valdez^, Chunqiang Li*
Two-Photon-Excited Tryptophan Fluorescence Microscopy For Leukocytes And Cancer Cells Imaging, Jesus A. Valdez^, Chunqiang Li*
COURI Symposium Abstracts, Spring 2011
Cancer screening and early diagnosis is an important yet controversial issue due to the safety and practicality of methods used. Our objective is to study the efficiency of an in vivo two-photon microscope developed in our laboratories to monitor cell inflammation. First, leukocytes were separated by subpopulation. The tryptophan fluorescence intensity level of each type of leukocyte was then quantified with two-photon microscopy, in their naïve and inflamed states, respectively. Finally the tryptophan fluorescence intensity of multiple myeloma cells was quantified and correlated to the resulting images. The cancerous tissue auto-fluorescence from NADH and FAD was also recorded as a …
New To Ols For Monitoring Gamma Camera Uniformity, Brad K. Lofton
New To Ols For Monitoring Gamma Camera Uniformity, Brad K. Lofton
Dissertations and 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 To Mography Image Sets For Stereotactic Body Radiation Therapy, David A. Zamora
Thoracic Target Volume Delineation Using Various Maximum-Intensity Projection Computed To Mography Image Sets For Stereotactic Body Radiation Therapy, David A. Zamora
Dissertations and 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
An Implantable Mosfet Dosimeter Modified To Act As A Fiducial Marker, Joseph S. Dick
Dissertations and 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 To Ol For Clinical Trials, Scott E. Davidson
Benchmarking And Implementation Of A New Independent Monte Carlo Dose Calculation Quality Assurance Audit To Ol For Clinical Trials, Scott E. Davidson
Dissertations and 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 …
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 and 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 …
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 and 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 …
Thoracic Radiotherapy Treatment Planning With Cine Pet/Ct, Adam C. Riegel
Thoracic Radiotherapy Treatment Planning With Cine Pet/Ct, Adam C. Riegel
Dissertations and 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 …
Unlv Magazine, Holly Ivy De Vore, Tony Allen, Barbara Cloud, Erin O'Donnell, Matthew K. Jacobsen, Gian Galassi, Michelle Mouton, Afsha Bawany, Shane Bevell
Unlv Magazine, Holly Ivy De Vore, Tony Allen, Barbara Cloud, Erin O'Donnell, Matthew K. Jacobsen, Gian Galassi, Michelle Mouton, Afsha Bawany, Shane Bevell
UNLV Magazine
No abstract provided.