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Dissertation/Thesis Abstract

Cherenkov Imaging in Linac Quality Assurance and Total Skin Electron Therapy Dose Studies
by Miao, Tianshun, Ph.D., Dartmouth College, 2020, 225; 28149698
Abstract (Summary)

Radiation therapy is widely used for treating cancer, and the linear accelerator (Linac) is the main tool to delivery this. Linac quality assurance (QA), treatment planning, and dosimetry are important tasks that are done to make sure that the radiation doses delivered to patients are appropriate and safe. This thesis covers the development of novel Cherenkov imaging methods for Linac QA, as well as for dosimetry verification in total skin electron therapy.

Basic Linac radiation field QA checks must be completed to confirm that the field shape precisely matches expectations based on configuration. These field checks were efficiently performed using remote Cherenkov imaging on a flat board. The agreement between the dose, the light field projected by the Linac, and the Cherenkov imaging validated that this type of imaging could be a surrogate dosimetry tool. The major benefit of using Cherenkov was that it is a video rate imaging approach, so that arbitrary shapes and entire treatment plans can be imaged without entering the treatment room.

Imaging Cherenkov light as a correlate of dose in total skin electron therapy (TSET) was examined for patients getting treatment following the Stanford technique, where 6 different patient positions are used during irradiation, with supplemental 3D measurement of the patient’s body. This dose distribution was projected onto the 3D body model of each position and recorded as a 2D surface texture map. The cumulative dose distribution was calculated by summing up the texture maps of all positions and displayed back on the body model. Statistical analysis was conducted to determine the overall dose uniformity throughout the whole delivery. A comparison of treatments in the Stanford and rotary techniques was done to compare the dose uniformity, using an angle-dose relationship based upon Monte Carlo simulations of TSET dosimetry. A treatment plan type simulation predicted the relative dose distributions on the body surface. 3D visualization and statistical analysis of these distributions showed that there is better dose uniformity in the rotational technique.

Imaging of a number of patients undergoing TSET at the University of Pennsylvania allowed for visual confirmation of the ability to image dose with Cherenkov imaging. The approach to visualization and display of Cherenkov with 3D modelling animation makes it more efficient to allow both TSET treatment planning and TSET dosimetry verification.

Indexing (document details)
Advisor: Williams, Benjamin B.
Commitee: Pogue, Brian W., Jermyn, Michael, Bruza, Petr, Zhu, Timothy C.
School: Dartmouth College
Department: Engineering
School Location: United States -- New Hampshire
Source: DAI-B 82/4(E), Dissertation Abstracts International
Subjects: Biomedical engineering, Medical imaging
Keywords: Animiation, Beam shape, Cerenkov, Computer graphics, Total skin electron therapy, Linac
Publication Number: 28149698
ISBN: 9798678182616
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