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The safety and comfort of a patient during robot-based positioning for accurate radiotherapyVon Hoesslin, Neil 12 1900 (has links)
Thesis (MScIng)--University of Stellenbosch, 2004. / Please refer to full text for abstract.
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New method of collecting output factors for commissioming linear accelerators with special emphasis on small fields and intensity modualted readiation therapyUnknown Date (has links)
Common methods for commissioning linear accelerators often neglect beam data for small fields. Examining the methods of beam data collection and modeling for commissioning linear accelerators revealed little to no discussion of the protocols for fields smaller than 4 cm x 4 cm. This leads to decreased confidence levels in the dose calculations and associated monitor units (MUs) for Intensity Modulated Radiation Therapy (IMRT).
The parameters of commissioning the Novalis linear accelerator (linac) on the Eclipse Treatment Planning System (TPS) led to the study of challenges collecting data for very small fields. The focus of this thesis is the examination of the protocols for output factor collection and their impact on dose calculations by the TPS for IMRT treatment plans. Improving output factor collection methods, led to significant improvement in absolute dose calculations which correlated with the complexity of the plans. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection
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Study of novel techniques for verification imaging and patient dose reconstruction in external beam radiation therapyJarry, Geneviève. January 2006 (has links)
Treatment delivery verification is an essential step of radiotherapy. The purpose of this thesis is to develop new methods to improve the verification of photon and electron beam radiotherapy treatments. This is achieved through developing and testing (1) a way to acquire portal images during electron beam treatments, (2) a method to reconstruct the dose delivered to patients during photon beam treatments and (3) a technique to improve image quality in kilovoltage (kV) cone beam computed tomography (CBCT) by correcting for scattered radiation. The portal images were acquired using the Varian CL21EX linac and the Varian aS500 electronic portal imaging device (EPID). The EGSnrc code was used to model fully the CL21EX, the aS500 and the kV CBCT system. / We demonstrate that portal images of electron beam treatments with adequate contrast and resolution can be produced using the bremsstrahlung photons portion of the electron beam. Monte Carlo (MC) calculations were used to characterize the bremsstrahlung photons and to obtain predicted images of various phantoms. The technique was applied on a head and neck patient. / An algorithm to reconstruct the dose given to patients during photon beam radiotherapy was developed and validated. The algorithm uses portal images and MC simulations. The primary fluence at the detector is back-projected through the patient. CT geometry to obtain a reconstructed phase space file. The reconstructed phase space file is used to calculate the reconstructed dose to the patient using MC simulations. The reconstruction method was validated in homogeneous and heterogeneous phantoms for conventional and IMRT fields. / The scattered radiation present in kV CBCT images was evaluated using MC simulations. Simulated predictions of the scatter distribution were subtracted from CBCT projection images prior to the reconstruction to improve the reconstructed image quality. Reducing the scattered radiation was found to improve contrast and reduce shading artifacts. / MC simulations, in combination with experimental techniques, have been shown to be valuable tools in the development of treatment verification methods. The three novel methods presented in this thesis contribute to the improvement of radiotherapy treatment verification. They can potentially improve treatment outcome by ensuring a better target coverage.
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Study of novel techniques for verification imaging and patient dose reconstruction in external beam radiation therapyJarry, Geneviève. January 2006 (has links)
No description available.
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Verification of patient position for proton therapy using portal X-Rays and digitally reconstructed radiographsVan der Bijl, Leendert 12 1900 (has links)
Thesis (MScEng (Applied Mathematics))--University of Stellenbosch, 2006. / This thesis investigates the various components required for the development
of a patient position verification system to replace the existing system used
by the proton facilities of iThemba LABS1. The existing system is based
on the visual comparison of a portal radiograph (PR) of the patient in the
current treatment position and a digitally reconstructed radiograph (DRR)
of the patient in the correct treatment position. This system is not only of
limited accuracy, but labour intensive and time-consuming. Inaccuracies in
patient position are detrimental to the effectiveness of proton therapy, and
elongated treatment times add to patient trauma. A new system is needed
that is accurate, fast, robust and automatic.
Automatic verification is achieved by using image registration techniques
to compare the PR and DRRs. The registration process finds a rigid body
transformation which estimates the difference between the current position
and the correct position by minimizing the measure which compares the
two images. The image registration process therefore consists of four main
components: the DRR, the PR, the measure for comparing the two images
and the minimization method.
The ray-tracing algorithm by Jacobs was implemented to generate the DRRs,
with the option to use X-ray attenuation calibration curves and beam hardening
correction curves to generate DRRs that approximate the PRs acquired
with iThemba LABS’s digital portal radiographic system (DPRS)
better.
Investigations were performed mostly on simulated PRs generated from DRRs, but also on real PRs acquired with iThemba LABS’s DPRS.
The use of the Correlation Coefficient (CC) and Mutual Information (MI)
similarity measures to compare the two images was investigated.
Similarity curves were constructed using simulated PRs to investigate how
the various components of the registration process influence the performance.
These included the use of the appropriate XACC and BHCC, the
sizes of the DRRs and the PRs, the slice thickness of the CT data, the
amount of noise contained by the PR and the focal spot size of the DPRS’s
X-ray tube.
It was found that the Mutual Information similarity measure used to compare
10242 pixel PRs with 2562 pixel DRRs interpolated to 10242 pixels
performed the best. It was also found that the CT data with the smallest
slice thickness available should be used. If only CT data with thick slices is
available, the CT data should be interpolated to have thinner slices.
Five minimization algorithms were implemented and investigated. It was
found that the unit vector direction set minimization method can be used
to register the simulated PRs robustly and very accurately in a respectable
amount of time.
Investigations with limited real PRs showed that the behaviour of the registration
process is not significantly different than for simulated PRs.
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