The expectation for continual improvements in the treatment of cancer has brought quality assurance in radiotherapy under scrutiny in recent years. After a cancer diagnosis a custom treatment plan is devised to meet the particular needs of the patient's condition based on their prognosis. A cancer treatment plan will typically comprise of several cancer treatment technologies combining to form a comprehensive programme to fight the malignant growth. Inherent in each cancer treatment technology is a percentage error in treatment accuracy. Quality assurance is the medical practice to minimise the percentage error in treatment accuracy. Radiotherapy is one of the several cancer treatment technologies a patient might receive as part of their treatment plan, and in-vivo dosimetry is a quality assurance technology specifically designed to minimise the percentage error in the treatment accuracy of radiotherapy. This thesis outlines the work completed in the design of a next generation dosimeter for in-vivo dosimetry. The proposed dosimeter is intended to modernise the process of measuring the absorbed dose of ionising radiation received by the target volume during a radiotherapy session. To accomplish this goal the new dosimeter will amalgamate specialist technologies from the field of particle physics and reapply them to the field of medical physics. This thesis describes the design of a new implantable in-vivo dosimeter, a dosimeter comprising of several individual stages of electronics working together to modernise quality assurance in radiotherapy. Presented within this thesis are the results demonstrating the performance of two critical stages for this new dosimeter, including: the oating gate metal oxide field effective transistor, a radiation sensitive electronic component measuring an absorbed dose of radiation; and the micro antenna, a highly specialist wireless communications device working to transmit a high frequency radio signal. This was a collaborative project between Rutherford Appleton Laboratory and Brunel University. The presented work in this thesis was completed between March 2007 and January 2011.

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Access to abstract permanently restricted to Ball State community only. / Literature review -- Interaction of radiation with matter -- Radiation dosimetry -- Materials and methods -- Results -- Discursion. / Access to thesis permanenty restricted to Ball State community only. / Department of Physics and Astronomy

In this work we introduce PARETO, a multiobjective optimization tool that simultaneously optimizes beam angles and fluence patterns in intensity-modulated radiation therapy (IMRT) treatment planning using a powerful genetic algorithm. We also investigate various objective functions and compare several parameterizations for modeling beam fluence in terms of fluence map complexity, solution quality, and run efficiency. We have found that the combination of a conformity-based Planning Target Volume (PTV) objective function and a dose-volume histogram or equivalent uniform dose -based objective function for Organs-At-Risk (OARs) produced relatively uniform and conformal PTV doses, with well-spaced beams. For two patient data sets, the linear gradient and beam group fluence parameterizations produced superior solution quality using a moderate and high degree of modulation, respectively, and had comparable run times. PARETO promises to improve the accuracy and efficiency of treatment planning by fully automating the optimization and producing a database of non-dominated solutions for each patient.

The modern day radiotherapy treatments are almost exclusively based on computed tomography (CT) images. The CT images are acquired using x-rays, and therefore reflect the radiation interaction properties of the material. This information is used to perform accurate dose calculation by the treatment planning system, and the data is also well suited for creating digitally reconstructed radiographs for comparing patient set up at the treatment machine where x-ray images are routinely acquired for this purpose. The magnetic resonance (MR) scanner has many attractive features for radiotherapy purposes. The soft tissue contrast as compared to CT is far superior, and it is possible to vary the sequences in order to visualize different anatomical and physiological properties of an organ. Both of these properties may contribute to an increase in accuracy of radiotherapy treatment. Using the MR images by themselves for treatment planning is, however, problematic. MR data reflects the magnetic properties of protons, and thus have no connection to the radiointeraction properties of the material. MRI also has inherent difficulty in imaging bone, which will appear in images as areas of no signal similar to air. This makes both dose calculation and patient positioning at the treatment machine troublesome. There are several clinics that use MR images together with CT images to perform treatment planning. The images are registered to a common coordinate system, a process often described as image fusion. In these cases, the MR images are primarily used for target definition and the CT images are used for dose calculations. This method is now not ideal, however, since the image fusion may introduce systematic uncertainties into the treatment due to the fact that the tumor is often able to move relatively freely with respect to the patients’ bony anatomy and outer contour, especially when the image registration algorithms take the entire patient anatomy in the volume of interest into account. The work presented in the thesis “Integration of MRI into the radiotherapy workflow” aim towards investigating the possibilities of workflows based entirely on MRI without using image registration, as well as workflows using image registration methods that are better suited for targets that can move with respect to surrounding bony anatomy, such as the prostate. / Modern strålterapi av cancer baseras nästan helt på datortomografiska (CT) bilder. CT bilder tas med hjälp av röntgenfotoner, och återger därför hur det avbildade materialet växelverkar med strålning. Denna information används för att utföra noggranna dosberäkningar i ett dosplaneringssystem, och data från CT bilder lämpar sig också väl för att skapa digitalt rekonstruerade röntgenbilder vilka kan användas för att verifiera patientens position vid behandling. Bildgivande magnetresonanstomografi (MRI) har många egenskaper som är intressanta för radioterapi. Mjukdelskontrasten i MR bilder är överlägsen CT, och det är möjligt att i stor utstäckning variera sekvensparametrar för att synliggöra olika anatomiska och funktionella attribut hos ett organ. Dessa bägge egenskaper kan bidra till ökad noggrannhet i strålbehandling av cancer. Att använda enbart MR bilder som planeringsunderlag för radioterapi är dock problematiskt. MR data reflekterar magnetiska attribut hos protoner, och har därför ingen koppling till materialets egenskaper då det gäller strålningsväxelverkan. Dessutom är det komplicerat att avbilda ben med MR; ben uppträder som områden av signalförlust i bilderna, på samma sätt som luft gör. Detta gör det svårt att utföra noggranna dosberäkningar och positionera patienten vid behandling. Många moderna kliniker använder redan idag MR tillsammans med CT under dosplanering. Bilderna registreras till ett gemensamt koordinatsystem i en process som kallas bildfusion. I dessa fall används MR bilderna primärt som underlag för utlinjering av tumör, eller target, och CT bilderna används som grund för dosberäkningar. Denna metod är dock inte ideal, då bildregistreringen kan införa systematiska geometriska fel i behandlingen. Detta på grund av att tumörer ofta är fria att röra sig relativt patientens skelett och yttre kontur, och många bildregistreringsalgoritmer tar hänsyn till hela bildvolymen. Arbetet som presenteras i denna avhandling syftar till att undersöka möjligheterna med arbetsflöden som baseras helt på MR data utan bildregistrering, samt arbetsflöden som använder bildregistrerings-algoritmer som är bättre anpassade för tumörer som kan röra sig i förhållande till patientens övriga anatomi, som till exempel prostatacancer.

A prototype rapid, high precision fan beam optical computed tomography (OptCT) scanner for three-dimensional polymer gel dosimetry of complex radiotherapy protocols has been developed. This study documents the design. construction and characterization of the system, as well as preliminary reconstructed optical attenuation images and dosimetric verification experiments. The principal goal in scanner design and implementation was to satisfy the Radiotherapy Accuracy and Precision (RTAP) criteria consisting of a spatial resolution of 1 x 1 x 1 mm3, an imaging time of 60 minutes, a dose accuracy within 3% and a precision within 1%. The scanner, which employs a sixty degree fan beam of 543 nm laser light to scan irradiated polymer gel samples up to 19 cm in cross-sectional diameter. has several defining attributes. Data acquisition for a single slice through a dosimeter is achieved in two minutes, using one signal acquisition per CT projection angle over a total of 360 projections. The effects of scatter and refraction of visible light are minimized by using the unique radial design of the matching medium tank, the concentric arrangement of a prototype, computer numerical control (CNC)-machined collimator and five Hamamatsu photodiode detector arrays for light detection. The novel tertiary collimation eliminates scattered light by 13% and improves reconstructed image contrast-to-noise ratio. Other characteristics of the scanner include: a laser power output variation of only 0.7%:, signal-to-noise ratio (SNR.) for calibration projections of up to 294:1, SNR for transmission projections through an irradiated polymer gel dosimeter of up to 161:1, a large absorbance dynamic range extending from 0.1 to 1.7 absorbance units and a spatial resolution of 0.25 mm2 in the axial plane of the scan¬ning geometry and 0.8 mm along the longitudinal z-axis of the scan plane. Images of optical attenuation coefficients and concomitant dose maps extracted from irradi¬ated, normoxic N--isopropylacylamide (NIPAM) polymer gels were used to investigate the potential of the system for dosimetric verification. Three different NIPAM gel irradiation experiments were performed and the resultant OptCT dose distributions were compared to the Eclipse® (Varian Medical Systems. Palo Alto. CA.) treatment planning system model. While the fan beam OptCT scanner provides promising ini¬tial images of reconstructed optical attenuation coefficients, its dosimetric accuracy compared to Eclipse - nominally 7% in low dose gradient regions and 5% on the field edges - constitutes the most significant area for future refinement.

Acuros External Beam (Acuros XB) is a new radiation dose calculation algorithm available as part of Varian Medical Systems' radiotherapy treatment planning system, ECLIPSE. Acuros XB calculates dose distributions by finding the deterministic solution to the linear Boltzmann transport equation which governs the transport of particles or radiation through matter. Among other things, Acuros XB claims an ability to accurately model dose perturbations due to increased photon and electron scatter within a high-density volume, such as a hip prosthesis. Until now, the only way to accurately model high-density scatter was with a Monte Carlo simulation which gives the stochastic solution to the same transport equation, but is time and computationally expensive. In contrast, Acuros XB solves the transport equation at time scales appropriate for clinical use. An evaluation of Acuros XB for radiation dose calculations involving high-density objects was undertaken using EGSnrc based Monte Carlo as the benchmark. Calculations were performed for geometrically ideal virtual phantoms, water tank phantoms containing cylindrical steel rods and hip prostheses, and for a clinical prostate treatment plan involving a unilateral prosthetic hip. The anisotropic analytical algorithm (AAA), a convolution-superposition algorithm used for treatment planning at the British Columbia Cancer Agency's Vancouver Island Center, was also used to illustrate the limitations of current radiotherapy planning tools. In addition, to verify the qualitative properties of dose perturbations due to high-density volumes, film measurements were taken and compared to Monte Carlo, Acuros XB and AAA data. Dose distributions calculated with Acuros XB agree very well with distributions calculated with Monte Carlo. Gamma-analyses performed at 2% and 2 mm using Monte Carlo as the reference dose were within tolerance for 92-99% of voxels considered. AAA, on the other hand, was within tolerance for 61-97% of voxels considered under the same gamma-constraints. For the clinical prostate plan, AAA produced localized dose underestimates that were absent when calculated by Acuros XB. As well, both Monte Carlo and Acuros XB showed very good agreement with the film measurements, while AAA showed large discrepancies at and beyond the location of measured dose perturbations. Acuros XB has been shown to handle does perturbations due to high-density volumes as well as Monte Carlo, at clinically appropriate time scales, and better than the current algorithm used for treatment planning at the Vancouver Island Center. / Graduate

Palliative radiotherapy (PRT) is proven to be effective in palliation of symptoms for end-stage cancer patients. However, little is known about its utilization at the end of life. This research aims to examine the utilization and the practice patterns of PRT at the end of life for cancer patients in British Columbia using population-based data. The pattern observed for PRT1Y dose-fractionation practice in BC are in line with published clinical guidelines and evidence from the literature, which advises “proper” use of PRT in BC as delivered to cancer patients at the end of life. However, after controlling for age, primary cancer site, and survival time, geographic access is found to be significantly associated with PRT1Y utilization. Variations found in PRT1Y rates by geographic access, which is operationalized by the Health Services Delivery Area (HSDA) and travel time, suggests potential underutilization of PRT1Y for patients with suboptimal access. / Graduate / 0992 / 0769 / 0574 / jinhuang@uvic.ca

Inaccurate dose calculation in radiotherapy can lead to errors in treatment delivery and evaluation of treatment efficacy. Respiration can cause of intra-fractional motions, leading to uncertainties in tumor targeting. These motions should therefore be included in dose calculation. The finite element method-based deformable registration platform MORFEUS is able to accurately quantify organ deformations. The dose accumulation algorithm included in MORFEUS takes organ deformation and tumor movement into account. This study has experimentally validated this dose accumulation algorithm by combining 3D gel dosimetry, respiratory motion-mimicking actuation mechanism, and finite element analysis. Results have shown that within the intrinsic measurement uncertainties of gel dosimetry, under normal conformal dose distribution conditions, more than 90% of the voxels in MORFEUS generated dose grids have met the criterion analogous to the gamma test. The average (SD) distance between selected pairs of isodose surfaces on the gel and MORFEUS dose distributions is 0.12 (0.08) cm.