Fan-beam optical computed tomography using solid tank designs for use in 3D radiation dosimetry

Three-dimensional dosimeters have potential to advance radiation treatment through comprehensive three-dimensional dose verification. While they offer a distinct advantage, their application is intricate, requiring specialized expertise for accurate readout. Optical computed tomography (CT) stands out as a primary modality for imaging three-dimensional dosimeters used in validating complex radiotherapy treatments. The objectives of this thesis are to (1) develop a ray-tracing simulator capable of calculating an optimized optical CT geometry given the optical properties of the dosimeter and manufacturing materials, (2) design, optimize, manufacture, and commission a fan-beam solid tank optical CT scanner for use on FlexyDos3D dosimeters, and (3) update the ray-tracing simulator to enable optimization for small-detection system scanners. A ray-tracing simulator was developed to find an optimized geometry for a prototype solid tank optical CT scanner. Five geometric variables were adjusted to assess the geometry’s performance based on three properties: effective radius, magnification, and beam uniformity. The optimization workflow flexibility was demonstrated by finding optimal geometries for two optically different 3D dosimeters, FlexyDos3D and ClearView™. An optimized optical CT scanner design for FlexyDos3D dosimeters was manufactured and commissioned. The prototype scanner exhibited a maximum spatial resolution of MTF₅₀ of 0.929 mm⁻¹. Geometric distortion was evaluated, revealing a center-of-intensity needle alignment of <0.25 mm irrespective of needle location. The system’s contrast-to-noise peak varied from 65-190, depending on the sample region for background attenuation. Iterative reconstruction was performed using the FISTA algorithm with a total reconstruction time of around 3 minutes for 200 iterations. The ray-tracing simulator was adapted to facilitate the optimization of designs utilizing small-detection systems such as CCD or CMOS detectors by shaping the acrylic block rear wall as a focusing lens. A high-scoring geometry is created by perturbing the rear lens using the proposed discretized lens creation method. The resulting lens converges all rays to a singular focal point, avoiding the aberrations found in conic lenses.Science, Irving K. Barber Faculty of (Okanagan)Computer Science, Mathematics, Physics and Statistics, Department of (Okanagan)Graduat

A Hybrid Direct Search and Model-Based Derivative-Free Optimization Method with Dynamic Decision Processing and Application in Solid-Tank Design

A derivative-free optimization (DFO) method is an optimization method that does not make use of derivative information in order to find the optimal solution. It is advantageous for solving real-world problems in which the only information available about the objective function is the output for a specific input. In this paper, we develop the framework for a DFO method called the DQL method. It is designed to be a versatile hybrid method capable of performing direct search, quadratic-model search, and line search all in the same method. We develop and test a series of different strategies within this framework. The benchmark results indicate that each of these strategies has distinct advantages and that there is no clear winner in the overall performance among efficiency and robustness. We develop the Smart DQL method by allowing the method to determine the optimal search strategies in various circumstances. The Smart DQL method is applied to a problem of solid-tank design for 3D radiation dosimetry provided by the UBCO (University of British Columbia—Okanagan) 3D Radiation Dosimetry Research Group. Given the limited evaluation budget, the Smart DQL method produces high-quality solutions

Unravelling the past, modelling the future

Britain’s landscape provides our recreational space, has inspired poets and artists, and has taken up countless hours of BBC TV airtime. It has absorbed the blood of hundreds of battles over thousands of years. It conceals the treasures of our multicultural origins and the spoils of the Industrial Revolution. Now it must support a population of slightly more than 61 million people. For all its long history of human occupation, geologically speaking it is a young landscape, sculpted by the waxing and waning of multiple ice ages and changing sea levels over the past two million years. The last extensive ice cover receded almost 20 000 years ago, leaving in its wake a landscape further sculpted by rising sea levels, deforestation, and the inexorable propagation of urban environments. The pristine and manicured landscape — the British countryside — that we cherish today is a far more dynamic environment than we might at first realise

The New England Neurosurgical Society: growth and evolution over 70 years

The New England Neurosurgical Society (NENS) was founded in 1951 under the leadership of its first President (Dr. William Beecher Scoville) and Secretary-Treasurer (Dr. Henry Thomas Ballantine). The purpose of creating the NENS was to unite local neurosurgeons in the New England area; it was one of the first regional neurosurgical societies in America. Although regional neurosurgical societies are important supplements to national organizations, they have often been overshadowed in the available literature. Now in its 70th year, the NENS continues to serve as a platform to represent the needs of New England neurosurgeons, foster connections and networks with colleagues, and provide research and educational opportunities for trainees. Additionally, regional societies enable discussion of issues uniquely relevant to the region, improve referral patterns, and allow for easier attendance with geographic proximity. In this paper, the authors describe the history of the NENS and provide a roadmap for its future. The first section portrays the founders who led the first meetings and establishment of the NENS. The second section describes the early years of the NENS and profiles key leaders. The third section discusses subsequent neurosurgeons who steered the NENS and partnerships with other societies. In the fourth section, the modern era of the NENS and its current activities are highlighted