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PET and SPECT imaging has improved to such a level that they are opening up exciting new horizons in medical diagnosis and treatment. This book provides a complete introduction to fundamentals and the latest progress in the field, including an overview of new scintillator materials and innovations in photodetector development, as well as the latest system designs and image reconstruction algorithms. It begins with basics of PET and SPECT physics, followed by technology advances and computing methods, quantitative techniques, multimodality imaging, instrumentation, pre-clinical and clinical imaging applications.
This work focuses on the simulated performance of a high-resolution, depth-of-interaction (DOI) capable PET detector module with a single-ended readout. I propose the use of a monolithic scintillator up to several centimetres thick directly coupled to a 2D array of Silicon Photomultipliers. High resolution of reconstructed energy and 3D position of gamma rays interacting with the detector is achieved through the implementation of Maximum Likelihood Estimation (MLE) of said parameters. A notable difference in the implementation of MLE described herein is the direct estimation of the interacting gamma-ray energy. Additionally, a performance evaluation of two prominent event windowing techniques used in PET -- energy windowing and likelihood windowing -- is presented. The proposed design and reconstruction algorithms have been validated using Geant4-based Monte Carlo simulations. Two different versions of the detector module -- one with an absorptive coating and the other with a reflective coating - were simulated, and a comparison of reconstruction performance is presented. It is found that the module with the reflective wrapping significantly out-performs the module with the absorptive wrapping in terms of the resolution of the reconstructed 3D position and energy of incoming gamma rays due to the increased amount of scintillation light detected with the reflective configuration. The reflective configuration simulated herein achieves an average 3D position resolution of ~ 1 mm, and an average energy resolution of ~ 11 %. Based on an analysis of the simulated detector module performance versus scintillator thickness presented in this thesis, a scintillator thickness of 1.5 cm was chosen for future prototypes in order to strike a balance between position and energy resolution performance and detection efficiency. A small bore PET system employing this configuration of module will have volumetric resolution of reconstructed images in the sub-millimeter range, energy resolution of ~ 11 % and sensitivity of ~ 28 %.
Pixel detectors are a particularly important class of particle and radiation detection devices. They have an extremely broad spectrum of applications, ranging from high-energy physics to the photo cameras of everyday life. This book is a general purpose introduction into the fundamental principles of pixel detector technology and semiconductor-based hybrid pixel devices. Although these devices were developed for high-energy ionizing particles and radiation beyond visible light, they are finding new applications in many other areas. This book will therefore benefit all scientists and engineers working in any laboratory involved in developing or using particle detection.
This state-of-the-art handbook, the first in a series that provides medical physicists with a comprehensive overview into the field of nuclear medicine, is dedicated to instrumentation and imaging procedures in nuclear medicine. It provides a thorough treatment on the cutting-edge technologies being used within the field, in addition to touching upon the history of their use, their development, and looking ahead to future prospects. This text will be an invaluable resource for libraries, institutions, and clinical and academic medical physicists searching for a complete account of what defines nuclear medicine. The most comprehensive reference available providing a state-of-the-art overview of the field of nuclear medicine Edited by a leader in the field, with contributions from a team of experienced medical physicists Includes the latest practical research in the field, in addition to explaining fundamental theory and the field's history
The objective of this project was to develop an understanding of the limits of performance for a high resolution PET detector using an approach based on continuous scintillation crystals rather than pixelated crystals. The overall goal was to design a high-resolution detector, which requires both high spatial resolution and high sensitivity for 511 keV gammas. Continuous scintillation detectors (Anger cameras) have been used extensively for both single-photon and PET scanners, however, these instruments were based on NaI(Tl) scintillators using relatively large, individual photo-multipliers. In this project we investigated the potential of this type of detector technology to achieve higher spatial resolution through the use of improved scintillator materials and photo-sensors, and modification of the detector surface to optimize the light response function. We achieved an average spatial resolution of 3-mm for a 25-mm thick, LYSO continuous detector using a maximum likelihood position algorithm and shallow slots cut into the entrance surface.
Positron Emission Tomography (PET) is a molecular imaging modality capable of imaging trace amounts of radiolabeled molecules targeting biomarkers. Accurate PET studies of small targets require high image resolution, for example, imaging small objects such as cancer lesions in early detection. The utility of PET in breast cancer imaging is in staging and follow-up observations. Another application of PET is in the monitoring of response to treatment in breast cancer patients, which can be done since small changes in tumor metabolism can be measured using PET. However, for accurate monitoring high resolution and sensitivity is required. Another disease in which PET has been proposed as a potential diagnostic tool is Rheumatoid Arthritis (RA). It has been shown that PET can measure the degree of inflammation in the synovium compartment of joints. PET imaging can be used in pre-clinical research to study murine models of arthritis. However, imaging arthritic mouse paws poses a significant challenge, since a very high resolution is required to image the very small mouse paw joints. These PET imaging applications motivate the development of high resolution detectors.High resolution detectors should have depth of interaction (DOI) encoding capabilities to maintain resolution uniformity across the image. The focus of this work is the development and characterization of high resolution DOI capable PET detectors and scanners for breast imaging and mouse paw imaging. The two PET detectors presented in this work were composed of arrays with LSO crystals of 1.5 x 1.5 x 20 mm3 and 0.5 x 0.5 x 8 mm3 dimensions, coupled to a position sensitive photomultiplier tube on one end and an avalanche photodiode on the opposite end. The array with the smaller crystal pitch was used to build the mouse paw scanner called PawPET. The performance characterization of both detectors is presented in terms of their spatial, DOI, energy, and timing resolution. In this dissertation, a description of the scanner gantry design for the breast scanner and PawPET scanner are given along with descriptions of the fabrication techniques used such as rapid prototyping using 3D printing technology.
The current generation of small-animal PET systems are being successfully used to understand a wide variety of biological problems, however the limitations in what can be visualized and quantified are readily apparent. The achievable spatial resolution of small- animal PET systems continues to be dominated by the detectors themselves and not by physical effects of positron decay. Prospects of new detector designs using solid-state photomultipliers (SSPM) have recently become available and the goal of this research was to understand the improvements detector designs utilizing SSPMs could bring to the field of small-animal PET. The dissertation work focuses on a new SSPM design, created in collaboration with Radiation Monitoring Devices, Inc. (Watertown, MA), which we refer to as the position-sensitive SSPM (PS-SSPM). The device is manufactured using a complementary-metal-oxide-semiconductor technology, and was designed and optimized for maximum spatial resolution.Two novel large-area PS-SSPMs were evaluated - at the time of production they were the largest area SSPMs ever manufactured - a continuous 10 mm x 10 mm, and a 2 x 2 array of 5 mm x 5 mm PS-SSPMs, both devices covering 1 cm2 area. Application specific electronics were developed and readout strategies were implemented for both large-area detector designs. The detectors were first optimized for operating bias voltage and temperature using a signal to noise analysis developed by our lab group. Their performance was then compared in terms of energy resolution, timing resolution, and spatial decoding ability. It was found that for ultra high spatial resolution applications the 2 x 2 array of 5 mm PS-SSPMs performed much better. Detector designs using a dual-ended readout of high resolution scintillation arrays were then evaluated. Scintillation arrays, composed of individual crystals of dimensions 0.7 mm x 0.7 mm x 20 mm, could be resolved at all depths and a depth of interaction resolution of 3.1 mm was measured; which if translated into a PET system would represent a large improvement in both spatial resolution and sensitivity, compared to current generation systems.