A. N. Grint

Prospectus: Development of a Compton Camera for Medical Imaging

Single Photon Emission Computed Tomography (SPECT) is an established method of studying physiological functions. However, novel gamma-ray Compton camera systems which provide electronic collimation have the potential to greatly improve the sensitivity of this technique. Compton cameras have been employed in high energy applications but have not yet been fully implemented for clinical applications at low energies. This paper describes the optimization of imaging efficiency for the ProSPECTus medical imaging Compton camera system with 99mTc. Experimental factors which degrade the image quality will also be assessed and quantified.

Status and Performance of an AGATA asymmetric detector

High‐resolution gamma‐ray detectors based on high‐purity germanium crystals (HPGe) are one of the key workhorses of experimental nuclear science. The technical development of such detector technology has been dramatic in recent years. Large volume, high‐granularity, electrically segmented HPGe detectors have been realised and a methodology to improve position sensitivity using pulse‐shape analysis coupled with the novel technique of gamma‐ray tracking has been developed. Collaborations have been established in Europe (AGATA) [1] and the USA (GRETA/GRETINA) [2] to build gamma‐ray tracking spectrometers. This paper discusses the performance of the first AGATA (Advanced GAmma Tracking Array) asymmetric detector that has been tested at the University of Liverpool. The use of a fully digital data acquisition system has allowed detector charge pulse shapes from a selection of well defined photon interaction positions to be analysed, yielding important information on the position sensitivity of the detector.

Design Considerations Of A Compton Camera For Low Energy Medical Imaging

Development of a Compton camera for low energy medical imaging applications is underway. The ProSPECTus project aims to utilize position sensitive detectors to generate high quality images using electronic collimation. This method has the potential to significantly increase the imaging efficiency compared with mechanically collimated SPECT systems, a highly desirable improvement on clinical systems. Design considerations encompass the geometrical optimisation and evaluation of image quality from the system which is to be built and assessed.

Orthogonal Strip HPGe Planar SmartPET Detectors in Compton Configuration

The evolution of germanium detectors over the last decade has lead to the possibility that they can be used in medical imaging and security scanning. The potential of increased sensitivity and energy resolution that germanium affords takes away the necessity of mechanical collimators that would be required in a gamma camera. Without mechanical collimation the resulting increase in statistics leads to the possibility of decreased patient dose or increased system throughput. In terms of security imaging segmented germanium provides directionality and excellent spectroscopic information for nuclide identification.

Quantification of the experimental limitations of a semiconductor PET camera

An investigation of the applicability of semiconductors to small animal positron emission tomography has been conducted. The SmartPET collaboration has been responsible for successful experimental work demonstrating how these detectors could enhance small animal imaging devices. Highly encouraging experimental results present an improvement in image resolution to 2mm (full width at half maximum). In order to understand current experimental limitations and overcome these in future systems, we have carried out a Monte Carlo study to systematically quantify experimental image distortions in terms of the image resolution of a point source. With a full understanding of experimental sources of error, the full potential of the existing SmartPET system can be understood. This ground work will allow the imaging of more complex phantom geometries to assist a transition into preclinical trials. This work also permits an optimized system to be designed in future.

A Semiconductor‐Based Positron Emission Tomography System

This paper shall summarize the research conducted employing the high‐purity germanium based small animal imaging system, SmartPET (SMall Animal Reconstructive Tomograph for Positron Emission Tomography). Geant4 simulations of the experimental setup were carried out in order to derive novel analysis procedures and quantify the system limitations. In this paper, we will focus on a gamma ray tracking approach devised to overcome germaniums high Compton scattering cross‐section and on imaging challenging and complex phantom geometries. The potential of the developed tools and of the system itself will be discussed.

First Results with TIGRESS and Accelerated Radioactive Ion Beams from ISAC: Coulomb Excitation of 20,21,29Na

The TRIUMF‐ISAC Gamma‐Ray Escape Suppressed Spectrometer (TIGRESS) is a state‐of‐the‐art γ‐ray spectrometer being constructed at the ISAC‐II radioactive ion beam facility at TRIUMF. TIGRESS will be comprised of twelve 32‐fold segmented high‐purity germanium (HPGe) clover‐type γ‐ray detectors, with BGO/CsI(Tl) Compton‐suppression shields, and is currently operational at ISAC‐II in an early‐implementation configuration of six detectors. Results have been obtained for the first experiments performed using TIGRESS, which examined the A = 20, 21, and 29 isotopes of Na by Coulomb excitation.