Optimising reconstruction to accommodate complex system models for SPECT.

There are a number of techniques used to image the human body to provide information on anatomy (structure) or function, to aid in diagnosing a range of diseases. One such technique is Single Photon Emission Computed Tomography (SPECT) which permits physicians to visualise the internal 3D distribution of administered radioactive compounds that typically reflect functional differences between normal and diseased tissues. SPECT is a widely available clinical tool. There are several fundamental difficulties in obtaining accurate and useful images using SPECT. Images tend to be quite blurred but also can have grainy appearance that detracts from the image interpretation. The main reason for this is the need to use a collimator to determine the origin of detected photons. The problem is that to improve image quality requires more counts which either results in additional study time and patient inconvenience or increased radiation dose, which is clearly undesirable. Optimising the collimator offers potential for both reduced study time and reduced radiation dose. A further practical problem is the time taken to compute the final images, which can be quite lengthy as the complexity increases. We propose to adapt computer cards that are currently used in domestic game systems that provide very fast computation. Given that we can improve the efficiency for processing of images, this also opens the possibility to explore even more complex approaches to processing that utilise additional information which is currently acquired but ignored. This offers further potential not only to reduce study time but to also improve clinical image quality. The project has a focus on delivering a practical solution that can be implemented in routine clinical practice.The work will be undertaken under the supervision of three investigators each with complementary skills; physics applied to nuclear medicine (Hutton), reconstruction algorithms (Arridge) and acceleration using graphics computer boards (Ourselin). The work will proceed initially with simulation studies in order to optimise design of collimators prior to these being manufactured and development of the computer programs that will be used for image reconstruction. The developed approach will be implemented on fast hardware and this implementation will be directly compared with conventional approaches to implementation in terms of both speed and image quality. Finally the complete system including collimators and fast computation will be evaluated in human subjects (ethics approval will be sought at the appropriate time prior to commencing human studies). The human studies will involve patients having additional images acquired but will not involve any additional radiation dose. The translation of our research findings directly into clinical practice is an important goal in the research.