A Method For Source – Depth Estimation Using A Hybrid Optical / Gamma Camera

This work describes a new imaging technique to estimate the depth of radionuclide accumulations in relation to patient anatomy using a novel small field of view (SFOV) hybrid gamma camera (HGC) which combines optical and gamma imaging. The HGC offers higher spatial resolution and good sensitivity, and allows for greater flexibility for staff and patients than the conventional gamma cameras that are currently in use in nuclear medicine departments. This study aims to optimise the depth estimation technique and to assess the use of the HGC in clinical settings. Two HGCs were used to estimate the depth of radioisotope sources within a variety of phantoms and over a wide range of operating distances. Three camera arrangements (perpendicular, convergent and divergent) were investigated to select the best design for estimating the depth of the radioisotope within the phantoms; the perpendicular arrangement was found to be preferable among these arrangements. In this thesis, prototype anthropomorphic phantoms were designed and used to simulate hot spots in various regions of the human body, such as tumour localisation and sentinel lymph nodes. The HGC was used to image these phantoms with the aim of simulating a number of clinical procedures and assessing the camera performance for each. The effect of source movement on depth estimation of radiolabelled tissues was studied to simulate the effects of breathing during surgery. The HGC was used to carry out hybrid gamma-optical imaging procedures on two patients who had attended routine single photon emission computed tomography (SPECT) imaging appointments in the nuclear medicine departments at the Queen’s Medical Centre and the Nottingham City Hospital – Nottingham University Hospitals NHS Trust, Nottingham as part of clinical evaluation of the HGC. The results of the first two clinical studies of the HGC to estimate the depth of accumulated radioisotope are presented.