Tomographic Reconstruction Methods for Optical and Intra-operative Functional Imaging

Tomographic imaging has revolutionized the medical domain over the last 50 years. Imaging modalities like CT, PET or SPECT have enabled non–invasive diagnosis, patient–specific modeling as well as more accurate treatment, and are increasingly establishing themselves also for interventional use. The theoretical basis for tomographic imaging has been developing over the last century as well, with series expansion methods quickly being adopted as the method of choice for many modalities due to their flexibility. This work explores series expansion based methods for two novel, emerging imaging modalities. Diffuse Optical Tomography together with new fluorescent tracers enables visualization of molecular processes in vivo using non–ionizing radiation. In this work an implementation for full–projection free–space Fluorescence Molecular Tomography based on series expansion methods was developed along with a thorough analysis of the system design for the new acquisition geometries. The system was evaluated on phantoms as well as on mice, both ex vivo and in vivo. While functional imaging is standard–of–care for many pathologies today, interventional use has been hampered by imaging system requirements incompatible with operating room realities. Over the course of this work, a new imaging modality called Freehand SPECT has been developed to overcome this incompatibility. By using tracked functional detectors and series expansion methods adapted to sparse ad–hoc acquisition geometries, Freehand SPECT enables localized intra–operative SPECT imaging. Experiments and evaluations were performed on phantoms as well as on patients both pre– and intra–operatively, and validated the feasibility of this new approach to imaging.