Development and implementation of quantitative methods for cardiac applications of positron emission tomography

The first topic addressed in this thesis was the characterization of a new hybrid PET/CT scanner (Discovery-690); that was later used for all of the studies (experimental and clinical)performed in this work. Subsequently an antropomorphic static cardiac phantom is described. This was used to analyze the performances of different reconstruction algorithms, encompassing di fferent levels of information such as: i) the Time Of Flight (TOF) of the photons and ii) the Point-Spread-Function (PSF) of the PET tomograph. A problem, own of cardiac studies in PET, is the motion blur due to the cardiac beat and to the breath of the patient. To study the e ffects of this combined motion, both quantitatively and qualitatively, a moving mechanical phantom was built, that executed both movements in a separate and controlled way. After this investigation this phantom was exploited to evaluate the e cacy of gating techniques (cardiac and respiratory), by using single and double gating. These techniques were also applied to patient data. Double gating revealed to be able to provide better spatial resolution but with noise levels too high for diagnostic purposes. To overcome this problem while maintaining the full spatial resolution two registration techniques were proposed. The fi rst one consists in an affi ne registration that can be applied to correct only for respiratory motion. The second technique aims at registering all of the gates using an elastic morphing technique. This is achieved by using a map of the myocardial surface to build a Thin-Plate-Spline deformation field, using a segmentation algorithm. Both techniques allowed the reduction of the noise. In both phantom and patient studies promising quality improvements were obtained. The last chapter of the thesis involved the quanti cation of absolute cardiac perfusion analyzing 13NH3 PET studies with kinetic models. Initially the mathematical proprieties of the models proposed to analyze this tracer were assessed. Following the e ect of the image reconstruction algorithms on the parameters quanti ed with a speci c model were assessed. Two di erent software programs that allow perfusion quanti cation were also compared. The results of the studies described allowed the de nition of a clinical 13NH3 PET protocol, currently in use.