Functional image reconstruction enhancement for MR spectroscopic and nuclear medicine images

Functional images in medicine, such as phosphorus magnetic resonance spectroscopic imaging (SI) images or perfusion studies in nuclear medicine (NM) using 99mTc-HMPAO, are low in resolution compared to x-ray CT or proton MR (anatomic) images. This paper describes an improved, rapid method for enhancing the accuracy and resolution of functional medical images. While both functional and anatomic images are often available for the organ under study, few attempts have been made to use the a priori information in the anatomic images to improve the poor resolution of the corresponding functional images. The proposed technique assumes that compartments can be identified in a high resolution anatomic image of the region under study, and each of these compartments is assumed to contain a spatially heterogeneous concentration of metabolite. The spatial variation of the metabolite is modelled by a series expansion. Application of the method is derived for both MR spectroscopic images, and scintigrams. Noise-free and noisy simulation studies of spectroscopic images are presented which show that the method is robust in the presence of noise, and also when the assumed model is mismatched to the function which describes the actual metabolite compartmental concentration.