A method for the visual analysis of early-stage Parkinson's disease based on virtual MRI-derived SPECT images

Objective: Nuclear medicine imaging of dopamine transporter (DAT) binding is used in the differential diagnosis of neurodegenerative Parkinsonism but DAT receptor density in the posterior part of the putamens is of difficult evaluation because it is strongly affected by the partial-volume effect. Since its quantitative correction is often difficult, we propose here a qualitative method to compare the real study to virtual images of the patient, obtained as if he/she was healthy. Method: The virtual images are obtained coregistering the magnetic resonance images to SPECT's; segmenting magnetic resonance images to obtain the real shape and position of caudates and putamens; digitally filling these volumes with an activity concentration close to normal condition; blurring and convolving images with the measured point-spread function of the SPECT system. Result: The method was applied to phantom and, retrospectively, to a small cohort of 20 patients, that underwent SPECT examination more than 3 years ago, to prove the feasibility of the method in a clinical environment. Conclusions: This method enhances the accuracy of the nuclear medicine interpretation by the inclusion of the proper morphological information of each patient, helping the physician to differentiate between partial-volume effects and real hypofixation of the tracer. The method proved to be feasible but is applicability is fostered by the need of a concomitant MR. © 2012 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 22, 172-176, 2012