Prognostic value of brain tissue pathological changes in patients with clinically isolated syndromes (CIS) suggestive of multiple sclerosis using magnetization transfer ratio (MTR).

The aim of this study is to investigate abnormalities in the brain tissue of patients with clinically isolated syndrome (CIS) suggestive of multiple sclerosis (MS). In this method, magnetization transfer ratio (MTR) parameter accompanied with segmentation regional measurements and histogram analysis were used to improve the evaluation of disease progression in CIS patients. Conventional MR imaging protocols such as T1-weighted, T2-weighted, T2-FLAIR as well as MT-2DSPGR were performed on four CIS patients and four normal subjects. White matter, gray matter and lesion masks were segmented from T2-weighted images and superimposed on MTR map using FSL software. Lesions were classified into isontense and severely hypointense according to their signal intensities relative to white matter on the T1-weighted images. MTR parameters of these two lesion types, normal appearing white matter (NAWM) and normal appearing gray matter (NAGM) were analyzed in comparison with those of normal controls. The MTR histograms of NAWM and NAGM were also generated for each segmented brain tissues. A significant reduction was found in mean white matter MTR and the histogram peak position between CIS patients and healthy subjects. The MTR histogram for NAWM showed also a total shift to the left. The MTR value for gray matter in CIS patients was similar to that of controls. Isointense lesions have significantly higher MTR values than severely hypointense lesions. Significant reduction in NAWM-MTR compared to normal subjects shows that pathological changes outside visible lesions on conventional MR images occur among patients with CIS at presentation. Quantitative MT imaging can help to evaluate the extent of global damage in the brain tissue.

Detection sensitivity of MRI using ultra-small super paramagnetic iron oxide nano-particles (USPIO) in biological tissues.

Today, by injecting iron oxide based nanoparticles (USPIO) as MRI contrast agents, it is possible to study lymphatic system and some specific tumors and their metastasis. The type of surface coating, and coating characteristics of the nanoparticles are important factors for the biological properties of nanoparticles and their destination target. On the other hand, these properties contribute to different signal intensities. This may confine application of all types of USPIO based contrast agents in routine daily experiments. In this study, the ability of detecting these particles having various sizes and coating properties was evaluated for MRI applications. Signal intensity changes after administration of these particles into tissues have been studied and their detection sensitivity was evaluated using a liver phantom and animal model (rat). IO based nanoparticles of various sizes (8-30 nm) functionalized and coated with various surface polymers such as dextran and starch, amine and hydroxide groups, and bear IO particles were used to investigate the signal changes. The optimized pulse sequences for proper demonstration of lymph nodes using these contrast agents were found (T2* FSPGR protocol with fat suppressions). A detection sensitivity of 98% was achieved in most experiments during applying a proper MR protocol. However, the type of surface coating, and coating characteristics such as thickness were shown to be essential factors for MRI signal intensity in both T1 and T2 protocols.