الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Multiple sclerosis is a progressive inflammatory demyelinating disorder affecting the central nervous system and results in variable degrees of neurodegeneration. MR imaging plays a crucial role in diagnosis and monitoring of patients with MS. Optimizing the MS protocol by adding SWI sequence can add relevant additional information to the study for better patient assessment.
This study aimed at determining the added value of SWI in evaluation of patients with multiple sclerosis.
The study was performed on 30 patients with a definite diagnosis of MS based on their clinical presentation and MRI findings. They were 8 males and 22 females and their ages ranged between 20-52 years.
Eighteen patients were scanned on a 1.5T Philips Gyroscan Intera whole body scanner. Twelve patients were scanned on a 3.0T Philips Ingenia whole body scanner. Imaging included conventional MRI sequences in addition to 3D FLAIR and SWI sequence using a standard quadrature head coil.
The findings of our study were:
1. SWI is the best when compared to standard MRI brain sequences in assessing for the presence of central veins in MS lesions. This is because SWI is superior in visualizing cerebral veins and venules owing to the blooming effect of deoxyhemoglobin within small cerebral veins. In our study 515/890 (58%) of all MS lesions were associated with central veins (central vein sign) and this sign was clearly visible on both 3T and 1.5T MRI.
2. SWI was the only sequence in our protocol to demonstrate intralesional iron in MS plaques and characterizes its distribution (peripheral or central).
3. Our study showed that there is a positive correlation between the number of iron containing lesions seen on SWI and the degree of brain atrophy determined using Pasquier’s Scale.
4. SWI poorly visualizes MS plaques. When compared to 3D FLAIR, SWI showed only 59% of the lesions visualized on 3D FLAIR. The need to use an anatomical based sequence such as 3D FLAIR for lesion localization is essential when assessing for central veins or intralesional iron. This might be time consuming and require some level of training. The availability of post processing software that co-registers SWI with an anatomical sequence such as FLAIR would potentially make it easier to assess for central veins and intralesional iron simultaneously.
5. Our study proves that SWI is not the only sequence to show MS lesions with central veins. 3D FLAIR, although not a susceptibility based sequence demonstrated central veins clearly in 388/890 (43%) of lesions. All of the linear central hypointensities in MS lesion seen on 3D FLAIR corresponded to blooming central veins on SWI. The bias or mean difference in number of lesions showing central veins between SWI sequence and 3D FLAIR sequence was assessed using the Bland Altman plot. SWI showed an average of 4 more lesions with central veins compared to 3D FLAIR. Although 3D FLAIR showed less central veins than SWI, the ability to demonstrate both the lesions and the central vein simultaneously without post processing software or a localizer was an added advantage. Whether the difference in number of central veins between 3D FLAIR and SWI is significant, would depend on the ability to fulfill the proposed 45% central vein diagnostic threshold in each patient. Our sensitivity values for the 45% CVS diagnostic threshold using 3D FLAIR was 50% and for SWI was 66%.
6. As regard to paramagnetic rim lesions, only one of our lesions showed a rim of diffusion restriction corresponding to the rim of enhancement seen on post contrast T1 and the rim of susceptibility seen on SWI. This stresses that diffusion restriction and post contrast enhancement will only visualize acutely active lesions and are weak indicators of chronic activity.
7. As regards to spatial distribution, our results show a significantly higher prevalence of lesions with central veins and paramagnetic rims in periventricular and deep white matter compared to other regions of the brain. This is likely explained by the higher number of veins in these locations compared to other locations of the brain.
8. Our study also shows that it is still possible to visualize paramagnetic rims on a 1.5T magnet. 3/73 paramagnetic rim lesions were clearly visualized on a lower strength 1.5T magnet. Therefore we recommend the search for paramagnetic rim lesions in every MS patients regardless of the magnet strength.
9. As regards to the effect of different MRI magnet field strengths on central vein sign assessment, we found no significant difference between the proportion of central veins on 1.5T compared to 3T.
10. Finally we found a positive correlation between paramagnetic rim lesions and the total lesion load. In other words, the higher the lesion load, the more likely it is to detect paramagnetic rims. However we found no correlation between paramagnetic rim lesions and age.
Therefore, our study shows SWI sequence can provide additional important information when evaluating MS patients. SWI can help in diagnosing MS by differentiating MS from mimicking diseases through the visualization of the central vein sign. In addition in patients with MS on follow up, the visualization of intralesional iron in MS plaques correlates with patient disability and can reflect the presence of chronic activity in rim lesions.