All four MR imaging methods had significant linear correlations with iron and could potentially be used to determine iron status of subcortical gray matter structures in MS, with R2* mapping being preferred. A reliable method of determining iron status within MS lesions was not established.

Widespread abnormalities are present in the deep gray matter nuclei of patients recently diagnosed with MS; these abnormalities can be detected via multi-modal high-field MRI. Imaging metrics, particularly R₂*, relate to disease severity in the pulvinar and other gray matter regions.

Purpose: To demonstrate 4.7 Tesla (T) imaging methods for visualizing lesions in multiple sclerosis in the human brain using phase susceptibility-weighting and T2 weighting. Materials and Methods:Seven patients with relapsingremitting multiple sclerosis were imaged at 4.7T using three-dimensional (3D) susceptibility-weighted imaging (SWI) with 0.90 mm 3 voxel volumes, and with 2D T2-weighted fast spin echo (T2WFSE) with 0.34 mm 3 voxels and 1.84 mm 3 voxels. The visibility of MS lesions at 4.7T with phase SWI and T2WFSE was assessed by independent lesion counts made by an experienced neuroradiologist, and by quantitative measures. Results:High resolution T2WFSE at 4.7T provided excellent depiction of hyperintense lesions. When combined with phase SWI, 124 total lesions were identified of which 18% were only visible on phase SWI and not on T2WFSE. The phase lesions had a mean phase shift relative to local background of Ϫ11.15 Ϯ 5.97 parts per billion. Conclusion:Imaging at 4.7T can provide both high quality, high resolution T2WFSE and SWI for visualization of lesions in multiple sclerosis. Phase susceptibility-weighting can identify additional lesions that are not visible with high resolution T2WFSE.

Purpose:To demonstrate the effects of inherent RF inhomogeneity on ramped RF excitation at 3.0T, and to introduce a simple correction for improving visualization of distal intracranial arteries in three-dimensional time-of-flight MR angiography (3D-TOF-MRA). Materials and Methods:At 3.0T, the effects of RF inhomogeneity arising from RF interference were demonstrated for ramped RF excitation in intracranial 3D-TOF-MRA. Computer simulations and experiments on phantoms and eight normal volunteers were performed. Four different ramp shapes were tested as a possible means of countering the reduced RF field that affects the distal intracranial arteries.Results: RF destructive interference alters the ramp pulse shape, which is problematic for vessels that proceed from the center to the edge of the brain. Increasing the ramp pulse slope was shown to be an effective yet simple correction to counter the falling-off of the RF field toward the periphery of the head. With this approach, circle-of-Willis 3D-TOF-MRA studies had improved distal visibility. Conclusion:Ramped RF excitation is severely affected by RF interference at 3.0T, which makes the ramp profile suboptimal for distal intracranial blood vessels. A simple correction of the ramp slope can make a marked improvement.

Local phase gradient fitting combined with minimal high pass filtering provides better tissue depiction and more accurate phase quantification than standard filtering.