[Show abstract][Hide abstract] ABSTRACT: Cortical lesions have recently been a focus of multiple sclerosis (MS) MR research. In this study, we present a white matter signal attenuating sequence optimized for cortical lesion detection at 7 T. The feasibility of white matter attenuation (WHAT) for cortical lesion detection was determined by scanning eight patients (four relapsing/remitting MS, four secondary progressive MS) at 7 T. WHAT showed excellent gray matter-white matter contrast, and cortical lesions were hyperintense to the surrounding cortical gray matter, The sequence was then optimized for cortical lesion detection by determining the set of sequence parameters that produced the best gray matter-cortical lesion contrast in a 10-min scan. Despite the B1 inhomogeneities common at ultra-high field strengths, WHAT with an adiabatic inversion pulse showed good cortical lesion detection and would be a valuable component of clinical MS imaging protocols.
Magnetic Resonance Imaging 05/2012; 30(7):907-15. · 2.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Magnetic resonance imaging of cortical lesions due to multiple sclerosis (MS) has been hampered by the lesions' small size and low contrast to adjacent, normal-appearing tissue. Knowing cortical lesion T1 and proton density (PD) would be highly beneficial for the process of developing and optimizing dedicated magnetic resonance (MR) sequences through computer modeling of MR tissue responses. Eight patients and seven healthy control subjects were scanned at 7 T using a series of inversion recovery turbo field echo scans with varying inversion times. Regions of interest were drawn in white matter, gray matter, cortical lesions, white matter lesions and cerebrospinal fluid. White matter and gray matter T1s were significantly higher in MS patients than in controls. Cortical and white matter lesion T1 and PD are also presented for the first time. The advantages of ultrahigh field MR imaging will be important for future investigations in MS research and sequence optimization for the detection of cortical lesions.
Magnetic Resonance Imaging 09/2011; 30(1):19-25. · 2.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To develop a protocol which optimizes contrast, resolution and scan time for three-dimensional (3D) imaging of the human eye in vivo using a 7 Tesla (T) scanner and custom radio frequency (RF) coil.
Initial testing was conducted to reduce motion and susceptibility artifacts. Three-dimensional FFE and IR-TFE images were obtained with variable flip angles and TI times. T(1) measurements were made and numerical simulations were performed to determine the ideal contrast of certain ocular structures. Studies were performed to optimize resolution and signal-to-noise ratio (SNR) with scan times from 20 s to 5 min.
Motion and susceptibility artifacts were reduced through careful subject preparation. T(1) values of the ocular structures are in line with previous work at 1.5T. A voxel size of 0.15 x 0.25 x 1.0 mm(3) was obtained with a scan time of approximately 35 s for both 3D FFE and IR-TFE sequences. Multiple images were registered in 3D to produce final SNRs over 40.
Optimization of pulse sequences and avoidance of susceptibility and motion artifacts led to high quality images with spatial resolution and SNR exceeding prior work. Ocular imaging at 7T with a dedicated coil improves the ability to make measurements of the fine structures of the eye.
Journal of Magnetic Resonance Imaging 11/2009; 30(5):924-32. · 2.57 Impact Factor