Fast Spin Echo Proton Density Research Articles

MR imaging of knee cartilage with FEMR.

Fluctuating equilibrium magnetic resonance (FEMR) is a rapid three-dimensional (3D) imaging sequence with high signal-to-noise ratio (SNR). FEMR may be useful for detecting cartilage defects in the knee. At 1.5 T, FEMR uses a TR with odd multiples of 2.2 ms for fat/water separation. With a TR of 6.6 ms, high-resolution 3D imaging of cartilage is possible. The knees of 10 volunteers and two patients were imaged on a GE Signa 1.5 T scanner using an extremity coil. Scans were preceded by a shimming sequence optimizing linear terms. Subjects were imaged with FEMR, proton-density fast spin-echo (PD-FSE), T2-weighted fast spin-echo (T2-FSE), and 3D fat-suppressed spoiled-gradient-recalled echo (3D-SPGR). SNR and contrast-to-noise efficiency measurements for cartilage using FEMR were superior to those using PD-FSE, T2-FSE, and 3D-FS-SPGR. FSE images showed bright synovial fluid with limited cartilage detail. 3D-SPGR had comparable resolution to FEMR but suboptimal cartilage/fluid contrast and longer scan times (8 min versus 2 min). Cartilage surface detail, outlined by bright synovial fluid, was best seen on the FEMR images. FEMR obtains high-resolution 3D images of the entire knee in 2 min with excellent cartilage/fluid contrast. FEMR is sensitive to field inhomogeneity and requires shimming. Surface defects are outlined by bright synovial fluid, and cartilage has higher signal-to-noise efficiency compared with PD-FSE, T2-FSE, and 3D-SPGR techniques.

SAI-24: Longitudinal study of lipid-modifying therapies on carotid atherosclerotic plaque morphology in vivo using magnetic resonance imaging

We hypothesize that high-resolution magnetic resonance imaging (MRI) in vivo can accurately quantify carotid plaque volume and differentiate carotid plaque elements that are related to ischemic events. A randomized, placebo-controlled pilot study in patients with clinically stable carotid atherosclerosis (n = 60) is currently underway using quantitative micro-MRI techniques to determine the effect of aggressive low-density lipoprotein (LDL) lowering (simvastatin 80 mg), moderate LDL lowering (simvastatin 10 mg), and LDL lowering with high-density lipoprotein elevation (simvastatin 20 mg and Niaspan [extended-release niacin; Kos Pharmaceuticals, Inc., Miami, FL] 2,000 mg) on MRI plaque characteristics over 12 months. MRI (1.5 T) consisted of 3D time-of-flight magnetic resonance angiography of the carotid bifurcation, axial T1-weighted spin echo, axial proton density fast spin echo (FSE), and axial T2-weighted FSE at the level of the bifurcation (approximately ± 1.6 cm). Total plaque volume was estimated from computer-assisted measurement of plaque cross-sectional area plaque area × slice thickness × number of slices (typically 2.0 mm × 16 slices). The intraclass correlation coefficient for plaque volume from repeat baseline scans (n = 8) was 0.95 using fat-suppressed proton density FSE images. In these patients, plaque volume was estimated at 1.34 ± 0.38 cm3 (mean ± SD). Plaque calcification, fibrous tissue content, lipid content, and hemorrhage are currently being estimated using the multiparametric imaging data. The effect of treatment on MRI indices will be correlated with changes in lipoproteins, serum inflammatory markers and urinary isoprostanes, indices of oxidant stress in vivo. Noninvasive micro-MRI techniques applied to carotid atherosclerosis in humans in vivo offers the potential to assess the longitudinal effect of therapies on quantitative indices of plaque morphology.

Longitudinal stress fractures of the tibia: diagnosis by magnetic resonance imaging.

Previous works describe magnetic resonance (MR) imaging characteristics of stress fractures. Diagnosis of the atypical, longitudinal type of stress fracture has been reported using computed tomography (CT). This report focuses on MR imaging of longitudinal stress fractures of the tibia. Six cases are presented in which a longitudinal linear abnormal marrow signal was detected in the middle and distal parts of the tibial shaft. Five patients were imaged using a 1.5 Tesla MR unit. Axial, sagittal and coronal T1 and T2-weighted or fat suppressed proton density fast spin echo images were obtained in all but one patient. One patient was imaged using a 0.5 Tesla MR unit with axial and coronal T1- and T2-weighted sequences. Initial conventional radiographs seen at clinical presentation were interpreted as normal in all cases. Two patients underwent radionuclide bone scan. and one patient was imaged with CT prior to MR imaging. In each instance, MR imaging demonstrated linear marrow signal abnormalities orientated along the long axis of the tibial shaft. Endosteal and periosteal callus was identified on axial images. In all cases, MR imaging clearly demonstrated a fracture extending through one cortex with abnormal signal in both the marrow cavity as well as adjacent soft tissues indicating edema. MR imaging was shown to be excellent for demonstration of fracture lines, callus, and marrow and soft tissue abnormalities seen in association with longitudinal stress fractures.