High contrast between lumbar nerve roots and surrounding structures using dual echo 3D turbo spin echo additional fusion images.

PURPOSE: We performed lumbar spinal magnetic resonance imaging of three-dimensional (3D) dual echo volumetric isotropic turbo spin echo acquisition (DE-VISTA) and constructed DE-VISTA additional fusion images (DE-VISTA-AFI), which is the addition of DE-VISTA proton density-weighted images (DE-VISTA-PDWI) to DE-VISTA T2-weighted images (DE-VISTA-T2WI). The aim of this study was to clarify whether DE-VISTA-AFI was able to clearly delineate spinal nerve roots. METHODS: A total of 677 patients underwent lumbar MR imaging, and the signal ratio (SR) between cerebrospinal fluid and nerve roots inside the dural sac and the SR between fat and nerve roots outside the dural sac were estimated using DE-VISTA-AFI, DE-VISTA-PDWI, DE-VISTA-T2WI, and 2D-T2WI. RESULTS: The SR between cerebrospinal fluid and nerve roots inside the dural sac on DE-VISTA-AFI was higher than that on DE-VISTA-PDWI (p < 0.0001) and on 2D T2WI (p < 0.0001). The SR between the fat tissue and nerve roots outside the dural sac on DE-VISTA-AFI was higher than that on DE-VISTA-PDWI (p < 0.0001) and 2D T2WI (p < 0.0001). CONCLUSION: DE-VISTA-AFI could clearly delineate the entire length of the lumbar nerve roots that run from the cauda equina in the spinal fluid through to the fat in the lateral recess, intervertebral foramen, and outside the intervertebral foramen.

Visualization of coronary arterial wall based on maximum intensity fusion of whole-heart MR angiograms and water suppression SPIR 3D T(1) TFE images.

PURPOSE: We estimated the coronary artery wall using maximum intensity fusion (MIF) of whole-heart magnetic resonance (MR) angiography (WHCA) and water suppression-spectral presaturation with inversion recovery (WS-SPIR) 3D T(1)-weighted turbo field echo (3DT(1) TFE). METHODS: We created a phantom using a wall of plastic bottles varied with plastic tapes measuring 0.4 to 3.0 mm thick (0-14 sheets) by vernier caliper and compared widths with those on profile curves. In 3 patients, to clarify the capacity to visualize the coronary wall in vulnerable plaque, we acquired WS-SPIR 3D T(1) TFE and WS-spectral attenuation with inversion recovery (SPAIR) (inversion time [TI] 400 ms) 3D T(1) TFE images of carotid vulnerable plaque; also termed "lipid-rich plaque," vulnerable plaque is considered to be visualized in high intensity. We utilized the same geometric parameters and rest period on WHCA as for WS-SPIR 3D T(1) TFE. We obtained MIF of WHCA and WS-SPIR 3D T(1) TFE and measured thickness of the right coronary artery (RCA) wall on the profile curve in 18 cases. RESULTS: The widths of the dip of the lower third of the bottom to head on the profile curve were consistent with actual measurement at 1-2 mm, the usual coronary artery wall thickness. Carotid plaques of high intensity by T(1)-weighted black-blood (T(1)BB) and T(2)-weighted BB (T(2)BB) methods showed high intensity on WS-SPAIR (TI 400 ms) 3D T(1) TFE and low intensity on WS-SPIR 3D T(1) TFE. With or without vulnerable plaque in the coronary artery wall, MIF of WHCA and WS-SPIR 3D T(1) TFE reflected the coronary artery wall. We obtained bands of low intensity in MIF between epicardial fat of WS-SPIR 3D T(1) TFE and coronary artery lumen of WHCA all but mid RCA in all 18 cases. We were unable to detect mid RCA in 5 cases. The outline of the obstructed mid RCA in 1 case was clear in WS-SPIR 3D T(1) TFE. The higher velocity of RCA movement caused blurring in another 4 cases in both WHCA and WS-SPIR 3D T(1) TFE. Those wall thickness of proximal or mid RCA averaged 1.3+/-0.2 mm. CONCLUSION: Bands of low intensity between epicardial fat and coronary artery lumen on MIF of WHCA and WS-SPIR 3D T(1) TFE can reflect the coronary artery wall.

Measuring visceral fat with water-selective suppression methods (SPIR, SPAIR) in patients with metabolic syndrome.

We attempted to measure the area and volume of visceral fat using magnetic resonance (MR) imaging to avoid radiation exposure. We used water suppression-spectral attenuation with inversion recovery (WS-SPAIR) as prepulses and conducted T(1) high-resolution isotropic volume examination (THRIVE). Image processing software can be used to estimate the area and volume of fat and separate the fat and water signals at a visually optimal threshold in the MR image, which requires contrast enhancement between intestinal contents and visceral fat. In 14 volunteers, we evaluated WS-SPAIR and water suppression-spectral presaturation with inversion recovery (WS-SPIR) with respect to the relationship between the flip angle of THRIVE and signal contrast. We used flip angles of 5 degrees, 10 degrees, and 20 degrees. The minimum threshold that allowed exclusion of intestinal contents from the masked region was determined for each technique. The volume and area of the masked region, which included subcutaneous fat, were measured at the umbilicus level. Both volume and area increased with a smaller flip angle. The masked region was larger with WS-SPIR-THRIVE (flip angle 5 degrees ). The size of the masked region was determined according to the minimum threshold that allowed exclusion of the intestinal contents from the masked region, expressing the contrast between the intestinal contents and fat in a relative manner. It was speculated that by separating the signals at the threshold, WS-SPIR-THRIVE (flip angle 5 degrees) was a more suitable technique for measuring the area and volume of visceral fat.

[Usefulness of the sagittal section imaging technique in whole-heart coronary MRA(WHCA)].

Whole-heart coronary MRA(WHCA)was performed in transaxial and sagittal sections in random order in 10 healthy volunteers to obtain coronal section multiplanar reconstruction(MPR)at an interval of 0.5 mm and thickness of 1 mm for evaluation. Visual evaluation showed sagittal section imaging to be superior to transaxial section imaging in 12 out of a total of 20 regions in the left and right proximal coronary arteries. Sagittal section imaging was found to be superior to transaxial section imaging in evaluation of the hepatic left lobe in all the cases as well as in evaluation of the right peripheral coronary arteries in 8 of 9 cases that could be evaluated. For quantitative evaluation, the difference in brightness between the peripheral adipose tissues(S fat)and the coronary arteries(S coronary)was assigned as CR(S coronary/S fat). Highly comparable results were obtained by quantitative and visual evaluation. Phantom experimentation was performed. The piston of the syringe was substituted for the diaphragm. Ghost artifact caused by movement of the diaphragm and phase return, i.e., the slice phase-encoding direction of the 3D sequence, were the origin of poor images in transaxial section imaging. We thus conclude that sagittal section imaging is useful in WHCA as a 3D sequence.

MR measurement of visceral fat: assessment of metabolic syndrome.

One diagnostic criterion for metabolic syndrome is obesity from the accumulation of visceral fat; others include abdominal circumference and area of visceral fat as measured by computed tomography (CT) at the umbilical level. We evaluated visceral fat using frequency-selective excitation magnetic resonance (MR) imaging SPAIR (spectral attenuation with inversion recovery) water suppression THRIVE (3D T1-high resolution isotropic volume examination). Fifty of 70 slices with 2-mm interval were used to render and measure volume of visceral fat ranging within 10 cm of the umbilicus; the area of visceral fat at the umbilical level was also measured. Imaging was completed using breath hold within 14 s. Image processing was easier than using CT.