Usefulness of dual echo volumetric isotropic turbo spin echo acquisition (VISTA) in MR imaging of the temporomandibular joint.

PURPOSE: We investigated the ability to detect the articular disk and joint effusion of the temporomandibular joint (TMJ) of a method of dual echo volumetric isotropic turbo spin echo acquisition (DE-VISTA) additional fusion images (AFI). METHODS: DE-VISTA was performed in the 26 TMJ of 13 volunteers and 26 TMJ of 13 patients. Two-dimensional (2D) dual echo turbo spin echo was performed in the 26 TMJ of 13 volunteers. On a workstation, we added proton density-weighted images (PDWI) and T2 weighted images (T2WI) of the DE-VISTA per voxel to reconstruct DE-VISTA-AFI. Two radiologists reviewed these images visually and quantitatively. RESULTS: Visual evaluation of the articular disk was equivalent between DE-VISTA-AFI and 2D-PDWI. The sliding thin-slab multiplanar reformation (MPR) method of DE-VISTA-AFI could detect all articular disks. The ratio of contrast (CR) of adipose tissue by the articular disk to that of the articular disk itself was significantly higher in DE-VISTA-AFI than DE-VISTA-PDWI (P<0.05) in patients and volunteers with closed or open mouth. In volunteers, the CR between adipose tissue and the disk on DE-VISTA-AFI was marginally significant to that on 2D-PDWI at opened mouth (P=0.071) and not significantly different (P=0.18) from that at closed mouth. Joint effusion could be identified in DE-VISTA-AFI in all 8 joints that had joint effusion in DE-VISTA-T2WI but in only 3 of those joints in 2D-T2WI. The CR of joint effusion to adipose tissue on DE-VISTA-AFI did not differ significantly from that on DE-VISTA-PDWI. However, using DE-VISTA-T2WI in addition to DE-VISTA-PDWI, we could visually identify joint effusion on DE-VISTA-AFI that could not be identified on DE-VISTA-PDWI alone. CONCLUSION: DE-VISTA-AFI can depict the articular disk and a small amount of joint effusion by the required plane of MPR using the sliding thin-slab MPR method.

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.

Hyperacute stroke patients and catheter thrombolysis therapy: correlation between computed tomography perfusion maps and final infarction.

PURPOSE: We investigated the correlation between abnormal perfusion areas by computed tomography perfusion (CTP) study of hyperacute stroke patients and the final infarction areas after intraarterial catheter thrombolysis. MATERIALS AND METHODS: CTP study using the box-modulation transfer function (box-MTF) method based on the deconvolution analysis method was performed in 22 hyperacute stroke patients. Ischemic lesions were immediately treated with catheter thrombolysis after CTP study. Among them, nine patients with middle cerebral artery (MCA) occlusion were investigated regarding correlations of the size of the prolonged mean transit time (MTT) area, the decreased cerebral blood volume (CBV) area, and the final infarction area. RESULTS: Using the box-MTF method, the prolonged MTT area was almost identical to the final infarction area in the case of catheter thrombolysis failure. The decreased CBV areas resulted in infarction or hemorrhage, irrespective of the outcome of recanalization after catheter thrombolysis. CONCLUSION: The prolonged MTT areas, detected by the box-MTF method of CTP in hyperacute stroke patients, included the area of true prolonged MTT and the tracer delay. The prolonged MTT area was almost identical to the final infarction area when recanalization failed. We believe that a tracer delay area also indicates infarction in cases of thrombolysis failure.

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.