Utility of Radial Scanning for the Identification of Arterial Hypervascularity of Hepatocellular Carcinoma on Gadoxetic Acid-Enhanced Magnetic Resonance Images.

OBJECTIVES: This study aimed to compare the accuracy of assessing the arterial hypervascularity of hepatocellular carcinoma (HCC) on dynamic computed tomography (CT) scans and gadoxetic acid (EOB)-enhanced magnetic resonance imaging (MRI) scans performed with radial sampling. METHODS: We studied the images of 40 patients with hypervascular HCC. A radiologist recorded the standard deviation of the attenuation (or the signal intensity [SI]) in subcutaneous fat tissue as the image noise (N) and calculated the contrast-to-noise ratio (CNR) as follows: (CNR) = (n-ROIT - n-ROIL)/N, where n-ROIT is the mean attenuation (or SI) of the tumor divided by the mean attenuation (or SI) of the aorta and n-ROIL is the mean attenuation (or SI) of the liver parenchyma divided by the mean attenuation (or SI) of the aorta. RESULTS: The CNR was significantly higher on EOB-enhanced MRI than on dynamic CT scans. CONCLUSIONS: For the assessment of HCC vascularity, EOB-enhanced MRI scans acquired with radial sampling were more accurate than dynamic CT images.

[Optimized magnetic resonance sequences and parameters with operative assisted images for radical prostatectomy at 3 tesla-magnetic resonance image].

The objective of our study was to optimize magnetic resonance image (MRI) sequences and parameters using operative assisted images (three-dimensional images) for radical prostatectomy at 3 tesla (T) MRI. Five healthy volunteers underwent MRI on the 3.0 T scanner. Various sequences and parameters [Cube (TE/TR = 18, 50, 90 ms/2000 ms), FIESTA (TE/TR/FA = 2.4 ms/5 ms/40 degrees, 90 degrees), fSPGR (TE/TR/FA = 2.3 ms/11.2 ms/20 degrees), slice thickness = 1.2 mm, matrix = 192 x 160] were respectively compared. Several structures of the pelvis (the central zones and transition zones of the prostate, the peripheral zones of the prostate, seminal vesicles, rectum wall, bladder, muscle and fat) were determined. The signal intensities of these structures were measured on reformatted axial images and compared against several structures of the pelvis. Correlation with various sequences and parameters was based on the signal-to-noise ratio (SNR), the contrast ratio (CR) and the presence of artifacts. Student's t-test was used for statistical analysis. With Cube (TE/TR = 50 ms/2000 ms), the average value of visual evaluation with artifacts was high, and SNR and CR were higher than for other sequence and parameters. Optimized MRI sequences and parameters were Cube (TE/TR = 50 ms/2000 ms) which provides improved SNR and CR and the presence of artifacts with operative assisted images for radical prostatectomy. These operative assisted images obtained from Cube (TE/TR = 50 ms/2000 ms) are likely to be useful for surgery.

Low b-value Diffusion Tensor Imaging to Analyze the Dynamics of Cerebrospinal Fluid: Resolving Intravoxel Pseudorandom Motion into Ordered and Disordered Motions.

PURPOSE: Analysis of cerebrospinal fluid (CSF) dynamics may be beneficial for understanding the mechanisms and diagnosis of several neurological diseases. Low b-value diffusion tensor imaging (low-b DTI) is useful for observing the slow and complex motion of the CSF. Theoretically, a mathematical framework suggests that low-b DTI provides the variance of the pseudorandom motion of the CSF. Furthermore, low-b DTI could provide comprehensive information on fluid dynamics. Accordingly, we proposed an analysis technique that resolves intravoxel pseudorandom motion into ordered (linear) and disordered (random) motions based on the mathematical framework. METHODS: The proposed analysis technique helps measure low-b DTI with multiple diffusion times and linearly fits its mean diffusivity (MD) with the diffusion time to obtain two parameters, double-slope Vv and y-intersect Dr, which represent the variance of the velocity distribution of linear motion and the diffusion coefficient of random motion, respectively. Seven healthy subjects were scanned to evaluate the proposed technique and investigate fluid dynamics in several representative ROIs. RESULTS: The obtained data showed the validity of the technique, repeatability, and consistency across the subjects in ROIs, such as the lateral ventricle (LV), third ventricle (3V), fourth ventricle (4V), and Sylvian fissure (SF). The obtained parameters Vv and Dr highlighted different characteristics of fluid dynamics in the representative ROIs: low Vv and low Dr in the LV, high Vv and moderate Dr in the 3V, and moderate Vv and moderate Dr in the 4V and SF. CONCLUSION: The proposed analysis technique will facilitate a comprehensive investigation of the complex dynamics of the CSF using resolved parameters representing ordered and disordered motions.

Age-related changes in intramyocellular lipid in humans by in vivo H-MR spectroscopy.

BACKGROUND: It is considered that the increasing intramyocellular lipid (IMCL) affects health risks and muscle attenuation. Though body fat increases significantly with age in lean humans, it is not known whether IMCL increases or not. In this study, we investigated the changes with age in IMCL concentrations in skeletal muscles using (1)H-MR spectroscopy and studied them in relation to body fat percentage, waist-hip ratio, and blood components. METHODS: Twenty-four lean young (age 21.2 +/- 1.9, BMI 21.5 +/- 1.8) and 23 lean old (age 70.9 +/- 2.4, BMI 21.7 +/- 1.3) subjects took part in the study. Subjects were grouped by gender into age- and BMI-matched young and old groups. The (1)H-MRS was obtained from the tibialis anterior (TA), medial gastrocnemius (MG) and soleus (SOL) muscles. RESULTS: The IMCL content in SOL and MG in the old was found to be higher (p < 0.01) than that in the young. No age difference in IMCL content in TA was found. IMCL concentrations in SOL were higher than those in MG and TA in the order of SOL > MG > TA (p < 0.01). IMCL content correlated significantly with waist-hip ratio in all skeletal muscles. A significant relationship was observed between percent body fat and IMCL in TA and MG (p < 0.05). However, no correlation was found between IMCL content in each muscle and BMI. The IMCL content in all skeletal muscles significantly correlated with HbA1c, triglyceride, total cholesterol and LDL cholesterol concentrations. CONCLUSION: These results suggest that increased IMCL in both lean older men and women might be related to body composition, blood lipids and lipoprotein profiles, and that this might affect muscle attenuation.

High-resolution MRI of the labyrinth: optimization of scan parameters with 3D-FSE.

The aim of our study was to optimize the parameters of high-resolution MRI of the labyrinth with a 3D-FSE sequence. We investigated TR, TE, Matrix, FOV, and coil selection in terms of CNR (contrast-to-noise ratio) and SNR (signal-to-noise ratio) by comparing axial images and/or three-dimensional images. The optimal 3D-FSE sequence parameters were as follows: 1.5 Tesla MR unit (Signa LX, GE Medical Systems), 3D-FSE sequence, dual 3-inch surface coil, acquisition time=12.08 min., TR=5000 msec, TE=300 msec, 3 NEX, FOV=12 cm, matrix=256 x 256, slice thickness=0.5 mm/0.0 sp, echo train=64, bandwidth=+/-31.5 kHz. High-resolution MRI of the labyrinth using the optimized 3D-FSE sequence parameters permits visualization of important anatomic details (such as scala tympani and scala vestibuli), making it possible to determine inner ear anomalies and the patency of cochlear turns. To obtain excellent heavily T2-weighted axial and three-dimensional images in the labyrinth, high CNR, SNR, and spatial resolution are significant factors at the present time. Furthermore, it is important not only to optimize the scan parameters of 3D-FSE but also to select an appropriate coil for high-resolution MRI of the labyrinth.

Investigation of intervertebral disc and facet joint in lumbar spondylolisthesis using T2 mapping.

PURPOSE: We measured T2 relaxation time of the intervertebral discs (IVD) and facet joints (FJ) in patients with degenerative spondylolisthesis (DS) and no spondylolisthesis (NS) and investigated the characteristics of these parts in DS. METHODS: In 40 patients with DS and 40 patients with NS, we measured T2 relaxation time of the IVD and FJ and compared them between groups. In the group with DS, we also examined the relationship between the degree of slippage using Meyerding grade and T2 relaxation of each part in the IVD and FJ. RESULTS: T2 relaxation time of the IVD tended to be lower in the DS than NS group and differed significantly (P < 0.01) within the anterior annulus fibrosus. T2 relaxation time in the FJ was significantly higher in the DS than NS group. T2 relaxation time in the FJ was significantly higher for those assessed Meyerding Grade II than Grade I, although we observed no significant differences in T2 relaxation time in any area of the IVD. CONCLUSION: T2 relaxation time decreased in the anterior annulus fibrosus of the IVD and increased in the FJ in patients with DS, suggesting an association of IVD and FJ degeneration with the development of lumbar DS.

Gadolinium-enhanced dynamic magnetic resonance imaging with endorectal coil for local staging of rectal cancer.

PURPOSE: The aim of this study was to evaluate the accuracy of dynamic gadolinium (Gd)-enhanced magnetic resonance imaging (MRI) with endorectal coil for assessing tumor invasion based on simple classification criteria. MATERIALS AND METHODS: A total of 58 patients with operable primary rectal cancer underwent preoperative MRI. An enhancement pattern in Gd-enhanced dynamic MRI with regard to tumor penetration was clarified. Retrospectively, two observers independently scored T2-weighted MRI and T2-weighted MRI combined with Gd-enhanced dynamic MRI for tumor penetration using the following criteria: With Gd-enhanced dynamic MRI, T1 tumors showed an early enhanced line around the tumor as rim enhancement; T2 tumors appeared as black lines or double layers, as the muscularis propria kept its integrity; T3 tumors showed partial discontinuity of the muscularis propria as a dotted line and a perforated area as an interrupted line. A confidence level scoring system was used, and receiver operating characteristic curves were generated. RESULTS: There were no significant differences at the T1 stage. There were significant differences for observer 1 (P = 0.001 for observer 1) at the T2 stage. There were significant differences for both observers (P = 0.001 for observer 1 and P = 0.005 for observer 2) at the T3 stage. CONCLUSION: Our criteria for Gd-enhanced dynamic MRI were effective for T3 stage tumors.

MR angiography for detecting the artery of Adamkiewicz and its branching level from the aorta.

PURPOSE: We evaluated the efficacy of magnetic resonance angiography (MRA) for detecting the artery of Adamkiewicz (AKA) and the vertebral level of its feeding arteries branching from the aorta. MATERIALS AND METHODS: Eighty-two patients (67 men, 15 women; aged 34 to 86 years, mean age 68.6 years) with thoracic descending and thoracoabdominal aortic lesions (aneurysm in 55, dissection in 25, coarctation in 2) underwent MRA to detect AKA. MRA was performed using 6-phase, dynamic-enhanced, 3-dimensional, fast spoiled gradient recalled acquisition in steady state (GRASS) on a 1.5-tesla (T) system, with double-dose bolus contrast injection. The vertebral levels of AKA branching and the AKA feeder artery branching from the aorta were determined. RESULTS: The AKA was detected in 67 patients (81.7%). Branching of AKA occurred at levels T7 to T12 on the left side (n=52) and on the right (n=15). Vascular continuity from the aorta to the anterior spinal artery was demonstrated in 55 patients (67.1%). Comparing the vertebral level of arterial branching from the aorta to that of the AKA at the intervertebral foramen, the AKA branched at the same vertebral level in 44 patients (80.0%), one vertebral level above/below in 10 (18.2%), and 2 vertebral levels above in one (1.8%). CONCLUSION: MRA can be useful in the preoperative work-up of patients with thoracoabdominal aortic lesions to localize AKA and the segmental trajectories of vessels supplying blood to the AKA.

Double-subtraction maximum intensity projection MR angiography for detecting the artery of Adamkiewicz and differentiating it from the drainage vein.

PURPOSE: To evaluate the efficacy of double-subtraction magnetic resonance angiography (MRA) (subtraction of the subtracted venous phase image from the subtracted arterial dominant phase image) for depicting the artery of Adamkiewicz and differentiating it from the drainage vein. MATERIALS AND METHODS: A total of 170 patients (123 men, 47 women; aged 17-84 years, mean = 67 years), with a thoracoabdominal vascular lesion underwent MRA for detection of the artery of Adamkiewicz. MRA was performed as a five-phase dynamic-enhanced three-dimensional (3D) fast spoiled gradient recalled acquisition in steady state (GRASS) sequence on a 1.5-T system, with double-dose bolus contrast and saline injection. The levels at which the artery of Adamkiewicz and drainage vein originated were determined. Signal intensities of the two vessels were measured with source images to assess the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and necessity of the double-subtraction technique. RESULTS: The artery of Adamkiewicz was detected in 140 patients (82.4%). Branching occurred at levels T8-T12 on the left and T8-T11 on the right. An additional anterior radiculomedullary artery was detected in 18 patients. The drainage vein was detected in 133 patients (78.2%). It merged at the T9-L2 level on both sides. In six of the 133 patients (4.5%), the drainage vein branched upwardly. Neither SNR nor CNR differed significantly between the artery of Adamkiewicz and the drainage vein in the arterial phase; but on the subtraction image, signal intensity of the artery was higher than that of the drainage vein (P < 0.05). CONCLUSION: Double-subtraction MRA is useful for detecting the artery of Adamkiewicz when it is necessary to differentiate it from the drainage vein.