Early Detection of Cardiac Amyloidosis in Transthyretin Mutation Carriers.

Diagnostic strategies for symptomatic transthyretin (ATTR) cardiac amyloidosis showing typical morphological features such as increased ventricular wall thickness and myocardial injury such as an elevation in serum troponin T level have been established, but those for subclinical cardiac amyloidosis are limited. In the era when effective therapies to suppress/delay progression of ATTR cardiac amyloidosis are available, early detection of cardiac involvement plays a crucial role in appropriate decision-making for treatment in TTR mutation carriers who have a family history of heart failure and death due to ATTR amyloidosis. Findings of three cases with known pathogenic transthyretin (TTR) mutations (p.Ser70Arg, p.Phe53Val, and p.Val50Met) and family histories of death for amyloidosis were presented. Two cases were asymptomatic, and a case carrying p.Phe53Val had gastrointestinal symptoms and autonomic neuropathy. Levels of plasma N-terminal fragment of pro-B-type natriuretic peptide and troponin T were within normal ranges in all cases, but results of cardiac magnetic resonance (CMR) and bone scintigraphy clearly revealed the presence of cardiac involvement in all cases, even in a case without echocardiographic abnormalities including left ventricular hypertrophy and relative apical sparing of longitudinal strain shown by two-dimensional speckle-tracking echocardiography. Electrocardiography revealed modest abnormalities including reduced R wave amplitude in V2 and a trend toward left axis deviation in all cases. In conclusion, CMR, bone scintigraphy, and electrocardiography are useful for early detection of ATTR cardiac amyloidosis in TTR mutation carriers. The role of comprehensive cardiac assessment in the early detection of cardiac amyloidosis in TTR mutation carriers is discussed.

Visualization of cerebellar peduncles using diffusion tensor imaging.

The cerebellum communicates with the cerebral cortex via the superior, middle, and inferior cerebellar peduncles (CPs). To preserve the structure and function of the brainstem and cerebellum, which is compressed in various pathological conditions, it is important to delineate the spatial interrelationship of the CPs for presurgical planning and intraoperative guidance. Diffusion tensor tractography (DTT) is a technique capable of depicting the major fiber bundles in CPs. However, routine use of this technology for brainstem visualization remains challenging due to the anatomical smallness and complexity of the brainstem and susceptibility-induced image distortions. Here, we attempt to visualize CPs using high-resolution DTT in a commercial equipment for the application of this technique in normal clinical settings. DTT and fast imaging employing steady-state acquisition-cycled phases (FIESTA) of the whole brainstem were performed. We rendered the DTT fiber bundle using a region-of-interest-based fiber tracking method onto the structural image generated in FIESTA by automatic image coregistration. Fibers of the CPs were clearly visualized by DTT. The DTT-FIESTA overlaid image revealed the cross-sectional and three-dimensional anatomy of the pyramidal tract and the ascending sensory fibers, in addition to the CPs. This could indicate a geometrical relationship of these fibers in the brainstem. The CPs could be visualized clearly using DTT within clinically acceptable scanning times. This method of visualizing the exact pathway of fiber bundles and cranial nerves in the skull base helps in the planning of surgical approaches.

3D neuromelanin-sensitive magnetic resonance imaging with semi-automated volume measurement of the substantia nigra pars compacta for diagnosis of Parkinson's disease.

INTRODUCTION: Neuromelanin-sensitive MRI has been reported to be used in the diagnosis of Parkinson's disease (PD), which results from loss of dopamine-producing cells in the substantia nigra pars compacta (SNc). In this study, we aimed to apply a 3D turbo field echo (TFE) sequence for neuromelanin-sensitive MRI and to evaluate the diagnostic performance of semi-automated method for measurement of SNc volume in patients with PD. METHODS: We examined 18 PD patients and 27 healthy volunteers (control subjects). A 3D TFE technique with off-resonance magnetization transfer pulse was used for neuromelanin-sensitive MRI on a 3T scanner. The SNc volume was semi-automatically measured using a region-growing technique at various thresholds (ranging from 1.66 to 2.48), with the signals measured relative to that for the superior cerebellar peduncle. Receiver operating characteristic (ROC) analysis was performed at all thresholds. Intra-rater reproducibility was evaluated by intraclass correlation coefficient (ICC). RESULTS: The average SNc volume in the PD group was significantly smaller than that in the control group at all the thresholds (P < 0.01, student t test). At higher thresholds (>2.0), the area under the curve of ROC (Az) increased (0.88). In addition, we observed balanced sensitivity and specificity (0.83 and 0.85, respectively). At lower thresholds, sensitivity tended to increase but specificity reduced in comparison with that at higher thresholds. ICC was larger than 0.9 when the threshold was over 1.86. CONCLUSIONS: Our method can distinguish the PD group from the control group with high sensitivity and specificity, especially for early stage of PD.

[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.

[Costal Cartilage Injury Using MRI: A Case Report].

A magnetic resonance imaging (MRI) scan was performed to rule out a sternal fracture in a woman in 30s. Short tau inversion recovery (STIR) coronal showed no signal change in the sternum but increased signal from the mediastinum to the anterior thoracic region. We could not detect significant findings until midway through the examination. T2-weighted fat-suppressed images revealed a suspected left first costal cartilage injury at the end of the examination. In addition, three-dimensional gradient-recalled echo (3D GRE) T1-weighted fat-suppressed images clearly revealed a lesion area with a high signal intensity in the costal cartilage and a low signal intensity in the surrounding tissue, and we diagnosed costal cartilage injury definitely. In case of MRI for posttraumatic chest pain, T1-weighted fat-suppressed images with 3D GRE may be useful for the detection of lesion area.

Optimal acceleration factor for image acquisition in turbo spin echo: diffusion-weighted imaging with compressed sensing.

In this study, the change in the image quality and apparent diffusion coefficient (ADC) with increase in the acceleration factor (AF) was analyzed and the most optimal AF was determined to reduce the scan time while preserving the image quality. The AF was changed from 2 to 20 in the MR acquisitions. The similarities between the accelerated and reference images were determined based on the structural similarity (SSIM) index for DWI image and coefficient of variation (%CV) for ADC. The SSIM index decreased significantly when the AF ≥ 8 compared with when the AF = 2 (p < 0.05). In the reference image, the %CV of the ADC increased significantly when the AF ≥ 10 (p < 0.01). In conclusion, a remarkable decrease in the image quality and ADC was observed when the AF was > 8. Thus, an AF < 8 would be optimal for reducing the scan time while preserving the image quality.

Analysis of intra and extramyocellular lipids in the multifidus muscle in patients with chronic low back pain using MR spectroscopy.

OBJECTIVE: To analyse the intra- (IMCL) and extramyocellular lipids (EMCL) concentration in the multifidus muscle (Mm) using MR spectroscopy (MRS) in patients with low back pain (LBP), and to evaluate the correlation between those lipid concentrations and age, obesity, atrophy of the Mm and LBP intensity. METHODS: 60 LBP patients underwent routine diagnostic MRI of the lumbar spine before undergoing imaging for the study. Body mass index, as an indicator of obesity and visual analogue scale, as an indicator of LBP were also measured. Proton MRS was acquired with a single-voxel point-resolved spectroscopy sequence. Furthermore, the MRS volume of interest for measuring the IMCL and EMCL concentration at L4/5 for the right Mm was determined, and we measured the cross-sectional area of Mm as an indicator of muscle atrophy. RESULTS: Age showed correlation with EMCL concentration (r = 0.314, p = 0.008). The body mass index showed correlation with EMCL concentration (r = 0.358, p = 0.005). The cross-sectional area of Mm showed correlation with EMCL concentration (r = -0.543, p < 0.001). Moreover, the LBP visual analogue scale showed correlation with IMCL concentration (r = 0.367, p = 0.004). CONCLUSION: There were correlations between age, obesity, muscle atrophy, and EMCL concentration in Mm. IMCL concentration in Mm showed a correlation with LBP intensity. This may suggest that IMCL concentration could become an effective objective indicator of chronic LBP intensity. Advances in knowledge: We investigated the characteristics of fat content in Mm with LBP patients. This study was demonstrated the association of the IMCL and EMCL concentration in Mm with various patient parameters.

Effect of respiratory and cardiac gating on the major diffusion-imaging metrics.

The effect of respiratory gating on the major diffusion-imaging metrics and that of cardiac gating on mean kurtosis (MK) are not known. For evaluation of whether the major diffusion-imaging metrics-MK, fractional anisotropy (FA), and mean diffusivity (MD) of the brain-varied between gated and non-gated acquisitions, respiratory-gated, cardiac-gated, and non-gated diffusion-imaging of the brain were performed in 10 healthy volunteers. MK, FA, and MD maps were constructed for all acquisitions, and the histograms were constructed. The normalized peak height and location of the histograms were compared among the acquisitions by use of Friedman and post hoc Wilcoxon tests. The effect of the repetition time (TR) on the diffusion-imaging metrics was also tested, and we corrected for its variation among acquisitions, if necessary. The results showed a shift in the peak location of the MK and MD histograms to the right with an increase in TR (p ≤ 0.01). The corrected peak location of the MK histograms, the normalized peak height of the FA histograms, the normalized peak height and the corrected peak location of the MD histograms varied significantly between the gated and non-gated acquisitions (p < 0.05). These results imply an influence of respiration and cardiac pulsation on the major diffusion-imaging metrics. The gating conditions must be kept identical if reproducible results are to be achieved.

Bilateral breast MRI by use of dual-source parallel radiofrequency excitation and image-based shimming at 3 Tesla: improvement in homogeneity on fat-suppression imaging.

In this study, we aimed to compare fat-suppression homogeneity on breast MR imaging by using dual-source parallel radiofrequency excitation and image-based shimming (DS-IBS) with single-source radiofrequency excitation with volume shim (SS-Vol) at 3 Tesla. Twenty patients were included. Axial three-dimensional T1-weighted turbo-field-echo breast images with DS-IBS and SS-Vol were obtained. Fat suppression was scored with four grade points. The contrast of the pectoral muscle and the fat in each breast area was obtained in the head medial, head lateral, foot medial, and foot lateral areas. The axillary space was calculated and compared between DS-IBS and SS-Vol. The average DS-IBS score was significantly higher than that of SS-Vol. The mean contrasts of fat in the foot lateral areas and axillary spaces on DS-IBS images were significantly higher than on SS-Vol images.

Effect of ankle flexion on the quantification of MRS for intramyocellular lipids of the tibialis anterior and the medial gastrocnemius.

Muscle proton magnetic resonance spectroscopy (MRS) has been developed for non-invasive measurement of intramyocellular lipid (IMCL) levels. The majority of previous studies measuring IMCL with MRS have been performed on the calf muscle. The appearance of muscle MRS is influenced by bulk magnetic susceptibility and residual dipolar couplings, which depend on the angle between the muscle fibers and the main magnetic field. Our objective in this study was to evaluate the effect of ankle flexion and of the pennation angle on IMCL quantification in the calf muscle using proton MRS. The subjects comprised ten healthy male volunteers. In proton MRS, the ankle flexion angle was changed, and the pennation angle was measured from the tibialis anterior (TA) and the medial gastrocnemius (MG), respectively. We considered the relationship between the quantification of IMCL with (1)H MRS and the pennation angle by ankle flexion angle. The pennation angle of the TA and MG changed with the ankle flexion angle. The IMCL on the TA decreased significantly with plantar flexion (p < 0.05). However, the IMCL on the MG demonstrated no significant difference. The MR spectrum and IMCL quantitation changed with the pennation angle. Therefore, when spectra of individual subjects in longitudinal studies or between subjects are compared in cross-sectional studies, the foot position or calf muscle orientation must be considered.

Evaluation of renal blood flow using multi-phase echo-planar magnetic resonance imaging and signal targeting with alternating radiofrequency (EPISTAR) in 3-T magnetic resonance imaging.

Most arterial spin labeling techniques apply the constant post-labeling delay time after the blood-labeling time point on the target artery. As the hemodynamic status cannot be estimated in each patient, quantitative values of the blood flow may not be accurate. To overcome this problem, we performed renal perfusion imaging of human kidneys using multi-phase echo-planar magnetic resonance imaging and signal targeting with an alternating radiofrequency (EPISTAR) sequence at 3-T magnetic resonance imaging. Multi-phase EPISTAR obtained 17 phases every 100 ms between 250 and 1850 ms from the arterial-labeling time point. The highest signal-intensity image obtained using multi-phase images was applied to renal blood flow (RBF) calculations. In five healthy volunteers, the mean cortical RBF was 286.6 ± 48.7 mL/100 g/min. This value was not significantly different from those in four previous studies. This technique was more useful than previous studies, in that multi-phase images could confirm the hemodynamic status on RBF calculations.

Visualization of the Superparamagnetic Iron Oxide (SPIO)-Labeled Bone Marrow Stromal Cells Using a 3.0-T MRI-a Pilot Study for Clinical Testing of Neurotransplantation.

Recent studies have elucidated that transplantation of the bone marrow stromal cells (BMSC) has therapeutic potential for the central nervous system (CNS) disorders. However, no imaging modalities have been established to track the engrafted cells in the CNS in clinical situation. This study aimed to investigate the ability of magnetic resonance imaging (MRI) to visualize the BMSC labeled with superparamagnetic iron oxide (SPIO). The BMSC of mice were labeled with SPIO. Various numbers of the cells were injected into the agar phantom and were visualized using a 3.0-T MR apparatus. The SPIO-labeled cells were injected into the temperature-sensitive gelation polymer (TGP) hydrogel and were cultured for 7 days. They were also visualized just after the injection and at 7 days postinjection. After a 7-day culture, they were stained with Turnbull blue technique. T2-, T2*-, and susceptibility-weighted imaging could identify minimally 1,000 cells in the agar or TGP hydrogel, although it was difficult to quantify their number on MRI. All of these sequences could track the SPIO-labeled BMSC for at least 7 days when injected into the TGP. Turnbull blue staining revealed the survival and proliferation of the SPIO-labeled BMSC in the TGP for 7 days. The findings strongly suggest that the SPIO labeling may enable to track minimally 1,000 cells engrafted in the CNS on clinical MR apparatus. These data would be valuable to consider the application of imaging technique into cell transplantation therapy for CNS disorders.

[Comparison of fat suppression techniques of bilateral breast dynamic sequence at 3.0 T: utility of three-point DIXON technique].

The purposes of this study were to determine optimum flip angles (FAs) and to compare the effectiveness of fat suppression and signal homogeneity among three techniques, spectral attenuated with inversion recovery (SPAIR), principle of selective excitation technique (PROSET), and three-point DIXON technique (DIXON), of the bilateral breast dynamic sequence acquired using the optimum FA at 3.0 T. Using a homemade phantom that represented a tumor, fat, and a mammary gland, the optimum FAs were determined from the change of fat signal intensity, signal-to-noise ratio (SNR) of the mammary gland, and contrast ratio (CR) between the tumor and mammary gland. The effectiveness of fat suppression and signal homogeneity were compared in ten breast cancer cases, using the CR between fat and pectoralis muscle signal intensities and the standard deviation (SD) of fat signal intensity, respectively. The optimum FAs for SPAIR, PROSET, and DIXON were 10, 20, and 20 degrees, respectively. The mean CR between fat and pectoralis muscle signal intensities achieved using SPAIR, PROSET, and DIXON were 0.19, 0.30 and 0.40, respectively, and the mean SDs of the fat signal intensities were 90.2, 103.1, and 30.5, respectively. The DIXON technique provided better fat suppression and signal homogeneity than the other two techniques. The results of this study suggest the possible application of the DIXON technique in combination with the optimum FA setting as an effective fat suppression technique for the bilateral breast dynamic sequence at 3.0 T.

Comparison of 1H MR spectroscopy, 3-point DIXON, and multi-echo gradient echo for measuring hepatic fat fraction.

PURPOSE: We evaluated and compared the reproducibility, diagnostic accuracy, and sequence dependency of the fat fraction (FF) determined by 3-point Dixon (DIXON) and multi-echo gradient-echo (MEGE) methods to those of the FF determined by magnetic resonance spectroscopy (MRS). METHODS: Our study included 98 volunteers, ten of whom underwent scanning twice to evaluate sequence reproducibility. We compared the FFs determined by the DIXON and MEGE methods to that by MRS as the gold standard, calculated sensitivity and specificity for each image analysis method at a threshold value of 6.25% of spectroscopic value, and used Pearson's correlation coefficient and Bland-Altman analysis to compare agreement among the repeated measurements and FF values with the 3 methods, in 98 volunteers. RESULTS: There was no significant difference in repeated scans in any sequence with Wilcoxon's t-test. Each correlation coefficient (r) exceeded 0.930 for the repeated measurements of all 3 sequences. Sensitivity of DIXON was 82% and specificity, 96%; sensitivity of MEGE was 70% and specificity, 99%. The FFs determined by DIXON and MEGE correlated well with that by MRS (r=0.920) but showed significant difference (paired t-test, P<0.001). The mean difference between the FF determined by DIXON and that by MEGE were 0.93 and -1.16, respectively. The slope of the regression lines as determined by DIXON was -0.655 (P<0.001) and that by MEGE was -0.527 (P<0.001). When the FF by MRS was less than 6.25%, the FF values by DIXON and MEGE were significantly higher; when the spectroscopic value was greater than 6.25%, their values were significantly lower. CONCLUSION: We demonstrated the high reproducibility of each FF measurement using MRS, DIXON, and MEGE. Compared to MRS, both DIXON and MEGE showed high sensitivity and specificity for determining FF. The FFs by DIXON and MEGE showed sequence dependency because DIXON had proportional and additional errors, and MEGE had a proportional error.