Prediction of histological grade of hepatocellular carcinoma using quantitative diffusion-weighted MRI: a retrospective multivendor study.

OBJECTIVE: To evaluate the usefulness of quantitative diffusion-weighted (DW) imaging acquired by multivendor magnetic resonance units for predicting grade of hepatocellular carcinoma (HCC). METHODS: 83 patients with 100 histologically diagnosed HCCs who underwent pre-operative liver DW imaging with b = 0 and1000 s mm-2 or b = 0 and800 s mm-2 at any of six institutions were included. Two radiologists independently measured the apparent diffusion coefficient (ADC) of the lesion as well as non-ADC parameters, such as the relative contrast ratio and the contrast-to-noise ratio (CNR) between the lesion and the liver parenchyma on high b-value DW images. The diagnostic performance of the DW parameters in discriminating poorly-differentiated HCCs was compared using receiver operating characteristic (ROC) analysis. RESULTS: The areas under the receiver operating characteristic curves for the CNR (86.4% [95% confidence interval (CI) (77.2-95.6] and 83.9% [95% CI 71.2-96.6] for b = 1000 and 800 s mm-2, respectively] and the relative contrast ratio (85.3% [95% CI 75.5-94.8] and 83.5% [95% CI 70.5-96.4]) tended to be superior to the ADC [71.1% [95% CI (56.9-85.2)] and 75.7% [95% CI (55.1-96.2)]; p < 0.05 for CNR vs ADC for b = 1000 s mm-2, but not significant for other parameters) for discrimination of poorly-differentiated HCCs. CONCLUSION: All DW parameters could discriminate HCC grade. Non-ADC parameters might be more useful than the ADC for predicting poorly-differentiated HCCs. Advances in knowledge: The utility of quantitative DW parameters for predicting HCC grade was demonstrated by using multivendor MR units.

Cylindrical Inversion Pulse for the Reduction of Cardiac Motion Artifacts in Contrast-enhanced Breast MRI.

We proposed a simple technique for reduction of cardiac-related motion artifacts on contrast-enhanced images in the breast by using cylindrical regional-suppression technique (CREST) that can directly suppress the heart signals. The purpose of this study was to select the optimal scan parameters and to evaluate the feasibility in the breast. We demonstrated that the optimized CREST could dramatically reduce the cardiac-related flow artifacts without any penalty to the acquisition time, signal-to-noise ratio and contrast-enhanced lesion-to-parenchyma contrast.

Hyperecho PROPELLER-MRI: Application to rapid high-resolution motion-insensitive T2 -weighted black-blood imaging of the carotid arterial vessel wall and plaque.

PURPOSE: To demonstrate the usefulness of hyperecho and PROPELLER (HEP) for carotid arterial vessel wall imaging by using a quantitative comparison with conventional methods. PROPELLER is a motion-insensitive turbo spin-echo (TSE) sequence and has recently been utilized in magnetic resonance (MR) plaque imaging instead of double inversion recovery TSE (DIR-TSE). Wider blade-width, higher k-space density, and an improved blood suppression effect result in better image quality. In this study we introduce a new combination of HEP. MATERIALS AND METHODS: A total of 17 subjects were examined on a 3.0T system. We conducted quantitative comparisons for signal-to-noise ratio (SNR), contrast-to-noise-ratio, and image sharpness among HEP, DIR-TSE, and conventional PROPELLER (c-PROPELLER). Subsequently, images obtained with DIR-TSE, c-PROPELLER, and HEP were visually evaluated using a three-point scale by two board-certified radiologists. RESULTS: HEP showed high SNR similar to c-PROPELLER, good T2 contrast approximating DIR-TSE, and better blood suppression compared with the other two methods (P < 0.05). The image sharpness of HEP (2.55 ± 0.53) was higher than that of DIR-TSE (1.89 ± 0.33) and the absence of ghost or streak artifacts in HEP (2.89 ± 0.33) was better than that in both other methods (2.22 ± 0.83 for DIR-TSE and 2.00 ± 0.50 for c-PROPELLER) (P < 0.05). Furthermore, the degree of blood suppression, particularly in cases of slow or turbulent flow close to the atherosclerotic plaque, was identical for HEP (2.80 ± 0.45) and DIR-TSE (2.80 ± 0.45) but was significantly better than for c-PROPELLER (1.60 ± 0.55) (P < 0.05). CONCLUSION: This study demonstrates the usefulness of HEP in the carotid arteries. HEP can provide higher-resolution T2 -weighted black-blood imaging without flow- and/or motion-related artifacts, compared to conventional techniques. LEVEL OF EVIDENCE: 3 J. Magn. Reson. Imaging 2017;45:515-524.

Volume isotropic simultaneous interleaved black- and bright-blood imaging: a novel sequence for contrast-enhanced screening of brain metastasis.

We introduced and optimized a novel sequence of fast (about 4 min), volumetric, high resolution, simultaneous bright- and black-blood imaging with sufficient T1 contrast between enhanced metastasis and surrounding brain parenchyma for their differentiation. This proposed sequence can be used for 3-dimensional volumetric T1-weighted bright- and black-blood imaging in contrast-enhanced studies and may be promising for detecting small brain metastases by improving differentiation between blood vessels and small brain metastases.

Improvement of T1 contrast in whole-brain black-blood imaging using motion-sensitized driven-equilibrium prepared 3D turbo spin echo (3D MSDE-TSE).

We demonstrated a new scheme for performing the T1-enhanced whole-brain black-blood imaging pulse sequence using motion-sensitized driven-equilibrium prepared 3-dimensional (3D) turbo spin echo (MSDE-TSE) with anti-driven-equilibrium post pulse. The use of an anti-driven-equilibrium pulse considerably improved the T1 contrast of MSDE-TSE black-blood images. This sequence can be used for whole-brain 3D volumetric T1-weighted black-blood imaging and may improve the accuracy of anatomical localization for certain brain lesions.

Simple method for whole-brain volumetric T(1)-weighted turbo spin-echo imaging.

We propose a simple scheme of 3D turbo spin echo (TSE) with low-refocusing flip angles (RFAs) for obtaining sufficient T1-weighted contrast. The low RFA can easily lead spins into a pseudo-steady-state (PSS) condition, but a preparation scheme is required for smooth transition into static PSS. For obtaining T1 contrast, PSS preparation is the most important factor, and therefore we focused on the PSS preparation. To optimize the T1 contrast in the proposed sequence, we compared the following parameters: RFAs of 90° and 30°, and a PSS preparation scheme of "90° + α/2" and asymptotic preparation. Subsequently, to demonstrate the quality of the proposed sequence, we compared the image quality regarding conventional 3D TSE and 2D spin echo (SE). A combination of an RFA of 30° and the "90° + α/2" preparation scheme showed the highest T1 contrast. The optimized sequence provided higher contrast and sharper images compared to 3D TSE, and it showed contrast and a signal-to-noise ratio similar to those of 2D SE.

Whole-brain black-blood imaging with magnetization-transfer prepared spin echo-like contrast: a novel sequence for contrast-enhanced brain metastasis screening at 3T.

In contrast-enhanced (CE) brain metastasis screening, coexistence of enhanced blood vessel suppression and higher tumor-to-parenchyma contrast may improve radiologists' performances in detecting brain metastases compared with conventional sequences. In this study, we propose a new scheme, allowing both suppression of blood signals and improvement of tumor-to-parenchyma contrast, using motion-sensitized driven equilibrium prepared 3D low-refocusing flip-angle turbo spin echo (TSE) ("magnetization transfer prepared spin echo"-like contrast volume examination: MATLVE) for brain metastasis screening at 3.0 T, and we compare MATLVE to conventional three-dimensional (3D)-gradient recalled echo (GRE) and 3D-TSE sequences. With the use of MATLVE, the signal intensity of CE blood decreased substantially. Furthermore, the contrast ratio of tumor-to-white matter was significantly higher than in either conventional 3D-GRE or 3D-TSE. MATLVE can be used for 3D volumetric post-CE black-blood imaging, and it may be effective in detecting small brain metastases by selectively enhancing tumor signals while suppressing blood signals.

Vessel-selective, non-contrast enhanced, time-resolved MR angiography with vessel-selective arterial spin labeling technique (CINEMA-SELECT) in intracranial arteries.

We demonstrate the feasibility of the vessel-selective, non-contrast, time-resolved magnetic resonance angiography (MRA) technique, "contrast inherent inflow enhanced multi-phase angiography combining vessel-selective arterial spin labeling technique (CINEMA-SELECT)". This sequence consists of two major techniques: pulsed star labeling of arterial regions (PULSAR) and Look-Locker sampling. We hypothesize that this technique allows selective labeling of single intracranial arteries, consisting of high-resolution four-dimensional data with a wide coverage of the brain. In this study, a new vessel-selective, time-resolved angiographic technique is demonstrated that can produce individual angiograms non-invasively by labeling the principal arterial vessels proximal to the circle of Willis. Clear vessel delineation is achieved, and the separation of the three vessels is evident in healthy volunteers. This technique could play an important role in the assessment of the structure and hemodynamics of intracranial arteries without the use of contrast agents.

[Non-contrast time-resolved magnetic resonance angiography combining high resolution multiple phase echo planar imaging based signal targeting and alternating radiofrequency contrast inherent inflow enhanced multi phase angiography combining spatial resolution echo planar imaging based signal targeting and alternating radiofrequency in intracranial arteries].

Detailed information on anatomy and hemodynamics in cerebrovascular disorders such as AVM and Moyamoya disease is mandatory for defined diagnosis and treatment planning. Arterial spin labeling technique has come to be applied to magnetic resonance angiography (MRA) and perfusion imaging in recent years. However, those non-contrast techniques are mostly limited to single frame images. Recently we have proposed a non-contrast time-resolved MRA technique termed contrast inherent inflow enhanced multi phase angiography combining spatial resolution echo planar imaging based signal targeting and alternating radiofrequency (CINEMA-STAR). CINEMA-STAR can extract the blood flow in the major intracranial arteries at an interval of 70 ms and thus permits us to observe vascular construction in full by preparing MIP images of axial acquisitions with high spatial resolution. This preliminary study demonstrates the usefulness of the CINEMA-STAR technique in evaluating the cerebral vasculature.