Hiroyuki Sugimori

Quantification of myocardial blood flow with dynamic perfusion 3.0 Tesla MRI: Validation with 15o‐water PET

To develop and validate a method for quantifying myocardial blood flow (MBF) using dynamic perfusion magnetic resonance imaging (MBFMRI) at 3.0 Tesla (T) and compare the findings with those of 15O‐water positron emission tomography (MBFPET).

Acceleration of ASL-based time-resolved MR angiography by acquisition of control and labeled images in the same shot (ACTRESS)

Noncontrast 4D‐MR‐angiography (MRA) using arterial spin labeling (ASL) is beneficial because high spatial and temporal resolution can be achieved. However, ASL requires acquisition of labeled and control images for each phase. The purpose of this study is to present a new accelerated 4D‐MRA approach that requires only a single control acquisition, achieving similar image quality in approximately half the scan time.

Evaluation of cerebral blood flow using multi-phase pseudo continuous arterial spin labeling at 3-tesla

PURPOSE Arterial spin labeling (ASL) methods have been widely used for evaluation of cerebral blood flow (CBF) by magnetic resonance imaging. However, ASL methods require setting of the post labeling delay (PLD) time for obtaining images. As the hemodynamic status cannot be estimated in each patient, the resultant quantitative values of blood flow may not be accurate. The multi-phase pseudo continuous arterial spin labeling (pCASL) method can be used to obtain images at various time-points. The purpose of this study was to create the transit-time maps for correcting the delayed blood flow and evaluate CBF using the transit-time maps obtained by the multi-phase pCASL method. MATERIALS AND METHODS Twelve patients who underwent both 3.0-tesla magnetic resonance imaging (MRI) and single photon emission computed tomography with iodine-123-N-isopropyl-p-iodoamphetamine (123I-IMP) were investigated. This study was approved by the institutional review board of our institution. MRI acquisitions included PLD time-fixed (1525ms) and multi-phase pCASL sequences. The transit-time maps were calculated from multi-phase pCASL images by software. The transit-time maps were applied to PLD-fixed pCASL images pixel by pixel, for calculating the CBF value corrected for peak blood transit time. Regions of interest were drawn on the brain. IMP-CBF, ASL-CBF (default and corrected) and transit time were measured for each segment. RESULTS Twelve patients and 264 segments were investigated. The mean IMP-CBF, ASL-CBF (default, corrected) and transit time were 28.4, 23.0, 29.6, [ml/min/100g] and 1977.5 [ms], respectively. There were no significant differences between IMP-CBF and ASL-CBF (corrected). CONCLUSION CBF values can be corrected by using the transit-time maps obtained using the multi-phase pCASL method.

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.

Three-dimensional Pseudo-continuous Arterial Spin-labeling Using Turbo-spin Echo with Pseudo-steady State Readout: A Comparison with Other Major Readout Methods

We evaluated 3D pseudo-continuous arterial spin labeling (pCASL) using turbo spin echo with a pseudo-steady-state (PSS) readout in comparison with the other major readout methods of 3D spiral and 2D echo-planar imaging (EPI). 3D-PSS produced cerebral blood flow (CBF) values well correlated to those of the 3D spiral readout. By visual evaluation, the image quality of 3D-PSS pCASL was superior to that of 2D-EPI. The 3D-PSS technique was suggested useful as pCASL readout.

Assessment of Coronary Flow Velocity Reserve in the Left Main Trunk Using Phase-contrast MR Imaging at 3T: Comparison with 15 O-labeled Water Positron Emission Tomography

Purpose: The aim of this study was to verify coronary flow velocity reserve (CFVR) on the left main trunk (LMT) in comparison with myocardial flow reserve (MFR) by 15O-labeled water positron emission tomography (PET) (MFR-PET) in both the healthy adults and the patients with coronary artery disease (CAD), and to evaluate the feasibility of CFVR to detect CAD. Methods: Eighteen healthy adults and 13 patients with CAD were evaluated. CFVR in LMT was estimated by 3T magnetic resonance imaging (MRI) with phase contrast technique. MFR-PET in the LMT territory including anterior descending artery and circumflex artery was calculated as the ratio of myocardial blood flow (MBF)-PET at stress to MBF-PET at rest. Results: There was a significant positive relationship between CFVR and MFR-PET (R = 0.45, P < 0.0001). Inter-observer calculations of CFVR showed good correlation (R2 = 0.93, P < 0.0001). The CFVR in patients with CAD was significantly lower than that in healthy adults (1.90 ± 0.61 vs. 2.77 ± 1.03, respectively, P = 0.01), which were similar to the results of MFR-PET (2.23 ± 0.84 vs. 3.96 ± 1.04, respectively, P < 0.0001). For the detection of patients with CAD, the area under the curve was 0.78 (P = 0.01). The sensitivity was 0.77 and specificity was 0.72 when a cut-off of 2.15 was used. Conclusion: CFVR by 3T was validated with MFR-PET. CFVR could detect the patients with CAD. This method is a simple and reliable index without radiation or contrast material.

Quantification of hand synovitis in rheumatoid arthritis: Arterial mask subtraction reinforced with mutual information can improve accuracy of pixel-by-pixel time-intensity curve shape analysis in dynamic MRI: Quantification of Hand Synovitis

Synovitis, which is a hallmark of rheumatoid arthritis (RA), needs to be precisely quantified to determine the treatment plan. Time–intensity curve (TIC) shape analysis is an objective assessment method for characterizing the pixels as artery, inflamed synovium, or other tissues using dynamic contrast‐enhanced MRI (DCE‐MRI).

Classification of Computed Tomography Images in Different Slice Positions Using Deep Learning

This study aimed at elucidating the relationship between the number of computed tomography (CT) images, including data concerning the accuracy of models and contrast enhancement for classifying the images. We enrolled 1539 patients who underwent contrast or noncontrast CT imaging, followed by dividing the CT imaging dataset for creating classification models into 10 classes for brain, neck, chest, abdomen, and pelvis with contrast-enhanced and plain imaging. The number of images prepared in each class were 100, 500, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, and 10,000. Accordingly, the names of datasets were defined as 0.1K, 0.5K, 1K, 2K, 3K, 4K, 5K, 6K, 7K, 8K, 9K, and 10K, respectively. We subsequently created and evaluated the models and compared the convolutional neural network (CNN) architecture between AlexNet and GoogLeNet. The time required for training models of AlexNet was lesser than that for GoogLeNet. The best overall accuracy for the classification of 10 classes was 0.721 with the 10K dataset of GoogLeNet. Furthermore, the best overall accuracy for the classification of the slice position without contrast media was 0.862 with the 2K dataset of AlexNet.

Composite assessment of power Doppler ultrasonography and MRI in rheumatoid arthritis: a pilot study of predictive value in radiographic progression after one year

OBJECTIVE Power Doppler ultrasonography (PDUS) and MRI are independently useful to predict structural damage in patients with rheumatoid arthritis (RA). We hypothesize that there is a complementary relationship between these modalities. The aim of this study is, therefore, to investigate the usefulness of the predictive value of composite assessment of PDUS and contrast-enhanced MRI in radiographic outcomes in patients with RA. METHODS 20 patients (17 females and 3 males) with RA on disease-modifying antirheumatic drugs underwent PDUS and MRI of both hands at baseline. Radiography of the bilateral hands was performed at baseline and at 1 year. Articular synovitis on PDUS was evaluated according to quantitative measurement. Synovitis, bone marrow edema and bone erosion were scored according to the RA MRI scoring method. The changes of joint space narrowing and bone erosion on radiograph were assessed by the Sharp/van der Heijde method. We applied t-statistics to combine the assessment of quantitative PDUS with semiquantitative MRI. RESULTS Structural damage progression for radiography was not correlated with any evaluations for MRI, while it showed significant correlation with synovitis on PDUS (rs = 0.597, p = 0.005). The composite assessment of both modalities (synovitis for PDUS and bone marrow edema for MRI) was correlated with structural damage progression on radiograph (rs = 0.792, p < 0.0001). CONCLUSION Composite assessment of PDUS and MRI may have a stronger predictive value in radiographic progression than PDUS or MRI alone in RA. Advances in knowledge: Composite assessment of PDUS and MRI may be an effective predictor of structural damage in RA.

Pixel-by-Pixel Arterial Spin Labeling Blood Flow Pattern Variation Analysis for Discrimination of Rheumatoid Synovitis: A Pilot Study

We examined the capability of a gray-scale arterial spin labeling blood flow pattern variation (BFPV) map with two different post labeling delay (PLD) times to discriminate pannus in patients with rheumatoid arthritis (RA) at 3T. There was a statistically significant difference in the BFPV values between artery, pannus, and surrounding tissue. Furthermore, the color-coded BFPV map was able to accurately distinguish pannus from other tissues. These results suggest this approach may be capable of identifying pannus noninvasively.