Pulmonary hypertension is defined as a mean pulmonary artery pressure of 25 mmHg or higher as detected by right heart catheterization. It is broadly classified into 5 categories based on the etiology. Various imaging modalities are used to evaluate patients with or suspected of pulmonary hypertension. Transthoracic echocardiography is the most frequently used modality for detecting pulmonary hypertension. Magnetic resonance imaging (MRI) is indicated during examination, since it allows for comprehensive image analysis of morphology, cardiac function, and hemodynamics in the great arteries. The recently developed 4D Flow MRI can visualize three-dimensional pulmonary vascular flow and measure advanced hemodynamic parameters. The degree of vertical flow in the pulmonary trunk may be a key aspect that reflects pulmonary hypertension. 4D Flow MRI can highlight the value of MRI for the clinical diagnosis and management of patients with pulmonary hypertension.

Background : During stress cardiac MRI (CMR), if there is sufficient adenosine, a splenic switch-off phenomenon (SSO) occurs. In Japan, adenosine triphosphate (ATP) is more commonly used as a stressor drug than adenosine.

Aims : We aimed to examine whether the effect of these drugs was adequate and whether there is a difference between adenosine and ATP with respect to changes in splenic blood flow and signals of stress and rest (stress/rest splenic signal intensity ratio ; SIR).

Methods : We visually analyzed stress perfusion CMR scans in a total of 71 patients. In total 33 patients were administered adenosine (0.12 mg/kg/min), and 38 patients with ATP (0.16 mg/kg/min) underwent stress/rest perfusion CMR examination after intravenous injection of 0.1 ml/kg of 38% meglumine gadoterate at 4.0 ml/sec. After comparing coronary angiogram (CAG) findings performed within 2 months of CMR and stress CMR images, we divided the patients into 3 groups ; positive CAG and CMR (true positive), both negative (true negative), and CAG positive CMR negative (false negative). SIR was then compared across all groups.

Results : No SSO was identified in 25% of patients (adenosine 21%, ATP 29%). The optimal threshold for SIR as an indicator of SSO was 0.87 AUC 0.957 for adenosine (0.888-1.000 95%CI, p=0.003) and 0.96 AUC 0.806 for ATP (0.659-0.954 95%CI, p=0.012). In patients administered adenosine, the SIR for the false negative group was significantly higher than in the true positive group and the true negative group (0.50±0.20, vs 0.58±0.36 vs 1.24±0.35* : p=0.001). In patients administered ATP, there was a trend towards an increase in SIR in the false negative group compared to the true positive group, but there was no statistically significant difference among the three groups (0.79±0.20 vs 0.86±0.32 vs 1.06±0.24 : p=0.074).

Conclusion : In stress CMR, SIR is a useful indicator stressor effectiveness. In addition, SIR was found to be different between patients administered adenosine or ATP, which suggests a difference in the coronary vasodilator effect. Assessment of CMR after ATP requires more caution than with adenosine.

　Patients with inflammation- or perforation-induced appendiceal mucocele may present with right lower abdominal pain, and a dilated appendix, resembling acute appendicitis, is demonstrated on imaging examination. Ruptured appendiceal mucocele due to appendiceal mucinous neoplasm may result in peritoneal dissemination and pseudomyxoma peritonei. Therefore, it is occasionally challenging but essential to distinguish appendiceal mucocele from acute appendicitis. A 65-year-old man presented with right lower abdominal pain. Computed tomography showed a dilated appendix without wall thickening, atypical of acute appendicitis. Magnetic resonance imaging (MRI) demonstrated high signal intensity on T₂-weighted imaging and low signal intensity on diffusion-weighted imaging (DWI) of the dilated appendiceal component. The appendiceal component had an apparent diffusion coefficient (ADC) value of 3.351×10⁻³ mm²/s. Based on the MRI findings, appendiceal mucocele due to appendiceal mucinous neoplasm, particularly low-grade appendiceal mucinous neoplasm (LAMN) was more likely than acute appendicitis. Laparoscopic right hemicolectomy with lymph node dissection was performed instead of routine appendectomy 17 days after the MRI examination. Histopathology revealed LAMN with a small perforation. The postoperative course was uneventful, and she discharged without complications. No recurrences were observed 1 year after the operation. The dilated appendix with thin wall showing high signal intensity on DWI, and the appendiceal component without significant diffusion restriction could be characteristic findings of appendiceal mucocele due to LAMN and helpful in distinguish them from acute appendicitis. Herein, we report this case with a literature review focused on the utility of MRI including DWI and ADC value in acute abdominal pain.

Purpose : Quantitative synthetic magnetic resonance imaging (MRI) enables the synthesis of various contrast-weighted images based on simultaneous relaxometry. Herein, we developed a deep learning algorithm to generate magnetic resonance angiography (MRA) from three-dimensional (3D) synthetic MRI data.

Materials and Methods : Eleven healthy volunteers underwent time-of-flight (TOF) MRA sequence and 3D synthetic MRI sequence, i.e., 3D-QALAS. Five raw 3D-QALAS images were used as inputs for deep learning (DL-MRA). A simple linear combination model was prepared for comparison (linear-MRA). Three-fold cross-validation was performed. The peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM) were calculated for DL-MRA and linear-MRA against TOF-MRA. The overall image quality and branch visualization were scored on a 5-point Likert scale by a neuroradiologist blinded to the data.

Results : The PSNR and SSIM were significantly higher for DL-MRA that those of linear-MRA. Overall image quality and branch visualizations were comparable for DL-MRA and TOF-MRA.

Conclusion : Deep learning based on 3D-synthetic MRI enabled the generation of MRA with quality equivalent to that of TOF-MRA.

　Magnetic resonance neurography of the crus is challenging because signals from the vessels and subcutaneous edema interrupt visualization of the nerves and water content of the nerves is small. Phase-cycling diffusion-sensitized driven-equilibrium (pcDSDE) can reduce signals from the neighboring structures and visualize the nerves in the crus using diffusion contrast.

　We attempted to detect and diagnose cerebral infarction on diffusion weighted image (DWI) using a machine learning model trained using normal brain data. Our machine learning model consisted of two parts. One consisted of an autoencoder (AE), which learned only normal DWI information. This AE model did not reproduce the lesion ; the input image was subtracted and the generated image contributed to abnormal signal detection. The other part was a classifier constructed with SqueezeNet, which distinguished between infarct and normal areas using the original DWI image, AE generated images, and subtraction images. The accuracy of the combination of AE and SqueezeNet in 2-class classification for abnormal detection on DWI was 0.97.

　Six hundred and ninety consecutive MRI images obtained on 1.5 T or 3.0 T devices were reviewed to investigate the prevalence and diagnostic pitfalls of the vacuum phenomenon (VP) of the knee joint. The VP was identified on 13 knees and 7 knees (53.8%) were diagnosed with osteoarthritis. Gradient-echo imaging facilitated the delineation of minute VP within the joint space with susceptibility artifacts.

　The evaluation of the networks within the hippocampus with magnetic resonance imaging is challenging. We evaluated the hippocampal networks in patients with major depressive disorder (MDD) and healthy participants in this study. We evaluated the hippocampal networks by extracting the intrinsic connectivity of each 0.9 mm isovoxel to every other 0.9 mm isovoxel using the data-driven approach. Disturbances in the network connecting the hippocampus on both sides were observed in patients with MDD.

　Time-resolved three-dimensional phase-contrast magnetic resonance imaging [four-dimensional (4D) Flow MRI] can provide objective and reliable information on blood flow including arterial pulsation and flow direction. We performed 4D Flow MRI in patients with internal carotid artery stenotic disease (ICS) and compared its results to those of single-photon emission computed tomography with acetazolamide challenge. Multiparametric flow analysis using 4D Flow MRI can clearly detect hemodynamic impairment in ICS by comprehensively assessing blood flow parameters including blood flow volume, pulsation, and collateral flow.

　In this study, subtype and stage inference analysis (SuStaIn) was performed based on the data obtained from cross-sectional brain structure magnetic resonance imaging, in order to clarify the differences in the temporal progression pattern of brain atrophy for progressive supranuclear palsy (PSP) and Parkinson's disease (PD). SuStaIn was able to estimate the spatial brain atrophy progression pattern in PD and PSP and was useful for the classification of these diseases.

　We identified and classified the morphology of the dorsal and palmar radioulnar ligaments (RUL) of the wrist using 3T MRI. Both dorsal and palmar RULs attach to the radial to the dorsal side of the ulnar styloid. The RUL was equally identified on high-resolution 2D and on isotropic 3D MRI.