This study aimed to investigate diffusion along the perivascular space (DTI-ALPS index), which may reflect glymphatic system function in adult patients with moyamoya disease. We evaluated 46 patients with moyamoya disease using multishell diffusion magnetic resonance imaging, perfusion parameters of ¹⁵O-gas positron emission tomography, and cognitive tests. Diffusion data were analyzed to evaluate the DTI-ALPS index and free water parameters of each hemisphere and compared with the DTI-ALPS index of 34 age-sex-matched normal controls. Compared to normal controls, patients with moyamoya disease showed a significantly lower DTI-ALPS index (mean (standard deviation)=1.93 (0.25) vs. 1.64 (0.22) ; p<0.001). The DTI-ALPS index of patients with moyamoya disease was significantly correlated with perfusion parameters (vs. mean transit time, r=0.33), free water parameters (vs. free water fraction created from free water eliminated diffusion tensor imaging of the cortex, r=−0.24), and executive function (vs. trail making test part B, r=−0.47). These results indicate that glymphatic system dysfunction may exist, correlate with the degree of hemodynamic disturbance, lead to increased parenchymal free water, and be related to cognitive dysfunction in adult patients with moyamoya disease.

　Tumor-related vessel length (TVE) was quantified as the number of pixels of skeletonized tumor vessels on ultrafast dynamic contrast-enhanced MRI (UF-DCE MRI). The association between TVE and breast cancer subtypes was investigated. Invasive breast cancer presenting with human epidermal growth factor receptor 2 (HER2) was associated with increased tumor-related vessel length.

　Synopsis : We developed a framework that quantifies voxel-level amyloid burden in the brain with MR fingerprinting (MRF) and neural networks. The neural network was trained voxel-wise on in vivo amyloid-PET imaging data and MRF acquisitions to estimate PET-derived amyloid deposition from the signal evolution.

　In this study, we combined TI dependent optimized reconstruction (TIDOR) with Variable TI UTE 4D-MRA and demonstrated the clinical usefulness of this combined method. Previously, we reported that the late phase vessel visibility of ASL based UTE 4D-MRA was improved by the Variable TI method, which has the extended TI in a manner of progression of difference to keep labeled magnetization away from saturation in late phases⁵⁾. For further improvement of peripheral vessel visibility, we developed the TIDOR, which takes into account the signal and noise level of each phase. Combining Variable TI UTE 4D-MRA with TIDOR improved the peripheral vessel visibility, especially in the late phases. We demonstrated that this method is effective for clinical applications.

Introduction

　Accumulating evidence has connected the dysfunction of the paraventricular thalamic nucleus (PVT) with psychiatric disorders, including anxiety and major depressive and bipolar disorders. This study aimed to identify PVT and its specific connectivity patterns using diffusion MRI tractography and a k-means clustering algorithm.

Methods

　The diffusion MRI data of 100 healthy individuals (55 women, mean age, 28.5±3.9 years) from the Human Connectome Project and 10 healthy individuals (5 women, mean age, 44.6±13.9 years) from the Juntendo University were assessed as the first and test cohorts, respectively. Probabilistic tractography was performed based on the Bayesian Estimation of Diffusion Parameters using FreeSurfer's magnocellular subdivision of the mediodorsal thalamus (MDm), which is predicted to contain PVT, as seed regions, and cortical and subcortical areas as targets. The MDm was subsequently segmented into two regions using a k-means clustering algorithm based on the frequency matrix of fibers originating from each seed voxel in the MDm and reaching the specific target. Furthermore, the partial Pearson's correlation tests were used to evaluate the associations of the number of streamlines in the structure considered to be PVT with alcohol-related scores and adjusted for age, sex, and intracranial volume.

Results

　In both the cohorts, we were able to segment the MDm into dorsomedial and ventrolateral regions consistently (Fig. 1A). The tracts originating from the dorsomedial part of the MDm predominantly projected to the limbic areas, including the amygdala, nucleus accumbens, and anterior cingulate cortex. Thus, they most likely represent the PVT (Fig. 1B). Significant correlations were found between the number of streamlines in the ventromedial part and alcohol−related scores (Fig. 2).

Conclusion

　Structural connectivity features from probabilistic tractography and k-means clustering enabled segmentation of PVT.

　T1 map of the liver was used to estimate the liver function by quantifying the uptake of the gadoxetic acid contrast agent. The modified Look-Locker inversion recovery (MOLLI) sequence is limited by the number of slices, and the variable flip angle method measures T1 values from two points, which may include substantial errors. Breath-hold is essential for acquire a T1 map of the liver for both sequences. In this study, we aimed to develop a free-breathing three-dimensional (3D) Look-Locker sequence with radial acquisition (3D Radial LL) and assess the quantitative accuracy of the T1 map. MOLLI and 3D Radial LL were acquired in seven healthy volunteers (33.6±6.6 years) to evaluate the accuracy of T1 values. MOLLI was imaged with a breath-hold sequence used as a T1 native (5s-[3s]-3s) on cardiac MRI. The acquisition time in the free-breathing 3D Radial LL sequence was set to 5 min to allow clinical examination. The differences in the T1 values of the liver, pancreas, and spleen between the two sequences in the same volunteers were 3.0±1.7%, 3.8±4.3%, and 2.1±1.4%, respectively. The T1 map using the free-breathing 3D Radial LL demonstrated equivalent T1 values compared with MOLLI in the upper abdomen.

　¹⁷O-MRI is expected to have clinical applications owing to its high biocompatibility and ability to directly track water movement. Fetuses grow with an active exchange of water with the mother ; therefore, understanding the water dynamics of the mother-fetus amniotic fluid cycle is important. However, water movement cannot be measured using echocardiography, and Gd contrast-enhanced MRI is contraindicated in pregnant women. In this study, ¹⁷O-labeled saline was administered to measure fetal water dynamics in pregnant mice. The results were compared with the signal changes induced by Gd administration. Dynamic scans of fetal mice using ¹⁷O-labeled saline were successfully obtained. The images showed signal changes that differed from those obtained using the Gd contrast agent. In the future, efforts will be made to improve the temporal and spatial resolution as well as to investigate the possibility of detecting correlations between the signals observed in various tissues.

　A simple software simulator was developed for MRI operation training and physics education. Users can learn slice prescription, image contrast, and SNR change on personal laptops or computers. The software helps users with elementary knowledge of MRI understand MR operation even with limited access to MRI scanners.

　A novel analysis for investigating cerebrospinal fluid (CSF) motion is proposed based on the previously presented mathematical framework of Low-b diffusion tensor imaging (DTI). The analysis estimates the covariance of flow-velocity distribution and coefficient of random motion of CSF. It successfully showed different characteristics of ROIs in CSF.

　A novel minimization technique was developed. The proposed method is based on a Gaussian random search in the parameter space and it can handle a wide range of problems, including bi-exponential curve fitting, in a reasonable time. It uses only function values, and does not require gradients.