Hisaaki Ochi

Quantitative Histological Validation of Diffusion Tensor MRI with Two-Photon Microscopy of Cleared Mouse Brain

1Department of Radiology, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan 2Research Institute for Diseases of Old Age, Juntendo University Graduate School of Medicine 3Research & Development Group, Hitachi Ltd. 4Department of Radiology, University of Tokyo 5Department of Radiological Sciences, Graduate School of Human Health Sciences 6Department of Neuropathology, Tokyo Medical and Dental University (Received November 22, 2015; Accepted February 10, 2016; published online March 30, 2016)

See-through Brains and Diffusion Tensor MRI Clarified Fiber Connections: A Preliminary Microstructural Study in a Mouse with Callosal Agenesis

Clearing methods that render the brain optically transparent allow high-resolution three-dimensional (3D) imaging of neural networks. We used diffusion tensor imaging (DTI) and two-photon imaging of cleared brains to analyze white matter in BTBR mice. We confirmed corpus callosum agenesis and identified an abnormal commissure close to the third ventricle. DTI and cleared-brain two-photon imaging revealed that these commissural fibers constituted a frontal clustering of the ventral hippocampal commissure and provided a detailed assessment of white matter structure in mice.

A three dimensional analysis of slotted tube resonator for MRI

A three dimensional model of a slotted tube resonator (STR) used as a probe in the magnetic resonance imaging (MRI), which is loaded by a dielectric body and surrounded by a conducting shield, is analyzed by using the variational method and the dyadic Greens function of a circular waveguide having a dielectric core. Three surface current modes are properly assumed to expand the currents on the STR. The characteristics such as the input impedance, the resonance frequency, the Q value, and the magnetic field distribution are obtained to show the effects of the dielectric body and the conducting shield. Some theoretical results are compared with the measured data to confirm the validity of the present analysis.

Quantitative Susceptibility Mapping Using the Multiple Dipole-Inversion Combination with k-space Segmentation Method

Quantitative susceptibility mapping (QSM) is a new magnetic resonance imaging (MRI) technique for noninvasively estimating the magnetic susceptibility of biological tissue. Several methods for QSM have been proposed. One of these methods can estimate susceptibility with high accuracy in tissues whose contrast is consistent between magnitude images and susceptibility maps, such as deep gray-matter nuclei. However, the susceptibility of small veins is underestimated and not well depicted by using the above approach, because the contrast of small veins is inconsistent between a magnitude image and a susceptibility map. In order to improve the estimation accuracy and visibility of small veins without streaking artifacts, a method with multiple dipole-inversion combination with k-space segmentation (MUDICK) has been proposed. In the proposed method, k-space was divided into three domains (low-frequency, magic-angle, and high-frequency). The k-space data in low-frequency and magic-angle domains were obtained by L1-norm regularization using structural information of a pre-estimated susceptibility map. The k-space data in high-frequency domain were obtained from the pre-estimated susceptibility map in order to preserve small-vein contrasts. Using numerical simulation and human brain study at 3 Tesla, streaking artifacts and small-vein susceptibility were compared between MUDICK and conventional methods (MEDI and TKD). The numerical simulation and human brain study showed that MUDICK and MEDI had no severe streaking artifacts and MUDICK showed higher contrast and accuracy of susceptibility in small-veins compared to MEDI. These results suggest that MUDICK can improve the accuracy and visibility of susceptibility in small-veins without severe streaking artifacts.

Diffusion-weighted Line-scan Echo-planar Spectroscopic Imaging Technique to Reduce Motion Artifacts in Metabolite Diffusion Imaging

Metabolite diffusion is expected to provide more specific microstructural and functional information than water diffusion. However, highly accurate measurement techniques have still not been developed, especially for reducing motion artifacts caused by cardiac pulsation and respiration. We developed a diffusion-weighted line-scan echo-planar spectroscopic imaging (DW-LSEPSI) technique to reduce such motion artifacts in measuring diffusion-weighted images (DWI) of metabolites. Our technique uses line-scan and echo-planar techniques to reduce phase errors induced by such motion during diffusion time. The phase errors are corrected using residual water signals in water suppression for each acquisition and at each spatial pixel specified by combining the line-scan and echo-planar techniques. We apply this technique to a moving phantom and a rat brain in vivo to demonstrate the reduction of motion artifacts in DWI and apparent diffusion coefficient (ADC) maps of metabolites. DW-LSEPSI will be useful for investigating a cellular diffusion environment using metabolites as probes.

Analysis of MRI antenna loaded by an elliptical subject

Previously, the authors developed a computer code for obtaining the current distribution on the MRI antenna loaded by a man model with an arbitrary geometry and material properties by incorporating the impedance method into Richmonds method. By this method, the relation between the position of the feeding point and the sensitivity of the 1.5 T-MRI antenna loaded by an elliptic cylindrical subject is discussed theoretically. It is found that the sensitivity of the antenna fed at the angle of 45 degrees measured from the minor axis of the ellipsoid of the subject is different from that of the antenna fed at the angle of - 45 degrees because the elliptic polarization is produced inside the antenna.

B1-control receive array coil (B-RAC) for reducing B1+ inhomogeneity in abdominal imaging at 3T-MRI

B1+ inhomogeneity in the human body increases as the nuclear magnetic resonance (NMR) frequency increases. Various methods have thus been developed to reduce B1+ inhomogeneity, such as a dielectric pad, a coupling coil, parallel transmit, and radio-frequency (RF) shimming. However, B1+ inhomogeneity still remains in some cases of abdominal imaging. In this study, we developed a B1-control receive array coil (B-RAC). Unlike the conventional receive array coil, B-RAC reduces B1+ inhomogeneity by using additional PIN diodes to generate the inductive loop during the RF transmit period. The inductive loop can generate dense and sparse regions of the magnetic flux, which can be used to compensate for B1+ inhomogeneity. First, B-RAC is modeled in the numerical simulation, and the spatial distributions of B1+ in a phantom and a human model were analyzed. Next, we fabricated a 12-channel B-RAC and measured receive sensitivity and B1+ maps in a 3T-MRI experiment. It was demonstrated that B-RAC can reduce B1+ inhomogeneity in the phantom and human model without increasing the maximum local specific absorption rate (SAR) in the body. B-RAC was also found to have almost the same the receive sensitivity as the conventional receive coil. Using RF shimming combined with B-RAC was revealed to more effectively reduce B1+ inhomogeneity than using only RF shimming. Therefore, B-RAC can reduce B1+ inhomogeneity while maintaining the receive sensitivity.

EARLY STAGE METABOLITE DIFFUSION IN A MOUSE MODEL OF ALZHEIMER’S DISEASE

cerebral small vessel health, were quantified byMRI. Results:After adjusting for age and cardiovascular risk factors, there was a significant negative association between Ab burden and FMD (p<0.01), such that for each 0.1 increase in Ab burden, FMD decreased by 0.8%. Decreased brachial artery FMD response was found in individuals with elevated Ab compared with the non-elevated group (p<0.01). The optimal cut point of FMD predicting Ab elevation was 5% (AUC1⁄40.836, p<0.01, 95%CI: 0.742 0.930), with 81.8% sensitivity and 75.4% specificity. Higher PI was demonstrated in elevated Ab individuals (p1⁄40.04), but was not correlated with Ab burden. WML were not associated with Ab. Conclusions:Among cognitively normal older adults, poor central and peripheral vascular health is predictive of Ab burden. FMD, specifically, has potential value as a vascular biomarker for neuropathologic changes associated with Alzheimer’s disease.

DETECTION OF INCREASED MAGNETIC SUSCEPTIBILITIES IN THE CEREBRAL CORTEX IN PATIENTS WITH ALZHEIMER’S DISEASE: COMPARISON OF QUANTITATIVE SUSCEPTIBILITY MAPPING BETWEEN CONVENTIONAL AND BRAIN SURFACE CORRECTION METHOD

acoustic radiation, ATR: anterior thalamic radiation, CGC: cingulate gyrus part of cingulum, CGH: parahippocampal part of cingulum, CST: corticospinal tract, FMA: forceps major, FMI: forceps minor, IFO: inferior fronto-occipital fasciculus, ILF: inferior longitudinal fasciculus, SLF: superior longitudinal fasciculus, PTR: posterior thalamic radiation, STR: superior thalamic radiation, UNC: uncinate fasciculus. Poster Presentations: Monday, July 23, 2018 P848

HYBRID SEQUENCE AND ANALYSIS OF T1-WEIGHTED IMAGING AND QUANTITATIVE SUSCEPTIBILITY MAPPING FOR EARLY DIAGNOSIS OF ALZHEIMER'S DISEASES

Barton Lane, Max Wintermark, Elizabeth Hitchner, Wei Zhou, VA Medical Center-Palo Alto, Palo Alto, CA, USA; Stanford University, School of Medicine, Stanford, CA, USA; Harvard Medical School, Boston, MA, USA; Palo Alto VAHCS, Palo Alto, CA, USA; The Neuroinformatics and Brain Connectivity Laboratory, Department of Physics, Florida International University, Miami, FL, USA; Intuitive Surgical, Sunnyvale, CA, USA; Heinrich-Heine-Universit€at D€usseldorf, D€usseldorf, Germany; University of Texas Health Science Center at San Antonio, San Antonio, TX, USA; Texas Tech University Health Science Center, El Paso, TX, USA; Palo Alto University, Palo Alto, CA, USA; Washington University, Saint Louis, MO, USA; University of Arizona, Tucson, AZ, USA. Contact e-mail: rosena@stanford.edu