Toru Shirai

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.

Simple modification of arm position improves B1+ and signal homogeneity in the thoracolumbar spine at 3T

To evaluate the homogeneity of the radiofrequency magnetic field (B1+) and signal intensity using different arm positions during 3T thoracolumbar spinal imaging.

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