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Biomedical subjects

Isao Muro

Publications and source records attributed to Isao Muro.

11 recordsLinked to original sources
PubMed2005

[Influence of respiratory motion in body diffusion weighted imaging under free breathing (examination of a moving phantom)].

Diffusion weighted imaging (DWI) theoretically aims to detect random motion over small distances, such as Brownian motion. Therefore, breath-hold scanning has been considered the only way to acquire DWI in the body without artifacts from bulk motion. Recent reports suggest that non-breath-hold scanning is feasible. The purpose of this study was to evaluate the influence of respiratory motion on DWI using a moving phantom model. Our results showed that the difference in apparent diffusion coefficient (ADC) was less than 10% between a static phantom and a moving phantom. There was no relation between the speed and stroke of the moving phantom and the calculated ADC. The results indicate that stable motion such as calm respiration does not cause signal loss on DWI, in contrast to intra-voxel incoherent motion (IVIM). The images obtained using this method showed high resolution and signal-to-noise ratio (SNR), suitable for three-dimensional display of the lesion.

Diffusion Magnetic Resonance Imaging↗
PubMed2005

[Basis examination of image contrast in fluid attenuated inversion recovery balanced turbo field echo (FLAIR-B-TFE)].

PURPOSE: We have made clinical use of FLAIR-B-TFE, where an image is taken at the null point (NP) of water with the addition of inversion pulse to B-TFE, and obtained highly effective results in many areas. Changes in NP and image contrast were reviewed to optimize this sequence. MATERIALS AND METHODS: Oil, water, and venous blood before and after Gd-DTPA dispensation as well as diluted (by 500/4000 times) Gd-DTPA solution were designated as the standard phantoms wherein shot intervals (SI), scan modes, k-space ordering, TFE factor, dummy pulse, and presence or absence of IR pulses were changed. RESULTS: What affects the NP of water most is the SI, and unless SI is long enough so that the longitudinal magnetization of water can recover to the full, NP will change. There is little difference in image contrast between the NP of water and that of blood, and a sluggish blood signal ascendance will necessitate intentional blood signal ascendance by contrast-enhancement. The signal intensity of blood after the angiographies will almost reach a plateau at an SI level of more than 2000 ms. Therefore, it is appropriate to apply SI 2000 ms, in view of the time necessary for contrast-enhancement.

Echo-Planar Imaging↗
PubMed2004

[Effect of motion correction associated with echo train length and number of blades in propeller MRI-computer simulation].

The PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) MRI method is available with a technique for motion correction. We studied changes in correction according to differences in echo train length (ETL) and number of blades, and measured correction accuracy according to linear translation and rotation, using computer simulation. A T(2)-weighted axial image of the head taken by FSE was utilized as the basic MR image. We reconstructed other images with differences in quantity of motion, ETL, and number of blades, also using computer simulation. After motion correction was performed, we measured correction accuracy with cross-correlation to the basic image. The method of motion correction was performed by the conversion of k-space data for each blade step using 2D Fourier-transform. After motion correction of the obtained image had been carried out, the image was converted to k-space data using reverse Fourier-transform. For data of 30 pixels with horizontal translation, cross-correlation coefficients for the stationary image were 0.6 for FSE without motion correction, 0.74 for the PROPELLER (ETL 8, blades 32) image without motion correction, and 0.99 for the PROPELLER (ETL 8, blades 32) image with motion correction. For data of 24 degrees with rotation, cross-correlation coefficients were 0.38 for FSE without motion correction, 0.53 for the PROPELLER (ETL 8, blades 32) image without motion correction, and 0.93 for the PROPELLER (ETL 8, blades 32) image with motion correction. The cross-correlation coefficient of liner translation is higher than its rotation. Correction accuracy was better with larger numbers of ETL than without motion correction. The spatial resolution of the image was decreased in the corrected image more by rotation than linear translation. This study indicated that the PR method was able to inspect the imaging technique with little influence on movement.

Computer Simulation↗
PubMed2004

[Studies of artifacts with TFE factor increase in heart delayed enhancement MRI sequence IR-T1TFE].

The characteristic of delayed enhancement MRI is high spatial resolution, which makes it possible to evaluate the degree of damage to the myocardium from the inner to the outer membrane of patients with ischemic heart disease. Therefore, this MRI technique is unique in its ability to detect myocardial condition and is necessary to obtain high-quality images. We experienced artifacts induced by TFE factor increase with delayed enhancement of IR-T1TFE. The purpose of this study was to determine the cause of such artifacts. IR-T1TFE changed signal intensity with phase direction as the TFE factor increased. Streak artifacts occurred because signal intensity caused changes with phase direction. Increases in TFE factor prolonged data collection time, such that marked artifacts were created because of changes in signal intensity. Ghost artifacts occurred because signal intensity changed between shots. When the TFE factor was increased, the difference in signal intensity was diminished between shots. The interval of acquired noise decreased in the raw data. Therefore, the interval of ghost artifacts became wider on images.

Artifacts↗
PubMed2002

Activation of pre-supplementary motor area (SMA) and SMA proper during unimanual and bimanual complex sequences: an analysis using functional magnetic resonance imaging.

Several functional imaging studies have shown that the extent of activation and percentage change in cerebral blood flow in the supplementary motor area (SMA) during a bimanual mirror performance of a simple repetitive movement are almost identical to those during a unimanual movement. The aim of this study was to investigate whether this finding was also applicable to a more complex movement. Eight right-handed, healthy volunteers performed unimanually (with their right and left hands) and bimanually (in a mirror fashion) thumb-finger opposition in a nonconsecutive order (index-middle-index-ring-index-little-index-middle ... fingers). The SMA proper was more activated during the bimanual movement than the unimanual movement with either hand. This is in accordance with the hypothesis that bimanual movement, even in a mirror fashion, is more difficult than unimanual movement when the task is complex but not when the task is simple. Pre-SMA was inconsistently activated. The results suggest that the SMA proper plays an active role in executive processing during bimanual mirror performance of complex movements.

Adult↗