Biomedical subjects

Takeshi Hirose

Publications and source records attributed to Takeshi Hirose.

5 recordsLinked to original sources

PubMed2006

In vivo isotropic 3D diffusion tensor mapping of the rat brain using diffusion-weighted 3D MP-RAGE MRI.

The purpose of this study was to examine the potential of diffusion-weighted (DW) three-dimensional (3D) MP-RAGE MRI for diffusion-tensor mapping of the rat brain in vivo. A DW-3D-MP-RAGE (3D-DWI) sequence was implemented at 2.0 T using six gradient orientations and a b value of 1000 s/mm2. In this sequence, the preparation sequence with a "90 degrees RF-motion proving gradient (MPG): MPG-180 degrees RF-MPG-90 degrees RF" pulse train (DW driven equilibrium Fourier transform) was used to sensitize the magnetization to diffusion. A centric k-space acquisition order was necessary to minimize saturation effects (T1 contamination) from tissues with short relaxation time. The image matrix was 128x128x128 (interpolated from 64x64x64 acquisitions), which resulted in small isotropic DW image data (voxel size: 0.273x0.273x0.273 mm3). Moreover, 3D-DWI-derived maps of the fractional anisotropy (FA), relative anisotropy (RA) and main-diffusion direction were completely free of susceptibility-induced signal losses and geometric distortions. Two well-known commissural fibers, the corpus callosum and anterior commissure, were indicated and shown to be in agreement with the locations of these known stereotaxic atlases. The experiment took 45 min, and shorter times should be possible in clinical application. The 3D-DWI sequence allows for in vivo 3D diffusion-tensor mapping of the rat brain without motion artifacts and susceptibility to distortion.

Animals↗

PubMed2005

Diffusion-weighted three-dimensional MP-RAGE MR imaging.

The advantages of three-dimensional (3D) acquisition are that you obtain thinner and more slices with better profiles, and better signal-to-noise ratio for an equivalent slice thickness. Three-dimensional acquisition is preferable for obtaining contiguous thin-slice MR images. However, the acquisition time extends compared with the two-dimensional acquisition because the second phase-encode axis is applied by the 3D acquisition. Therefore, 3D acquisition should be a high-speed imaging method. In this paper, a new diffusion-sensitive 3D magnetization-prepared rapid gradient-echo (3D MP-RAGE) sequence was studied. In this sequence, a preparation phase with a 90 degrees RF-motion proving gradient (MPG): MPG-180 degrees RF-MPG-90 degrees RF pulse train (diffusion-weighted driven-equilibrium Fourier transform) was used to sensitize the magnetization to diffusion. Centric k-space acquisition order is necessary to minimize saturation effects from tissues with short relaxation times. From phantom experimental results, the effect of the diffusion weighting was changed by the centric vs. sequential k-space acquisition order. The effect of centric k-space acquisition order was larger than the effect of sequential k-space acquisition order. The contrast of centric k-space acquisition order became equal to the contrast of conventional diffusion-weighted spin echo. From rat experimental results, small isotropic diffusion-weighted image data (voxel size: 0.625 x 0.625 x 0.625 mm3) were obtained. This sequence was useful in vivo.

Acetone↗

PubMed2003

Myocardial perfusion during transient slow-flow in the patient with old vein graft intervention: assessment by serial measurement of pressure-derived fractional flow reserve and thermodilution-derived coronary flow reserve.

A patient with distal slow-flow after stenting in the old vein graft intervention was reported. This case is a first in whom guidewire-based serial measurement of pressure-derived fractional flow reserve (FFR(myo)) and thermodilution-based coronary flow reserve (CFR(thermo)) clearly demonstrated the serial change of microvascular circulation. During slow-flow, CFR(thermo) remained in low value despite significant improvement of FFR(myo) from 0.61 to 0.90. After thrombus aspiration and nicorandil injection, coronary flow reestablished immediately. CFR(thermo) improved significantly from 1.3 during slow-flow to 3.6 after restoration of flow.

Aged↗

PubMed2003

Evidence of pharmacologic preconditioning during PTCA by intravenous pretreatment with ATP-sensitive K+ channel opener nicorandil.

BACKGROUND: It is not known whether pretreatment with nicorandil, an ATP-sensitive K+ channel (K(ATP)channel) opener, induces a preconditioning effect independent of increased collateral recruitment. METHODS: Forty-four patients with angina who underwent percutaneous transluminal coronary angioplasty (PTCA) to proximal left anterior descending artery (LAD) stenosis were randomly allocated for pretreatment with an intravenous injection of 80 g/kg nicorandil 5 min before initial ballooning (n=22) or saline (n=22). 99mTc tetrofosmin was injected during balloon inflation, quantitative analysis of occlusion images by SPECT was conducted, and the defect severity score (SS) was calculated. An ECG was recorded during the 2-min inflation to calculate the sum of ST elevation (sigmaST). RESULTS: SigmaST levels were significantly reduced in patients with nicorandil pretreatment compared with control patients (control:1.89+/-0.85 mV nicorandil:1.24+/-0.57 mV, p=0.0052). However, no difference was observed in defect severity (control: 79.0+/-32.5, nicorandil: 98.7+/-48.9 ns). A close correlation was observed between SS and sigmaST in both groups (nicorandil group R(2)=0.505, control group R(2)=0.599). A multivariate regression model demonstrated that both defect severity (p<0.0001) and pretreatment with nicorandil (p<0.001) were significantly related to the level of sigmaST, suggesting a cellular protective effect against ischaemia by nicorandil, independent of myocardial blood flow. CONCLUSION: Nicorandil pretreatment resulted in the induction of myocardial preconditioning independent of the severity of ischaemia.

Aged↗

PubMed2002

Evidence of a cellular protective effect by antecedent angina independent of collateral flow recruitment during coronary angioplasty in humans.

The main aim of this study was to elucidate whether the beneficial effect of antecedent angina is a cellular protective effect or the result of an increase of collateral flow. Of 42 patients with angina who underwent percutaneous transluminal coronary angioplasty (PTCA) for proximal left anterior descending artery (LAD) stenosis, 22 had experienced antecedent anginal pain (AP) within 7 days prior to PTCA. 99mTc-sestamibi was injected during balloon inflation, and quantitative analysis of ischemic severity during coronary occlusion was calculated (SS). An electrocardiogram was recorded during ballooning to calculate the sum of ST elevation (sumST). SumST was significantly reduced in patients with AP compared with patients without AP (1.88+/-0.89 mV vs 1.18+/-0.74 mV, p=0.0088); however, no difference was observed in defect severity. A close correlation was observed between SS and sumST in both groups. The multivariate regression model demonstrated that both a large SS (p<0.0001) and the absence of preceding AP (p=0.001) were significantly related to the elevation of sumST. Recent angina can render the myocardium more resistant to subsequent ischemia during angioplasty and is true preconditioning rather than simply an increase of flow.

Aged↗