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Tsuyoshi Matsuda

Publications and source records attributed to Tsuyoshi Matsuda.

17 recordsLinked to original sources
PubMed2005

Optical system for double-biprism electron holography.

A novel system of electron interferometry and holography using two electron biprisms has been developed. The first biprism is installed in the image plane of the objective lens and the second one is set behind the first magnifying lens, inside the shadow area of the first biprism. The system can independently control two important parameters for interferograms and holograms, the fringe spacing and interference width. Thus, it gives us more flexibility on performing electron interferometry and holography. The good performance of the system was demonstrated using a 1MV field-emission electron microscope. We introduce a variety of optical set-ups for the system and explain the advantages of each set-up in detail, with experimental results.

Journal Article↗
PubMed2004

Correlation between flow-sensitive alternating inversion recovery perfusion imaging with different inversion times and cerebral flow reserve evaluated by single-photon-emission computed tomography.

The purpose of this study was to evaluate the effect of different inversion times (TIs) on flow-sensitive alternating inversion recovery (FAIR) perfusion imaging and compare them with the cerebral blood flow reserve evaluated by acetazolamide challenge using single-photon-emission computed tomography (SPECT). The subjects were nine patients with unilateral obstruction of the internal carotid artery. The signal ratio (SR16/8) of two images with different TIs (1,600 ms and 800 ms) was calculated, and the cerebral blood flow reserve (CFR) was evaluated by the increase in the ratio of cerebral perfusion after administration of acetazolamide in the SPECT study. A reversed linear correlation ( r=0.75) was found between SR and CFR, indicating that differences of FAIR images with changes of TI will be affected by cerebral flow reserve.

Acetazolamide↗
PubMed2004

[Fundamental study of magnetization transfer contrast (MTC) effect: optimization of MT pulse condition using experimental phantom].

Magnetization transfer contrast (MTC) was evaluated by changing the off-set frequency and pulse intensity of MTC with the spoiled gradient echo (SPGR) sequence (T2*-weighted image) using an experimental phantom that included olive oil, protein, fiber, collagen, and pure water. The intensity of pure water reached a constant level just above the off-set frequency (1200 Hz) regardless of MT pulse power. The contrast-to-noise ratio (CNR) in each of the phantom materials was maximal at the MT pulse power of 2500 degrees (equivalent flip angle). The CNR and image noise obtained by body coil were inferior to those obtained with an extremity coil. In clinical application, the MTC effect on chondrosarcoma was higher (MT ratio, ROI-1:0.448, ROI-2:0.382) than those of other cases in this study. Since the image contrast was improved between the malignant fibrous histiocytoma (MFH, MT ratio, ROI-1:0.282, ROI-2:0.289) and peripheral tissues, extraskeletal extension could be observed more easily than without MTC imaging. In conclusion, the effects of MTC might be in providing useful information, in presuming composed tissues, differential diagnoses, and extent to the surrounding structures because of changing the image contrast to surrounding tissues corresponding to the rate of included bound water.

Bone Neoplasms↗
PubMed2003

Dynamic T1 estimation of brain tumors using double-echo dynamic MR imaging.

PURPOSE: To assess the clinical utility of a new method for real-time estimation of T1 during the first pass of contrast agent by using this method to examine brain tumors. MATERIALS AND METHODS: The multi-phase spoiled gradient-echo pulse sequence using the double-echo magnetic resonance (MR) technique was modified. In the first half of the pulse sequence, the flip angle was varied systematically. Then, static T1 values were calculated using differences in MR signal intensities between different flip angles. In the latter half of this sequence, changes in absolute T1 were calculated using differences in signal intensities before and after injection of contrast agent. The double-echo MR data were used to minimize the T2* effect. Five cases of neurinoma and seven cases of meningioma were examined. Changes in T1 during the first pass of contrast agent were compared between neurinoma and meningioma. RESULTS: Changes in absolute T1 were clearly demonstrated on the parametric map. Although the changes in absolute T1 during the first pass of contrast agent did not allow differentiation between the two types of tumors, the mean gradient after the first pass was statistically higher for neurinoma than for meningioma (P < 0.05; meningioma, 0.011 +/- 0.012 second(-1)/second; neurinoma, 0.034 +/- 0.020 second(-1)/second). CONCLUSION: The present method appears to be useful for estimation of dynamic T1 changes in brain tumors in clinical settings.

Adult↗
PubMed2003

Centrally fat-saturated three-dimensional magnetic resonance angiography of the abdomen using selective central fat-saturation of k-space.

PURPOSE: To assess the usefulness of centrally fat-saturated three-dimensional magnetic resonance (MR) angiography of the abdomen using an elliptical centric view order and selective placement of fat-saturation pulses in the central 30% portion of the k-space in terms of fat signal reduction, image contrast of post-contrast images, and breath-holding time. METHODS: Fat signal in abdomen and breath-holding time were compared between centrally fat-saturated three-dimensional sequence and partially fat-saturated three-dimensional sequence or conventional fat-saturated three-dimensional sequence. Abdominal contrast-enhanced centrally fat-saturated three-dimensional MR angiography was obtained at arterial and equilibrium phases, and image quality was quantitatively and visually evaluated. RESULTS: Centrally fat-saturated three-dimensional sequence suppressed fat signal, as did the conventional fat-saturated three-dimensional sequence, and the breath-hold was prolonged only by 1.5 seconds compared to the partially fat-saturated three-dimensional sequence. Contrast-enhanced centrally fat-saturated three-dimensional MR angiography provided abdominal MR arteriography with large signal difference between vessels and fat, while venous signal was insufficient at equilibrium phase. CONCLUSION: Abdominal contrast-enhanced centrally fat-saturated three-dimensional MR angiography using an elliptical centric view order and selective central fat-saturation of k-space reduced fat signal comparable to conventional fat-saturated three-dimensional sequence, and provided contrast-enhanced MR arteriography with high vascular contrast and minimum prolongation of breath-hold.

Abdomen↗
PubMed2003

Comparison of FAIR technique with different inversion times and post contrast dynamic perfusion MRI in chronic occlusive cerebrovascular disease.

The purpose of this study was to examine the signal change occurring with different inversion times (TIs) of the flow-sensitive alternating inversion recovery (FAIR) technique and to compare with the perfusion image obtained with Gd-DTPA injection. The subjects were 11 patients with unilateral occlusive cerebrovascular disease. Two FAIR images with different TIs (800 ms and 1600 ms) were measured for each patient and dynamic perfusion MRI was performed to produce four kinds of parameter maps: mean transit time (MTT), time to peak (TTP), relative cerebral blood flow (rCBF) and relative cerebral blood volume (rCBV) maps. Asymmetry ratios (ARs) between the affected and contra-lateral vascular sides were measured in both FAIR images and the four dynamic parameter maps. The AR of the MTT map of the four parameters showed the highest correlation with that of the FAIR images, especially with that of TI = 1600 ms (r = 0.829), and the AR of the rCBV map revealed the worst correlation with the FAIR images. The AR of the FAIR image with TI = 800 ms was less correlated with that of MTT than that with TI = 1600 ms. These results suggested that the signal intensity of the FAIR image was influenced by flow transition time and the change in TI could be used to select the flow with a different transition time. Our study suggested that a longer TI in the FAIR technique might be more useful than a shorter TI for evaluating chronic occlusive cerebrovascular disease in the clinical setting.

Brain↗
PubMed2003

Profile structure of magnetic flux lines in type-II superconductor from a rectangular electron hologram.

Profile magnetic configuration of a quantized flux line and flux-line lattice penetrating a type-II superconductor thin foil, niobium, was observed by electron holography and Lorentz microscopy using a 300 kV field-emission electron microscope. Each single flux line was distributed periodically as lattice structure in the mixed state just below its critical temperature of 8.5 K, while at low temperature of 5 K the flux lines were weakly bound as bundles. In order to observe the flux-line distribution over a wide area, discrete Fourier transform reconstruction in the holography was extended for a rectangular area without loss of information and data precision.

Journal Article↗
PubMed2003

[Dynamic contrast-enhanced T(1) measuring MRI using variable flip angle SPGR].

We modified the multi-phase spoiled gradient recalled echo (SPGR) pulse sequence using the double-echo MR technique for estimation of T(1) during the first pass of contrast agent, and examined its precision. In the first half of the pulse sequence, the flip angle was varied systematically to calculate static T(1) values. It was necessary to choose optimal flip angles to minimize the calculation error of static T(1) values. In the latter half of this sequence, changes in absolute T(1) were calculated using differences in signal intensities before and after the injection of contrast agent. The optimal flip angle was 20 degrees for precise conversion to T(1) values under the short TR (33.3 ms) condition. Double echo MR data were used to minimize the T(2)* effect. The present method appears to be useful for quantitative estimation of dynamic contrast-enhanced MRI.

Brain Neoplasms↗
PubMed2003

[Study of elliptical centric view ordering technique with spectrally selected inversion recovery pulse (spec-IR pulse)].

Among several techniques for contrast-enhanced MRA, the elliptical centric view ordering method, originally developed at the Mayo Clinic, is a promising one. It has been difficult to apply a fat-suppression prepulse, mainly because the conventional fat suppression method requires a longer acquisition time during sampling of the low-frequency domain in k-space, and it causes severe image distortion due to the great change in longitudinal magnetization derived from fat tissue. We developed a novel method to append fat saturation to the elliptical centric view ordering technique, and assessed the feasibility of its use. Our method is to apply fat-saturation pulses only at selected sampling points when any gradient is applied in the slice-encoding direction. In this way, we achieved efficient suppression of fat-derived signal within a relatively short time, comparable to that of the conventional fat-saturation method, and succeeded in minimizing artifacts.

Artifacts↗
PubMed2002

Fat-suppressed three-dimensional MR angiography technique with elliptical centric view order and no prolonged breath-holding time.

PURPOSE: To determine the appropriate rate of fat-suppression pulses (using spec IR-spectral selective inversion recovery) for fat-suppressed 3D magnetic resonance angiography (MRA) with an elliptical centric view order. MATERIALS AND METHODS: In abdominal 3D fast spoiled gradient echo (fast SPGR) with an elliptical centric view order, the spec IR pulse rate was changed from zero to one every 15 repetitions (in nine steps) in eight volunteers. In the equilibrium phase, abdominal contrast-enhanced 3D MRA was obtained by 3D fast SPGR using an elliptical centric view order without fat-suppression and with two spec IR, and by fat-suppressed 3D fast SPGR with a sequential-centric view order (efgre3D) in 18 cases. Fat and vascular signals were estimated. RESULTS: Although 3D fast SPGR using an elliptical centric view order with spec IR placed every 15 TR and efgre3D effectively decreased fat signals, these sequences lengthened the breath-hold by 4-6 seconds compared with non-fat-suppressed sequence. 3D fast SPGR using an elliptical centric view order and two spec IR reduced the fat signal by 30% and provided good 3D MR angiography without substantial prolongation of breath-hold. CONCLUSION: Two spec IR can be used for generation of partially fat-suppressed abdominal 3D MRA without prolongation of the breath-hold when performing 3D fast SPGR using an elliptical centric view order.

Abdomen↗
PubMed2002

Diffusion-weighted in vivo localized proton MR spectroscopy of human cerebral ischemia and tumor.

The apparent diffusion coefficients (ADCs) of water and brain metabolites were determined by proton MR spectroscopy on a clinical MR scanner for healthy volunteers and for pathological changes in cases of acute cerebral infarction and brain tumor. The ADCs of N-acetyl aspartate (NAA) and creatines in tissue involved in acute infarction were decreased compared to normal control values, while in tumors they showed increased values. Since NAA is a neuronal marker, these findings suggest that neuronal cell viscosity changes according to the pathological status of the tissue. The lactate ADC was significantly larger than the values for other major metabolites in cases of ischemia and tumor, suggesting that lactate is present in a different compartment. These results indicate that metabolite diffusion data can be used to reveal changes in the intracellular environment depending on the pathological status.

Adult↗
PubMed2002

Differentiation of prostate cancer from benign prostate hypertrophy using dual-echo dynamic contrast MR imaging.

OBJECTIVE: To investigate the usefulness of dynamic contrast magnetic resonance (MR) imaging in the differentiation of prostate cancer (PC) from benign prostate hypertrophy (BPH). MATERIALS AND METHODS: Eleven PC patients and 13 BPH patients were entered into the analysis. The mean gradient (MG) was calculated from the T2* term-eliminated time-signal intensity curve obtained from dynamic contrast MR data, and the MG of PC and that of BPH were compared. RESULTS: The MG of PC was significantly higher than that of BPH. When the threshold value was set to 1.88% per s for discriminating PC from BPH, the sensitivity, specificity, and accuracy were 100, 85, and 92%, respectively. CONCLUSION: The MG, which is derived from the T2* term-eliminated time-signal intensity curve, may be a useful index for differentiating PC from BPH.

Adult↗
PubMed2002

Measurement of the vascularity and vascular leakage of gliomas by double-echo dynamic magnetic resonance imaging: a preliminary study.

RATIONALE AND OBJECTIVE: To evaluate the vascularity and vascular leakage of well-enhanced gliomas by double-echo dynamic magnetic resonance (MR) imaging. MATERIALS AND METHODS: Eight patients with glioblastoma multiforme (GBM) and two patients with juvenile pilocytic astrocytoma (JPA) were studied. Double-echo dynamic MR imaging was utilized to separate the T2* shortening effect and the T1 shortening effect. The former was represented by the vascularity index, and the latter was represented by the leakage index. These indexes were compared with histopathologic data. RESULTS: The mean vascularity index of the GBM was higher than that of the JPA (mean +/- SD, 3.48 +/- 1.57 [GBM] versus 0.51 +/- 0.29 [JPA]), and the mean leakage index of the JPA was higher than that of the GBM (1.35 +/- 0.87 [JPA] versus 0.27 +/- 0.15 [GBM]). Abundant vascularity was noted in the tight interstitial space in the pathologic specimen of GBM. Conversely, sparse vasculature was observed in the wide interstitial space in the pathologic specimen of JPA. CONCLUSION: This method may enable better characterization of grade in well-enhanced glioma by providing the information on the vascularity and leakage indexes.

Adult↗
PubMedDate not supplied

H(2) (15)0 positron emission tomography validation of semiquantitative prostate blood flow determined by double-echo dynamic MRI: a preliminary study.

PURPOSE: Information regarding prostate blood flow as determined by positron emission tomography (PET) with H 0 may provide useful information about tumor diagnosis; however, PET requires a cyclotron for the production of an extremely short half-life (2 minutes) tracer. Therefore, the aim of this study was to propose a complementary index for blood flow as determined by MRI to validate the results and compare them with PET, especially for prostate tissue. METHODS: Six consecutive patients with prostate disease were studied. The two semiquantitative indices for tumor blood flow were calculated from the time-concentration curve measured from double-echo MR images. The theory of nondiffusible tracers by means of indicator dilution theory was applied to MR data. The relative regional blood flow (rrBF) was calculated as the ratio of the relative regional blood volume to relative regional mean transit time. Another proposed index was the maximum height of the time-concentration curve. PET studies were also performed, and absolute blood flow values were calculated for each subject. These indices calculated from different modalities were then compared. RESULTS: A significant correlation was found between the rrBF and the absolute blood flow as determined by PET (r = 0.69, p < 0.005). A significant correlation was also found between the maximum height of the time-concentration curve and the absolute blood flow (r = 0.85, p < 0.0001). CONCLUSIONS: The semiquantitative tumor blood flow indices measured with MRI have a good correlation with the corresponding measurements by PET; therefore, these indices may provide useful information about tumor diagnosis in clinical settings.

Aged↗