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MR parameter mapping is a technique that obtains distributions of parameters such as relaxation time and proton density (PD) and is starting to be used for disease quantification in clinical diagnoses. Quantitative susceptibility mapping is also promising for the early diagnosis of brain disorders such as degenerative neurological disorders. Therefore, we developed an MR quantitative parameter mapping (QPM) method to map four tissue-related parameters (TTissue-related parameters are estimated by varying four scan parameters of the 3D pRSGE: flip angle, RF-pulse phase increment, TR and TE, performing multiple image scans, and finding a least-squares fit for an intensity function (which expresses the relationship between the scan parameters and intensity values). The intensity function is analytically complex, but by using a Bloch simulation to create it numerically, the least-squares fitting can be used to estimate the quantitative values. This has the advantage of shortening the image-reconstruction processing time needed to estimate the quantitative values than with methods using pattern matching.A 1.1-mm isotropic resolution scan covering the whole brain was completed with a scan time of approximately 12 minutes, and the reconstruction time using a GPU was approximately 1 minute. The phantom experiments confirmed that both the accuracy and repeatability of the quantitative values were high. The volunteer scans also confirmed that the accuracy of the quantitative values was comparable to that of conventional methods.The proposed QPM method can map T

To increase the number of images that can be acquired in MR examinations using quantitative parameters, we developed a method for obtaining arterial and venous images with mapping of proton density (PD), RF inhomogeneity (B1), longitudinal relaxation time (T1), apparent transverse relaxation time (T2*), and magnetic susceptibility through calculation, all with the same spatial resolution.The proposed method uses partially RF-spoiled gradient echo sequences to obtain 3D images of a subject with multiple scan parameters. The PD, B1, T1, T2*, and magnetic susceptibility maps are estimated using the quantification method we previously developed. Arterial images are obtained by adding images using optimized weights to emphasize the arteries. A morphology filter is used to obtain venous images from the magnetic susceptibility maps. For evaluation, images obtained from four out of five healthy volunteers were used to optimize the weights used in the arterial-image calculation, and the optimized weights were applied to the images from the fifth volunteer to obtain an arterial image. Arterial images of the five volunteers were calculated using the leave-one-out method, and the contrast between the arterial and background regions defined using the reference time-of-flight (TOF) method was evaluated using the area under the receiver operation characteristic curve (AUC). The contrast between venous and background regions defined by a reference quantitative susceptibility mapping (QSM) method was also evaluated for the venous image.The AUC to discriminate blood vessels and background using the proposed method was 0.905 for the arterial image and 0.920 for the venous image.The results indicate that the arterial images and venous images have high signal intensity at the same region as determined from the reference TOF and QSM methods, demonstrating the possibility of acquiring vasculature images with quantitative parameter mapping through calculation in an integrated manner.

We propose a novel processing method for reducing shading artifacts in quantitative susceptibility mapping (QSM) for prostate imaging. In the conventional method, calculation errors in the boundary regions between water and fat cause shading artifacts that degrade the image quality for QSM. In the proposed method, water and fat regions are separated, and susceptibilities in these two regions are calculated separately and then combined. Susceptibility in the water regions is calculated by using the fat regions as a background susceptibility source to remove shading artifacts. Susceptibility in the fat regions is calculated by using the constraint that shading artifacts in the water regions are suppressed to improve accuracy. In quantitative evaluation of the method with a numerical simulation, calculation errors for the water and fat regions were reduced by 62% and 85%, respectively, compared with the conventional method. In visual evaluation using human prostate imaging, the proposed method also reduced the shading artifacts unlike the conventional method. The proposed method is expected to improve the performance of QSM in diagnosing such diseases as prostate cancer.

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.

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.

To realize susceptibility-weighted imaging in vertical-field magnetic resonance imaging (MRI), we developed an image-processing method called “susceptibility difference weighted imaging” (SDWI). In SDWI, contrasts are enhanced using a susceptibility map calculated by using a weighted least-square algorithm with a small iteration number. Experiments were performed on human volunteers to compare image contrast obtained from the conventional method (SWI) and SDWI. In horizontal-field MRI, SDWI results show that veins and deep-gray-matter nuclei were visualized as well as those with SWI. In vertical-field MRI, SDWI visualized veins and deep-gray-matter nuclei without severe streaking artifacts, while SWI did not. In our experiments, the time taken to calculate the susceptibility map in SDWI was less than 10 s. The results indicate that susceptibility-weighted imaging is feasible in vertical-field MRI using SDWI.

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We developed a double-tuned radiofrequency (RF) coil using a novel circuit method to double tune for fluorine-19 (19F) and 1H magnetic resonance imaging, whose frequencies are very close to each other. The RF coil consists of 3 parallel-connected series inductor capacitor circuits. A computer simulation for our double-tuned RF coil with a phantom demonstrated that the coil has tuned resonant frequency and high sensitivity for both 19F and 1H. Drug distribution was visualized at 7 tesla using this RF coil and a rat administered perfluoro 15-crown-5-ether emulsion. The double-tune RF coil we developed may be a powerful tool for 19F and 1H imaging.

We have introduced prioritizing of issues in science and technology for a safe and secure society conducted by "Study Group on Science and Technology Policy for a Safe and Secure Society" of MEXT. Risks and threats have been collected and classified from various sources. Among the collected risks and threats, 17 areas including crime, terrorism, disaster, and infectious disease have been selected. Based on criteria for prioritizing issues, 35 priority issues (technologies for detection of hazardous materials, disaster mitigation, protection from infectious diseases, etc.) and eight common priority issues (simulation technologies for damage evaluation, sensor technologies, etc.) have been selected. Language: ja

To achieve stable operations of high-Tc superconducting (HTS) single-flux-quantum circuits, we have studied the reproducibility and uniformity of inductances for HTS striplines. Optimizing a fabrication process of the striplines, the sheet inductances of the striplines for four samples were ranged from 0.77 to 0.93 pH per square at 4.2 K. The differences between these values and a designed value (Ld) of the sheet inductance were less than 10% of Ld. A 4 h oxygen annealing at 450 °C in 1 atm oxygen decreased the 1σ-spread of the stripline inductances from 12 to 4.9% at 4.2 K. It was found that taking into account the reproducibility and spread of inductances, the designed value of the sheet inductance should be less than 0.8 pH/ in order to obtain low inductance (less than 1 pH/) in a circuit area.

To optimize the conditions of oxygen annealing for YBa 2 Cu 3 O 7− x (YBCO) multilayered structures, we have investigated the effects of annealing on the characteristics of bilayers of CeO 2 /YBCO and surface-modified junctions. The annealing time required to recover a loss of oxygen in the YBCO layer increased as the number of precipitates on the YBCO layer decreased and the thickness of the CeO 2 layer increased. The oxygen annealing increased the critical current ( I c ) of the junction and decreased its normal resistance ( R n ). These changes in I c and R n indicate that oxygen annealing recovered a loss of oxygen at the interface of the junctions, thus decreasing the effective thickness of the barrier. We found that recovering a loss of oxygen in the ground planes requires oxygen annealing for more than 4 h, and the annealing time must be optimized for the designed value of I c .

We developed a new patterning process that combined electron beam (EB) and optical lithography. In this process, large and rough patterns are formed by optical lithography and fine patterns are formed by EB lithography on the same photoresist layer. Significant savings in terms of exposure time can be expected by using this patterning method. We found that the AZ5206 photoresist could be utilized as an EB resist by using an optimal concentration developer. The accuracy of between designed and fabricated pattern could be maintained above 1 μm. The critical current density of fabricated YBa2Cu3O7−x bridges was above 2 × 106 A/cm2 at 77 K even in the 0.3-μm-wide bridge. This indicated that this process caused no serious deterioration in the superconducting properties. Exposure time was reduced to about one-tenth compared with that for original EB lithography.

The deposition condition of superconducting YBa 2 Cu 3 O y (YBCO) thin films grown by 90° off-axis dc sputtering was investigated to obtain large and smooth YBCO thin films. The composition of the deposited Y–Ba–Cu–O thin films strongly depended on the distance from the target and sputtering pressure. The composition and phase variations in Y–Ba–Cu–O thin films was consistently described in the simple model. Under the optimized deposition condition, single-phase YBCO thin films with stoichiometric composition could be obtained. YBCO thin films with critical temperatures above 85 K and surface roughnesses of 5 nm were successfully obtained in an area approximately 2-in. in diameter by rotating the substrate.

Circuit simulations were used to study the capability of a high-temperature superconducting (HTS) sigma-delta modulator using interface-engineered-Josephson junctions (IEJ's). The dynamic range was calculated while varying the temperature (T) and input-signal frequency (f/sub 0/), and in the resultant power spectra, correct noise shaping (6 dB/oct) was found. Investigation of the dynamic range in terms of effective number of bits (ENOB) showed that ENOB was 6.7 for f/sub 0/ 40 K.

We have developed processes for fabricating a YBa/sub 2/Cu/sub 3/O/sub 7-x/-multilayered structure which contains surface-modified junctions and a ground plane. A process of Ar-and-oxygen-ion milling, which was developed for fabricating the ramp-edges of the junctions, was applied to planarization of the structure's insulating layers. A process of milling with 500-V O/sub 2/ ions, which was developed for cleaning the ramp-edge surfaces, was applied to improve the critical current values for via-contacts in the structure. The fabricated junctions exhibited an average I/sub c/R/sub n/ product of 0.7 mV and a 1/spl sigma/-spread in the critical current of about 10% at 30 K. The sheet inductance of the strip-lines in the structure was less than 1.0 pH per square in the range below 60 K. The obtained values for I/sub c/R/sub n/ product, 1/spl sigma/-spread, and sheet inductance allow us to realize the high-speed operation of single-flux-quantum circuits at temperatures from 20 to 40 K.

A high-T/sub C/ superconducting quantum interference device (SQUID) magnetometer - in which a room-temperature pickup coil is used to detect an impedance magnetocardiogram (I-MCG) signal - has been developed. The pickup coil (30-mm diameter) is installed outside the cryostat and is connected to the input coil of the high-T/sub C/ SQUID. The magnetometer's noise level is 150 fTHz/sup -1/2/ (>10 kHz). The magnetometer was used to measure I-MCG signals (about 12 pT), which were obtained by applying an ac current (15 kHz) of constant amplitude (7 mA, peak-to-peak) to a healthy male subject.

We fabricated and tested a high-temperature superconducting sigma–delta modulator using interface-engineered Josephson junctions. Proper dc-characteristics were obtained with a sampling frequency of 100 GHz at 20 K. To achieve high-speed sampling, Josephson junctions with a higher critical-current normal-resistance product were used. Circuit simulations with thermal noise were performed for the analysis of switching characteristics and SFQ dynamics. Further numerical analysis was made for the estimation of signal to noise ratio. Resultant bit accuracy was found to be 10.4 for 122 MHz input signal band.

We fabricated and tested a high-temperature superconducting (HTS) sigma–delta modulator using interface-engineered Josephson junctions. Proper dc-characteristics were obtained with a sampling frequency of 100 GHz at 20 K. To achieve high-speed sampling, Josephson junctions with a higher critical-current normal-resistance product were used. Circuit simulations with thermal noise were performed for the analysis of switching characteristics and SFQ dynamics.

We have investigated the properties of YBa/sub 2/Cu/sub 3/O/sub 7-x/ ramp-edge Josephson junctions with surface-modified barriers produced by Ar-ion irradiation followed by oxygen annealing. The fabricated junctions displayed RSJ-like I-V characteristics and excellent uniformity. The stray capacitance of the junctions was estimated from the ramp-edge structure. The junction capacitance was obtained by subtracting the stray capacitance from the shunting capacitance. We estimated the barrier thickness from the junction capacitance, and found that the critical current density of the junction increased exponentially with decreasing barrier thickness. The relative dielectric constant of the barriers ranged from 13 to 18.

We fabricated and tested high-temperature superconducting (HTS) rapid-single-flux-quantum (RSFQ) circuits using interface-engineered Josephson junction (IEJ). The characteristics of high-speed operation were examined by voltage-divider operation based on the toggle-flip-flop circuit. An operation at 155 GHz was obtained at 15 K and the proper functioning of the voltage divider was observed up to 27 K. Temperature dependence of the maximum operation speed was analyzed by circuit simulation with thermal-noise sources. To achieve higher speed operation using a Josephson junction with a higher I/sub c/R/sub n/ product, we also fabricated an RSFQ balanced comparator using IEJ; proper switching characteristics of the circuit was confirmed up to 190 GHz at 30 K. The bias condition dependencies were studied based on the circuit simulations in the relationship of the I/sub c/R/sub n/ product. The results of circuit simulation indicate that a Josephson junction with an I/sub c/R/sub n/ product of more than 0.7 mV is required for high-speed operation (100 GHz) in high-temperature range (30-40 K). We believe that the IEJ is a promising junction candidate for realizing high-speed operation in a high-temperature range.

High-T/sub c/ directly coupled magnetometers made from thin films of single layer YBa/sub 2/Cu/sub 3/O/sub y/ deposited on bicrystal substrates were investigated. A series 2-SQUID structure with a common pickup coil was designed to increase voltage modulation depth (/spl Delta/V). A second bias current was introduced to compensate for the disagreement between the two optimal bias currents and the voltage peak positions. The distribution of the second bias current was controlled by selecting the proper electrodes formed on the pickup coil, thus eliminating the difference in the voltage peak positions. The value of /spl Delta/V was doubled. The white noise in the magnetometer decreased by using this 2-SQUID design, but the low-frequency noise increased slightly. In addition, another type of the 2-SQUID magnetometer was proposed. This magnetometer has SQUIDs with different inductances. The overlapped V-/spl Phi/ curve showed the modulation beat caused by the difference in V-/spl Phi/ periodicity, and a high /spl Delta/V was observed at several /spl Phi//sub 0/ intervals.

We have fabricated Josephson junctions in YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBaCuO) thin films by the irradiation of focused ion beam (FIB). We used Be/sup 2+/ ions with the energy of 200 keV. When the fluence of Be/sup 2+/ ions was 1.2/spl times/10/sup 16/ ions/cm/sup 2/, the I-V characteristics of the junctions at 4.2 K showed RSJ-like characteristics with the excess current. The I/sub c/R/sub n/ product of the junctions was 1.1 mV at 6.3 K. Shapiro steps up to 20th step could be observed by the irradiation of 8.47 GHz microwave at 6.3 K. The magnetic modulation curve of the junction at 4.2 K was similar to the Fraunhofer pattern. These characteristics remained unaltered after preservation in a desiccator for 6 months.

The YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// co-planar Josephson junctions by Focused Ion Beam were fabricated by changing the width and the thickness of a YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin film. The magnetic properties of the junctions were measured at different temperatures. In the junction with 300 nm thickness, the magnetic field modulation of the critical current at 4.2 K was not observed. Near the critical temperature of the junction, the magnetic modulation curve was similar to that of a dc-SQUID. From the SEM observation, some microshorts were observed on the junction. In the junction with 200 nm thickness, the I-V curve was changed from flux-flow junction type to RSJ type. The magnetic modulation curve of the 7 /spl mu/m wide junction at 4.2 K was similar to a Fraunhofer pattern. Thus it is considered that the coupling region was changed from a microshort to weak coupling region, when the thickness of the YBaCuO film was decreased from 300 nm to 200 nm.

We have fabricated YBa 2 Cu 3 O 7− x ramp-edge junctions with surface-modified barriers on a ground plane. The fabricated junctions exhibited current–voltage characteristics that were consistent with the resistive-shunted-junction model up to 70 K. However, the critical temperature of the ground plane decreased to about 40 K. A 4 h annealing in 1-atm O 2 at 450 °C fully oxidized the buried ground plane under superconducting and insulating layers. After annealing, the critical temperature of the ground plane increased to 80 K. A sheet inductance of ∼1 pH per square was measured below 40 K. We also investigated the influence of the annealing on the properties of the junctions.

A rapid-single-flux-quantum toggle-flip-flop logic gate was fabricated using high-temperature superconducting interface-engineered Josephson junctions. It was shown that the gate can operate as a voltage divider up to 155 GHz at 15 K and 19 GHz at 27 K. At the same time, the temperature dependence of the IcRn product and the maximum divided voltage was compared. As a result, it was found that the ratio of these values is 0.4–0.1 for 15 K>T>27 K. Circuit simulation with noise sources reveals this peculiar temperature dependence of the maximum divided voltage.

We have developed a multilayer process for fabricating crossover and via structures. A crossover structure with Tc>85 K was fabricated by using an SrTiO3 buffer layer to repair the SrTiO3 surface damaged during etching. The interlayer resistance of a 10 µm × 50 µm crossover area was 150 k. Via contacts fabricated under various process conditions all showed residual resistance with reduced Tc, indicating the formation of damaged layers at the contact interfaces. However, the Ic measured through the via contacts fabricated under the optimal conditions exceeded 3 mA at 77 K which was high enough for most superconducting device applications.

We have developed and tested a new circuit simulation procedure for superconducting integrated circuits which can be used to optimize circuit parameters. This method reveals a stable operation region in the circuit parameter space in connection with the global bias margin by means of a contour plot of the global bias margin versus the circuit parameters. An optimal set of parameters with margins larger than these of the initial values has been found in the stable region.

We have fabricated YBa2Cu3O7-x ramp-edge Josephson junctions with a surface-modified barrier. The surface-modified barrier was formed by Ar-ion irradiation of a YBa2Cu3O7-x ramp surface after fabrication of a ramp-edge. We investigated the composition and structure of the surface-modified barrier using XPS and TEM. Our XPS analysis suggested that the surface modified barriers were created by recrystallization of amorphous YBa2Cu3O7-x that was modified by the Ar-ion irradiation. The atomic ratio of Y:Ba:Cu in the surface-modified barrier was 1:1.2:1.1. Our TEM observations revealed no difference in the crystal structures between the barrier and the YBa2Cu3O7-x at the interface. The structure of the surface-modified barrier is appeared to be very similar to that of YBa2Cu3O7-x.

YBaCuO/nonsuperconductive-YBaCuO/YBaCuO co-planar Josephson junction using Focused Ion Beam was fabricated by changing the size of the junction, and the magnetic field characteristic of these junctions was measured. The magnetic field modulation of the critical current increased with decreasing junction width. When the thickness of a YBaCuO thin film was reduced from 300nm to 200nm, the magnetic field modulation of the 5μm wide junction changed from dc-SQUID like pattern to Fraunhofer diffraction pattern. It is considered that the some Josephson current paths existed on the surface of the junction using the thin film 300nm thick.

We have fabricated a YBaCuO coplanar Josephson junction whose coupling region was a nonsuperconductive YBaCuO grown on an MgO substrate damaged locally by a scan of Focused Ion Beam (FIB). Shapiro steps could be observed for junctions with 0.4 to 1 μm length of the coupling region. The coupling region was found to be an electrically normal conductor whose characteristic length was ≈ 0.1 μm. We found out that there were microscopic changes of stoichiomertic composition on the coupling region, and that nonsuperconductive YBaCuO thin film was the mixed crystal.