Satoshi Aida

Method and apparatus for ultrasonic wave medical treatment using computed tomography

An ultrasonic wave medical treatment in which the position of the focal point of the ultrasonic waves, the temperature in a vicinity of the object to be treated, and the effect of the treatment can be determined easily and accurately. The three-dimensional image information of the object to be treated obtained by a computed tomography device is utilized in locating the focal point. In case of using a nuclear magnetic resonance imaging device as the computed tomography device, the T2 weighted image and the chemical shift data can be used in checking the effect of the treatment and the temperature in a vicinity of the object. The endocavitary probe equipped with temperature and intensity sensors may also be used. The ultrasound tomographic images obtained by the ultrasound tomographic imaging device may also be used in conjunction with the three-dimensional image information. Sequential shifting of the focal point of the ultrasonic waves may be employed to reduce adverse influence due to the cavitation.

Calculation of aortic regurgitant volume by a new digital Doppler color flow mapping method : An animal study with quantified chronic aortic regurgitation

OBJECTIVES The aim of the present study was to quantitate aortic regurgitant volume and regurgitant fraction in a chronic animal model with surgically created aortic regurgitation using a new semiautomated color Doppler flow calculation method. BACKGROUND The conventional noninvasive methods for evaluating the severity of aortic regurgitation have not been accepted widely nor compared with truly quantitative reference standards. METHODS Eight to 20 weeks after aortic regurgitation was surgically induced in six sheep, a total of 22 hemodynamic states were studied. Electromagnetic flow probes and meters provided reference flow data. Epicardial color Doppler echocardiographic studies were performed to image left ventricular outflow tract forward and aortic regurgitant blood flows. The new method digitally integrated spatial and temporal color flow velocity data for left ventricular outflow tract forward flow and ascending aortic regurgitant flow. The pulsed Doppler method using the velocity-time integral was also used to obtain regurgitant volumes and regurgitant fractions. RESULTS Regurgitant volumes and regurgitant fractions by the new method agreed well with those obtained electromagnetically, whereas the pulsed Doppler method overestimated these reference data (mean [+/-SD] difference 0.23 +/- 2.9 ml vs. 11 +/- 5.8 ml, p < 0.0001 for regurgitant volume; mean difference 1.2 +/- 7.6% vs. 19 +/- 13%, p < 0.0001 for regurgitant fraction). CONCLUSIONS This animal study, using strictly quantified aortic regurgitant volumes, demonstrated that the digital color Doppler method provides accurate aortic regurgitant volumes and regurgitant fractions without cumbersome measurements.

Semisuperjunction MOSFETs: new design concept for lower on-resistance and softer reverse-recovery body diode

A new superjunction (SJ) structure offering remarkable advantages compared with the conventional SJ structure is proposed and demonstrated for a power-switching device. In the proposed structure (semi-SJ structure), an n-doped layer is connected to the bottom of the SJ structure. According to the results of experiment and simulation, the semi-SJ structure has both lower on-resistance and softer recovery of body diode than conventional SJ MOSFETs. The fabricated semi-SJ MOSFETs with breakdown voltage of 690 V realize on-resistance 28% lower than that of the conventional SJ MOSFET with same aspect ratio. The softness factor of the body diode is also improved by a factor of five. The proposed MOSFET is very attractive for H bridge topology applications, such as switching mode power supplies and small inverter systems, thanks to the low on-resistance and the soft recovery body diode.

A 15.5m&#937;cm 2 -680V Superjunction MOSFET Reduced On-Resistance by Lateral Pitch Narrowing

Si-MOSFETs with the breakdown voltage of 680 V and the specific on-resistance of 15.5 mOmegacm2 were demonstrated by the superjunction (SJ) structure. The lateral pitch for the SJ structure was narrowed to 12 mum for the on-resistance reduction. The demonstrated on-resistance is the lowest one among previously reported 600 V-class SJ-MOSFETs. The fabricated MOSFET also realized low RonQgd of 1.8 OmeganC and high avalanche current of 175 A/cm2

Validation of the accuracy of both right and left ventricular outflow volume determinations and semiautomated calculation of shunt volumes through atrial septal defects by digital color Doppler flow mapping in a chronic animal model

OBJECTIVES The aim of the present study was to quantitate shunt flow volumes through atrial septal defects (ASDs) in a chronic animal model with surgically created ASDs using a new semiautomated color Doppler flow calculation method (ACM). BACKGROUND Because pulsed Doppler is cumbersome and often inappropriate for color flow computation, new methods such as ACM are of interest. METHODS In this study, 13 to 25 weeks after ASDs were surgically created in eight sheep, a total of 24 hemodynamic states were studied at a separate open chest experimental session. Electromagnetic (EM) flow probes and meters were used to provide reference flow volumes as the pulmonary and aortic flow volumes (Qp and Qs) and shunt flow volumes (Qp minus Qs). Epicardial echocardiographic studies were performed to image the left and right ventricular outflow tract (LVOT and RVOT) forward flow signals. The ACM method digitally integrated spatial and temporal color flow velocity data to provide stroke volumes. RESULTS Left ventricular outflow tract and RVOT flow volumes obtained by the ACM method agreed well with those obtained by the EM method (r = 0.96, mean difference = 0.78 +/- 1.7 ml for LVOT and r = 0.97, mean difference = -0.35 +/- 3.6 ml for RVOT). As a result, shunt flow volumes and Qp/Qs by the ACM method agreed well with those obtained by the EM method (r = 0.96, mean difference = -1.1 +/- 3.6 ml/beat for shunt volumes and r = 0.95, mean difference = -0.11 +/- 0.22 for Qp/Qs). CONCLUSIONS This animal study, using strictly quantified shunt flow volumes, demonstrated that the ACM method can provide Qp/Qs and shunt measurements semiautomatically and noninvasively.

High breakdown voltage (>1000 V) semi-superjunction MOSFETs using 600-V class superjunction MOSFET process

Si-MOSFETs with the breakdown voltage of over 1000 V were demonstrated, for the first time, realizing low on-resistance below the theoretical Si limit. The fabricated MOSFETs have a semi-superjunction (SemiSJ) structure, which is the combination of a superjunction (SJ) structure and an n-bottom assisted layer. The SemiSJ MOSFETs realize both the high breakdown voltage of 1110 and 1400 V and the low on-resistance of 54 and 163 m/spl Omega/cm/sup 2/, respectively. The fabrication process for the high-voltage SemiSJ-MOSFET was completely equivalent to a 600-V class SJ-MOSFET process, which implies that a single optimized process for forming SJ structure for 600 V-class MOSFET can be used for a wide voltage range extending up to 1200 V MOSFET. Additionally the fabricated MOSFETs realized low R/sub on/Q/sub gd/ of 4.6 /spl Omega/nC for a 1110-V device and 13.1 /spl Omega/nC for a 1400-V device, and recovery characteristics of the body diode were softer than those for the SJ MOSFET. These results show the possibility of new Si power-MOSFET with a higher application voltage range.

Over 1000V semi-superjunction MOSFET with ultra-low on-resistance below the Si-limit

Si-MOSFETs with the breakdown voltage of over 1000 V were demonstrated, for the first time, realizing low on-resistance below the theoretical Si-limit. The fabricated MOSFETs have semi-superjunction (SemiSJ) structure, which is the combination of superjunction (SJ) structure and n-bottom assisted layer (BAL). The SemiSJ MOSFETs realize both the high breakdown voltage of 1100 and 1400 V and the low on-resistance of 54 and 163 m/spl Omega/cm/sup 2/, respectively. The fabrication process for the high voltage SemiSJ-MOSFET was completely equivalent to a 600-V class SJ-MOSFET process, which implies that a single optimized process for forming SJ structure for 600 V-class MOSFET can be used for a wide voltage range extending up to 1200 V MOSFET. These results show the possibility of new Si power-MOSFET with higher application voltage range.

600V semi-superconjunction MOSFET

New superconjunction (SJ) structure is proposed and demonstrated for the power-switching device with remarkable advantage over conventional SJ structure. An n-doped layer is connected to the bottom of the SJ structure for the proposed structure. It is found with experiment and simulation that the proposed structure shows both the lower on-resistance and the softer recovery of body diode than conventional SJ MOSFET. The fabricated Semi-SJ MOSFETs realize Ron as low as 54 m/spl Omega/cm/sup 2/ (48 m/spl Omega/cm/sup 2/ in calculation) at 690 V breakdown voltage with only half depth of the p-column than the conventional SJ MOSFET. The softness factor of body diode is also improved in the factor of 4.5. The proposed MOSFET is very attractive for H-bridge topology applications such as UPSs and small inverter systems thanks to the low on-resistance and the soft recovery body diode.

Fundamental Study in Extracorporeal Shock Wave Lithotripsy Using Piezoceramics

An experimental extracorporeal shock wave lithotripsy system consisting of a piezoceramic shock wave generator and an ultrasonic imaging apparatus has been made. The generated 500 kHz ultrasound wave converts to the shock wave in the focussing region by nonlinear interaction. The measured peak pressure at the focussing point is 130 MPa and the focussing region, in which pressure is more than half of the peak pressure, is about 3 mm in width and 13 mm in depth. Model urological stones in water and a human renal stone implanted in the right renal pelvis of a mongrel dog are successfully disintegrated into less than 3 mm fragments.

Improvement of switching trade-off characteristics between noise and loss in high voltage MOSFETs

A new MOS-gate structure was proposed and demonstrated to improve the switching trade-off characteristics between noise and loss in high-voltage MOSFETs. The lightly p-doped dummy base layer under the gate electrode modulates Cgd-Vds curve due to the depletion under high applied voltage and the turn-off dV/dt can be suppressed even with high-speed switching. The fabricated device showed the surge voltage suppression of 50 V or the turn-off loss reduction of 20% in the turn-off switching test with an inductive load. In the flyback converter operation, it was also shown that the trade-off characteristics between the radiation noise and total power loss were improved by the proposed dummy base structure.