Yasuo Miyajima

Ultrasonic imaging apparatus for color display of flow velocity

An ultrasonic imaging apparatus comprises an ultrasonic transducer for emitting an ultrasonic beam onto an interest region of a living body containing a blood flow and outputting an echo signal, a correlation circuit for determining a correlation of the signals obtained from the ultrasonic transducer and a velocity calculation circuit for calculating the velocity of the blood flow from the correlation data obtained by the correlation circuit. A zero shift process circuit zero-shifts the velocity data obtained from the velocity calculation circuit and compresses the zero-shifted velocity data in correspondance with an amount of zero shift. The zero-shifted flow velocity data is displayed within a possible display range.

RSNA QIBA ultrasound shear wave speed Phase II phantom study in viscoelastic media

Using ultrasonic shear wave speed (SWS) estimates has become popular to noninvasively evaluate liver fibrosis, but significant inter-system variability in liver SWS measurements can preclude meaningful comparison of measurements performed with different systems. The RSNA Quantitative Imaging Biomarker Alliance (QIBA) ultrasound SWS committee has been developing elastic and viscoelastic (VE) phantoms to evaluate system dependencies of SWS estimates. The objective of this study is to compare SWS measurements between commercially-available systems using phantoms that have viscoelastic properties similar to those observed in normal and fibrotic liver. CIRS, Inc. fabricated three phantoms using a proprietary oil-water emulsion infused in a Zerdine® hydrogel that were matched in viscoelastic behavior to healthy and fibrotic human liver data. Phantoms were measured at academic, clinical, government and vendor sites using different systems with curvilinear arrays at multiple focal depths (3.0, 4.5 & 7.0 cm). The results of this study show that current-generation ultrasound SWS measurement systems are able to differentiate viscoelastic materials that span healthy to fibrotic liver. The deepest focal depth (7.0 cm) yielded the greatest inter-system variability for each phantom (maximum of 17.7%) as evaluated by IQR. Inter-system variability was consistent across all 3 phantoms and was not a function of stiffness. Median SWS estimates for the greatest outlier system for each phantom/focal depth combination ranged from 12.7-17.6%. Future efforts will include performing more robust statistical analyses of these data, comparing these phantom data trends with viscoelastic digital phantom data, providing vendors with study site data to refine their systems to have more consistent measurements, and integrating these data into the QIBA ultrasound shear wave speed measurement profile.

A two-dimensional array probe that has a huge number of active channels

A novel 2D array ultrasound probe for volumetric imaging has been fabricated and evaluated. This 2D array probe is a random sparse array probe with 1024 channels exclusively for transmission and 1024 channels exclusively for reception. The probe includes a 2D array transducer consisting of a fully populated 64/spl times/64 array of elements with a 0.25-mm pitch in each direction and a 2.5-MHz center frequency. The internal electronic circuits module of the probe assigns 1024 transducer elements exclusively for transmission and 1024 transducer elements exclusively for reception, and sets the rest as inactive. The probe also contains preamplifiers in the receive channels and a cable assembly consisting of more than 2000 coaxial cables. In this paper, details of the design and fabrication of the subunits of this 2D array probe are presented together with the results of evaluation of a prototype of the probe.

Maximum flow velocity estimation based on Doppler spectral analysis (haemodynamics)

A novel maximum-frequency estimator based on Doppler spectral analysis is presented and demonstrated on experimental results obtained by a newly constructed versatile pulse-echo Doppler system. The system employs a fast (12-b at 20 MHz) data-acquisition system that enables recording of raw RF data, which allows computation of Doppler spectra in software. Given a Doppler spectrum, the maximum-frequency estimator makes use of the total spectral power. This feature makes the estimator less susceptible to noise. The maximum-frequency estimator has been applied to a series of pulsatile flow phantom data obtained at 3.5 MHz. Maximum-frequency curves obtained from pulsatile flow velocities in the 2 m/s range are presented. The efficacy of the estimator is further demonstrated on preliminary results obtained from data taken from a human carotid artery using a real-time scanner.<<ETX>>