Masao Kuroda

Image restoration from non-uniform magnetic field influence for direct Fourier NMR imaging

A new technique is proposed for NMR image restoration from the influence of main magnetic field non-uniformities. This technique is applicable to direct Fourier NMR imaging. The mathematical basis and details of this technique are fully described. Modification to include image restoration from non-linear field gradient influence is also presented. Computer simulation demonstrates the effectiveness of this technique for both Fourier zeugmatography and spin-warp imaging.

Multiple acoustic beamformer step scanner

In an ultrasonic imaging system including an array of ultrasonic oscillators, ultrasonic beams are electronically scanned by sequentially selecting a plurality of oscillator sets for beam transmission and reception. For one transmission of ultrasonic waves, at least two receiver oscillator sets having at least some oscillators in common are simultaneously selected, and the respective outputs from the oscillators in the at least two receiver oscillator sets are phase-adjusted so that echoes received by the at least two receiver oscillator sets effectively correspond to echoes substantially emanating from at least two respective different points on a depth level distanced from the plane of the oscillator array by a predetermined depth, whereby at least two signals and hence at least two successive scan lines relating to the echoes from those respective different points are produced. As a result, improved line resolution and rapid line acquisition can be obtained.

A new method of measuring T2 using steady-state free precession

Abstract Comparison of steady-state free-precession signals just before and after the rf pulse gives a measure of transverse relaxation time T2. Particularly when a spectral line is inhomogeneously broadened far over the pulse-repetition frequency width ( 1 T ), the effective transverse relaxation time becomes one-half T2. This method is applicable to spin systems where the longitudinal relaxation time T2 is at least several times longer than T2 and therefore suitable for T2 imaging of biological systems. It possesses the useful property that rf inhomogeneity has no effect on the measured T2 value as long as T ⪡ T1.

Method for transmission and reception of ultrasonic beams using ultrasonic transducer element array

Disclosed is a method for transmission and reception of ultrasonic beams using an array of ultrasonic transducer elements in which a plurality of transducer element sets each including the selected number of transducer elements for the transmission and/or reception of ultrasonic beams are sequentially selected. First and second sets having different focal axes defined relative to the plane of the transducer array are selected for the transmission and reception modes of operation respectively during the production of a single scan line. The position of at least one of the transducer elements in the first set is different from those of the transducer elements in the second set.