摘要:
A method and system are provided for 3-D acoustic microscopy using short pulse laser excitation. A 3-D acoustic microscope for use in such a system is also provided. In a first embodiment, wherein optical detection is utilized, a focused excitation beam is scanned by a first acoustooptic scanning device across an absorbing layer of an opto-acoustic transducer (if needed) coupled to an object under investigation to create spherical ultrasonic waves within the object which may be living tissue. The reflected spherical ultrasonic waves are detected through the use of an unfocused probe beam and an optical detector array or a focused probe beam and a single photodetector which receive the probe beam from a reflecting surface of the opto-acoustic transducer. A second acoustooptic scanning device scans the probe beam at a plurality of positions on the reflecting surface of the opto-acoustic transducer. In another embodiment, an ultrasound transducer is utilized to acoustically detect the reflected spherical ultrasonic waves. Signals from the optical detector array, the photodetector, or the ultrasound transducer are subsequently digitized and reconstructed via 3-D synthetic aperture beam-forming equations to generate a 3-D representation of the object. Then the 3-D representation of the image is displayed as an image. The microscope includes the first and second acoustooptic scanning devices and the opto-acoustic transducer housed in a housing to define a needle probe such as a conventional biopsy needle.
摘要:
A phased array sector scanning (PASS) ultrasonic imaging system produces a fixed focus, steered transmit beam with an array of transducer elements. A receiver forms the echo signals received from an ultrasonic energy reflecting object at the array elements into a receive beam steered in the same direction as the transmit beam and dynamically focused. A midprocessor in the receiver makes corrections to the receive beam samples to offset errors caused by the transmit beam being out of focus at all but its fixed focal range.
摘要:
A beam former in a PASS ultrasonic imaging system includes a set of sigma-delta modulators which operate to separately digitize the received echo signal from each transducer element. The oversampled one-bit digital representations of each echo signal are delayed as required for beam steering and focusing, and are summed together. A decimator filter reduces the sample rate of the digitized receive beam prior to display of the image resulting from the receive beam.
摘要:
A phased array sector scanning ultrasonic imaging system produces digitized baseband samples of the received ultrasonic echo signals amplified by a time gain control (TGC) to compensate for dispersion losses in the media in which the ultrasonic signals propagate. A time frequency control filter employs the same TGC control signal to calculate a phase shift correction as well as the coefficients which determine the characteristics of a bandpass filter such that the frequency dependent dispersion losses in the ultrasonic echo signals are compensated.
摘要:
A method for generating an output stream of digital data words, with each data word representing the amplitude of an analog signal at one of a multiplicity F samples each second and with substantially equally spaced time intervals T therebetween, is obtained from a digital baseband demodulation system used for array beam forming. A data stream, formed of interleaved ADC output digital data words acquired from a set of converters, is at a rate of F total samples/second. Subsequent digital demodulation, filtration, and decimation provides digital output signals which need less delay resolution prior to the formation of coherent sum signals, thereby reducing overall channel memory requirements. The output baseband data stream has enhanced dynamic range, thereby reducing the ADC bit density requirements.
摘要:
A method for magnetic resonance imaging of fluid flow, and particularly in vivo blood flow, uses multiple-echo phase-contrast sequences of signals both in the magnetic field gradient in the direction in which fluid flow is to be determined, and in the radio-frequency (RF) magnetic field utilized with the magnetic field gradient. The magnetic field gradient has a pair of phase-encoding pulses having a zero mean value effect upon the sample, either alone or with inversion by an intermediate 180.degree. RF pulse signal. A first multi-echo sequence, provided with the phase-encoding pulse pair, provides information of both the amplitude and phase-shift of each pixel of the imaged flowing material while a second multiple echo sequence, devoid of the phase-encoding-gradient pulses, provides information as to the amplitude and the undesired initial phase-shift of each pixel of both stationary and flowing material. Information provided responsive to the second sequence is subtracted from the information provided responsive to the first sequence to provide an image having an intermediate grey-scale value for stationary sample material and with differential grey-scale encoding for differential flow velocities of fluid passing through the image plane.
摘要:
The present invention relates to multicomponent glasses and their use in powdered form as an additive in personal care products such as toothpastes.
摘要:
A current source density mapping system includes an ultrasound transducer emitting an ultrasound wave traveling along an ultrasound beam directed at a mapping field in a region of living tissue and an ultrasound pulser delivering a transmit pulse to said ultrasound transducer. The system includes a timing device producing controlled excitation of the transmit pulse; a plurality of recording electrodes positioned in contact with the living tissue detecting an acoustoelectric voltage signal generated at a bioelectric current source and within a focal zone of said ultrasound beam. An amplifier operatively connected to the recording electrodes amplifying the acoustoelectric voltage signal at a predetermined gain; and an analyzing component comprising a digitizer, a sampling device, a signal processor and a display unit operatively connected to the amplifier determining the location of the bioelectric current source by analyzing the acoustoelectric voltage signal detected by the recording electrodes in response to an interaction between the ultrasound wave and the presence of a current source in the mapping field.
摘要:
A method and system to create and acoustically manipulate without destroying a microbubble which, in biological applications, can manipulate structures such as cells and subcellular structures at a nanoscopic scale.
摘要:
A polymer waveguide resonator device for high-frequency ultrasound detection having a optical resonator coupled to a straight optical waveguide which serves as input and output ports. Acoustic waves irradiating the waveguide induce strain modifying the waveguide cross-section or other design property. As a consequence, the effective refractive index of optical waves propagating along the ring is modified. The sharp wavelength dependence of the high Q-factor resonator enhances the optical response to acoustic strain. High sensitivity is demonstrated experimentally in detecting broadband ultrasound pulses from a 10 MHz transducer.