US with extended field of view: phantom-tested accuracy of distance measurements.

To evaluate the accuracy of distance measurements obtained with the extended-field-of-view (FOV) software of a commercially available ultrasonographic scanner, two custom-designed phantoms that allowed scanning of flat and curved surfaces were used. Five hundred forty measurements of various known distances in the phantoms were made by three examiners using various transducers. Although minor differences were observed between operators and transducers, 99.4% (537 of 540) of the distance measurements were accurate within plus or minus 4%. This extended-FOV technology provides accurate measurements of large objects in vitro.

US extended-field-of-view imaging technology.

PURPOSE: To develop an ultrasound (US) extended-field-of-view scanning technique that combines the convenience of a real-time scanner with the spatial advantages of a static B-mode scanner and provides a panoramic image in real time without position sensors or cumbersome articulated arms. MATERIALS AND METHODS: An image-registration-based position-sensing technique was used to track probe motion and reconstruct a large composite image during real-time scanning. The probe motion (translation and rotation) was estimated by combining multiple local motion vectors. This computationally intensive process required a special programmable image processor. RESULTS: Large, resolution-preserved composite images up to 60 cm long were obtained. Measurement accuracy as determined with phantom experiments was better than 5%. The method could be applied to any probe or image format. CONCLUSION: In addition to providing a panoramic image to expand diagnostic capabilities, extended-field-of-view US provides a more easily interpretable image and is an effective cross-specialty communication tool.

Synthetic receive aperture imaging with phase correction for motion and for tissue inhomogeneities. I. Basic principles.

The use of a synthetic receive aperture (SRA) system to increase the resolution, of a phased-array imaging system severalfold, by utilizing the available number of parallel receiver channels to address a larger number of transducer elements through a multiplexer system, is considered. Recent studies indicate that transducers with a very large number of elements will improve the detectability of small or low contrast targets when adaptive focusing is used to compensate for the effects of acoustic velocity inhomogeneities in tissue. With the effectively increased transducer element count afforded by an SRA system, a 1-by-N phased array could be split into an M-by-N array in order to improve resolution in the elevation dimension. Simulation results illustrate the lateral resolution achievable with several types of imaging systems: SRA, synthetic focus, and conventional phased array. Simulated images demonstrate the improvement in contrast resolution achievable using SRA. Experimental results show the improvement in beam width achieved by an experimental SRA system.

Synthetic receive aperture imaging with phase correction for motion and for tissue inhomogeneities. II. Effects of and correction for motion.

For Pt.I see ibid., vol.39, p.489 (1992). The effects of tissue/transducer motion and artifacts from adaptive focusing on synthetic receive aperture (SRA) imaging are explored using experiment, simulation, and theory. The impact of these issues on the selection of SRA subaperture geometry is discussed, and a technique to address this problem is demonstrated. The results indicate that SRA with phase correction holds promise in improving ultrasonic image quality.

In vivo measurements of ultrasonic beam distortion in the breast.

The phase aberrations encountered by ultrasonic pulses propagating through breast tissue in twenty-two female volunteers were measured. The experiments were designed to assess the impact of these aberrations on clinical ultrasonic image quality for a variety of transducer and imaging geometries. The phase aberration profiles of a given patient were correlated with the amount of parenchymal tissue determined from that patient's mammogram. These data are useful in assessing the image quality achievable with conventional ultrasonic imaging systems, and the potential application of adaptive ultrasonic imaging systems. The results indicate that phase aberrations significantly degrade breast image quality for typical transducer frequencies and sizes.