Quasi real-time Fourier reconstructive imaging from acoustic backscatter data

A reconstructive imaging method was implemented for determining the fine-scale structural features within an object from acoustic backscattered echo amplitude data. A focused narrowband pulse (7.5 MHz with 10% bandwidth) approximates a Gaussian modulated, spherically symmetric sample volume and is used to interrogate a two-dimensional grid of points. The sample volume diameter is approximately 1.2 mm, full-width, half-maximum (FWHM). The 2-D grid of points, or region of interest (ROI), is roughly circular, with a diameter of 18 mm. Each point in the ROI is interrogated from 120 beamformer positions along a curved linear array with a 5.0-cm radius of curvature and 60° arc. An image of the local structural features is constructed at each sample volume point within the ROI. An image of the entire object plane is constructed from localized images. Processing time per image is 14 min on a PC-386, including 8 s to acquire backscattered echo amplitudes. Results of this imaging technique applied to veins of the leg demonstrate its ability to elucidate structural features not apparent in simple B-mode images