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3-D Voxel-level Tissue Classification of Ultrasound Scattering using a Sparse Matrix Array Transducer

Three-dimensional (3-D) H-scan ultrasound (US) is a high-resolution imaging technology for tissue characterization in volume space. The objective of this research was to implement and test H-scan US imaging of relative scatterer size using a sparse matrix array transducer. Experimental data was collected using an US system (Vantage 256, Verasonics Inc) equipped with a 1024-element (32 × 32) matrix array transducer (Vermon Inc). Sparse imaging was implemented by using the best combination of randomly selected 256 elements for transmission and radiofrequency (RF) data sequences were collected with four sub-apertures (8 × 32). Plane wave imaging at five angles was performed at a center frequency of 8 MHz. To produce the H-scan US images, a set of convolution filters were applied to the RF data to measure the relative strength of the received signals. Preliminary studies were conducted using tissue-mimicking phantoms embedded with polyethylene microspheres (CoSpheric LLC) with size ranging from 27 to 45, 63 to 75, or 106 to 125 µm in diameter. Preliminary results reveal that H-scan US imaging is more sensitive than B-mode US for discriminating US scatterers of varying size. Overall, this study proves the feasibility of evaluating tissue scatterer patterns in volume space using a new 3-D H-scan US imaging technique and spare matrix array transducer technology.