3D ultrasound (US) provides physicians with a better understanding of human anatomy. By manipulating the 3D US data set, physicians can observe the anatomy in 3D from a number of different view directions and obtain 2D US images that would not be possible to directly acquire with the US probe. In order for 3D US to be in widespread clinical use, creation and manipulation of the 3D US data should be done at interactive times. This is a challenging task due to the large amount of data to be processed. Our group previously reported interactive 3D US imaging using a programmable mediaprocessor, Texas Instruments TMS320C80, which has been in clinical use. In this work, we present the algorithms we have developed for realtime 3D US using a newer and more powerful mediaprocessor, called MAP-CA. MAP-CA is a very long instruction word (VLIW) processor developed for multimedia applications. It has multiple execution units, a 32-kbyte data cache and a programmable DMA controller called the data streamer (DS). A forward mapping 6 DOF (for a freehand 3D US system based on magnetic position sensor for tracking the US probe) reconstruction algorithm with zero-order interpolation is achieved in 11.8 msec (84.7 frames/sec) per 512×512 8-bit US image. For 3D visualization of the reconstructed 3D US data sets, we used volume rendering and in particular the shear-warp factorization with the maximum intensity projection (MIP) rendering. 3D visualization is achieved in 53.6 msec (18.6 frames/sec) for a 128×128×128 8-bit volume and in 410.3 msec (2.4 frames/sec) for a 256×256×256 8-bit volume.

As part of ongoing research on hardware and software technologies for telemedicine, we have explored compression algorithms for ultrasound. Efficient compression is essential to PACS and telemedicine systems supporting ultrasound video sequences due to limited system resources such as archival storage and bus and network bandwidths. We have studied MPEG compression of ultrasound sequences and the impact of varying encoding parameters such as quantization scale on B and BC mode sequences. Our results indicate that standard interframe MPEG coding is not optimal for all echocardiographic sequences. Adjustment of MPEG quantization and sequencing parameters can provide improvements in compression ratio and/or image quality. Three areas for improvement in MPEG compression of ultrasound sequences have been identified and methods are suggested by which these issues may be addressed.