5 May 2005 -- High-resolution Ultrasonic Transmission Tomography (HUTT) offers 3D images of soft tissue that are superior to those produced by existing commercial X-ray, ultrasound or MRI units, claims the University of Southern California.
Professor Vasilis Marmarelis at the university’s Viterbi School has developed the technique, which offers 0.4mm resolution in soft tissue.
The system transmits a 250ns pulse of 4-12MHz sound and, crucially, picks up signals from the other side of the object unlike traditional ultrasound systems which detect reflections.
“Only a tiny fraction of the transmitted sound comes back as echo on soft tissues, while a much larger fraction, about 2,000 times bigger, is transmitted through the soft tissue,†said the university. The pulses come from an array of sub-millimetre ultrasonic transducers and are received by a second array on the other side of the body.
“A coding-decoding signal scheme recognises a small sweet-spot of the signal coming from the opposite transducer, and only that transducer, and ignores all other pulses transmitted by neighbouring transducers,†said the university.
Signal processing algorithms, specially developed by Marmarelis’ group, then form the images based on the frequency-dependent attenuation of that signal path. “Typically the resulting images represent minute variations in relative attenuation over various frequency bands and they define the different sections of the tissue in the image,†said Marmarelis.
The object must be in water, so a vertical drum with transmit and receive arrays mounted on opposite sides has been constructed.
