X-ray tomography, or the CAT scan, was invented in the 1960s and has become one of the main staples of medical imaging. Since then, many other tomographies or modalities have been introduced, all based on different types of radiation.
MRI, for example, uses strong magnetic fields; ultrasound tomography uses high-frequency acoustic waves, and so forth.
Unfortunately, no particular type of radiation is perfect. A wave sent to propagate through a patient’s body must accomplish two tasks: first, detect features of interest within the tissues and then deliver that information to the measuring device. Nature is not without irony.
Waves that excel at one of these tasks usually struggle with the other. For example, visible or infrared light is very good for detecting cancerous tumors, but as everybody knows, it does not propagate well through the body. Conversely, X-rays will go through soft healthy tissues and tumors equally well, without noticing the difference.
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Scientists in search of better ways to see what matters — cancerous tumors, bone cracks, blood clots — are trying to combine two (or more) different types of radiation. For example, ultrasound, known for its ability to carry high-resolution spatial information, is frequently coupled with electromagnetic fields that are good in finding cancer or blood clots.
Dr. Russell Witte from the University of Arizona department of medical imaging and I are investigating one of these “coupled-physics” modalities, magneto-acousto-electric tomography.
This combines electric measurements with ultrasound excitation of biological tissues placed into a strong magnetic field. The information about the studied object is encoded in the data in a very complex way, and obtaining a picture requires solving a large system of equations.
However, developing magneto-acousto-electric tomography is well worth the effort; it is expected that this modality would excel in cancer detection and would provide life-saving diagnostic information unobtainable by other means.
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