A real time dual-energy probe for tissue characterization during fluoroscopy.

In the past dual-energy techniques have been applied with a variety of detector systems. However, making clinical decisions during a diagnostic x-ray procedure by using dual-energy information has not been possible. This paper looks at the development of a dual-energy probe that permits real time analysis. The technique is based on the local analysis procedure introduced by Speller and co-workers and uses spectral filtering for energy separation. The split-detector probe is optimized using computer models, and the effects of beam hardening and scattered radiation are considered. It is shown that a 0.25 mm CsI/25 mm NaI combination of detector elements with a 0.3 mm Cu filter offers the best performance. Preliminary results using the probe for in vivo analysis of gall stone composition compare well with the more accepted methods of x-ray diffraction and atomic absorption spectroscopy. The two groups of stones evaluated were found to have mean effective atomic numbers of 5.6 +/- 1.7 and 9.6 +/- 0.5. It is suggested that such a procedure could prove useful in patient management in the use of lithotripsy.