Dual-energy x-ray imaging technique for in vitro tissue composition measurement.

A dual-energy in vitro radiographic technique has been developed to study the thickness of tissue and bone within atherosclerotic plaques. Results concerning the accuracy and precision of the thickness measurements using this technique are presented and discussed. Planar radiographs of phantoms were obtained with a low-energy spectrum (45 kVp, no added filtration) and a high-energy spectrum (100 kVp, 2.88-mm copper-added filtration), and then decomposed into bone-equivalent and Lucite basis-material images. Thickness measurements from these images yielded average accuracies of +/- 750 microns for the Lucite images, and +/- 25 microns for the bone-equivalent images. The imprecision (one standard deviation) of the thickness measurements was +/- 192 and +/- 47 microns for the Lucite and the bone-equivalent images, respectively (for thin sections). Although the accuracy and precision of Lucite thickness measurements were not as good as those obtained with other techniques, such as the iodine displacement technique, the accuracy and precision of the bone thickness measurements are shown to be much better. The high accuracy and precision of the bone measurement makes dual energy a very appealing technique for analyzing the physical properties of calcified atherosclerotic plaques in excised arterial specimens.