X-ray imaging technique for in vitro tissue composition measurements using saline/iodine displacement

An in vitro radiographic technique has been developed to study the composition of arterial specimens, quantifying both the calcified and soft tissue components. In the authors' new method, planar radiographs of a phantom were obtained when the phantom was immersed in: (a) a saline bath using a 45-kV, spectrum with no added filtration; and, (b) an iodine bath using a 100-kV, spectrum with 12.5 mm Al added filtration. These radiographs were then digitized and converted into bone-equivalent and Lucite images using calibration data obtained from images of Lucite and bone-equivalent step wedges. Thickness measurements from these images yielded average accuracies of /spl plusmn/300 /spl mu/m for the bone-equivalent image, and /spl plusmn/80 /spl mu/m for the Lucite image. The precision (one standard deviation) of the thickness measurements was 200 /spl mu/m and /spl plusmn/150 /spl mu/m for the bone-equivalent and the Lucite images respectively. Although the accuracy and precision of bone-equivalent thickness measurements were not as good as those obtained with dual-energy X-ray imaging, the accuracy and precision of the Lucite thickness measurements are shown to be much better. The high accuracy and precision of the Lucite thickness measurements make this technique a very good complement to dual-energy radiography (with its high accuracy and precision of bone-equivalent thickness measurement) to study the physical properties of excised arterial specimens.