Selective iodine imaging using lanthanum K fluorescence.

Time-dependent subtraction techniques have tremendously improved the visualization of iodinated vessels. These techniques suffer from motion artifacts, however, since the mask image is acquired several seconds prior to the contrast image. A K-edge subtraction technique for selectively imaging iodine using the characteristic x rays from a lanthanum secondary target is presented. The K alpha lines of lanthanum closely straddle the K edge of iodine. A prepatient iodine filter will alter the ratio of K alpha 1 to K alpha 2 intensities; by subtracting two images made with different K alpha 1/K alpha 2 ratios, iodinated structures can be isolated. Since the method requires no mask image, motion artifacts are reduced. Preliminary images acquired with an image intensifier/photodiode array detector system are shown. Theoretical performance of this method is compared to other iodine-selective imaging techniques on the basis of exposure and dose. The feasibility of using lanthanum K fluorescence for rapid clinical iodine-selective imaging is discussed.