Timothy Betts MS, Presenter: Nothing to Disclose

Michael Speidel PhD, Abstract Co-Author: Nothing to Disclose

Michael Scott Van Lysel PhD, Abstract Co-Author: Nothing to Disclose

To find a metallic substitute for liquid iodine contrast agent for use in angiographic imaging phantoms.

Iodine contrast agent is problematic as a phantom material because of its tendency to leak, dry out, and form bubbles. Metal alloys were investigated as a surrogate material. The key constraint was that the alloy have the same radiographic contrast as an iodine solution when used in the same volume, from 60 to 120 kVp and for a typical range of coronary artery diameters (up to 3 mm). Based on material density, metallic solubility, and the dependence of the photoelectric effect on atomic number, attention was focused on MgCd and LiMgCdHo. Composition was determined by searching for the minimum modeled difference in contrast between the alloy and a specified iodine solution. Iodine concentrations of 350 mg I/mL and 175 mg I/mL, corresponding to full and half-strength Iohexol, were specified in the search. At our request, MgCd and LiMgCdHo wires were fabricated by a commercial vendor in five diameters, ranging from 0.5 mm to 2.8 mm. Wire contrast was measured from 60-120 kVp using acrylic phantoms to mimic the patient. Results were compared to the measured contrast of tubes filled with Iohexol (140 and 350 mg I/mL). Measured contrast was also compared to the contrast predicted by the model, which included measured corrections for scatter fraction and system blurring.

Based on the assayed compositions and densities of the received wires, the predicted equivalent iodine concentrations for full- and half-strength formulations were 350 and 175 mg I/mL for MgCd, and 390 and 195 mg I/mL for LiMgCdHo. The mean difference between the contrast of the alloy wires measured in the imaging experiment and the respective iodine solution equivalents was less than 2.5%. The direct contrast comparison between the 350 mg I/mL iodine solution and its MgCd alloy equivalent agreed to within 1% across all kVps and diameters.

Metal alloys were found whose contrast matches the contrast of iodine solution at the same thickness for diagnostic x-ray beam qualities. These materials represent a useful and convenient alternative to iodine contrast agent in angiographic phantoms.

Betts, T, Speidel, M, Van Lysel, M, Metallic Phantom Material Is Radiographically Equivalent to Iodine Contrast Media.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4412969.html