X-ray computed tomography for finding tumor without using contrast agent

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To find cancers by X-ray computed tomography (CT), iodine contrast agent is injected into blood vessel. The iodine contrast agent, however, has side effect, such as a fatality among ten thousand patients. It is desirable to find cancers without using iodine contrast agent. To meet this demand, we performed effective atomic number measurements with energy-resolved CT. Normally, the measurement of effective atomic number is conducted with using two monochromatic X-rays. We employed white X-rays with defining two narrow energy ranges as quasi-monochromatic X-rays in the analysis. Employed phantom was a cylindrical acrylic 3 cm in diameter with 2 diameter aluminum rod in the center. We measured linear attenuation coefficients for X-rays in two narrow energy ranges and estimated the ratio of them. The obtained effective atomic numbers showed excellent agreement with the theoretical ones within 1% of errors.