Opportunities for new CT contrast agents to maximize the diagnostic potential of emerging spectral CT technologies

The introduction of spectral CT imaging in the form of fast clinical dual-energy CT enabled contrast material to be differentiated from other radiodense materials, improved lesion detection in contrast-enhanced scans, and changed the way that existing iodine and barium contrast materials are used in clinical practice. More profoundly, spectral CT can differentiate between individual contrast materials that have different reporter elements such that high-resolution CT imaging of multiple contrast agents can be obtained in a single pass of the CT scanner. These spectral CT capabilities would be even more impactful with the development of contrast materials designed to complement the existing clinical iodine- and barium-based agents. New biocompatible high-atomic number contrast materials with different biodistribution and X-ray attenuation properties than existing agents will expand the diagnostic power of spectral CT imaging without penalties in radiation dose or scan time.

Conventional CT (A, in rabbit) with intravascular and enteric contrast material provides high-resolution depiction of anatomy, but the two contrast materials are indistinguishable except by anatomic context. Modern dual-energy CT (DECT) can improve the conspicuity of contrast agents, but since only iodinated and barium-based agents are clinically available, the enteric and intravascular agents cannot be distinguished from each other, even with DECT. If contrast materials with non-iodine/non-barium reporter atoms are developed, then material decomposition of DECT scans simultaneously enhanced with currently available and the new materials (B, in rabbit) could allow each contrast agent to be differentiated without added radiation dose. In this example case, bismuth enteric contrast material is color coded in green, vascular iodinated contrast is red, and soft tissues are blue.136