Report from SCBT/MR: Rads see right heart clearly during CTA

A new three-phase contrast administration protocol that involves the simultaneous injection of contrast and saline during coronary CT angiography allows improved visualization of the right heart, according to researchers from the Medical University of South Carolina.

A triphasic protocol of contrast injection for coronary CT angiography improves visualization of the right heart in comparison with biphasic or monophasic protocol. (Provided by J. Kerl)

Saline chasing during coronary CTA reduces streak artifacts from dense contrast in the right heart. However, the flushing can be so efficient that right heart structures, and possibly pathology, are not visible.

The triphasic protocol, which reduced streak artifacts without compromising right heart image quality, is possible because of Dual Flow (Medrad, Pittsburgh, PA) technology. This two-syringe device allows a second phase of contrast/saline ratio to be administered following the initial iodine bolus.

Medical student Matthias Kerl reported the study results at the annual meeting in Phoenix of the Society of Computed Body Tomography and Magnetic Resonance.

Researchers divided 75 patients into three equal groups to compare three contrast administration protocols:

• group 1: monophasic protocol, 50 to 70 mL at 5 mL/sec iodine-only using a single-syringe injector

• group 2: biphasic protocol, 50 to 70 mL at 5 mL/sec iodine followed by 50 mL saline chaser bolus using a dual-syringe injector

• group 3: triphasic protocol, 50 to 70 mL at 5 mL/sec iodine followed by 50 cc 70:30 saline/contrast mixture with dual-syringe injector (both pistons move simultaneously) and a final 50 mL saline chaser bolus

Two radiologists rated the visualization of right and left heart structures and the degree of artifacts. One observer performed attenuation measurements of the left and right heart and of the coronary arteries.

Contrast attenuation in the right heart was significantly lower in the biphasic group (mean 217 HU) than in the monophasic (342 HU) and triphasic groups (322 HU). Investigators saw no significant differences for the coronary arteries, Kerl said.

While left heart structures showed no significant differences among the protocols, visualization of right heart structures was significantly better and artifacts occurred less frequently in the triphasic group.

"Triphasic contrast injection for coronary CTA in comparison with a biphasic and monophasic protocol with a 64-slice CT provides sufficient enhancement for assessment of the right heart and avoids streak artifacts from dense contrast material," Kerl said.

Radiologists at MUSC now routinely use the triphasic protocol on all patients, senior author Dr. U. Joseph Schoeph told Diagnostic Imaging. Initially, they were concerned to use the protocol in triple-rule-out patients, because of potential loss of enhancement in the pulmonary artery. That fear has not been borne out, and the triphasic protocol works just as well in these patients, he said.

Dual Flow is the only product of its kind approved in the U.S. Similar products have been approved in Europe, Schoepf said.

For more information from the Diagnostic Imaging archives:

64-slice CT enters clinical practice realm

Researchers confront strengths and limitations of 64-slice CTA

Demand overwhelms supply of cardiac CT training slots

Coronary CTA establishes new markets, standards