Effect of contrast concentration, tube potential and reconstruction kernels on MDCT evaluation of coronary stents: an in vitro study.

Introduction: To evaluate effect of different kVp, reconstruction kernels and contrast concentrations on stent luminal diameter measurements and luminal contrast attenuation values.

Methods: Two metallic coronary stents (2.75 mm and 3.0 mm) were deployed in silicone tubes and tubes were filled with diluted iodinated contrast (1:20 dilution of Iohexol 350 mg% to achieve an attenuation value of 550 HU at 120 kVp). The tubes were scanned at 80, 100, 120 and 140 kVp. Each scan acquisition was reconstructed using B10f, B25f, B31f, B36f, B41f, B46f, B60f, and B80f kernels. Scans were repeated using 1:35 contrast dilution (350 HU at 120 kVp). Luminal diameter was measured at mid stent level for each stent, in datasets acquired at different kVp, contrast concentrations, and reconstruction kernels. Luminal attenuation values (HU) were measured at the mid stent level and at a distance of 1 cm from the stent entrance within the tube lumen.

Results: kVp did not have a significant effect on the visualization of stent luminal diameter (P > 0.277). The change in kernel significantly affected the difference in luminal HU values at stent and non-stent levels (P < 0.001), with B46f showing the least difference in HU values. The lower contrast concentration (350 HU) showed substantially less artifactual stent stenosis compared to high contrast concentration (550 HU) (P < 0.001). There was excellent inter-observer agreement for stent luminal diameters and attenuation value measurements (r (2)=0.971, P < 0.001).

Conclusions: For lower spatial resolution kernels, 120 kVp or 140 kVp provides better estimate of stent lumen. Reconstruction kernels and contrast concentration (HU) have significant effect on visualization of in-stent luminal diameter and artifactual stenosis. In clinical practice, B46f kernel and lower contrast enhancement value ( approximately 350 HU) may be optimal for evaluating the stent lumen.