Increasing contrast agent concentration improves enhancement in first-pass CT perfusion

Abstract

Background and purpose: Our aim was to evaluate whether increasing iodine concentration, at a constant total iodine dose, resulted in better brain tissue opacification in patients with acute stroke symptoms during their evaluation by first-pass CT perfusion (CTP).

Materials and methods: One hundred two patients presenting to the emergency department within 3 hours of onset of acute stroke symptoms underwent CTP scanning. Three different concentrations of iodinated nonionic contrast material were used (300, 350, or 400 mg/mL). Total iodine dose (15 g) and injection rate (7 mL/s) were kept constant. There were 25, 53, and 19 patients in the different concentration groups, respectively; 5 patients were excluded due to uncorrectable motion artifacts. CTP scanning was performed at the level of the putamen, and data were analyzed by determining peak opacification for normal gray and white matter, arterial input, and venous output. Mean and SD values were calculated, and 3 concentration groups, stratified by region-of-interest location, were compared by using a single-tailed unpaired t test.

Results: Monotonic increasing peak opacification was observed in all region-of-interest locations. Statistically significant differences were observed between the 300 and 350 mg/mL, 300 and 400 mg/mL, as well as the 350 and 400 mg/mL groups (P<.01) in white matter, gray matter, and the arterial input. Statistical significance was seen in the venous output group between the 300 and 400 mg/mL (P<.005) and 350 and 400 mg/mL (P<.007) groups, but not between the 300 and 350 mg/mL (P=.2) groups.

Conclusion: Increasing contrast concentration improves peak opacification of tissue, suggesting that CTP evaluation of patients with acute stroke is better performed with the highest available concentration contrast agent.

Fig 1.

The regions of interest (ROI) for an arterial input (ACA) and venous output (sagittal sinus) (A) and for gray matter and white matter (B). The corresponding time-concentration curves are presented in C, in which curve 1 indicates the artery and curve, 2 the vein, and in D, in which curve 3 indicates gray matter and curve 4, white matter.

Fig 2.

Presented are the regression lines for each category of region of interest. There is a 25% increase in opacification for gray matter (A), 21% for white matter (B), 30% for the arterial input (C), and 12% for the venous output (D), between 300- and 400-mg/mL formulations of contrast agent.