Relationship Between Simulated Gadolinium-Based Contrast Agent Injection Profile and Achievable Resolution Metrics in Contrast-Enhanced Magnetic Resonance Angiography

Background Contrast bolus variation during contrast-enhanced magnetic resonance angiography (CE-MRA) acquisition may lead to vessel blurring. Purpose To combine knowledge of how contrast signal intensity (SI) evolves for different injection strategies with anatomically familiar parametric computer models to measure and visually assess the effects of a wide range of variables on modeled CE-MRA, and in doing so develop contrast rate injection guidelines. Study Type Computer modeling. Phantom Digital three-dimensional phantom consisting of orthogonal aorta, 7 mm diameter renal arteries (with 57% and 86% diameter stenoses), and 7 mm diameter superior mesenteric artery (with 57% diameter stenosis). Field Strength/Sequence One millimeter in-plane resolution arterial CE-MRA imaging at 3 T. Assessment Background (time invariant) and vascular (time varying) components of the phantom were each Fourier transformed into the spatial frequency domain, the latter modulated by the SI evolution of a contrast bolus of varying plateau lengths and tail heights. Data are presented as surface plots of stenosis measurement error and blurring vs. a reference-standard injection. Statistical Tests Descriptive. Results Shorter plateau lengths and lower tail heights resulted in increased measured stenosis error and blurring vs. the reference standard. Under a 44-second acquisition, full width half maximum stenosis error of the 86% stenosis with 25% plateau length and 25% tail height is 24% as compared to that from the reference standard. As plateau length and tail height approach 100%, stenosis error and blurring approach a floor defined by the MR acquisition's limitations. Data Conclusion We propose that to achieve minimal degradation with CE-MRA, one can create a contrast bolus with either 60% plateau and 50% tail height or 80% plateau with any tail. These considerations may well prove to be of practical importance, possibly via manipulating the tail by means of multiphasic contrast injections. Level of Evidence 3 Technical Efficacy Stage 1

Automated summary

This study utilized computer modeling to evaluate the impact of contrast signal intensity evolution under different injection strategies on CE-MRA imaging. The results indicate that shorter plateau lengths and lower tail heights lead to increased measurement errors and blurring in the imaging. Optimal contrast injection guidelines were proposed for minimal degradation in CE-MRA imaging.