Effect of injection rate on contrast-enhanced MR angiography image quality: Modulation transfer function analysis.
PURPOSE
Contrast-enhanced (CE)-MRA optimization involves interactions of sequence duration, bolus timing, contrast recirculation, and both R1 relaxivity and R2*-related reduction of signal. Prior data suggest superior image quality with slower gadolinium injection rates than typically used.


METHODS
A computer-based model of CE-MRA was developed, with contrast injection, physiologic, and image acquisition parameters varied over a wide gamut. Gadolinium concentration was derived using Verhoeven's model with recirculation, R1 and R2* calculated at each time point, and modulation transfer curves used to determine injection rates, resulting in optimal resolution and image contrast for renal and carotid artery CE-MRA. Validation was via a vessel stenosis phantom and example patients who underwent carotid CE-MRA with low effective injection rates.


RESULTS
Optimal resolution for renal and carotid CE-MRA is achieved with injection rates between 0.5 to 0.9 mL/s and 0.2 to 0.3 mL/s, respectively, dependent on contrast volume. Optimal image contrast requires slightly faster injection rates. Expected signal-to-noise ratio varies with both contrast volume and cardiac output. Simulated vessel phantom and clinical carotid CE-MRA exams at an effective contrast injection rate of 0.4 to 0.5 mL/s demonstrate increased resolution.


CONCLUSION
Optimal image resolution is achieved at intuitively low, effective injection rates (0.2-0.9 mL/s, dependent on imaging parameters and contrast injection volume). Magn Reson Med 78:357-369, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
['Clark|Toshimasa J|TJ|0000-0003-4058-5632', 'Wilson|Gregory J|GJ|', 'Maki|Jeffrey H|JH|']
D001158:Arteries D001783:Blood Flow Velocity D003198:Computer Simulation D003287:Contrast Media D004305:Dose-Response Relationship, Drug D005682:Gadolinium D006801:Humans D007090:Image Interpretation, Computer-Assisted D018810:Magnetic Resonance Angiography D008955:Models, Cardiovascular D019047:Phantoms, Imaging D015203:Reproducibility of Results D012680:Sensitivity and Specificity
MR angiography Modulation transfer function contrast injection rate