Optimization of saturation-recovery dynamic contrast-enhanced MRI acquisition protocol: monte carlo simulation approach demonstrated with gadolinium MR renography

• Published in: NMR in biomedicine 2016-07, Vol.29 (7), p.969-977
• Main Authors: Zhang, Jeff L., Conlin, Chris C., Carlston, Kristi, Xie, Luke, Kim, Daniel, Morrell, Glen, Morton, Kathryn, Lee, Vivian S.
• Format: Article
• Language: English
• Subjects: Computer Simulation; Contrast Media - pharmacokinetics; dynamic contrast-enhanced imaging; Female; Gadolinium - pharmacokinetics; glomerular filtration rate; Glomerular Filtration Rate - physiology; Heterocyclic Compounds - pharmacokinetics; Humans; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; Kidney - diagnostic imaging; Kidney - metabolism; Magnetic Resonance Imaging - methods; Male; Models, Biological; Models, Statistical; Monte Carlo Method; MR renography; Organometallic Compounds - pharmacokinetics; Radioisotope Renography - methods; renal plasma flow; Reproducibility of Results; Sensitivity and Specificity; tracer kinetic modeling
• ISSN: 0952-3480; 1099-1492
• DOI: 10.1002/nbm.3553

Dynamic contrast‐enhanced (DCE) MRI is widely used for the measurement of tissue perfusion and to assess organ function. MR renography, which is acquired using a DCE sequence, can measure renal perfusion, filtration and concentrating ability. Optimization of the DCE acquisition protocol is important for the minimization of the error propagation from the acquired signals to the estimated parameters, thus improving the precision of the parameters. Critical to the optimization of contrast‐enhanced T1‐weighted protocols is the balance of the T1‐shortening effect across the range of gadolinium (Gd) contrast concentration in the tissue of interest. In this study, we demonstrate a Monte Carlo simulation approach for the optimization of DCE MRI, in which a saturation‐recovery T1‐weighted gradient echo sequence is simulated and the impact of injected dose (D) and time delay (TD, for saturation recovery) is tested. The results show that high D and/or high TD cause saturation of the peak arterial signals and lead to an overestimation of renal plasma flow (RPF) and glomerular filtration rate (GFR). However, the use of low TD (e.g. 100 ms) and low D leads to similar errors in RPF and GFR, because of the Rician bias in the pre‐contrast arterial signals. Our patient study including 22 human subjects compared TD values of 100 and 300 ms after the injection of 4 mL of Gd contrast for MR renography. At TD = 100 ms, we computed an RPF value of 157.2 ± 51.7 mL/min and a GFR of 33.3 ± 11.6 mL/min. These results were all significantly higher than the parameter estimates at TD = 300 ms: RPF = 143.4 ± 48.8 mL/min (p = 0.0006) and GFR = 30.2 ± 11.5 mL/min (p = 0.0015). In conclusion, appropriate optimization of the DCE MRI protocol using simulation can effectively improve the precision and, potentially, the accuracy of the measured parameters. Copyright © 2016 John Wiley & Sons, Ltd. MR renography was simulated to test the impact of injection dose (D) and time delay (TD, for saturation recovery). High D and TD caused signal saturation, and thus the overestimation of renal plasma flow (RPF), glomerular filtration rate (GFR) and mean transit time of kidney (MTTK). Low TD underestimated arterial input function (AIF) and overestimated RPF and GFR, which was verified with 22 patients. For T1‐weighted saturation‐recovery MR renography at 3 T, a low dose of 3–6 mL is sufficient for precise parameter estimation and, with such a dose, TD should be 300–600 ms.