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

Abstract

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.

Exercise-induced calf muscle hyperemia: quantitative mapping with low-dose dynamic contrast enhanced magnetic resonance imaging

“…For example, Luo et al (29) detected a decrease in the DCE MRI-measured muscle perfusion index (PI) after the induction of femoral artery ligation in a rat model. To date, published studies have used a relatively high dosage of contrast agent (0.1~0.2 mmol/kg), often leading to arterial signal saturation (59). To avoid this artifact, Isbell et al (15) proposed to acquire muscle and arterial signals with different sequence settings.…”

“…Nevertheless, high dosages of contrast agent have precluded repeated perfusion studies and the performance of same-day contrast-enhanced MR angiography. DCE MRI using a low dosage of gadolinium chelates (~0.05 mmol/kg or less) has been established for measuring tissue perfusion with high precision and spatial resolution (1,59,61,63). This technique has been mostly applied in renal imaging (25,55,62).…”

Value of Magnetic Resonance Urography Versus Computerized Tomography Urography (CTU) in Evaluation of Obstructive Uropathy: An Observational Study

“…1T images are considered adequate as they are sufficient in diagnosing lower kidney stones. MRU is accurate in assessing renal functions, and could be used as a single modality for diagnosing obstruction in cases, where patients would not be compromised due to renal function contraindications [ 23 ]. Moreover, Jung et al .…”