A tri-exponential model for intravoxel incoherent motion analysis of the human kidney: In silico and during pharmacological renal perfusion modulation

作者：van der Bel Rene; Gurney Champion Oliver J; Froeling Martijn; Stroes Erik S G; Nederveen Aart J; Krediet C T Paul^*

来源：European Journal of Radiology, 2017, 91: 168-174.

DOI：10.1016/j.ejrad.2017.03.008

• Intravoxel incoherent motion
• Kidney
• Perfusion
• Magnetic resonance imaging
• Angiotensin II
• Diffusion-weighted imaging
• Functional imaging

In the kidneys, there is both blood flow through the capillaries and flow of pre-urine through the tubuli and collecting ducts. We hypothesized that diffusion-weighted (DW) MRI measures both blood and pre-urine flow when using a tri-exponential intravoxel incoherent motion (IVIM) model. Our aim was to systematically investigate and optimize tri-exponential IVIM-analysis for the kidney and test its sensitivity to renal perfusion changes in humans.
The tri-exponential fit probes the diffusion coefficient (D), the intermediate (D*i) and fast (D*f) pseudo-diffusion coefficients, and their signal fractions, f(D), f(i) and f(f). First, we studied the effects of fixing the D*-coefficients of the tri-exponential fit using in silico simulations. Then, using a 3T MRI scanner, DW images were acquired in healthy subjects (18-24 years) and we assessed the within-subject coefficient of variation (wsCV, n = 6). Then, renal perfusion was modulated by Angiotensin II infusion during which DW imaging of the kidneys and phase contrast MRI of the renal artery was performed (n = 8). Radioisotope clearing tests were used to assess the glomerular filtration rate.
Simulations showed that fixing the D*-coefficients - which could potentially increase the fit stability - in fact decreased the precision of the model. Changes in D*-coefficients were translated into the f-parameters instead. Fixing D*-coefficients resulted in a stronger response of the fit parameters to the intervention. Using this model, the wsCVs for D, f(D), f(i) and f(f) were 2.4%, 0.8%, 3.5%, 19.4% respectively. fi decreased by 14% (p = 0.059) and ff increased by 32% (p = 0.004) between baseline and maximal Angiotensin II dose. ff inversely correlated to renal plasma flow (R = -0.70, p < 0.01) and fi correlated to glomerular filtration rate (R = 0.39, p = 0.026).
We validated a kidney-specific method for IVIM analysis using a tri-exponential model. The model is able to track renal perfusion changes induced by Angiotensin II.

• 出版日期2017-6