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

René van der Bel; Oliver J Gurney-Champion; Martijn Froeling; Erik S G Stroes; Aart J Nederveen; C T Paul Krediet

doi:10.1016/j.ejrad.2017.03.008

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

Eur J Radiol. 2017 Jun:91:168-174. doi: 10.1016/j.ejrad.2017.03.008. Epub 2017 Mar 21.

Authors

René van der Bel¹, Oliver J Gurney-Champion², Martijn Froeling³, Erik S G Stroes¹, Aart J Nederveen⁴, C T Paul Krediet⁵

Affiliations

¹ Dept. Internal Medicine - Nephrology, Academic Medical Center at the University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands.
² Radiology, Academic Medical Center at the University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands; Radiation Oncology, Academic Medical Center at the University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands.
³ Radiology, Academic Medical Center at the University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands; Radiology, University Medical Center Utrecht, Heidelberglaan 100, 3584CX, Utrecht, The Netherlands.
⁴ Radiology, Academic Medical Center at the University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands.
⁵ Dept. Internal Medicine - Nephrology, Academic Medical Center at the University of Amsterdam, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands. Electronic address: c.t.krediet@amc.uva.nl.

PMID: 28629565
DOI: 10.1016/j.ejrad.2017.03.008

Abstract

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. f_i decreased by 14% (p=0.059) and f_f increased by 32% (p=0.004) between baseline and maximal Angiotensin II dose. f_f inversely correlated to renal plasma flow (R=-0.70, p<0.01) and f_i 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.

Keywords: Angiotensin II; Diffusion-weighted imaging; Functional imaging; Intravoxel incoherent motion; Kidney; Magnetic resonance imaging; Perfusion.

MeSH terms

Diffusion Magnetic Resonance Imaging / methods*
Humans
Kidney*
Magnetic Resonance Imaging / methods*
Motion
Renal Artery