Modulation of renal oxygenation and perfusion in rat kidney monitored by quantitative diffusion and blood oxygen level dependent magnetic resonance imaging on a clinical 1.5T platform.

Neil P Jerome,James D’Arcy,Jessica K R Boult,Simon P Robinson,Matthew R Orton,Martin O Leach,David J Collins,Dow-Mu Koh

doi:10.1186/s12882-016-0356-x

Abstract

BackgroundTo investigate the combined use of intravoxel incoherent motion (IVIM) diffusion-weighted (DW) and blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) to assess rat renal function using a 1.5T clinical platform.MethodsMultiple b-value DW and BOLD MR images were acquired from adult rats using a parallel clinical coil arrangement, enabling quantitation of the apparent diffusion coefficient (ADC), IVIM-derived diffusion coefficient (D), pseudodiffusion coefficient (D*) and perfusion fraction (f), and the transverse relaxation time T2*, for whole kidney, renal cortex, and medulla. Following the acquisition of two baseline datasets to assess measurement repeatability, images were acquired following i.v. administration of hydralazine, furosemide, or angiotensin II for up to 40 min.ResultsExcellent repeatability (CoV <10 %) was observed for ADC, D, f and T2* measured over the whole kidney. Hydralazine induced a marked and significant (p < 0.05) reduction in whole kidney ADC, D, and T2*, and a significant (p < 0.05) increase in D* and f. Furosemide significantly (p < 0.05) increased whole kidney ADC, D, and T2*. A more variable response to angiotensin II was determined, with a significant (p < 0.05) increase in medulla D* and significant (p < 0.05) reduction in whole kidney T2* established.ConclusionsMultiparametric MRI, incorporating quantitation of IVIM DWI and BOLD biomarkers and performed on a clinical platform, can be used to monitor the acute effects of vascular and tubular modulating drugs on rat kidney function in vivo. Clinical adoption of such functional imaging biomarkers can potentially inform on treatment effects in patients with renal dysfunction.Electronic supplementary materialThe online version of this article (doi:10.1186/s12882-016-0356-x) contains supplementary material, which is available to authorized users.

Highlights

To investigate the combined use of intravoxel incoherent motion (IVIM) diffusion-weighted (DW) and blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) to assess rat renal function using a 1.5T clinical platform
Diffusion characteristics showed no substantive change, except for D, which showed a significant decrease (p < 0.05) for the whole kidney Region of interest (ROI), this result was not mirrored in the apparent diffusion coefficient (ADC) fitting, which showed no significant change (Table 1)
coefficients of variation (CoV) were comparable for ADC and D in each of the ROIs considered, indicating the robustness of fitting true diffusion, with the fast pseudodiffusion constant D* from the IVIM model having a substantially higher CoV

Summary

Introduction

To investigate the combined use of intravoxel incoherent motion (IVIM) diffusion-weighted (DW) and blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) to assess rat renal function using a 1.5T clinical platform. The biexponential intravoxel incoherent motion (IVIM) model reports two distinct diffusion constants as fractional components; the pseudodiffusion constant D*, of fractional volume f, associated with a faster incoherent flow component, and D which reflects random tissue water diffusion [9]. Vascular tissues such as the kidney show nonmonoexponential signal decay with increasing diffusion weighting (b-value) [10, 11], thought to reflect a rapidly decaying signal component visible at lower b-values. Using IVIM DWI may improve the understanding of the contribution of renal tubular flow towards the diffusion signal [12]

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