Diffusion tensor imaging of renal ischemia reperfusion injury in an experimental model

Abstract

Renal ischemia reperfusion injury (IRI) is a major cause of acute renal failure. It occurs in various clinical settings such as renal transplantation, shock and vascular surgery. Serum creatinine level has been used as an index for estimating the degree of renal functional loss in renal IRI. However, it only evaluates the global renal function. In this study, diffusion tensor imaging (DTI) was used to characterize renal IRI in an experimental rat model. Spin-echo echo-planar DTI with b-value of 300 s/mm(2) and 6 diffusion gradient directions was performed at 7 T in 8 Sprague-Dawley (SD) with 60-min unilateral renal IRI and 8 normal SD rats. Apparent diffusion coefficient (ADC), directional diffusivities and fractional anisotropy (FA) were measured at the acute stage of IRI. The IR-injured animals were also examined by diffusion-weighted imaging with 7 b-values up to 1000 s/mm(2) to estimate true diffusion coefficient (D(true)) and perfusion fraction (P(fraction)) using a bi-compartmental model. ADC of injured renal cortex (1.69 +/- 0.24 x 10(-3) mm(2)/s) was significantly lower (p < 0.01) than that of contralateral intact cortex (2.03 +/- 0.35 x 10(-3) mm(2)/s). Meanwhile, both ADC and FA of IR-injured medulla (1.37 +/- 0.27 x 10(-3) mm(2)/s and 0.28 +/- 0.04, respectively) were significantly less (p < 0.01) than those of contralateral intact medulla (2.01 +/- 0.38 x 10(-3) mm(2)/s and 0.36 +/- 0.04, respectively). The bi-compartmental model analysis revealed the decrease in D(true) and P(fraction) in the IR-injured kidneys. Kidney histology showed widespread cell swelling and erythrocyte congestion in both cortex and medulla, and cell necrosis/apoptosis and cast formation in medulla. These experimental findings demonstrated that DTI can probe both structural and functional information of kidneys following renal IRI.

Preliminary Study of MR Diffusion Tensor Imaging of Pancreas for the Diagnosis of Acute Pancreatitis

“…With pancreatic microcirculation ischemia aggravated, pancreatic glandular tissue appears necrosis and liquefaction, which restricts water molecules diffuse movement and reduces anisotropy diffusion of extracellular water molecules. Similarly, Cheung et al[37] found that both ADC and FA of kidney medulla in renal ischemia reperfusion injury were significantly less (p < 0.01) than those of contralateral intact medulla. Therefore, our results showed that ADC and FA values might be a supplementary indicator for determining the severity of AP.…”

Diffusion-weighted MR imaging of transplanted kidneys: Preliminary report

“…Therefore some of the authors suggest that multi-directional diffusion tensor imaging (DTI) would better imitate the nature of diffusion and thereby structural integrity of tubules. Additionally, one of the advantages of DTI is the capacity of measuring fractional anisotropy of the motion of water, which can be of a specific use in the assessment of the renal medulla [3,11]. …”

Current MRI techniques for the assessment of renal disease

“…Further, intravoxel incoherent motion (IVIM) is another advanced diffusion imaging approach that differentiates between water motion due to perfusion and diffusion [20, 21]. A body of literature demonstrates that a reduction in ADC or FA correlates with decreased renal function in many renal diseases in human and animals, including chronic kidney disease (CKD) [22, 23], acute kidney injury (AKI) [9, 24], and renal transplantation [25, 26]. Further, recent studies show that renal ADC values correlate with histological measures of fibrosis in patients with CKD and experimental renal disease [22, 27–29].…”