Comparison of blood oxygen level‐dependent imaging and diffusion‐weighted imaging in early diagnosis of acute kidney injury in animal models

Abstract

Background Early diagnosis of acute kidney injury (AKI) has clinical importance. Current methods are neither adequately sensitive nor specific. Blood oxygen level‐dependent (BOLD) imaging and diffusion‐weighted imaging (DWI) may help to assess AKI in the early phase. Purpose To investigate the feasibility of BOLD imaging and DWI in the assessment of AKI and compare the sensitivities of both techniques in early detection of renal damage. Study Type Prospective animal study. Animal Model Thirty New Zealand white rabbits. Field Strength/Sequence 3 T clinical MRI/BOLD and DWI. Assessment Thirty rabbits were divided into three groups (severe AKI group, mild AKI group, and control group). Transarterial renal embolization with different doses of microspheres was performed to create severe and mild AKI disease models. All the MRI scans of kidneys were conducted within 2 hours after the embolization procedure. Histological examinations with hematoxylin and eosin staining were performed to validate renal damage. Statistical Tests Analysis of variance (ANOVA) for comparisons between groups, and paired t‐test for tests within the same group. P < 0.05 was considered statistically significant. Results Both R2* and apparent diffusion coefficient (ADC) showed significant differences between the severe AKI group (56.34 ± 3.45 s‐1 for R2*, 1.14 ± 0.23 mm2/s for ADC) and the control group (28.24 ± 2.26 s‐1 for R2*, 1.94 ± 0.33 mm2/s for ADC, both P < 0.01). However, the ADC values did not show significant differences (P = 0.41) between mild AKI group (1.88 ± 0.31 mm2/s for ADC) and the control group (1.94 ± 0.33 mm2/s for ADC), while R2* was still useful in differentiating the two groups (52.32 ± 4.1 s‐1 vs. 28.24 ± 2.26 s‐1 for R2*, P < 0.01). The histopathologic results were found to be correlated with MRI findings. Data Conclusion BOLD contrast and DW images are both effective in detecting AKI noninvasively, but BOLD imaging is more sensitive in early detection of mild ischemia than DWI. Level of Evidence: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:719–724.

Dynamic R2' Imaging can Be a Biomarker for Diagnosing and Staging Early Acute Kidney Injury in Animals

“…Differences of dR2' were found when absolute R2' values were still similar in different severities of AKI, which indicates the advantage of dR2' in sensitivity. Similar with our previous reports (8), the ADC values were also different in control and AKI groups and could not distinguish between different AKI stages effectively in the present study.…”

“…Animal experiments were conducted following the guidelines and approval of the institutional animal protection committee (J201740). The model establishement methods were similar as previously reported (8). Twenty New Zealand white rabbits (male, weight range: 2.5-3.5 kg) were randomly divided into mild, moderate, and severe AKI groups and control groups, with five rabbits in each group.…”

“…Magnetic resonance imaging (MRI) has been identified as a promising modality for identifying early AKI (7)(8)(9). Blood oxygenation level-dependent (BOLD) technique, by which deoxyhemoglobin is used as an endogenous contrast agent to probe tissue oxygenation, has been applied to evaluate renal oxygenation status (8,10). T2 * weighted images of BOLD can provide quantitative information about the changes of tissue deoxyhemoglobin.…”

Clinical and experimental approaches for imaging of acute kidney injury

“…BOLD MRI is effective in evaluating changes with pharmacological or physiological manipulations, including furosemide, water load, and vasoactive substances [ 92 , 93 ]. Additionally, BOLD MRI has been reported in IRI-AKI and CI-AKI models [ 69 , 94 , 95 ]. Hofmann et al [ 96 ] reported that post-AKI changes in R 2 * values were induced by several drugs, including indomethacin, radio-contrast media, cyclosporine, and tacrolimus.…”

Probing renal blood volume with magnetic resonance imaging

“…Insights into renal oxygenation can be derived from blood oxygenation level–dependent (BOLD) MRI, which offers a non‐invasive in vivo technique . Renal BOLD‐MRI methodology has progressed and a large body of literature on (pre)clinical applications is available. The growing number of reports eloquently speaking about renal BOLD‐MRI and the consensus papers on technical recommendations document the value of non‐invasive MRI to renal (patho)physiology.…”