Abstract
Diffusion-weighted imaging (DWI) magnetic resonance imaging can evaluate alterations in the microstructure of the kidney. The purpose of this study was to assess the apparent diffusion coefficient (ADC) and the intravoxel incoherent motion model (IVIM) parameters of a normal kidney in healthy dogs, to evaluate the effect of b-value combinations on the ADC value, and the reproducibility and test-retest repeatability in monoexponential and IVIM analysis. In this experimental study, the ADC, pure diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (f p) were measured from both kidneys in nine healthy beagles using nine b-values (b = 0, 50, 70, 100, 150, 200, 500, 800, and 1,000 s/mm2) twice with a 1-week interval between measurements. Interobserver and intraobserver reproducibility, and test-retest repeatability of the measurements were calculated. ADC values were measured using 10 different b-value combinations consisting of three b-values each, and were compared to the ADC obtained from nine b-values. All the ADC, D, D*, and f p values measured from the renal cortex, medulla, and the entire kidney had excellent interobserver and intraobserver reproducibility, and test-retest repeatability. The ADC obtained from a b-value combination of 0, 100, and 800 s/mm2 had the highest intraclass correlation coefficient with the ADC from nine b-values. The results of this study indicated that DWI MRI using multiple b-values is feasible for the measurement of ADC and IVIM parameters with high reproducibility and repeatability in the kidneys of healthy dogs. A combination of b = 0, 100, and 800 s/mm2 can be used for ADC measurements when multiple b-values are not available in dogs.
Highlights
In veterinary medicine, the diagnosis and staging of chronic kidney disease (CKD) are based on the detection of structural change and renal dysfunction [1, 2]
Renal Diffusion-weighted imaging (DWI) was acquired with nine b-values from the bilateral renal cortex and medulla, and analyzed for the measurement of the apparent diffusion coefficient (ADC) using the monoexponential model, and the intravoxel incoherent motion model (IVIM) parameters using the bi-exponential model
The ADC value was significantly higher in the renal cortex than renal medulla in both kidney, and D value was significantly higher in the left renal cortex than in
Summary
The diagnosis and staging of chronic kidney disease (CKD) are based on the detection of structural change and renal dysfunction [1, 2]. Symmetric dimethylarginine is routinely used as a more sensitive biomarker than creatinine in estimating GFR. These biochemical markers are insensitive to early renal injury and they can only assess the global renal function but not insight of the morphological change of the kidney. Renal fibrosis is the histologic hallmark of CKD It is final pathway in the progression of chronic kidney disease regardless of the initial insult and lead to irreversible kidney damage occurs and the kidney decrease in size [3]. The severity of renal fibrosis in cats with CKD was higher in the later stage than in the early stage, each IRIS stage was no consistent with severity of renal fibrosis [7]
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