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Objectives To assess inter observer variability of renal blood oxygenation level dependent MRI (BOLD MRI) using a new method of analysis called the concentric objects (CO) technique in comparison with the classical ROI (region of interest) based technique. Methods MR imaging (3 T) was performed before and after furosemide in 10 chronic kidney disease (CKD) patients (mean eGFR 43 ± 24 ml/min/1.73 m2) and 10 healthy volunteers (eGFR 101 ± 28 ml/min1.73 m2) and R2 maps were determined on four coronal slices. In the CO technique R2 values were based on a semi automatic procedure that divided each kidney in six equal layers whereas in the ROI technique all circles (ROIs) were placed manually in the cortex and medulla. The mean R2values as assessed by two independent investigators were compared. Results With the CO technique inter observer variability was 0.7–1.9 across all layers in non CKD versus 1.6–3.8 in CKD. With the ROI technique median variability for cortical and medullary R2 values was 3.6 and 6.8 in non CKD versus 4.7 and 12.5 in CKD; similar results were observed after furosemide. Conclusion The CO technique offers a new investigator independent highly reproducible alternative to the ROI based technique to estimate renal tissue oxygenation in CKD. |
