Measurement of renal volumes with contrast‐enhanced MRI

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Abstract
Purpose To determine the accuracy of in vivo magnetic resonance imaging (MRI) measurement of total renal parenchymal volume and medullary fraction. Materials and Methods Sixteen kidneys in eight pigs were imaged with a multiphasic contrast‐enhanced fast three‐dimensional sequence on a 1.5‐T imager. Kidney segmentation, followed by a process of signal intensity thresholding for cortical and nephrographic phase datasets, allowed for MRI measurements of parenchymal volume and medullary fraction. Autopsy provided reference standards of renal volume, weight, and medullary fraction. Results An excellent correlation was found between MRI measurement of total renal parenchymal volume and autopsy volume (R2 = 0.86) and weight (R2 = 0.90). Medullary fraction (mean ± SD) measured with MRI was 0.120 ± 0.067, and with autopsy was 0.116 ± 0.025 (t‐test P = 0.84, F‐test P = 0.001). Conclusion MRI measurements of total renal volume are accurate. MRI measurements of medullary fraction show promise, but precision is limited when using a simple signal intensity thresholding algorithm. J. Magn. Reson. Imaging 2002;15:174–179.