Different strategies for MRI measurements of renal cortical volume

Abstract

Purpose: First, to measure renal cortical volume (Vc) using different MRI methods combined with a semiautomatic segmentation method. Second, to compare MRI measurements of Vc using the semiautomatic segmentation method with a manual segmentation method. Third, to evaluate the reproducibility of Vc measurements. Materials and Methods:A total of 22 pigs, 13 with healthy kidneys and nine with diseased kidneys, underwent MRI with two non-contrast-agent methods (MRI 100ϫ900 and MRI 300ϫ1100 ) and one contrast-agent method (MRI Gd ). For each of these methods, Vc was estimated using semiautomatic (Vc 100ϫ900 , Vc 300ϫ1100 , and Vc Gd ), as well as manual (Vc MANUAL ) segmentation. Reference volumes were estimated by stereological means (Vc STEREOLOGY ). MRI-derived volumes were compared with reference volumes using a two-tailed paired t-test, and variances between methods were visualized with Bland Altman plots. Reproducibilities were analyzed using covariance analysis.Results: Neither measurements of Vc 100ϫ900 , Vc 300ϫ1100 , nor Vc Gd differed markedly from Vc STEREOLOGY using semiautomatic segmentation. Vc was comparable when semiautomatic and manual segmentations were performed at the same scan. Reproducibility of MRI estimated Vc values offered intra-and interindividual differences Ͻ5%. Conclusion:Vc can in both healthy and diseased kidneys be measured accurately with MRI using both semiautomatic and manual segmentation, and measurements can be obtained with a high reproducibility. Measurements of Vc 100ϫ900 may in the future become suitable in patients with chronic renal failure.

Renal cortical and medullary blood flow during modest saline loading in humans

“…In pigs, it is possible to identify the renal cortex on MRI images based on signal intensity (Karstoft et al . ). In this species, MRI measurements of total renal volume and determination of the fraction that constitutes the medulla have been compared with postmortem autopsy.…”

Advantages and Controversies in the Era of Intrarenal Volumetry

“…Both MRI and stereological means demonstrated pronounced intrarenal changes in the UO kidney compared to the control group [29]. For example, calculation of V c revealed a volume reduction of 28.9% in the obstructed kidney compared to V c of healthy kidneys.…”

“…In this application, V c could be calculated from the sum-of-areas principle [33]. Interestingly, we found that V c in both healthy and UO kidneys could be measured accurately with MRI using semiautomatic as well as manual segmentation, and measurements were obtained with a high intra- and inter-observer reproducibility (covariance level <5%) [29]. …”

“…To demonstrate the usefulness of the proposed MRI and stereology means, we draw attention to our motivating findings reported in a UO animal model [27,28,29]. As mentioned, UO is followed by several renal complications and is known to upregulate the renin-angiotensin system, leading to intrarenal hypoxia and resulting in loss of nephrons over time [30].…”

Evaluation of renal cortical thickness by non-contrast-enhanced MR imaging with spatially selective IR pulses: comparison between cirrhotic and non-cirrhotic patients

“…2 Meanwhile, renal cortical volumes and cortical thicknesses have been found to correlate with renal function. [6][7][8][9][10][11][12][13] It has been reported that non-contrast-enhanced steady-state free precession (SSFP) MRI with a spatially selective inversion recovery (IR) pulse can emphasize the difference in T 1 values between the renal cortex and the medulla by suppressing the background signal and the target tissue signal. Therefore, compared with conventional MRI sequences, this technique can improve the visualization of renal corticomedullary differentiation and facilitate the measurement of renal cortical thickness even in patients with renal dysfunction compared with conventional MRI sequences.…”