Related Experiment Video
Updated: Sep 15, 2025
Author Spotlight: Aiding Research in Kidney Biology by Labeling Glomeruli in Cleared Tissues
Published on: February 9, 2024
Counting glomeruli in human kidney specimens using ex vivo MRI without contrast agents
Nyoman D Kurniawan1, Aurel J Amar1, Luise A Cullen-McEwen2
1Center for Advanced Imaging, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St. Lucia, Queensland, Australia.
Purpose:
The total number of glomeruli is an important indicator of kidney function and susceptibility to disease. Glomeruli, however, are difficult to image using MRI without contrast enhancement. For this reason, previous studies have used cationic ferritin as a contrast agent to detect glomeruli in ex vivo and in vivo perfused kidneys. This study aimed to develop a new technique using MR microimaging at ultrahigh field, without contrast agents, to visualize and quantify glomeruli in human nephrectomy samples.
Methods:
MRI was performed at 16.4 T using three-dimensional T1/ -weighted gradient-echo imaging at 30 to 200 μm isotropic resolution on cortical samples with volumes ranging from 155 to 1384 mm3. A segmentation pipeline based on shape recognition and clustering was developed to count glomeruli on MR images at 30-μm isotropic resolution. Glomerular number and density were estimated after MRI using unbiased stereology, and glomerular distribution was visualized using a subset of samples imaged using confocal microscopy.
Results:
Glomeruli were identified in the MR images as hypointense spheres. High spatial concordance between glomeruli identified by MRI, histology, and confocal microscopy was observed. Statistical analyses showed that glomerular counts from stereology and MR images were similar, with Pearson correlation and intraclass correlation coefficients of 0.98.
Conclusion:
High-resolution microimaging at 16.4 T combined with automated segmentation allowed identification and quantitation of human glomeruli ex vivo without the need for contrast agents. The results showed strong agreement with the gold-standard stereological method for glomerular counting.
Insights
This study developed a new MRI technique to visualize and count human glomeruli without contrast agents. The method showed high accuracy, matching traditional stereology for glomerular quantification.
Area of Science:
- Nephrology
- Medical Imaging
- Biophysics
Background:
- Glomeruli number is key for kidney function assessment.
- Imaging glomeruli with MRI is challenging without contrast agents.
- Previous methods used cationic ferritin, limiting applications.
Purpose of the Study:
- To develop a novel MR microimaging technique for visualizing and quantifying human glomeruli.
- To achieve this without the need for contrast agents.
- To assess the technique's accuracy against established methods.
Main Methods:
- Utilized ultrahigh field (16.4 T) MR microimaging with 3D T1/T2*-weighted gradient-echo sequences.
- Employed a segmentation pipeline for glomeruli identification and counting on MR images.
- Validated counts using unbiased stereology and confocal microscopy.
Main Results:
- Successfully identified glomeruli as hypointense spheres in MR images.
- Demonstrated high spatial concordance between MRI, histology, and confocal microscopy.
- Achieved highly similar glomerular counts between MRI and stereology (r=0.98).
Conclusions:
- High-resolution MR microimaging at 16.4 T enables contrast-agent-free visualization and quantitation of human glomeruli.
- Automated segmentation combined with ultrahigh-field MRI provides accurate glomerular counts.
- This technique offers a promising alternative to traditional methods for ex vivo kidney sample analysis.
Related Concept Videos
01:27Imaging Studies IV: Magnetic Resonance Imaging
01:28Imaging Studies I: Kidney, Ureter, and Bladder Studies
01:24Magnetic Resonance Imaging