Functional Sodium MRI Helps to Measure Corticomedullary Sodium Content in Normal and Diseased Human Kidneys
Bibliographic record
Abstract
Background To the knowledge of the authors, urinary osmolarity is the only tool currently available to assess kidney corticomedullary gradient (CMG). Comparisons between CMG and urinary osmolarity and the use of modalities such as sodium MRI to evaluate renal disease in humans are lacking. Purpose To investigate the ability of sodium MRI to measure CMG dynamics compared with urinary osmolarity after water load in healthy volunteers and CMG in participants with kidney disease. Materials and Methods A prospective study was conducted from July 2020 to January 2021 in fasting healthy volunteers undergoing water load and participants with chronic kidney disease (CKD) from cardiorenal syndrome included in a clinical trial. In both groups, CMG was estimated by measuring the medulla-to-cortex signal ratio from sodium MRI at 3.0 T. A custom-built two-loop (diameter, 18 cm) butterfly radiofrequency surface coil, tuned for sodium frequency (33.786 MHz), was used to acquire renal sodium images. Two independent observers measured all sodium MRI cortical and medullary values for each region of interest to compute the intraclass correlation coefficient. Pearson correlation was performed between urinary osmolarity and CMG. Results Five participants with CKD (mean age, 77 years ± 12 [standard deviation]; all men) and 10 healthy volunteers (mean age, 42 years ± 15; six men, four women) were evaluated. A reduction was observed between baseline and peak urinary dilution time for both mean medulla-to-cortex ratios (1.55 ± 0.11 to 1.31 ± 0.09, respectively; P < .001) and mean urinary osmolarity (756 mOsm/L ± 157 to 73 mOsm/L ± 14, respectively; P < .001) in healthy volunteers. Medulla-to-cortex and corresponding urinary osmolarity were correlated in both groups (r2 = 0.22; P < .001). Kidney sodium tissue content was successfully acquired in all five participants with CKD. The intraclass correlation coefficient measurement was 0.99 (P < .001). Conclusion Functional sodium MRI accurately depicted corticomedullary gradient (CMG) dynamic changes in healthy volunteers and demonstrated feasibility of CMG measurement in participants with reduced kidney function. Clinical trial registration no. NCT04170855. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Laustsen and Bøgh in this issue.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.006 | 0.020 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.002 |
| Bibliometrics | 0.003 | 0.001 |
| Science and technology studies | 0.001 | 0.003 |
| Scholarly communication | 0.003 | 0.004 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.013 | 0.016 |
| Insufficient payload (model declined to judge) | 0.004 | 0.003 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".