Quantitative in vivo 23 Na MR imaging of the healthy human kidney: determination of physiological ranges at 3.0T with co
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RESEARCH ARTICLE
Quantitative in vivo 23Na MR imaging of the healthy human kidney: determination of physiological ranges at 3.0T with comparison to DWI and BOLD Stefan Haneder • Paul Kettnaker • Simon Konstandin John N. Morelli • Lothar R. Schad • Stefan O. Schoenberg • Henrik J. Michaely
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Received: 29 May 2012 / Revised: 25 January 2013 / Accepted: 29 January 2013 / Published online: 9 March 2013 Ó ESMRMB 2013
S. Konstandin L. R. Schad Computer Assisted Clinical Medicine, Heidelberg University, Mannheim, Germany
direction of the renal medulla. By using external standard reference phantoms, [23Na] was calculated in mmol/L of wet tissue volume (mmol/l WTV). Axial diffusion-weighted images (spatial resolution = 1.7 9 1.7 9 5.0 mm3) and 2D GRE BOLD images (spatial resolution = 1.2 9 1.2 9 4.0 mm3) were acquired. Mean values ± standard deviations for [23Na], apparent diffusion coefficient (ADC) values, and R2* values were computed for each volunteer. The corticomedullary 23Na-concentration gradient (in mmol/l/mm) was calculated along the area of linear concentration increase from the cortex in the direction of the medulla. Correlations between the [23Na] and DWI, BOLD, and the physiologic parameters were assessed with Pearson correlation coefficients. Results The mean corticomedullary [23Na] for all healthy volunteers increased from the renal cortex (58 ± 17 mmol/l WTV) in the direction of the medulla (99 ± 18 mmol/l WTV). The inter-individual differences ranged from respective cortical and medullary values of 27 and 63 mmol/L WTV to 126 and 187 mmol/L WTV. No statistically significant differences in renal [23Na] were found based on differences in individual or physiologic parameters (age, gender, [23Na]serum, BMI, GFR). No ADC or R2* gradients were identified, and [23Na] did not correlate with these parameters. Conclusion Renal corticomedullary [23Na] values increase from the cortex in the direction of the medullary pyramid, demonstrating wide inter-individual ranges and no significant correlations with age, gender, [23Na]serum, BMI, GFR, ADC, or R2* values. For future clinical evaluations, an approach relying on renal stimulation (e.g. pharmacologically induced diuresis) may be applicable to account for wide inter-individual ranges of normal [23Na].
J. N. Morelli Scott and White Memorial Hospital and Clinic, Texas A&M University Health Sciences Center, Temple, TX, USA
Keywords 23Na MR imaging Kidney Humans DWI/BOLD Physiological ranges
Abstract Objectives The purpose of this prospective study was to assess the normal physiologic ranges of the renal corticomedullary 23Na-concentration ([23Na]) gradient at 3.0T in healthy volunteers. The corticomedullary [23Na] gradient was correlated with other functional MR imaging parameters—blood oxygenation level dependent (BOLD) and diffusion-weighted imaging (DWI)—and to individual and physiologic parameters—age, gender, estimated glomerular filtration rate (eGFR), body mass index (BMI), and blood serum sodium concentration ([23Na]serum). Methods and materials 5
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