Table 1.
Scanning protocol.
Fig 1.
Evaluation of the compartments of the lower leg.
The compartments of the lower leg were determined before (left) and after (right) diuretic therapy by an experienced reader. The different anatomical regions of interest (ROI) were drawn guided by the anatomical image (lower images, T1-weighted fast-low-angle-shot (FLASH)-sequence). To measure the cutis one pixel was marked along the coil surface. The value of the whole lower leg = grey-values > 2 x background noise. Four tubes containing aqueous solutions with increasing Na+ concentrations (10, 20, 30, and 40 mmol/L NaCl) were positioned in a custom-made device positioned inside the coil just below the patient’s lower leg. Gray-scale measurements of the tubes served as calibration standards for 23Na-MRI of the skeletal muscle and skin by relating intensity to a concentration in a linear trend analysis. For H2O quantification, the 10 mmol/L NaCl tube served as a calibration standard for tissue water in a linear trend analysis defining a water content of approximately 1 liter water per liter volume. ROIs: 1 = cutis, 2 = triceps surae muscle, 3 = whole lower leg, 4–7 = calibration solutions, 8 = background noise.
Fig 2.
Na+ and H2O in muscle and skin in the lower leg of acute heart failure patients before and after diuretic treatment and of a healthy cohort.
Upper: Mean Na+ concentrations determined by 23Na magnetic resonance imaging in muscle (A) and skin (B) significantly decreased during furosemide diuretic therapy (p ˂ 0.05 and p ˂ 0.01). Mean Na+ concentrations in muscle and skin of the lower leg of patients before and after therapy for acute heart failure were significantly higher compared to corresponding values of healthy subjects. Middle: Mean H2O contents determined by 1H magnetic resonance imaging in muscle (A) and skin (B) did not significantly decrease during furosemide diuretic therapy (p > 0.05). Lower: Box plots show the relative change ((AT-BT)/BT) of Na+ and H2O during furosemide diuretic therapy determined by magnetic resonance imaging in muscle (A), skin (B) and the whole lower leg (C) (upper horizontal line of box: 75th percentile; lower horizontal line of box: 25th percentile; horizontal bar within box: median; box within box: mean; upper and lower horizontal bar outside box: standard deviation). The asterisks indicate significant differences (p < 0.05). C = controls (healthy subjects), BT = before therapy, AT = after therapy, AU = arbitrary unit.
Fig 3.
Correlation between the change of the Na+ concentration and the change of the area of the lower leg of acute heart failure patients during diuretic treatment.
Table 2.
Demographic data and results.
Fig 4.
Exemplary 23Na/1H-MRI-images of a patient with acute heart failure before and after diuretic treatment and of a matched healthy subject.
Upper row: 23Na scans (gradient echo 23Na sequence) of a 71-year-old patient before and after heart failure therapy. The amount of Na+ in skin and subcutaneous tissues, as well as in skeletal muscle was reduced, compared to the 10, 20, 30, and 40 mmol/L NaCl solutions (below). At far right is a normal 71-year-old control person with little sodium in skin and muscle. Lower row: The same patient before and after furosemide and the control subject viewed with conventional (1H) MRI (fat-suppressed inversion recovery (IR) sequence). The salt solutions appear white because of their water content.
Table 3.
Interreader reliability.