Fig. 5: Application of the r1-r2* relaxivity on meningioma brain tumors.
From: Non-invasive assessment of normal and impaired iron homeostasis in the brain
a From top to bottom: Gd-enhanced T1-weighted image, R1 map and R2* map in a representative subject with a meningioma brain tumor (white arrow). b The dependency of R1 on R2* (the r1-r2* relaxivity) for the white-matter (WM, frontal), gray-matter (GM, frontal) and tumor tissue of the same subject. R2* and R1 measurements across voxels were binned (dots represent the median; shaded areas represent the mean absolute deviation), and a linear fit was calculated. The slopes of the linear fit represent the r1-r2* relaxivity. Tumor tissue exhibits distinct r1-r2* relaxivity relative to non-pathological tissue. The r1-r2* relaxivity is calculated across voxels (R1 and R2* values shown in a) for each ROI. A voxel-wise visualization of the r1-r2* relaxivity available in Supplementary section 8. c–f The contrast between the white-matter (WM), gray-matter (GM) and tumor tissues across patients for the Gd-enhanced contrast (inverted and scaled relative to the maximal value across subjects for visualization, [a.u.], N = 17) (c), R2* (N = 18) (d), R1 (N = 18) (e) and the r1-r2* relaxivity (N = 18) (f). Only the r1-r2* relaxivity produces significant differences between tumor and GM tissues without contrast agents. Left: boxes present the variation in the contrasts across patients. The 25th, 50th, and 75th percentiles and extreme data points are shown. The d-values represent the effect size (Cohen’s d) of the differences between tissue types, and the significance level is based on a paired-sample t test (two-sided). Gray lines extend between values of the same patient. Right: the distribution of the values between WM, GM and tumor tissue across patients. Estimates in non-pathological tissues are for the tumor-free hemisphere. p < 0.05; **p < 0.01; ***p < 0.001 (full statistics are in supplementary table 3).
