Article Figures & Data
Figures
- Fig 1.
Anatomic images and IVIM perfusion maps for 4 clinical cases. fbiexponential is the perfusion fraction estimate of the conventional biexponential fit (16 b-values) and flinear is the perfusion fraction estimate of the simplified linear fit using 2–7 nonzero b-values. Upper row: T2-weighted image, postgadolinium T1-weighted image, and perfusion maps for a patient with a histopathologically confirmed low-grade glial tumor (World Health Organization grade II). A subtle T2-hyperintense, hypoenhancing lesion in the left insular cortex corresponds to a focal region of low perfusion fraction on all perfusion maps. Second row: T2-weighted image, postgadolinium T1-weighted image, and perfusion maps for a patient with histopathologically confirmed glioblastoma (World Health Organization grade IV). A solid enhancing right frontal mass corresponds to a region of increased perfusion fraction on all perfusion maps. Third row: b=0 (ie, T2-weighted) image, ADC map, and perfusion maps for a patient with a large acute right MCA territory infarct, demonstrating a wedge-shaped area of decreased perfusion fraction corresponding to the area of restricted diffusion (infarct core). Lower row: Similar findings in a different patient with a smaller left MCA territory infarct. ROIs for tumors and strokes are shown overlaid on the conventional fbiexponential perfusion maps (dotted white lines).
- Fig 2.
Plots comparing the perfusion fraction estimated using the conventional 16 b-value biexponential fit (fbiexponential) with those using simplified linear fitting of 7 nonzero b-values (flinear) for tumors (left) and infarcts (right). Solid line indicates the least squares optimal linear regression; dotted lines indicate the 95% confidence interval for the line of best fit. The slope and its 95% confidence interval are also provided for each regression line.
- Fig 3.
Comparison of the perfusion fraction between low- and high-grade tumors (left) and between acute infarcts and contralateral brain tissue (right). Triangle, square, diamond, and inverted triangle markers indicate the mean perfusion fraction calculated by the simplified linear method using 2, 3, 4, and 7 nonzero b-values, respectively (Table 1). Circle markers indicate the mean perfusion fraction calculated using the conventional 16 b-value biexponential method. Error bars indicate 95% confidence intervals.
- Fig 4.
Correlation between IVIM perfusion fraction (f) and DSC-derived relative CBV for patients with brain gliomas. The relationship between f and rCBV is shown for conventional biexponential fitting (left panel) and for simplified linear fitting of 7 nonzero b-values (right panel). Plotted values indicate the mean perfusion fraction and rCBV over the tumor ROI for n = 40 patients. The correlation coefficient (r) for each relationship is also provided.
Tables
No. of Nonzero b-Values b-Values (sec × mm−2) 7 300, 400, 500, 600, 700, 800, 900 4 300, 500, 700, 900 3 300, 600, 900 2 300, 900 No. of Nonzero b-Valuesa ROI Tumors (n = 49) Infarcts (n = 17) R2 RMSE R2 RMSE 7 0.913 0.0131 0.887 0.0128 4 0.890 0.0140 0.871 0.0113 3 0.870 0.0152 0.749 0.0139 2 0.853 0.0164 0.719 0.0144 Note:—R2 indicates coefficient of determination for linear regression of flinear on fbiexponential; RMSE, root mean square error.
↵a Indicates the total number of nonzero b-values used in the estimation of flinear (specific b-values are provided in Table 1).
