An approach to identify, from DCE MRI, significant subvolumes of tumors related to outcomes in advanced head-and-neck cancera)
An example of postcontrast T1-weighted MRI (left), T2 FLAIR (second left), BV (second right), and BF (right) slices of a patient pre-RT (top row) and at week 2 (bottom row). White contour indicates the GTV.
Illustration of the process of classification of the whole GTV into subvolumes based upon their characteristic physiological features. (a) and (b) Two different parameter maps (e.g., BV and BF). The white contour depicts the GTV. (c) A two-dimensional feature space, onto which each voxel from the two parameter maps is projected based upon their values. The voxels are partitioned into three clusters (triangles, circles, and squares) using FCM clustering analysis, which optimizes homogeneity of the parameters within the clusters and separation between the clusters.
Two representative examples of the subvolumes of the primary GTVs with low BV, pre-RT and at week 2. BV maps are color-coded and overlaid on post-Gd T1-weighted images. White contours: primary GTV; blue color: the subvolumes of the GTV with low BV. (a) A local failure case with the whole GTV of 61.4 ml and the subvolume of the tumor with low BV of 28.6 ml pre-RT (left); and 44.8 ml, 20.9 ml, respectively, at week 2 (right). (b) A local control case with the whole GTV of 97.5 ml and the subvolume of the tumor with low BV of 16.5 ml pre-RT (left); and 52.3 ml, 17.4 ml, respectively, at week 2 (right).
Correlation of the subvolumes with low BV at the two time-points (pre- vs during-RT). The subvolumes at the two time-points are highly correlated (ρ = 0.96). Circle: local failure; triangle: local control; solid line: linear regression line; dashed line: diagonal line.
Comparison of fitted ROC curves of five metrics for prediction of local failure. Note that the subvolume of the primary tumor with low BV at week 2 has the greatest area under the curve than the pre-RT tumor volume, the percentage change in the tumor volume at week 2, the change in the mean of the tumor blood volumes, and the subvolume of the primary tumor with low BV pretreatment. Az: Area under the curve; FPF: false positive fraction; TPF: true positive fraction.
Summary of tumor BV and BF analysis results.
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