Figure 1. Significance of selecting number of patterns (NPs).

(A) As shown for a representative HEK tumor slice (HEK #5), PCA produced 2 distinct PCs followed by higher-order PCs depicting noise. The first 2 PCs explain 97.92% of signal-versus-time curves behavior in this tumor slice. (B) To the tumor slice depicted in (A) corresponding cNMF maps (left) with associated cNMF curves (right) for NPs set to 2 (top) and 3 (bottom), respectively. For NP = 2, two distinct cNMF patterns are identified; for NPs = 3 however, the second and third pattern are very noisy and show overlap due to data over-fitting resulting in the inability to reproducibly/accurately assign a pixel to pattern 2 or 3. (C) In a second example, PCA on two slices of a heterogeneous HEK flank tumor (HEK #1), the first five PCs and their corresponding weight maps are displayed. The % variability of each PC to explain the contrast agent (CA) uptake behavior in their respective slice is shown below each PC. Despite the % contribution to the overall signal of the 3^rd PC in slice 1 and 2 being similar (0.19% and 0.15% respectively), the numbers of significant signal-related PCs identified visually for slice 1 and slice 2 respectively are 2 and 3, as the signal in the 3^rd PC in slice 1 is within twice the size of the noise and similar to higher-order PCs. The overall signal explained by the number of significant signal-related PCs is 98.08% in slice 1 and 98.89% in slice 2. The varying NPs between slices attest to the vascular heterogeneity of this tumor across the thickness of the tumor.