Fig. 6
From: Photoacoustic imaging for monitoring radiotherapy treatment response in head and neck tumors
The photoacoustic signal of the submandibular gland at 1000 nm shows a strong correlation to the treatment phase (A). In line with this finding, the linear mixed model (LMM) analysis reveals an increase in explained photoacoustic signal variation for the treatment parameter (green) with longer wavelengths, where water becomes a primary absorber (B). Other LMM parameters like the individual (subject) and the depth of the structure stay constant or decrease with longer wavelengths like the unexplained (residual) signal variation. The box shows the interquartile range (IQR) with the median as center line. The whiskers extend to points that lie within 1.5 \(\times\) IQR of the 1st or 3rd quantile. All data points are plotted on top, and color-coded by measurement side (left or right neck).
