  Quantitative information on tumor heterogeneity and cell load could assist in
designing effective and refined personalized treatment strategies. It was
recently shown by us that such information can be inferred from the diffusion
parameter D derived from the diffusion-weighted MRI (DWI) if a relation between
D and cell density can be established. However, such relation cannot a priori
be assumed to be constant for all patients and tumor types. Hence to assist in
clinical decisions in palliative settings, the relation needs to be established
without tumor resection. It is here demonstrated that biopsies may contain
sufficient information for this purpose if the localization of biopsies is
chosen as systematically elaborated in this paper. A superpixel-based method
for automated optimal localization of biopsies from the DWI D-map is proposed.
The performance of the DWI-guided procedure is evaluated by extensive
simulations of biopsies. Needle biopsies yield sufficient histological
information to establish a quantitative relationship between D-value and cell
density, provided they are taken from regions with high, intermediate, and low
D-value in DWI. The automated localization of the biopsy regions is
demonstrated from a NSCLC patient tumor. In this case, even two or three
biopsies give a reasonable estimate. Simulations of needle biopsies under
different conditions indicate that the DWI-guidance highly improves the
estimation results. Tumor cellularity and heterogeneity in solid tumors may be
reliably investigated from DWI and a few needle biopsies that are sampled in
regions of well-separated D-values, excluding adipose tissue. This procedure
could provide a way of embedding in the clinical workflow assistance in cancer
diagnosis and treatment based on personalized information.
