PA detection and magnetic enrichment of CTCs in tumor-bearing mice. (A) The size of the primary breast cancer xenografts at different stages of tumor development. (B) The average rate of CTCs in 200-μm abdominal skin vein over a period of several weeks. (C) Average rate of bulk CTCs and stem-like CTCs in the abdominal skin blood vessels at week 4 of tumor development. (D) PA signals from CTCs in abdominal skin vessels obtained with fibre schematics at week 1 of tumor development before and after magnet action. The average standard deviation for each wavelength is 24%. (E) PA signals from CTCs in abdominal skin vessels before, during (3 min) and after magnetic action at week 2 of tumor development. The error bars in b, c and e represent standard error (n = 3). Figures were adapted with permission from: (A), (C), ref 15, copyright 2009 Wiley; (B), (D), (E), ref 13, copyright 2009 Nature Publishing Group.