• flow cytometry;
  • spectral imaging;
  • photoacoustic and photothermal methods;
  • fluorescence;
  • Raman spectroscopy;
  • blood and lymph flows;
  • circulating tumor cells, bacteria, and multicolor nanoparticles;
  • theranostics


Flow cytometry (FCM) has been a fundamental tool of biological discovery for many years. Invasive extraction of cells from a living organism, however, may lead to changes in cell properties and prevents studying cells in their native environment. These problems can be overcome by use of in vivo FCM, which provides detection and imaging of circulating normal and abnormal cells directly in blood or lymph flow. The goal of this review is to provide a brief history, features, and challenges of this new generation of FCM methods and instruments. Spectrum of possibilities of in vivo FCM in biological science (e.g., cell metabolism, immune function, or apoptosis) and medical fields (e.g., cancer, infection, and cardiovascular disorder) including integrated photoacoustic-photothermal theranostics of circulating abnormal cells are discussed with focus on recent advances of this new platform. © 2011 International Society for Advancement of Cytometry