Laser Doppler and Speckle Techniques for Bioflow Measurements

In vivo flow cytometry: A horizon of opportunities

“…FCM uses acute preparations in rodent models to expose the vessels of mesentery, skin flap, bone, brain, liver, kidney, lungs, and cremaster muscle (109, 118). Less invasive are models of eye conjunctiva (99), iris (119), and retina (59, 60), which are directly applicable in humans. A widely spread and intensively developing human noninvasive model is the nailfold model, which has been used in in vivo capillaroscopy for many years (16, 17).…”

“…Briefly, the capacity of clinically relevant in vivo PA FCM technologies was demonstrated by the real‐time detection in blood and lymph flows of circulating individual normal cells (e.g., erythrocytes and leukocytes) in different functional states (e.g., normal, apoptotic, or necrotic), tumor cells (melanoma, breast, and squamous), bacteria (e.g., E. coli and S. aureus ), NPs (e.g., gold nanorods, carbon nanotubes, magnetic and golden carbon nanotubes, and dyes [e.g., Lymphazurin, Evans Blue, and Indocyanine Green; (15,19–42)]. Compared to other promising approaches PT FCM and PA FCM offer the following advantages: 1) use of low‐toxicity NPs approved for a pilot study in humans; 2) high‐resolution (300 nm) PT and optical imaging (in vivo image FCM) of flowing single cells of interest at velocities up to 2 m/s (23, 34, 40); 3) PT and PA measurements of the velocity of individual flowing cells (19, 29, 42) and of cell flows using optical speckle measurements (96, 97, 99); 4) theranostic of circulating abnormal cells (e.g., CTCs) as integration of PA diagnostics, real‐time highly localized (i.e., not harmful for surrounding normal blood cells) PT killing using the same laser, and control efficiency of therapy through decreased PA signal amplitudes and CTC counts (29, 31); 5) PA detection of disseminated tumor cells in lymphatics as the earliest prognostic marker of metastasis, compared to sentinel lymph node and blood assessment (30); 6) use of magnetic NPs as multifunctional PA‐PT‐magnetic resonance imaging contrast agents for in vivo magnet‐induced NP clustering, nanobubble‐related signal amplification, imaging, and cell enrichment/sorting/separation (15, 31); and 7) the use of PA FCM both with noninvasive transcutaneous laser irradiation and minimally invasive approach using tiny needle or catheter for delivery of laser radiation theoretically in any vessels inside the body (25, 29). Recent applications include real‐time monitoring of blood rheology parameters and its change during pathological processes [review in this issue (38)], label‐free detection of circuiting clots using negative PT and PA contrasts for early cardiovascular disease diagnosis and potentially prevention stroke [this issue (39)], in vivo real‐time monitoring of dye‐cell interaction, circulating dead cells, and potential blood volume [this issue (41)], and cell identification based on their different velocity in circulation (42).…”

“…This can be done taking into account circulation properties and features. Significant contribution in developing optical methods for in vivo imaging of blood and lymph flow, measuring flow velocity, and study of circulation at different conditions has been made by Valery Tuchin's group at Saratov State University since 1994 (82–99). It included the speckle techniques for cell velocity measurements in mostly used rat mesentery as an animal model and vessels of eye conjunctiva in humans.…”