A portable, dual-channel oblique back-illumination capillaroscope for in vivo human blood cell imaging in hematology clinics

Oblique back-illumination capillaroscopy (OBC) has recently demonstrated high resolution, label-free images of human blood cells in vivo. This technology shows promise for a new chapter in blood analysis, where blood cell counts, morphology, and dynamics can be probed non-invasively. OBC provides high quality blood cell images when applied to the ventral tongue, where capillaries are superficial and melanin is minimal. However, the anatomy of this location has a unique and challenging constraints due to the highly muscular and mobile nature of the tongue, and its presence within the oral cavity. This manuscript presents a portable and ergonomic dual- channel OBC system that is optimized for imaging the ventral tongue. The portable OBC system uses pneumatic stabilization to reduce capillary motion and is built upon an ophthalmic slit lamp housing to allow comfortable stabilization of the head and fine, 3-axis translation of the imaging probe. The signal from two diametrically opposed LEDs (530nm and 650nm) are imaged onto two time-synchronized CMOS sensors, providing combined phase-weighted and absorption-weighted contrast of blood cells at 200 Hz with a 165 x 220μm field-of-view. This functional implementation of OBC technology will enable high resolution blood cell imaging of patients with hematologic disease.