Miniaturized video-rate epi-third-harmonic-generation fiber-microscope

Abstract

With a micro-electro-mechanical system (MEMS) mirror, we successfully developed a miniaturized epi-third-harmonic-generation (epi-THG) fiber-microscope with a video frame rate (31 Hz), which was designed for in vivo optical biopsy of human skin. With a large-mode-area (LMA) photonic crystal fiber (PCF) and a regular microscopic objective, the nonlinear distortion of the ultrafast pulses delivery could be much reduced while still achieving a 0.4 microm lateral resolution for epi-THG signals. In vivo real time virtual biopsy of the Asian skin with a video rate (31 Hz) and a sub-micron resolution was obtained. The result indicates that this miniaturized system was compact enough for the least invasive hand-held clinical use.

Imaging Cytometry of Human Leukocytes with Third Harmonic Generation Microscopy

“…At 120 Hz frame-rate, to avoid 1 μm image distortion, the lateral flow speed of leukocytes should be lower than 120 μm/sec. According to our previous work, the typical flow speed of blood cells in human capillaries are about 300 μm/sec21. To increase the frame rate of imaging, fast tomographic imaging methods like harmonic generation temporal focusing22 should be employed.…”

Third harmonic generation microscopy of cells and tissue organization

“…Abnormal vessel structures and altered hemodynamic factors are important parameters for diagnosing malignancies, and this has motivated the development of a miniaturized video-rate THG microscope for use in optical biopsies that has a sufficiently high spatial and temporal resolution to record blood flow in skin capillaries (Chia et al, 2010). Transcutaneous THG detection of blood cell flow in dermal capillaries of human volunteers is sensitive enough to capture blood flow dynamics, and the ratios of erythrocytes and white blood cells ; this can be exploited for in vivo cytometry and hematological analysis without the need to draw blood.…”

Neurophotonics: optical methods to study and control the brain

“…However, the miniaturization level of systems for optical-harmonic generation microscopy is not enough to apply this technology to studies of freely moving animals. The available compact microscopes allow in vivo second-and third-harmonic microscopy of human skin to be implemented with a penetration depth of up to 200 mm [160]. Femtosecond laser pulses needed for such studies were delivered through a large-mode-area photonic crystal fiber, supporting a single-mode guidance at 1260 nm.…”