The development of miniaturized nonlinear optical microscopy or endoscopy is essential to complement the current imaging modalities for diagnosis and monitoring of cancers. We report on a nonlinear optical endoscope based on a double-clad photonic crystal fiber and a two-dimensional (2-D) microelectromechanical system mirror, enabling the three-dimensional (3-D) nonlinear optical imaging through in vitro gastrointestinal tract tissue and human breast cancer tissue with a penetration depth of approximately 100 µm and axial resolution of 10 µm. The 3-D high-resolution and high-sensitive imaging ability of the nonlinear optical endoscope facilitates the visualization of 3-D morphologic and cell nuclei arrangement within tissue, and therefore will be important for histopathologic interpretation without the need of tissue excision.
A translationally-scanning mirror is always desired for the axial scanning in optical coherence tomography (OCT),
but conventional scanners are bulky and have relatively slow scanning speed. This paper reports a micromirror that
has the potential to achieve both the scanning speed and range required by OCT. The large piston motion of the
micromirror is obtained using a large-vertical-displacement (LVD) microactuator. The device is fabricated using a
deep-reactive-ion-etch (DRIE) CMOS-MEMS process. A pair of electrothermal bimorph actuators is employed to
achieve tilt-free mirror plate and large piston motion. A linear voltage divider with a voltage ratio of 1:2.3 between
the two electrothermal actuators has been used to obtain static displacements up to 200 &mgr;m. The frequency response
of this device was obtained using a laser Doppler vibrometer, and resonant peaks were observed at 1.18 and 2.62
kHz. AC signals at 50 Hz with a voltage ratio of 1:1.2 were supplied to the actuators, and the maximum dynamic
piston motion was measured to be 26 &mgr;m. The decreasing amplitude over increasing frequency was caused by the
heat-sink effect of the mirror plate. A phase delay between the two actuators was also observed.
This paper summarizes the development of new 2D MEMS mirrors and the pertinent modification to improve OCT endoscopic catheter packaging suitable for in vivo imaging diagnosis of bladder cancers. Comparative study of the newly developed endocopic OCT versus the bench-top OCT is presented. Results of in vivo OCT cystoscopy based on a porcine acute inflammation model are presented to compare time-domain OCT and spectral-domain OCT for in vivo imaging. In addition, results of spectral-domain Doppler OCT are presented to image blood flow in the lamina propria of the bladder. The results of our in vivo animal study using the presented OCT endoscope are discussed for potential problems in the future clinical applications.