Daniel J. MacDonald

Fiber-optic scanning two-photon fluorescence endoscope

We report on the development of a miniature, flexible, fiber-optic scanning endoscope for two-photon fluorescence imaging. The endoscope uses a tubular piezoelectric actuator for achieving two-dimensional beam scanning and a double-clad fiber for delivery of the excitation light and collection of two-photon fluorescence. Real-time imaging of fluorescent beads and cancer cells has been performed.

Real-time in vivo blood-flow imaging by moving-scatterer-sensitive spectral-domain optical Doppler tomography

We present a moving-scatterer-sensitive optical Doppler tomography (MSS-ODT) technique for in vivo blood flow imaging in real time by using a spectral-domain optical coherence tomography system. In MSS-ODT the influence of stationary scatterers is suppressed by subtracting adjacent complex axial scans before calculating the Doppler frequency shift. We demonstrate that MSS-ODT is a useful technique for accurate determination of blood vessel size by imaging flow in a small capillary tube with a 75 microm inner diameter. The flow profile obtained with MSS-ODT yields a substantially more accurate tube diameter than that obtained with the conventional phase-resolved method, which underestimates the diameter by about 23%. We also demonstrate that MSS-ODT provides improved sensitivity over the conventional phase-resolved method for imaging in vivo blood flow in small vessels in a mouse ear.

High-resolution OCT Balloon Catheter for Systematic Imaging of the Esophagus

An OCT balloon imaging catheter was developed using small compound rod lenses to achieve superb lateral resolution at a large working distance. The balloon catheter enables systematic assessment of human esophagus for Barretts screening.

Functional Assessment of Cutaneous Wound Healing Using Spectral-Domain Optical Doppler Tomography

We show that spectral-domain optical coherence tomography can monitor blood flow in and around the wound bed during the cutaneous wound healing process in a mouse model.

Flexible Scanning MicroEndoscope for Two-photon Fluorescence and SHG Imaging

We report an all-fiber-optic approach for beam delivery, collection, scanning and dispersion management in a microendoscope for nonlinear optical imaging. Preliminary result of ex vivo rat tail tendon imaging is presented.

Stationary scatterer filtering in spectral domain optical Doppler tomography

We report a method for improving the accuracy in determining blood flow rate and small vessel size by implementing a delay line filter when processing real-time spectral domain optical coherence tomography images of flow.

Two-Photon Fiber-Optic Scanning Endoscope

We present a flexible fiber-optic scanning endoscope for two-photon fluorescence imaging and demonstrate it on live cells. Two-dimensional beam scanning at kilohertz frequencies was achieved using a PZT tube to actuate a double-clad fiber.

Phase-Shifted Delay Line Filter for Moving Scatterer Sensitive Spectral Domain Optical Doppler Tomography

A phase-shifted delay line filter is implemented in a spectral domain optical Doppler tomography system to suppress the influence of stationary scatterers on blood flow rate estimation.