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  1. CDRH Research Programs

High Resolution Optical Imaging


Anant Agrawal, Ph.D.


Over the last several decades, a variety of high resolution in vivo optical imaging methods have emerged which enable visualization of biological structures and processes on the micrometer scale, near the diffraction limit of light. The concomitant rise in computational power has propelled the sophistication of these imaging techniques: from two dimensional slices to three dimensional volumes, from static to dynamic processes, from qualitative to quantitative information. Real-time analysis and display of these detailed optical images now empowers scientists and clinicians with unprecedented insights into previously unseen biological phenomena.

The overall vision of the High Resolution Optical Imaging (HROI) program has two components:

  1. To better understand the safety and effectiveness of HROI technologies integrated into medical devices
  2. To apply HROI methods in targeted regulatory science investigations of medical devices and biological tissue
OCT images of phantom and human retina
OCT images of phantom and human retina

OCT images of (a) retina phantom and (b) human retina. Scale bar is 100 µm optical depth.

OCT and TPFM composite image of  mouse cortex

Composite image showing optical coherence angiography (OCA, grayscale) of capillaries and two-photon fluorescence microscopy (TPFM, in green) of neurons (layer 5 pyramidal cells) in the mouse motor cortex. Both OCA and TPFM images are 100 µm thick maximum intensity projections below an implanted window. Scale bar is 100 µm.

The primary imaging methods under study in the HROI program include optical coherence tomography (OCT), adaptive optics (AO), two-photon fluorescence microscopy (TPFM), and photoacoustic microscopy (PAM). Because of its subsurface and 3D imaging capabilities, OCT is now widely used as a clinical tool to visualize and measure disease processes in ophthalmology, but it has also established its value in cardiovascular medicine and other areas of the body. Motivated by the first component of the HROI program vision, we have been developing physical models known as phantoms to characterize OCT medical device imaging performance through controlled bench testing (see OCT images). The second component of our program vision encompasses the application of HROI techniques (OCT and TPFM) to investigate the neurological system response to implanted electrodes under development for medical device applications such as a brain-computer interface (see composite image). Beyond these ongoing research projects, we are also exploring other novel in vivo and in vitro HROI modalities and applications aligned with regulatory and public health needs.

Current funding sources

FDA Critical Path Initiative
FDA Medical Countermeasures Initiative


FDA Staff:
Anant Agrawal, Ph.D.
Ethan Cohen, Ph.D.
Daniel X. Hammer, Ph.D.
Zhuolin Liu, Ph.D.
Joshua Pfefer, Ph.D.

External collaborators

University of Pittsburgh Medical Center
National Eye Institute
Johns Hopkins University

Resource facilities

  • Three spectral domain OCT systems with 850 nm, 1070 nm, and 1310 nm source wavelengths
  • Adaptive optics ophthalmoscope with 780 nm source wavelength
  • Two-photon fluorescence microscope with 690-1030 nm tunable laser source
  • Photo-acoustic microscope with 550-700 nm tunable dye laser source

Relevant standards & guidances

International Standard ISO 16971, Ophthalmic instruments — Optical coherence tomograph for the posterior segment of the human eye

Selected peer-review publications

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