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  1. CDRH Research Programs

Optical Spectroscopy and Spectral Imaging


Joshua Pfefer, Ph.D.
William Vogt, Ph.D.


The Optical Spectroscopy and Spectral Imaging (OSSI) research program focuses on innovative light-based technologies that provide clinicians and patients with real-time information on biological tissue status. The OSSI program supports regulatory decision-making on device submissions in a wide variety of clinical areas, from gastroenterology, gynecology and dermatology, to cardiology, neurology and surgery. These submissions include endoscopic, implantable, intraoperative, non-invasive and mobile OSSI devices. We perform research in established and emerging optical, or “biophotonic” technologies including photoacoustic imaging, fluorescence imaging, hyperspectral reflectance imaging, near-infrared spectroscopy, and implantable biosensors. Many OSSI devices can also be used with nanoparticles or other contrast agents to improve sensitivity and/or enable targeting of specific molecular biomarkers. In order to provide information critical to regulatory science, our researchers perform benchtop, in vivo and computational studies. These studies help us to understand the basic working mechanisms (light-tissue interactions) of OSSI technologies and how device design and patient-to-patient differences affect clinical performance. They also provide us with information necessary to evaluate potential photothermal and photochemical safety hazards, and to develop best practices for clinical, animal and bench testing of novel OSSI devices. In recent years, we have become increasingly involved in efforts to develop international consensus standards that can facilitate device development and regulatory processes. By performing regulatory science research early in the life cycle of a technology, we are able to improve FDA’s ability to provide swift, science-based regulatory decision-making on promising new technologies with the potential to improve patient care.

Current funding sources

Image of Multi-spectral photoacoustic imaging

Multi-spectral photoacoustic imaging
Photoacoustic Imaging (PAI) is a revolutionary spectroscopic approach for deep functional and structural imaging of tissue using pulsed lasers and acoustic/ultrasound detection. Our work to develop test methods based on stable tissue phantoms with biologically realistic bi-modal (optical and acoustic) properties will facilitate device image quality testing and standardization. One emerging area of PAI involves the use of plasmonic nanoparticles (PNPs) for enhancing disease detection. We are working to evaluate issues of safety and effectiveness with pulsed-laser-irradiated PNP-based contrast agents for PAI, such as cavitation effects and the impact of tissue scattering and heterogeneity on measurement of PNP spectral signatures.

FDA Collaborative Opportunities for Research Excellence in Science (CORES) Program
FDA Critical Path Initiative
FDA Medical Countermeasures Initiative
FDA Office of Minority Health
FDA Office of Women’s Health
National Science Foundation (NSF)/FDA Scholar-In-Residence Program


FDA Staff:
Joshua Pfefer, Ph.D., Optical Diagnostic Devices Laboratory Leader
William Vogt, Ph.D.
Anant Agrawal, Ph.D.
Quanzeng Wang, Ph.D.

Research Fellows:
Pejhman Ghassemi, Ph.D.
Udayakumar Kanniyappan, PhD (Univ. of Maryland)
Yi Liu (Univ. of Maryland)

External collaborators

Beckman Laser Institute and Medical Clinic, University of California, Irvinedisclaimer icon
Fischell Dept. of Bioengineering, University of Maryland, College Park disclaimer icon
Florida International Universitydisclaimer icon
National Institute of Standards and Technology (NIST)
National Cancer Institute (NCI)

Resource facilities

  • Spectrophotometer with integrating sphere
  • Spectrofluorometer with dual monochromator excitation and emission
  • Custom photoacoustic tomography system (near-IR OPO, research-grade ultrasound system)
  • Hyperspectral imaging system (near-IR, LCTF-based)
  • Clinical narrow band imaging device (endoscopic)
  • Portable fiberoptic reflectance and fluorescence spectroscopy systems
  • Custom near-infrared spectroscopy (NIRS) system
  • Clinical NIRS oximeters for general tissue (muscle) and brain
  • Near-infrared fluorescence imaging systems based on CCD and mobile phone cameras 
  • 3D printers for standard and biomimetic phantom fabrication
  • Custom optical-thermal light-tissue interaction modeling software in C/C++

Relevant standards & guidances

Reporting of Computational Modeling Studies in Medical Device Submissions - Draft Guidance for Industry and Food and Drug Administration Staff

Image of Computational modeling of light-tissue interactions

Computational modeling of light-tissue interactions
Optical-thermal numerical models of OSSI technologies can provide insight into light-tissue interaction mechanisms, potential tissue safety issues and the effect of tissue and device parameters on performance. Simulations provide a convenient way to estimate trends across a wide parameter space, such as wavelengths, or different device geometries. We have modified and implemented a previously developed voxel-based Monte Carlo model to perform studies to quantitatively elucidate the working mechanisms of narrow band imaging devices (e.g., wavelength differences in vessel contrast with depth) for gastrointestinal tissue surveillance. Additionally, we have linked this optical model to a finite-difference thermal model to elucidate highly dynamic photothermal processes that occur during photoacoustic tomography imaging of breast tissue vasculature.

Near-infrared spectroscopy and imaging

Near-infrared spectroscopy and imaging
Near-infrared (NIR) wavelengths allow penetration of light to a depth of several centimeters in tissue, along with reduced interference from biological fluorophores and environmental light sources. As a result, NIR OSSI technologies that provide real-time information on tissue structure, function and molecular properties have become increasingly popular tools for medicine. NIR spectroscopy and hyperspectral imaging techniques enable noninvasive evaluation of blood-related parameters such as oxygenation in skin and muscle, and are increasingly used for evaluating brain function and the impact of traumatic brain injury. NIR fluorescence imaging with contrast agents enables imaging of molecular biomarkers for early cancer detection, as well as surgical visualization of tumors, nerves and blood vessels. We have worked to understand the tradeoffs in performance with optical device design – including emerging mobile devices – by performing studies in ex vivo tissues (left image). Furthermore, we develop test methods for evaluation of device performance, and have pioneered the use of 3D-printed biomimetic models for testing devices such as imaging oximeters (right image). This work has resulted in novel, practical tools for device development, inter-comparison and quality control/assurance. These methods may also form the basis of future international consensus standards designed to facilitate regulatory review and medical technology innovation.

Selected peer-review publications

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