The Martinos Optics Research facilities consists of multiple separate lab facilities including 1) fiber optic and electronics fabrication and testing, 2) instrumentation system development and testing, 3) small animal studies, 4) optical physics labs with floating tables, and 5) human subject testing. Instrumentation in the Optics Division includes:
(See also the Optical Microscopy Core website)
A multi-modal microscopy system, built in house, which includes:
- 2-Photon Microscope. The microscope uses the galvo-scanning mirrors, 4 PMT detectors covering the 440-710 nm emission spectral range, and it is capable of measuring phosphorescence lifetimes, fluorescence intensity and fluorescence lifetimes.
- A home built 850 nm Spectral domain Optical Coherence Tomography (OCT) system operating at 22,000 axial scans per second.
- Laser-Speckle Flowmeter (910 nm wavelength, thermoelectrically-cooled CCD camera: CoolSnap fx).
- Confocal Microscope (532 nm excitation; photon counting APD from Perkin Elmer).
A commercial four-channel multi-photon microscope from Prairie Technologies.
A prototype 1300 nm Spectral domain OCT system from Thorlabs, Inc. operating at 47,000 axial scans per second.
CCD-based microscopy system for imaging of cortical oxygen tension and blood flow, built in house (180 mJ pulsed laser at 532 nm, Brilliant B, Quantell; TE-cooled 12-bit CCD camera, Imager QE, LaVision; 100 mW laser diode, 830 nm, DL7032-001, Thorlabs).
Near Infrared Spectroscopy and Imaging Core
Our Near Infrared Spectroscopy and Imaging Core facility includes an extensive and expanding inventory of state-of-the-art near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS) equipment and related laboratories and fully-equipped testing rooms. Training on brain, skeletal muscle and breast cancer applications is available. The core facility is available for use to all qualified investigators from academic, medical, government and industry labs.
Near-Infrared spectroscopy (NIRS)
Near-Infrared Spectroscopy (NIRS) measures light attenuation due to absorption of hemoglobin, and from the absorption at two or more wavelengths, it estimates changes in hemoglobin concentration (HbT, or cerebral blood volume (CBV)) and quantifies cerebral hemoglobin oxygenation (SO2).
Our group led the development of one of the first imaging systems using continuous-wave near-infrared spectroscopy (CW-NIRS) for functional brain imaging, which is being disseminated commercially by Techen, with customers in North America, Europe, Asia, Australia, and Brazil. We have also contributed to the development of frequency-domain (FD) and time-domain (TD) NIRS systems to improve quantification of optical properties of tissue and to increase sensitivity to deeper structures. We are now working on the miniaturization of these systems, and we have recently developed wearable wireless devices.
Diffuse Correlation Spectroscopy (DCS)
DCS was developed in the ’90s by Dr. David Boas and Dr. Arjun Yodh. Since then, DCS has been widely adopted and its utility is now being tested in several clinical applications. DCS measures how fast coherent light loses coherence because of the movement of red blood cells. The correlation diffusion equation relates the motion of red blood cells in vessels to the temporal autocorrelation decay. Since the correlation decay depends on both the speed of moving red blood cells in the media and on the number of scattering events with the moving particles, which depends on the area of the blood vessels, the slope of the correlation decay is proportional to actual blood flow and not simply flow velocity as in ultrasound methods. By fitting the correlation diffusion equation to the measured autocorrelation we derive a cerebral blood flow index (CBFi, cm2∕s).
Our group started adapting DCS for clinical studies in 2006. Since then, we have made several advances in DCS theory and instrumentation, which we have applied in animals4and infants to establish CBFi normative values and demonstrate differences with therapy and disease. We have also used DCS as a continuous monitor, first demonstrating the ability of DCS to measure CBFi changes during functional activity in infants, then moving into clinical applications as a powerful neuromonitoring tool.