Raman FastEEM: Clinical instrumentation

Motivation
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Figure 1.Schematic of clinical Raman instrument.

Unit 1. Clinical Raman spectroscopy apparatus for diagnosing disease
The instrument uses an 830 nm diode laser, delivered through the probe, to excite Raman scattering. The probe delivers to and collects light with the probe tip in contact with tissue. Light from an 830 nm InGaAs diode laser (Process Instruments, Salt Lake City, UT) is passed through a holographic bandpass filter centered at 830 nm (Kaiser Optical Systems Incorporated, Ann Arbor, MI). The light is then collimated and coupled into the 200 μm core diameter excitation fiber of the Raman probe. Illumination of the sample is gated by a high-speed, 6 mm aperture, computer-controlled shutter (LS6ZM2, Vincent Associates, Rochester, NY). The excitation fiber is terminated with an FC connector to provide day-to-day reproducibility of alignment. For 100 mW of excitation power, the resultant irradiance is 318 W/cm2 which has been clearly shown to not cause any tissue damage. The proximal end of the probe contains the collection fibers that are arranged in a vertical array and serve as the entrance slit to the spectrograph (Holospec f/1.8i, Kaiser Optical Systems), attached by means of a modified BNC connector. The collected Raman light is dispersed onto a back-illuminated, deep-depletion CCD detector with a 1024×256 array of pixels. The CCD detector is thermoelectrically cooled to -70C. The probe is 4 m long and is 2 mm in overall diameter. Integrated software (LabVIEW and Matlab) in the system enables rapid collection of Raman spectra (1s) and real-time analysis of the spectral parameters.

Figure 2.Typical Raman spectrum acquired in 0.5s from breast tissue.

Unit 2. Clinical DRS/IFS spectroscopy apparatus for diagnosing disease

Figure 3. Schematic of clinical DRS/IFS instrument.

The DRS/IFS instrument uses two different light sources including a 337 nm N2 laser (NL100, Stanford Research Systems, Sunnyvale, CA) for fluorescence spectroscopy and a Xe lamp (L7684, Hamamatsu Corp., Bridgewater, NJ) for reflectance spectroscopy. The Xe lamp provides a 2.9 μs FWHM pulse of white light, 1 J/pulse max, given an external trigger supplied by the software. The N2 laser provides a 3.5 ns FWHM pulse of 337 nm light, 170 μJ per pulse. Light is delivered and collected from tissue via DRS/IFS probe and is brought to the entrance slit of the diffraction grating spectrometer (Spectra Pro 150, Acton Research, Acton, MA). The collected light is dispersed onto an intensified CCD detector (PIMAX, Roper Scientific, Princeton, NJ). To insure easy reproducibility, the collection fibers have individual SMA adapters that connect to the spectrograph. The CCD is operated in a gated mode and is thermoelectrically cooled to -20C. The total collection time for fluorescence and reflectance spectra is approximately 0.3 s. Several of these acquisitions can be averaged together to increase the SNR, making a typical acquisition time on the order of 1.5 s. Integrated software (LabVIEW and Matlab) in the system enables rapid collection of DRS and IFS spectra.

Figure 4.Example of DRS and IFS spectra acquired in 1.5s from breast tissue.

Recent Publications

1. Please send information to Mei if applicable.