Significance: Raman spectroscopy has been developed for surgical guidance applications interrogating live tissue during tumor resection procedures to detect molecular contrast consistent with cancer pathophysiological changes. To date, the vibrational spectroscopy systems developed for medical applications include single-point measurement probes and intraoperative microscopes. There is a need to develop systems with larger fields of view (FOVs) for rapid intraoperative cancer margin detection during surgery.
Aim: We design a handheld macroscopic Raman imaging system for in vivo tissue margin characterization and test its performance in a model system.
Approach: The system is made of a sterilizable line scanner employing a coherent fiber bundle for relaying excitation light from a 785-nm laser to the tissue. A second coherent fiber bundle is used for hyperspectral detection of the fingerprint Raman signal over an area of 1 cm2. Machine learning classifiers were trained and validated on porcine adipose and muscle tissue.
Results: Porcine adipose versus muscle margin detection was validated ex vivo with an accuracy of 99% over the FOV of 95 mm2 in ∼3 min using a support vector machine.
Conclusions: This system is the first large FOV Raman imaging system designed to be integrated in the workflow of surgical cancer resection. It will be further improved with the aim of discriminating brain cancer in a clinically acceptable timeframe during glioma surgery.
KEYWORDS: Imaging systems, Raman spectroscopy, Neuro-oncology, Spatial resolution, In vivo imaging, Real time imaging, Coherence imaging, Endoscopes, RGB color model, Cameras
We present the development and preliminary results of a novel intraoperative line-scanning Raman imaging system, developed for neurosurgery applications. The system records fingerprint Raman spectral images over a large field of view of 1.0cm2 through a handheld imaging probe placed in gentle contact with the interrogated tissue. With a spatial resolution of 250µm2 and an acquisition time on the order of 10s, brain structure margins can be identified within an adequate timeframe for clinical applications. The system was designed using detailed optical simulations and its performance was verified on tissue phantoms and in vivo on animals using our laboratory’s Raman point system as reference.
The following article describes the coatings of both Fabry-Perot (FP) etalons to be installed in the integral
field spectrometer 3D-NTT. This simultaneous use of two FP etalons of high and low resolution respectively
is the new concept upon which the 3D-NTT is built. Design and fabrication of the coatings of those etalons is
a critical step to be able to achieve the desired performances of the instrument. More precisely, these etalons
will have to show less than a 10% variation of the finesse from 370 to 900nm and a better than lambda/100
cumulative optical uniformity over a Ø100mm surface. The aim is thus to design high-reflectivity coatings for
each of the FP etalon. The design process of the two sets of coatings will be described first, then the expected
performances of each etalon will be presented and finally the progresses in the making of these coatings will be
discussed.
The 3D-NTT is a visible integral field spectro-imager offering two modes. A low resolution mode (R ~ 300 to 6 000)
with a large field of view Tunable Filter (17'x17') and a high resolution mode (R ~ 10 000 to 40 000)
with a scanning Fabry-Perot (7'x7'). It will be operated as a visitor instrument on the NTT from 2009.
Two large programmes will be led: "Characterizing the interstellar medium of nearby galaxies with 2D maps of
extinction and abundances" (PI M. Marcelin) and "Gas accretion and radiative feedback in the early universe" (PI J.
Bland Hawthorn). Both will be mainly based on the Tunable Filter mode. This instrument is being built as a
collaborative effort between LAM (Marseille), GEPI (Paris) and LAE (Montreal). The website adress of the instrument
is : http://www.astro.umontreal.ca/3DNTT
GHαFaS is a new Fabry-Perot system available at the William Herschel Telescope. It was mounted, for the first
time, at the Nasmyth focus of the 4.2 m WHT in La Palma in 2007 July. With a spectral resolution of the order
R~15000 and a seeing limited spatial resolution, GHαFaS provides a new look at the Hα-emitting gas over a 4
arcminutes circular field in the nearby universe. Many types of objects can be observed with a scanning Fabry-Perot system on a 4.2 m class telescope such as galaxies, HII regions, planetary nebulae, supernova remnants
outflows from stars and the diffuse interstellar medium. Astronomers from the Laboratoire d'Astrophysique
Experimentale (LAE) in Montreal, the Laboratoire d'Astrophysique de Marseille (LAM), and the Instituto de
Astrofisica de Canarias (IAC), have inaugurated GHαFaS by studying in detail the dynamics of nearby spiral
galaxies. A robust set of tools for reducing and analyzing the data cubes obtained with GHαFaS has also been
developed.
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