Miniature standoff Raman probe for neurosurgical applications.

Oliver A C Stevens,William Gray,John C Day,Rosa Louise Vincent,Joanne Hutchings

doi:10.1117/1.jbo.21.8.087002

Oliver A C Stevens, William Gray + Show 3 more

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https://doi.org/10.1117/1.jbo.21.8.087002

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Removal of intrinsic brain tumors is a delicate process, where a high degree of specificity is required to remove all of the tumor tissue without damaging healthy brain. The accuracy of this process can be greatly enhanced by intraoperative guidance. Optical biopsies using Raman spectroscopy are a minimally invasive and lower-cost alternative to current guidance methods. A miniature Raman probe for performing optical biopsies of human brain tissue is presented. The probe allows sampling inside a conventional stereotactic brain biopsy system: a needle of length 200 mm and inner diameter of 1.8 mm. By employing a miniature stand-off Raman design, the probe removes the need for any additional components to be inserted into the brain. Additionally, the probe achieves a very low internal silica background while maintaining good collection of Raman signal. To illustrate this, the probe is compared with a Raman probe that uses a pair of optical fibers for collection. The miniature stand-off Raman probe is shown to collect a comparable number of Raman scattered photons, but the Raman signal to background ratio is improved by a factor of five at Raman shifts below ∼500 cm(−1). The probe’s suitability for use on tissue is demonstrated by discriminating between different types of healthy porcine brain tissue.

Highlights

Removal of intrinsic brain tumors, gliomas, is a challenging process, and requires careful consideration to selectively and completely remove tumor tissue, improving outcome without damage to healthy brain.[1]
We demonstrate a miniature Raman probe design that uses an alternative approach: reducing the background by avoiding the use of fibers in the main section of the probe altogether, reducing the internal Raman background and eliminating the need for additional components to be inserted into the brain
As this patch cable is behind the dichroic filters, it has negligible impact on the internal silica Raman signal generated within the probes

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Introduction

Removal of intrinsic brain tumors, gliomas, is a challenging process, and requires careful consideration to selectively and completely remove tumor tissue, improving outcome without damage to healthy brain.[1] Surgical guidance is currently assisted by a variety of imaging techniques, such as pre- or intraoperative magnetic resonance imaging (MRI), computerized tomography (CT), intraoperative ultrasound, 5-aminolevulinic acid (5-ALA) fluorescent imaging,[2] and reflectance spectroscopy,[3] many of which have been shown to improve patient prognosis[4,5] by ensuring maximal resection of radiologically identified tumor. Optical biopsies using Raman spectroscopy have been demonstrated to be a less invasive and potentially more effective alternative to traditional biopsy for a number of different applications,[6,7,8] and potentially offer a reliable and lower cost method of identifying residual tumor intraoperatively, as well as defining apparent tumor edges.[9] This is especially relevant to glial tumors in which edges are invasive and indistinct. A variety of such probes for different applications have been constructed, and shown to be effective in providing spectra information of clinical value.[10,11,12,13,14,15,16,17,18,19]

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