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TECH FOCUS LASER MICROSCOPY


Laser-augmented


diagnostics Doctors are cutting tumour diagnosis times using laser-based microscopes


N


eurosurgeons and pathologists at the University of Michigan


are using fibre lasers in the operating room to dramatically reduce the time of tumour diagnosis during brain surgery. The methods have been published in the journal Nature Biomedical Engineering. The new approach uses a


fibre laser-based microscope to diagnose tumours with the same accuracy and up to ten times faster than conventional pathology methods, which can involve waiting up to 30 minutes for tissue sample results to come back from a dedicated pathology lab. The researchers proved the new method by using both approaches to image tissue from 101 neurosurgical patients. ‘By achieving excellent


image quality in fresh tissues, we’re able to make a diagnosis during surgery,’ said Dr Daniel Orringer, assistant professor of neurosurgery at the University of Michigan Medical School. ‘Our technique may disrupt the intraoperative diagnosis process in a great way, reducing it from a 30-minute process to about three minutes.’ The new technique, called stimulated Raman histology (SRH), uses a fibre laser to highlight the cellular and architectural features of brain tumours with virtual colouring, producing similar results to conventional staining methods. Pathologists are then able to differentiate the tumour from normal brain tissue to ensure that only the minimal amount is removed during surgery. This is especially important in a brain operation. ‘It’s very similar to what we do in our intraoperative


42 Electro Optics March 2017


with multiple laser beams and digitally reconstructs high- definition images to determine the severity of atherosclerosis and other qualities of the vessel wall.


‘The camera actually


diagnosis, with the exception that the tissue is fresh, has not been processed or stained,’ said Dr Sandra Camelo-Piragua, assistant professor of pathology at the medical school. SRH is based on a technique


developed in 2008. However, back then the lasers available were unsuitable for use in the operating room. The new approach uses a fibre laser- based microscope that can be mounted on a clinical cart and plugged into the wall of any operating theatre. The researchers are now


moving forward by teaching a computer to use SRH to make diagnoses through developing a machine learning process that is able to predict brain tumour subtypes with 90 per cent accuracy in a subset of 30 patient samples. ‘The more we feed the computer, the more accurate its diagnoses will become,’ Orringer said. According to Orringer, SRH


may be able to improve the workflow of small medical facilities that don’t currently have access to expert neuropathologists: ‘Bringing the SRH to smaller hospitals would extend their capabilities because the images can be


“By achieving excellent image quality in fresh tissues, we’re able to make a diagnosis during surgery”


interpreted remotely. Sample preparation is minimal and the SRH could quickly deliver virtual histologic sections to aid diagnosis remotely.’ The next step for the


new technique is a large- scale clinical trial, Orringer commented, with the eventual goal of showing equivalence between SRH and conventional methods for making diagnoses. The current prototype system is intended for research only.


Lasers for endoscopy Elsewhere at the University of Michigan, a laser-based camera has been developed to improve the achievable view of the carotid artery when monitoring atherosclerosis. In Nature Biomedical Engineering, proof-of-concept reports have been given for the new imaging platform, known as the scanning fibre endoscope (SFE). The authors of the paper generated images of human arteries using the SFE, which illuminates tissues


goes inside the vessels,’ said Dr Luis Savastano, a Michigan Medicine resident neurosurgeon. ‘We can see with very high resolution the surface of the vessels and any lesions, such as a ruptured plaque, that could cause a stroke. This technology could possibly find the “smoking gun” lesion in patients with strokes of unknown cause, and may even be able to show which silent, but at-risk, plaques may cause a cardiovascular event in the future.’


The SFE was invented and


developed by co-author and University of Washington mechanical engineering research professor Dr Eric Seibel. The device was originally designed to image cancer cells that are currently invisible with clinical endoscopes in early cancer detection. Instead, the Michigan team used the instrument to acquire high-quality images of possible stroke-causing regions of the carotid artery. According to Seibel, the


applications of the SFE don’t end here: ‘In addition to discovering the cause of the stroke, the endoscope can also assist neurosurgeons with therapeutic interventions by guiding stent placement, releasing drugs and biomaterials and helping with surgeries.’ The SFE can also use fluorescence indicators to show key biological features associated with increased risk of stroke and heart attacks in the future. EO


@electrooptics | www.electrooptics.com


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