Abstract
Chemical imaging in the field of vibrational spectroscopy is developing into a promising tool to complement digital histopathology. Applications include screening of biopsy tissue via automated recognition of tissue/cell type and disease state based on the chemical information from the spectrum. For integration into clinical practice, data acquisition needs to be speeded up to implement a rack based system where specimens are rapidly imaged to compete with current visible scanners where 100's of slides can be scanned overnight. Current Fourier transform infrared (FTIR) imaging with focal plane array (FPA) detectors are currently the state-of-the-art instrumentation for infrared absorption chemical imaging, however recent development in broadly tunable lasers in the mid-IR range is considered the most promising potential candidate for next generation microscopes. In this paper we test a prototype quantum cascade laser (QCL) based spectral imaging microscope with a focus on discrete frequency chemical imaging. We demonstrate how a protein chemical image of the amide I band (1655 cm(-1)) of a 2 × 2.4 cm(2) breast tissue microarray (TMA) containing over 200 cores can be measured in 9 min. This result indicates that applications requiring chemical images from a few key wavelengths would be ideally served by laser-based microscopes.
Highlights
During the last decade interest in the eld of digital pathology, that related to cancer diagnosis, has increased enormously
The wide availability of large liquid nitrogen-cooled focal plane array (FPA) detectors in infrared microscopes coupled to rapid scan Fourier transform infrared (FTIR) spectrometers has lead to a dramatic increase in the number of papers published demonstrating the concept of infrared spectral diagnosis
If the full spectrum is not necessary, the data collection process can be revolutionised with the use on non-FTIR, discrete wavelength, non-interferometry based, infrared Quantum Cascade Laser (QCL) microscopy.[10,11,12]. In this communication we show preliminary data from a quantum cascade laser (QCL) microscope system that illustrates the signi cant potential advantages for the chemical imaging tissue microarray (TMA)
Summary
During the last decade interest in the eld of digital pathology, that related to cancer diagnosis, has increased enormously This interest has been fuelled by a combination of drivers including (i) need to reduce the pathologist work load (ii) increase diagnostic accuracy (iii) decrease the time between biopsy and result and (iv) reduce the need for repeat biopsies. A full interferogram dataset for a TMA is typically greater than 100 GB which has already had the mean of co-added scans computed This shows the enormous quantity of data that is collected by the MCT FPA which is a major limitation as data read out to the operating computer is slow forming a major bottleneck in the data acquisition. For the last decade or so, the mainstay of data analysis has been a host of multivariate methods, (largely necessitated by the need for data reduction) but recently a number of papers have been published that indicate it is possible to gain valuable information with just 3856 | Analyst, 2014, 139, 3856–3859
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