High-throughput assessment of biopsy tissue using infrared spectroscopic chemical imaging: Can it be achieved on a clinically acceptable timeframe?

Fourier transform infrared (FTiR) chemical imaging has been demonstrated as a promising technique to construct automated systems to compliment histopathological evaluation of biomedical tissue samples. Current histopathology practice involves preparing thin tissue sections and depositing them onto glass slides. After staining, most commonly haematoxylin and eosin (H&E), a histopathologist visually evaluates the tissue. This is a manual process and can be time consuming in cases where several sections using different stains are required.

Studies have shown that there is variation in the agreement between operators viewing the same tissue [1] suggesting that a complimentary technique for verification could improve the robustness of the evaluation, and improve patient care. FTiR chemical imaging allows the spatial distribution of chemistry to be rapidly imaged at a high (diffraction limited) spatial resolution where a pixel represents an area of 5.5 x 5.5 μm² of tissue. At each pixel there is a full infrared spectrum providing a chemical fingerprint which studies have shown contains the diagnostic potential to discriminate between different cell types, and even the benign or malignant state of prostatic epithelial cells [2-4]. We report a label-free (i.e. no chemical de-waxing, or staining) method of imaging large pieces of prostate tissue (typically 1 cm x 2 cm) in tens of minutes yielding images containing millions of spectra. Spectra are then automatically classified as one of seven cell-types in prostate tissue in a matter of seconds. This can be extended to classify the tissue as cancerous or non-cancerous and even predict the grade of the cancer [5]. Similar methodology has been used to assess breast cancer sample in tissue micro arrays [6].

References

1. Allsbrook WC, et al. interobserver reproducibility of Gleason grading of prostatic car- cinoma: Urologic pathologists. Human Pathology, 2001; 32(1): 74-80.
2. Fernandez DC, et al. infrared spectroscopic imaging for histopathologic recogniti- on. Nature Biotechnology, 2005; 23(4): 469-474.
3. Baker MJ, et al. FTiR-based spectroscopic analysis in the identification of clinically aggressive prostate cancer. British Journal of Cancer, 2008; 99(11): 1859-1866.
4. Gazi E, et al. A correlation of FTiR spectra derived from prostate cancer biopsies with Gleason grade and tumour stage. European Urology, 2006; 50(4): 750-761.
5. Bassan P, et al. Automated high-throughput assessment of prostate biopsy tissue using infrared spectroscopic chemical imaging, Proceedings of SPiE Accepted.
6. Bassan P, et al. The potential use of glass substrates for FTiR chemical imaging of ti-ssue microarrays (TMA), Anal. Chem. 2014; 86(3): 1648-1653.