Dynamic Chemical Imaging: A New Tool

Dr Om P. Yadava, CEO and chief cardiac surgeon of the National Heart Institute in New Delhi, India, and Dr Jai Raman of the Austin Hospital and St. Vincent’s Hospital in Melbourne, Australia, discuss dynamic chemical imaging (DCI). Simply put, DCI involves light beams, reading the chemical signatures of the tissues from the reflected light, and then using computational techniques to convert this data into an image, which correlates with histopathology - a kind of digital histopathology (1). This is like ‘replicating histopathology at the end of the probe.’ Unlike conventional histopathology, which is time consuming, DCI can be performed within 90 seconds, with the additional advantage of being automated, and therefore the variability of pathologist interpretation gets eliminated. Secondly, combining infrared and Dr Raman’s spectroscopy, one can look at small metabolites like lactate, pyruvate, free fatty acids, glucose, and simple proteins, and get diagnoses regarding myocardial infarction and viability in quick time.

Dr Yadava asks if this can be called functional imaging and and if it would challenge fluoro deoxy glucose (FDG) position emission tomography (PET) and other similar metabolism-based investigations. Dr Raman vociferously retorts an affirmation. He feels, going forward, it will be used intraoperatively and with miniaturization, and it has the potential to be made a catheter-based technique. Talking of specific applications, it can be used for monitoring rejection (2) instead of endomyocardial biopsy, or in mapping for electrophysiology studies, as varied an application as through a bronchoscope to look at the edges of the tumor. With further experience and evaluation, it may even be used for prognostication. Fibrosis is the low-lying fruit in this arena which they are trying to profile and study. Looking at efficacy, especially in detection of rejection after heart transplant, it has been validated against myocardial biopsy, and both sensitivity and specificity were more than 90%. Though at present it is not FDA approved, and thus not available for clinical use, Dr Raman is confident that in the future, it will be a cost-effective ubiquitous technology challenging histopathology.

References

1. Tiwari S, Raman J, Reddy V, Ghetler A, Tella RP, Han Y, et al. Towards translation of discrete Frequency infrared spectroscopic imaging for rapid digital histopathology of clinical biopsy samples. Anal Chem. 2016;88(20):10183-10190. PMID:27626947.
2. Tiwari S, Reddy VB, Bhargava R, Raman J. Computational chemical imaging for cardiovascular pathology: chemical microscopic imaging accurately determines cardiac transplant rejection. PLoS One. 2015;10(5):e0125183.

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