Mueller Polarimetric Imaging in 2017 and Beyond

Schematic of the single mode fibre Mueller polarimeter (Image: Wiley, J. Qi)

Mueller polarimetric imaging has emerged as a promising technique in recent years for tissue imaging, improving image contrast and providing a unique perspective to reveal additional information that cannot be resolved by other optical imaging modalities. But it has its difficulties:  to translate the polarimetric imaging technique from an optical laboratory to the clinic is not an easy task. Clinical interpretation of polarimetric images remains another challenge as well.

But Mueller polarimetric imaging has demonstrated such compelling potential for biomedical applications in recent years that a lot of these challenges were addressed in recent studies, says Ji Qi of Imperial College London in the United Kingdom. “The progress is paving the way to translate this technique into in vivo preclinical trials and for potential adoption into clinical practice for better tissue diagnosis and surgical guidance in the future.” Many ongoing studies in this field are looking at further clinical applications, which can be combined with pathological inspections and statistical analysis to further translate physically meaningful data interpreted from the Mueller matrices into clinically meaningful data.

Interpretation of Mueller matrices can improve the understanding of how the fundamental polarization properties of tissue correlate with pathological features in a consistent and reproducible manner, and form a bridge between polarimetric data and clinically meaningful information. Therefore, a number of image contrast mechanisms besides traditional unpolarized radiation intensity have been obtained from Mueller polarimetric imaging, and have a broad range of applications.

Polarized stereo-endoscope (Image: Wiley, J. Qi)

The latest advances in this field include the investigation of the polarized light tissue interactions, the instrumentation of Mueller polarimeters, the interpretation of Mueller matrices and the development of Mueller polarimetric endoscopes and fibre sensors. Recently polarimetric imaging has been utilized to guide scanning mass spectroscopic analysis of a pathological slide of breast cancer tissue to detect suspicious cancerous regions. Mass spectrometry is able to give quantitative pathological classification but suffers from long acquisition time if used to generate an image. Polarimetric imaging, especially depolarization imaging was demonstrated to be helpful to improve scanning efficiency and significantly shorten the diagnostic tim. Mueller polarimetric spectroscopy – as an extension to polarized light scattering spectroscopy – can not only provide depolarization spectra that are independent of azimuthal angle, but can also probe additional information about tissue diattenuation and retardance for tissue diagnosis

Mueller polarimetric imaging for surgical and diagnostic applications is still in its infancy, and there is no doubt that much research still needs to be done but it is anticipated that Mueller polarimetric imaging can become an accessory imaging modality for surgical imaging in the future. (Source: ICL)

Reference: J. Qi et. Al.: Mueller polarimetric imaging for surgical and diagnostic applications: a review, J. Biophotonics, online 2 May 2017, DOI: 10.1002/jbio.201600152

Link: Institute of Global Health Innovation, Imperial College London, United Kingdom

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