Polarimetric assessment of healthy and radiofrequency ablated porcine myocardial tissue

Abstract

Radiofrequency (RF) ablation offers a potential treatment for cardiac arrhythmia, where properly titrated energy delivered at critical sites can destroy arrhythmogenic foci. The resulting ablation lesion typically consists of a core (coagulative necrosis) surrounded by a rim of mixed viable and non-viable cells. The extent of the RF lesion is difficult to delineate with current imaging techniques. Here, we explore polarization signatures of ten ex-vivo samples from untreated (n = 5) and RF ablated porcine hearts (n = 5), in backscattered geometry through Mueller matrix polarimetry. Significant differences (p < 0.01) in depolarization, ΔT , were observed between the healthy, RF ablated and rim regions. Linear retardance, δ, was significantly lower in the core and rim regions compared to healthy regions (p < 0.05). The results demonstrate a novel application of polarimetry, namely the characterization of RF ablation extent in myocardium, including the visualization of the important lesion rim region. White light photo (top) of porcine myocardium tissue with radiofrequency ablation lesion and corresponding depolarization map (bottom). Depolarization is useful for visualizing the lesion core and rim.

Mueller polarimetric imaging for surgical and diagnostic applications: a review

“…The retardance contrast between healthy and obstructed regions of the bladder would be potentially useful to guide augmentation surgeries and monitoring the tissue functionality following tissue engineering therapies [21]. Mueller polarimetry or polarimetric imaging has furthermore been used to investigate muscles [146], normal and precancerous human cervix [147], oral [13] and lung tissues [148], radiofrequency ablated porcine myocardial tissue [149], skeletal muscle [150], growth of bacteria colonies [151], skin [152][153][154][155] including melanoma [156], animal tissues [144], bladders [137], the orientation of collagen fibres in 3-D space [23], red blood cell suspensions [157], etc.…”

Review of the emerging role of optical polarimetry in characterization of pathological myocardium

“…The minimum number of combinations of S in and S out necessary to calculate the Mueller matrix M of the tissue sample are 16, as discussed in detail in our previous studies. 14,19 3 Polarimetric Characterization of Infarcted Myocardium MI, notorious for its silent lethality, is the major trait of heartrelated deaths globally. 24 MI is typically linked to an occlusion of coronary artery, which propels to ischemia, followed by necrosis of the affected cardiomyocytes, and thereafter buildup of collagenous scar tissue.…”

“…13,14 Importantly, polarimetry has earned a reputation by enabling the visualization of clinically important rim region, characterization of which usually presents a major challenge to the conventional medical imaging tools such as US and CT and other large pool of optical imaging techniques. Specifically, these imaging modalities have only focused to distinguish the RFA lesion core from the surrounding healthy myocardium and have not investigated the sandwiched rim region, despite its potential clinical importance, as the residual viable myocytes in this region might complicate or resist the targeted "electric isolation," resulting in RFA treatment failure.…”

“…To this end, a variety of the prevailing medical imaging techniques such as ultrasound (US), magnetic resonance (MR), and computed tomography (CT) have been explored; however, each of these imaging modalities has its own advantages and limitations, as discussed elsewhere. 13,14 Alternatively optical imaging, including optical polarimetry, represents a powerful tool in the investigation of structural characteristics of myocardial tissues, particularly those bearing structural remodeling such as infarction, stem cell regeneration, and RFA ablation. In particular, cardiac tissue comprises fibrous constituents (e.g., cardiomyocytes and collagen fibers), which are highly anisotropic in nature, a feature of prime significance for optical polarimetry evaluation of cardiac pathology.…”

“…It is worth mentioning that such applications of polarized light are not limited to cardiac tissues, [13][14][15][16][17] rather have been described in the investigation of several other tissue types with various pathology platforms; indicative examples include skin and colon cancers, 18,19 structural disorders of bladder wall, 20 etc. Recently, many studies have investigated polarized light measurements for the characterization of various pathologies pertaining to cardiac tissue, proving the growing interest of the research community for such applications.…”