Laser speckle imaging can identify hearts suitable for transplantation

Newswise —

The vast majority of instances of graft failure following heart transplantation can be traced back to anomalies such as significant coronary artery disease. As donors who possess additional qualifications like pre-existing heart conditions and advanced age become candidates for heart transplantation, it has become imperative to meticulously scrutinize them for inherent abnormalities. Invasive coronary angiography plays a pivotal role as a screening instrument that can identify coronary artery disease (CAD), a condition that involves the accumulation of cholesterol deposits in the heart's arteries. Nonetheless, logistic impediments restrict its effectiveness, and it is employed in less than a third of at-risk donors.

To surmount this constraint, a novel technique for heart preservation called "ex situ heart perfusion" (ESHP) has been formulated. ESHP enables physicians to observe the heart's operation and check for any flaws outside of the body by permitting the supply of oxygenated nutrients to the heart through blood vessels. Nonetheless, ESHP's application of coronary angiography has been reported to cause harm to the heart and culminate in primary graft failure. Consequently, alternative methods for imaging the coronary arteries are necessary to detect irregular blood flow in donor hearts and assess their suitability for transplantation.

The Journal of Biomedical Optics (JBO) has documented that a group of researchers headed by Professor Elise Colin of Paris Saclay University in France has introduced a secure and non-intrusive optical method that facilitates the imaging of coronary blood flow in donor hearts during ESHP. The technique employs a recently developed speckle imaging method, called Laser Speckle Orthogonal Contrast Imaging (LSOCI), which was devised to identify the multiple scattering of mobile red blood cells.

The researchers enhanced the imaging ability of LSOCI in this investigation to visualize minor blood vessels in the heart. The suggested approach examines blood flow in the heart utilizing a unique polarimetric filtering technique that can eliminate surface scattering. Consequently, the time-varying speckle patterns employed in the imaging technique are predominantly produced by the multiple scattering of mobile red blood cells inside peripheral vessels.

“The optical technique allows high-resolution imaging of the entire peripheral vasculature of the heart in real time,” says Colin.

To assess this technique, the researchers constructed a clinical model to investigate coronary circulation in donor hearts before transplantation. Subsequently, they utilized a laser and a camera installed on an articulated arm positioned above the perfusion module, which held the donor heart. This equipment generated and examined swiftly varying speckle patterns.

To surmount the difficulties encountered in monitoring the vasculature caused by the heart's beating, the researchers further refined the technique using a process known as Multi-Period-Enhanced Signal-to-Noise Ratio (MPE-SNR). They captured a sequence of images over time to produce a series of frames that portrayed the vasculature at identical heart positions. Subsequently, each image in this sequence was refined using the other images to decrease noise and enhance details. The optimized image illustrated the vasculature at a distinct time point, and the researchers utilized a sequence of such images to visualize vasculatures as small as 100 microns in a few seconds.

The recently developed imaging technique permits accurate visualization of blood circulation. In the future, this method has the potential to identify myocardial perfusion anomalies that signify underlying heart diseases, like coronary artery disease.

Amy Oldenburg, who is a Professor at the University of North Carolina at Chapel Hill and JBO Associate Editor, stated that "the laser speckle-based non-contact technique allows imaging of blood circulation in donor hearts and has significant implications for recognizing hearts that are secure and appropriate for transplantation."

Indeed, these findings hold great promise for making heart transplantation surgeries safer and more successful for patients who require this life-saving procedure. With further research and development, this noninvasive imaging technique could help improve the selection of donor hearts, reduce the risk of graft failure, and ultimately increase the success rates of heart transplantation surgeries.

Here’s hoping that these findings can make heart transplantation surgeries safer and more successful for patients in need of this life-saving procedure.

Read the Gold Open Access article by A. Plyer et al., “Imaging the vasculature of a beating heart by dynamic speckle: the challenge of a quasiperiodic motion,” J. Biomed. Opt. 28(4) 046007 (2023), doi 10.1117/1.JBO.28.4.046007.