Non-invasive thermal imaging detects cardiac remodeling in mice

Rafael Brzezinski ¹ Zehava Ovadia-Blechman ² Nir Lewis ¹ Neta Rabin ² Yair Zimmer ² Lapaz Levin-Kotler ¹ Olga Tepper-Shaihov ¹ Nili Naftali-Shani ¹ Olga Tsoref ¹ Ehud Grossman ¹ Jonathan Leor ¹ Oshrit Hoffer ²

¹Neufeld Cardiac Research Institute, Sackler Faculty of Medicine; Tamman Cardiovascular Research Institute at Sheba Medical Center, Tel Aviv University, Israel
²School of Medical Engineering and School of Electrical Engineering, Afeka Tel Aviv Academic College of Engineering, Israel

Objective: Thermal infrared imaging has been suggested as a non-invasive alternative to monitor physiological processes and diseases. However, the use of this technique to image internal organs, such as the heart, has not yet been investigated. We sought to determine the ability of our novel thermal image-processing algorithm to detect structural and functional changes in a mouse model of hypertension and cardiac remodeling.

Methods: Twelve mice were randomly assigned to receive either the pro-inflammatory, hypertensive hormone angiotensin-II (2 mg/kg/day, n=6) or saline (n=6) infusion for 28 days. We performed weekly blood pressure measurements, together with serial trans-thoracic echocardiography studies and histopathological evaluation of the hearts. Thermal images were captured with the commercially available FLIR-One camera, and images were processed by our novel algorithm.

Results: Angiotensin-infusion increased blood pressure together with cardiac hypertrophy and fibrosis. Thermal imaging at day 28 detected an increase in the fraction of the skin heated by the heart in angiotensin-treated mice. Thermal image findings were significantly correlated to left ventricular volume and mass parameters seen on echocardiography (r=0.8, p< 0.01 and r= 0.6, p=0.07). Unlike control hearts, all angiotensin-treated hearts displayed a triangle-like shape of heat distribution, reflecting remodeling processes in the hypertensive heart. A machine learning-based model using thermal imaging parameters predicted intervention status in 10 out of 11 mice similarly to a model using echocardiographic measurements.

Conclusion: Our findings suggest, for the first time, that a thermal camera using a new image-processing algorithm, successfully identified cardiac structural changes in mice with hypertensive heart disease.