Many complex diseases such as diastolic dysfunction and some types of cardiomyopathy are often characterized by an increased stiffness of heart muscles which can potentially cause heart failure. While changes of heart muscle’s geometry could be detected by various imaging methods, non-invasive measurements of stiffness of the heart muscle are desired to assess such areas of the heart tissues without invasive surgery.
A novel minimally-invasive method of stiffness assessment of heart muscle – optical coherent elastography (OCE) – is based on a combination of applied acoustic radiation force for mechanical excitation of tissue with subsequent phase-sensitive optical coherence tomography (psOCT) measurements of spatio-temporal response of tissue. A minimally invasive probe comprising a small, 2x2 mm size, low-frequency (<5MHz) ultrasound transducer and a clinically approved psOCT imaging fiber was incorporated into a single housing such that psOCT beam and acoustic excitation beam were parallel. Acoustic radiation pressure pulse was applied to initiate tissue displacement and propagation of shear waves that were detected by psOCT. Given the known offset between ultrasound and psOCT beams, the speed of shear waves was measured and shear elastic modulus of the heart tissues can be reconstructed.
The initial results demonstrate that our OCE probe can produce and measure the displacements on the order of several ten nanometers in heart tissue-mimicking phantoms. The results indicate that translate-rotate scanning of OCE probe can simultaneously image the tissue and map its shear elastic modulus.
Andrei B. Karpiouk, Don J. VanderLaan, Kirill Larin, and Stanislav Y. Emelianov, "Optical coherent elastography method for stiffness assessment of heart muscle tissues (Conference Presentation)," Proc. SPIE 10496, Optical Elastography and Tissue Biomechanics V, 104961A (Presented at SPIE BiOS: January 29, 2018; Published: 15 March 2018); https://doi.org/10.1117/12.2295762.5752219183001.
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