Cardiac Multifrequency Time-harmonic Elastography: In Silico Validation and In Vivo Application

Area of Science:

• Cardiovascular Imaging
• Medical Ultrasound
• Biomedical Engineering

Background:

• Myocardial stiffness, particularly diastolic stiffness, is a key indicator of cardiac dysfunction.
• Transthyretin amyloidosis (ATTRwt) is a progressive disease characterized by abnormal myocardial stiffening.
• Accurate, non-invasive methods are needed to assess myocardial stiffness and diagnose conditions like ATTRwt.

Purpose of the Study:

• To introduce and validate an optimized multifrequency cardiac time-harmonic elastography (THE) technique.
• To assess THE's ability to detect abnormal diastolic stiffness using portable drivers and multi-heartbeat acquisitions.
• To investigate THE's diagnostic performance in patients with cardiac wild-type transthyretin amyloidosis (ATTRwt) compared to healthy controls.

Main Methods:

• Cardiac THE was performed using a portable driver inducing continuous vibrations at 60, 70, and 80 Hz.
• Shear wave speed (SWS) maps, a proxy for myocardial stiffness, were acquired over 4 seconds.
• In silico simulations using CT-data-based anatomies validated the technique and optimized parameters. Diagnostic performance was assessed using ROC analysis.

Main Results:

• The study included 10 healthy controls and 11 patients with ATTRwt.
• Cardiac THE accurately detected ATTRwt with an AUC of 1.00 (95% CI: 0.94-1.00).
• In silico SWS estimations showed strong agreement with ground truth (r²=0.94) across various stiffnesses and thicknesses.

Conclusions:

• Cardiac THE accuracy was quantified for the first time in silico and in vivo, including an ATTRwt cohort.
• Multifrequency shear waves from portable drivers, encoded in standard ultrasound, offer rapid, low-cost contrast.
• This technique aids in detecting cardiomyopathies such as amyloidosis by assessing myocardial stiffness.