Fast strain mapping in abdominal aortic aneurysm wall reveals heterogeneous patterns

Area of Science:

• Biomedical Engineering
• Cardiovascular Imaging
• Medical Ultrasound

Background:

• Abdominal aortic aneurysm (AAA) rupture risk is currently assessed using maximum diameter, a criterion with limited predictive ability.
• Monitoring AAA progression and rupture risk is crucial for patient management.
• There is a need for clinically relevant tools to complement existing AAA guidelines.

Purpose of the Study:

• To develop a fast and semi-automatic method for post-processing dynamic clinical ultrasound sequences to enable biomechanical estimations in the AAA wall.
• To map cross-sectional strains on B-mode images for a better understanding of AAA wall mechanics.
• To provide a tool that can complement current AAA monitoring guidelines.

Main Methods:

• Employed the Sparse Demons algorithm to track AAA wall motion across cardiac cycles in 2D ultrasound sequences.
• Utilized radial basis function interpolation and differentiation to map cyclic strains.
• Validated the tracking method against simulated ultrasound data and compared strain calculations with the finite-element method.

Main Results:

• The semi-automatic analysis processed each cardiac cycle in under 1.5 minutes.
• The wall motion tracking achieved a maximum root mean square error of 0.22 mm against simulated data.
• Calculated strains showed excellent agreement with the finite-element method, with mean differences significantly smaller than image resolution.

Conclusions:

• The developed method provides a fast and accurate measurement of cyclic wall strains from clinical ultrasound sequences.
• This technique shows promise as a tool for investigating AAA wall biomechanics.
• Observed strain patterns in patients suggest potential interaction with the spine, warranting further investigation.