Acoustic Radiation Force Impulse imaging for aneurysms

A method for reliable, noninvasive estimation of Abdominal Aortic Aneurysms (AAA) wall mechanics may be a useful clinical tool for rupture prediction. An in vitro AAA model was developed from an excised porcine aorta, with elastase treatment. The AAA model behaviour was analysed using Acoustic Radiation Force Impulse (ARFI) imaging techniques to generate displacements in both aneurysmal and normal aortic tissue. The incremental modulus of the arteries was indicative of early collagen recruitment, typical in aneurysms due to elastin degradation. Opening angle measurement showed a four fold decrease from healthy aorta to AAA model. The mechanical changes that occur during aneurysm formation were found to be detectable using ARFI imaging. An in vivo aorta was imaged to demonstrate the viability of excitation of abdominal aorta using ARFI imaging. B-mode and ARFI images were acquired for one diseased aorta in a female volunteer. Cardiac motion was minimized using ECG-triggered beam sequences, and ARFI images were acquired during diastole. Residual motion was treated with a linear motion filter. Diseased aortic images revealed greater displacement in the intraluminal thrombus than the wall of the aorta.