In vivo acoustic radiation force impulse imaging of cardiac ablations
Radiofrequency ablation (RFA) has been demonstrated to be an effective procedure for the treatment of rapid or irregular heartbeats such as atrial fibrillation. Assessing lesion size and growth with ultrasound has been limited, as the changes within conventional B-mode images often are subtle. Acoustic radiation force impulse (ARFI) imaging is a promising modality to monitor cardiac ablations, as it is capable of imaging variations in local stiffnesses of within the tissue that are associated with the developing lesion. By using an intra-cardiac probe, the transducer can be positioned closer to the ablation site where quality ARFI images of the developing lesions can be made. We describe ARFI imaging with an intra-cardiac probe to monitor cardiac ablations in vivo. Radiofrequency ablations were performed within the heart of a live ovine subject, while B-mode and ARFI imaging with the intra-cardiac probe were used to monitor the developing lesions. Ablations were performed within the right atrium with the intra-cardiac probe monitoring the ablation 1-2 cm away. Although there was little indication of a developing lesion within the B-mode images, the corresponding ARFI images displayed regions around the ablation site that displaced less, suggesting the creation of a lesion. The ARFI images showed a semicircular region of increased stiffness around the ablation site whose maximum displacement decreased from 8.9 ± 2.1 μm before the ablation to 4.6 ± 0.9 μm afterward. © 2005 IEEE.
