Challenges and implementation of radiation-force imaging with an intracardiac ultrasound transducer

Abstract

Intracardiac echocardiography (ICE) has been demonstrated to be an effective imaging modality for the guidance of several cardiac procedures, including radiofrequency ablation (RFA). However, assessing lesion size during the ablation with conventional ultrasound has been limited, as the associated changes within the B-mode images often are subtle. Acoustic radiation force impulse (ARFI) imaging is a promising modality to monitor RFAs as it is capable of visualizing variations in local stiffnesses within the myocardium. We demonstrate ARFI imaging with an intracardiac probe that creates higher quality images of the developing lesion. We evaluated the performance of an ICE probe with ARFI imaging in monitoring RFAs. The intracardiac probe was used to create high contrast, high resolution ARFI images of a tissue-mimicking phantom containing stiffer spherical inclusions. The probe also was used to examine an excised segment of an ovine right ventricle with a RFA-created surface lesion. Although the lesion was not visible in conventional B-mode images, the ARFI images were able to show the boundaries between the lesion and the surrounding tissue. ARFI imaging with an intracardiac probe then was used to monitor cardiac ablations in vivo. RFAs were performed within the right atrium of an ovine heart, and B-mode and ARFI imaging with the intracardiac probe was used to monitor the developing lesions. 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.

Quantitative evaluation of atrial radio frequency ablation using intracardiac shear‐wave elastography

“…It was shown in vivo that the stiffening of a thermally ablated tissue is linked to the applied thermal dose 28 and thus, to its viability. Acoustic radiation force imaging (ARFI), an ultrasound technique that provides images of relative tissue elasticity, 27,29 was recently shown capable to visualize intracardiac thermal lesions in canines in vivo. 30 However, ARFI required acquisition of several ECG-gated heart beats which may not be feasible in arrhythmic situations such as in AF.…”

Contrast in Intracardiac Acoustic Radiation Force Impulse Images of Radiofrequency Ablation Lesions

“…12 Intracardiac echocardiography (ICE), or catheter-based B-mode imaging, is frequently used to visualize the cardiac anatomy and ablation electrode–tissue contact in real time, but the acoustic contrast between ablated and unablated tissue is insufficient for lesion characterization. 13–19 …”

Ultrasound attenuation estimation using backscattered echoes from multiple sources

“…However, ultrasound has also been used for removing tissue in a controlled manner ͑Parsons et Xu et al, 2005;Xu et al, 2004͒, gene transfection ͑Christiansen et al, 2003Duvshani-Eshet and Machluf, 2005;Feril et al, 2005;Frenkel et al, 2002;Liang et al, 2004;Manome et al, 2005;Ogawa et al, 2002;Wei et al, 2004;Zarnitsyn andPrausnitz, 2004͒, localized drug delivery ͑Shortencarier et al, 2004;van Wamel et al, 2004͒, and the acceleration of thrombolysis ͑Everbach and Francis, 2000͒. In tissue characterization, backscattered ultrasound echoes have been used to estimate the characteristic scatterer correlation length for tissue microstructure ͑Insana and Lizzi et al, 1997;Lizzi et al, 1983;Oelze et al, 2004;Oelze and Zachary, 2006͒ as well as to estimate tissue displacement/stiffness after using acoustic radiation force ͑ARFI͒ to push the tissue ͑Fahey et Fahey et al, 2004;Hsu et al, 2007;Nightingale et al, 2002͒. In all of these applications, an accurate estimate of attenuation along the propagation path could improve the clinical utility of the technique. For the therapy applications, knowing the attenuation would improve therapy planning by allowing for an estimate of ultrasound fields at the sight of the therapy prior to initializing the therapy.…”