The utility of acoustic radiation force impulse (ARFI) imaging for real-time visualization of abdominal malignancies was investigated. Nine patients presenting with suspicious masses in the liver (n = 7) or kidney (n = 2) underwent combined sonography/ARFI imaging. Images were acquired of a total of 12 tumors in the nine patients. In all cases, boundary definition in ARFI images was improved or equivalent to boundary definition in B-mode images. Displacement contrast in ARFI images was superior to echo contrast in B-mode images for each tumor. The mean contrast for suspected hepatocellular carcinomas (HCCs) in B-mode images was 2.9 dB (range: 1.5-4.2) versus 7.5 dB (range: 3.1-11.9) in ARFI images, with all HCCs appearing more compliant than regional cirrhotic liver parenchyma. The mean contrast for metastases in B-mode images was 3.1 dB (range: 1.2-5.2) versus 9.3 dB (range: 5.7-13.9) in ARFI images, with all masses appearing less compliant than regional non-cirrhotic liver parenchyma. ARFI image contrast (10.4 dB) was superior to Bmode contrast (0.9 dB) for a renal mass. To our knowledge, we present the first in vivo images of abdominal malignancies in humans acquired with the ARFI method or any other technique of imaging tissue elasticity.
Previous studies have established the feasibility of monitoring radiofrequency (RF) ablation procedures with acoustic radiation force impulse (ARFI) imaging. However, questions remained regarding the utility of the technique in clinically realistic scenarios and at scanning depths associated with abdominal imaging in adults. We address several of these issues and detail recent progress towards the clinical relevance of the ARFI technique. Results from in vitro bovine tissues and an in vivo ovine model are presented. Additional experiments were conducted with a tissue-mimicking phantom and parallel receive tracking techniques in order to further support the clinical feasibility of the method. Thermal lesions created during RF ablation are visualized with high contrast in both in vitro and in vivo hepatic tissues, and radial lesion growth can be monitored throughout the duration of the procedure. ARFI imaging is implemented on a diagnostic ultrasonic scanner, and thus may be a convenient option to guide RF ablation procedures, particularly when electrode insertion is also performed with sonographic guidance.
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