Using the Acoustic Interference Pattern to Locate the Focus of a High-Intensity Focused Ultrasound (HIFU) Transducer
Journal
Ultrasound in Medicine and Biology
Journal Volume
34
Journal Issue
1
Pages
137-146
Date Issued
2008
Author(s)
Abstract
One of the main problems encountered when using conventional B-mode ultrasound (US) for targeting and monitoring purposes during ablation therapies employing high-intensity focused US (HIFU) is the appearance of strong interference in the obtained diagnostic US images. In this study, instead of avoiding the interference noise, we demonstrate how we used it to locate the focus of the HIFU transducer in both in vitro tissue-mimicking phantoms and an ex vivo tissue block. We found that when the B-mode image plane coincided with the HIFU focal plane, the interference noise was maximally converged and enhanced compared with the off-focus situations. Stronger interference noise was recorded when the angle (α) between the US image plane and the HIFU axis was less than or equal to 90°. By intentionally creating a target (group of bubbles) at the 3.5-MHz HIFU focus (7.1 mm in length and 0.7 mm in diameter), the position of the maximal noise convergence coincided well with the target. The differenced between the predicted focus and the actual one (bubbles) on x and z axes (axes perpendicular to the HIFU central axis, Fig. 1) were both about 0.9 mm. For y axis (HIFU central axis), the precision was within 1.0 mm. For tissue block ablation, the interference noise concentrated at the position of maximal heating of the HIFU-induced lesions. The proposed method can also be used to predict the position of the HIFU focus by using a low intensity output scheme before permanent changes in the target tissue were made. (E-mail: wenshiang@gmail.com). ? 2007 World Federation for Ultrasound in Medicine & Biology.
SDGs
Other Subjects
Acoustic noise measurement; Acoustic wave interference; Medical imaging; Optimization; Tissue; High-Intensity Focused Ultrasound (HIFU); Interference noise; Tissue block ablation; Ultrasonic transducers; accuracy; article; cancer therapy; device; diagnostic imaging; heating; high intensity focused ultrasound; noise; phantom; prediction; priority journal; solid tumor; ultrasound; ultrasound transducer; Acoustics; Animals; Humans; Liver; Muscle, Skeletal; Phantoms, Imaging; Sus scrofa; Transducers; Ultrasonic Therapy; Ultrasonography, Interventional
Type
journal article