![]() ![]() Despite much great progress, MR thermometry is still relatively expensive to maintain and operate. reducing susceptibility in patient breathing motion and inhomogeneity within the tissues. MR thermometry has been developed and improved ever since to enhance its capabilities in real-time thermometry, e.g. It took MR thermometry another decade for this imaging technique to be first introduced for monitoring HIFU and subsequently in FUS. This imaging technique was introduced in the late 1980s, and is now known as MR thermometry. In particular, MRI imaging measures the proton resonance frequency shift, and produces a real-time temperature map of tissue (within a region of interest). Imaging guidance in FUS is extremely important as any form of unwanted and/or extensive tissue damage can be minimised.Įach imaging guidance modality has a different approach in imaging, tracking and guiding FUS. Relying on the hyperthermia effect of HIFU, magnetic resonance imaging (MRI) and ultrasound (US) imaging have been adapted in the past for planning and guiding FUS. One clinical application of HIFU is known as focused ultrasound surgery (FUS), where HIFU is mainly used as a hyperthermia therapy.Īs HIFU delivers high-energy and prolonged ultrasonic pulse into biological tissue within a well-defined focus, the temperature at said focus elevates quickly above hyperthermia threshold in a few seconds. High intensity focused ultrasound (HIFU) is a general term for the application of high-power ultrasonic wave within a well-defined focus. ![]() Further studies will explore the relationship between the physical transducer characteristics and the HIFU-induced shear wave. The results could benefit other imaging techniques in tracking and guiding HIFU focus. The second study explores a non-linear correlation between the (HIFU) numbers of cycles per pulse, and the maximum shear wave displacement.Ĭonclusion: PhS-OCT demonstrates excellent tracking and detection of HIFU-induced shear wave. Results: A linear relationship between acoustic power output and the maximum shear wave displacement was found in the first study. The lowest HIFU acoustic power output for the detection of shear wave was found to be 0.36 W (1.02 MHz, 100 cycles/pulse), or with the number of cycles/pulse as low as 20 (1.02 MHz, 0.98 W acoustic power output). Shear wave was induced on the sample surface by HIFU and was captured in full under PhS-OCT. The transducer was then embedded inside a 1% agar phantom, which was placed under PhS-OCT for observation, under various HIFU power settings (acoustic power, and number of cycles per pulse). ![]() Method: A miniature HIFU transducer (1.02 MHz, 20 mm aperture diameter, 15 mm radius of curvature) was produced in-house, pressure-field mapped, and calibrated. The experiments studied the effect of varying HIFU power on the induction of shear wave, which can be implemented as a new technique to monitor focused ultrasound surgery (FUS). ![]() Purpose: Phase-sensitive optical coherence tomography (PhS-OCT) is proposed, as a new high intensity focused ultrasound (HIFU) imaging guidance to detect and track HIFU focus inside 1% agar samples in this work. ![]()
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