Quantitative measurement of high intensity focused ultrasound pressure field by optical phase contrast method applying non-continuous phase unwrapping algorithm

Abstract

A fast and accurate ultrasound pressure field measurement is necessary for the progress of ultrasound application in medicine. In general, a hydrophone is used to measure the ultrasound field, which takes a long measurement time and might disturb the ultrasound field. Hence, we proposed a new method categorized in an optical method called Phase Contrast method to overcome the drawback in the hydrophone method. The proposed method makes use of the spatial DC spectrum formed in the focal plane to measure the modulated optical phase induced by ultrasound propagation in water. In this study, we take into account the decreased intensity of the DC spectrum at high ultrasound intensity to increase the measurement accuracy of the modulated optical phase. Then, we apply a non-continuous phase unwrapping algorithm to unwrap the modulated optical phase at high ultrasound intensity. From, the unwrapped result, we evaluate the quantitativeness of the proposed method.

Surface hardness monitoring of cement during curing by high-intensity aerial ultrasonic waves

“…The device consisted of a highintensity aerial ultrasonic sound source, [30][31][32] an LDV, a data logger, and a PC that controls the other instruments. To generate high-pressure [33][34][35] aerial ultrasonic waves, a pointconverged aerial ultrasonic sound source with a stripe-mode vibration plate (driving frequency: 28 kHz) was used. This sound source focused the acoustic waves to a point about 130 mm from the sound source opening.…”

Quantitative measurement of ultrasonic pressure field using combination of optical phase contrast and nonlinear acoustic holography methods

“…This can be a disadvantage of the direct measurement of the entire field including the focal region unless we have a dependable phase unwrapping algorithm. 22) The steps in combination with acoustic holography to avoid the above-described problem were as follows.…”

“…Although optical measurement methods [14][15][16][17][18][19][20][21][22][23][24][25] are fast and have no risk of disturbing the field, such conventional methods are qualitative. [16][17][18] However, they can be improved to be quantitative enough to measure a 3D pressure field by combining them with a computed tomography (CT) algorithm 26) in a very short time.…”

“…Firstly, the nonaxisymmetric 3D pressure field upstream of the focus was measured by an optical phase contrast method 15,20,22,23) and reconstructed by a CT algorithm in this study. Secondly, by using this obtained upstream field as the input to the simulation, the downstream 3D nonaxisymmetric pressure field was numerically simulated.…”

Improved highly accurate localized motion imaging for monitoring high-intensity focused ultrasound therapy

“…Many methods were proposed for US-guided HIFU therapy. [7][8][9] In several studies, HIFU therapy was monitored by conventional B-mode US imaging. 10,11) B-mode imaging is well studied and its images can be obtained in real time.…”