Progress in medical ultrasound exposimetry

Abstract

Biomedical applications of ultrasound have experienced tremendous growth over the past 50 years. Early work in thermal therapy and surgery soon was followed by diagnostic imaging and Doppler. Because patient safety was an important issue from the beginning, the study of methods for measuring exposure levels, and their relationship to possible biological effects, paralleled the growth of the various therapeutic and diagnostic techniques. The diverse conditions of use have presented a range of exposure measurement challenges, and the sensors and techniques used to evaluate ultrasound fields have had to evolve as new or expanded clinical applications have emerged. In this paper some of the more notable of these developments are presented and discussed. Topics covered include devices and techniques, methods of calibration, progress in standardization, and current problem areas, including the effects of nonlinear propagation. Some early methods are described, but emphasis is given to more recent work applicable to present and future uses of ultrasound in medicine and biology.

Membrane fluidity altering and enzyme inactivating in sarcoma 180 cells post the exposure to sonoactivated hematoporphyrin in vitro

“…Our previous investigation indicated that the acoustic power in continuous wave mode could be about 60-70% of the electrical power. Acoustic power measurement for the transducer was determined by the precision ultrasound power meter (Medisonics Ltd., Watford, UK) using radiation pressure technique with ±5% measure veracity [26,27]. So, the output electrical power from the amplifier was 2.0 W/cm 2 , and the acoustic power I SATA was 1.4 ± 0.07 W/cm 2 in this study.…”

Potential mechanism in sonodynamic therapy and focused ultrasound induced apoptosis in sarcoma 180 cells in vitro

“…Our previous investigation indicated that the acoustic power in continuous wave mode could be about 60-70% of the electrical power. Acoustic power delivered from the transducer was measured by Precision Ultrasound Power Meter (Medisonics Ltd, Watford, UK) using radiation force balance technique with ±5% measure veracity [24,25]. Therefore, the output electrical power from the amplifier is 2.0 W/cm 2 , and the acoustic power I SA-TA was 1.4 ± 0.07 W/cm 2 in this study.…”

Acoustic characterization of high intensity focused ultrasound fields: A combined measurement and modeling approach

“…9 If the acoustic field at the point of measurement does not have a uniform planar pressure distribution over the active area of the receiver, then the true acoustic pressure at the focus can be underestimated. This effect is referred to as spatial averaging.…”

“…Although this approach is widely used in medical US, the challenge of directly measuring and modeling HIFU fields is worth revisiting since experimental tools and numerical models may improve over time, and no standard method, such as that for diagnostic US, 8 has yet been agreed upon for HIFU devices. 9 The most common parameter to characterize the acoustic output of a HIFU device is the spatially averaged intensity ͑I SAL ͒. 10 The calculation of I SAL for a given source is achieved through measurement of the acoustic power output of the device and the focal cross-sectional area of the HIFU beam.…”