Underwater measurements

1. Ultrasound wattmeter is based on the Ultrasonic Power principle by Radiation Force Balance Method

①The first of these mechanisms is the basis of biomedical applications of ARF related to assessing viscoelastic properties of biological tissues and fluids, and specifically to elasticity imaging.
The simplified equation for the ARF, F, generated due to absorption and scattering in tissue is given as

f =(−2"αI" )/𝐶  

Where

α is the absorption coefficient

I is the ultrasound intensity, and

c is the longitudinal wave speed in the medium.

②The second of the listed mechanisms is the basis of one of the oldest applications of ARF, proposed by Wood and Loomis in the 1920s to measure total power in ultrasonic beams which later was implemented in radiation balances that were widely used to measure the power output from physiotherapy ultrasound units. Until now, it is the standard method of measuring output power for physiotherapy systems.

③The third mechanism presents generation of ARF in media without attenuation or acoustic wave reflection. Gradients of acoustic properties of medium, such as variations of sound velocity, cause gradients of the energy density in the propagating acoustic wave. As a result, radiation force is generated.

④The fourth mechanism of generation of ARF is related to an actively explored area of manipulation of biological cells and particles in standing ultrasonic wave fields. It has been known since the 19th century that an object in a sound field is affected by a steady-state acoustic radiation force.

[cited from Wikipedia free encyclopedia]

필요성

- 초음파 영상 진단기 및 초음파 치료기 시장의 확대에 따라 초음파 출력 측정의 정확성 증대와 초음파 출력 측정 장비의 현대화가 절실히 요구되고 있음.

- 초음파 출력 측정 장비는 전량 영국과 미국의 전문화 업체 제품을 수입하여 사용하고 있음. 따라서, 국외 제품에 비하여 정밀성이 증대되고 측정 범위가 증대된 제품을 개발하여 공급할 시 국내뿐만아니라 국외 수출 가능성이 높고 한국의 초음파 관련 기술력에 대한 홍보 효과도 가져올 수 있음.

- 국내에 병원에서는 강도 집속 초음파(HIFU) 암 치료기, 초음파 영상 진단기, 저강도 맥동 초음파(LIPUS) 치료기, 초음파 자극기등 여러 종류의 초음파 의료기를 사용하고 있으며 주기적으로 사용하는 초음파의 출력을 검사하도록 요구되고 있음. 초음파 치료기를 사용하는 병원은 초음파 장비에 노출되는 환자의 안전성 확보를 위하여 주기적으로 사용 장비의 출력을 측정하여 치료기와 진단기를 점검해야 함에도 불구하고 측정 분석 장비의 높은 가격, 측정 분석을 위해 필요한 전문적 지식의 부족, 국외 장비의 사용 절차의 까다로움 등으로 현실적으로 실현되고 있지 못한 것이 현실임.

Ultra high resolution ultrasound

Resolution ±0.2 mW

Example of drift in the deviated weight mea- sured from the electrobalance0 due to the buoyancy change of the target, and its compensation by the ap- proximation and extrapolation methods.

[A PRIMARY LEVEL ULTRASONIC POWER MEASUREMENT SYSTEM DEVELOPED AT NATIONAL INSTITUTE OF METROLOGY, THAILAND, Komgrit Jaksukam1 and Sumet Umchid2]

2. Ultrasound wattmeter is based on the Ultrasonic Power principle by Radiation Force Balance Method

The RFB method is based on the (Langevin) acoustic radiation force theory in lossless fluids. The time-averaged ultrasonic power level is related to the time-averaged ultrasonic radiation force linearly by a factor proportional to the speed of sound in the fluid. As most of the medical ultrasound concerns human tissues, the RFB method uses water as the medium of measurement. Based on its working principle, the RFB method can be categorized into two main schemes. They are absorption and reflection schemes. For the RFB system in NMC, we adopt the absorption scheme as it is relatively easier to realize. An absorber or absorbing target is used to absorb the ultrasonic radiation. The gravimetric change in the absorbing target is then reflected by a weighing balance. The fundamental equation for the absorption scheme can be expressed as:

𝑃 = 𝑐𝐹 --------------------------------------------------(1)

where ?? represents the time-averaged ultrasonic power, ?? is the speed of sound in water which is temperature dependent, and ?? is the time-averaged radiation force. ?? can be determined as ?? = ????, where?? = ??????? ? ???????? ? is the difference of the mass readings from the weighing balance when switching on and off of the ultrasonic transducer. ?? is the local gravity which is 9.78056498 ??/??2 in the Acoustic & Vibration Laboratory of NMC where the RFB system is located [cited from "Realization of Medical Ultrasound Power Measurement by Radiation Force Balance Method" Cui Shan ? Chua Hock Ann ? Chan Chee Keong]

3D acoustic measurement system

㈜혜민의 HM-AOMT는 초음파 장비의 성능 평가를 위한 3차원 음장 측정 수조입니다. 4 자유도를 활용한 3D 데이터 획득 및 오실로스코프와 펑션 제너레이터와의 동기화로 인하여 보다 정확한 데이터를 획득 할 수 있습니다. IEC 60601 기준 필수 측정 항목인 Acoustic output table을 확인 할 수 있는 알고리즘을 제공 합니다.