An improved method to estimate ultrasonic absorption in agar-based gel phantom using thermocouples and MR thermometry
An improved method to estimate ultrasonic absorption in agar-based gel phantom using thermocouples and MR thermometry
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DOI：
10.1016/j.ultras.2020.106089
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发表时间：
2020-04-01
期刊：
影响因子：
4.2
通讯作者：
Damianou, C.
中科院分区：
文献类型：
--
作者：
Drakos, T.;Giannakou, M.;Damianou, C.
在本文中，开发了一种新的实验装置，测量吸收系数。在琼脂基凝胶体模中评价了拟定系统。新的实验系统可以准确、快速地测量体模内的温度变化率。使用热电偶测量温度变化率，并使用MR测温法进行确认。为了减少传导效应，使用了具有宽波束的超声换能器。使用4%琼脂、30%淡牛奶和4%二氧化硅时，琼脂基体模的吸收系数为0.26 dB/cm-MHz。吸收系数随淡炼乳和琼脂体积的增加而增加。吸收系数在低二氧化硅浓度（< 4%）时增大，在高二氧化硅浓度（> 4%）时减小。通过适当选择淡炼乳、琼脂和二氧化硅浓度，可以实现与软组织相似的系数。声吸收测量被认为是超声学中的困难测量，因为获得焦点中的精确温度变化具有挑战性。由于热电偶在超声波束处的快速准确放置，因此所提出的系统可以在不到一分钟的时间内进行吸收测量。
In this paper, a novel experimental set-up was developed that measures the absorption coefficient. The proposed system was evaluated in an agar-based gel phantom. The new experimental system provides accurate and fast measurement of the rate of temperature change within the phantom. The rate of temperature change was measured using thermocouple and was confirmed using MR thermometry. An ultrasonic transducer with a broad beam was used in order to reduce the conduction effect. The absorption coefficient of the agar-based phantom was 0.26 dB/cm-MHz using 4% agar, 30% evaporated milk and 4% silica. The absorption coefficient increased by increasing the volume of the evaporated milk, and agar. The absorption coefficient increased at low silica concentration (< 4%) and then decreased at higher concentration of silica (> 4%). By proper selection of evaporated milk, agar and silica concentration, it is possible to achieve similar coefficient like in soft tissues. Acoustic absorption measurement is considered as a difficult measurement in ultrasonics because obtaining the precise temperature change in the focus is challenging. Due to the quick and accurate placement of the thermocouple at the ultrasonic beam, it is possible with the proposed system to perform absorption measurement is less than one minute.