Hitachi, Ltd., Higashi-Koigakubo, Kokubunji-shi, Tokyo, Japan.
Hitachi, Ltd., Higashi-Koigakubo, Kokubunji-shi, Tokyo, Japan.
Ultrasound Med Biol. 2019 Sep;45(9):2554-2567. doi: 10.1016/j.ultrasmedbio.2019.05.011. Epub 2019 Jun 11.
To evaluate the quantitative accuracy of the measured speed of sound in ultrasound computed tomography for breast imaging, it is necessary to use a phantom with inclusions whose speed of sound is known. Accordingly, a phantom with known-speed-of-sound inclusions (e.g., containing water and saltwater solution) under the control of temperature was developed. In addition, an oil gel was used as the phantom material for mimicking wave refraction from fatty breast tissue to dense breast tissue. The oil gel was generated by adding SEBS (styrene-ethylene/butylene-styrene, 10% w/w) to paraffin oil. The oil gel-based phantom has a cylindrical shape and contains rod-shaped inclusions that can be filled with water or saltwater solution (3.5% w/w sodium chloride in water). When temperature increases, the speed of sound in the water increases, while that in the oil gel decreases; in particular, the speed of sound in the oil gel was higher than that in the water at temperatures <20.6°C, while the speed of sound in the oil gel was lower than that in the water at temperatures >20.6°C. It has been reported that the speed of sound in dense breast tissue is higher than that in water, while that in fatty breast tissue is lower than that in water. Ultrasound is refracted owing to the difference between the speed of sound in the breast tissue and that in the background water. By controlling the temperatures of the oil gel and water, the oil gel-based phantom simulates the refraction of an ultrasound wave from fatty breast tissue to dense breast tissue. For 43 d, the variation ranges of the speed of sound and attenuation in the oil gel in the reconstructed images were 0.7 m/s and 0.03 dB/MHz/cm, respectively. The concentration of the saltwater solution in the polyacrylamide gel-based phantom decreased from 1% (w/w) to 0.48% (w/w) after 24 h, while that in the oil-gel-based phantom was constant. In addition, magnetic resonance imaging of the oil gel-based phantom revealed that NiSO solution was stably contained in the phantom for 42 d. It is therefore concluded that the liquid cannot penetrate the oil gel. This oil gel-based phantom with such high temporal stability is suitable for multicenter distribution and may be used for standardization of data acquisition and image reconstruction across centers.
为了评估超声计算机层析成像中测量的声速的定量准确性，有必要使用具有已知声速的包含体的体模。因此，开发了一种具有已知声速包含体（例如，包含水和盐水溶液）的体模，该体模可以控制温度。此外，还使用油凝胶作为模拟脂肪性乳房组织到致密性乳房组织的波折射的体模材料。油凝胶是通过向石蜡油中添加 SEBS（苯乙烯-乙烯/丁烯-苯乙烯，10%w/w）生成的。油凝胶基体模为圆柱形，包含可填充水或盐水溶液（水中 3.5%w/w 氯化钠）的棒状包含体。当温度升高时，水中的声速增加，而油凝胶中的声速降低；特别是，在温度<20.6°C 时，油凝胶中的声速高于水中的声速，而在温度>20.6°C 时，油凝胶中的声速低于水中的声速。据报道，致密性乳房组织中的声速高于水中的声速，而脂肪性乳房组织中的声速低于水中的声速。由于乳房组织和背景水中的声速不同，超声波会发生折射。通过控制油凝胶和水的温度，油凝胶基体模模拟了从脂肪性乳房组织到致密性乳房组织的超声波折射。在 43 天内，重建图像中油凝胶的声速和衰减的变化范围分别为 0.7 m/s 和 0.03 dB/MHz/cm。聚丙烯酰胺凝胶基体模中的盐水溶液浓度在 24 小时内从 1%（w/w）降至 0.48%（w/w），而油凝胶基体模中的浓度保持不变。此外，油凝胶基体模的磁共振成像显示，NiSO 溶液在 42 天内稳定地包含在体模中。因此，可以得出结论，液体不能渗透到油凝胶中。这种具有如此高时间稳定性的油凝胶基体模适合于多中心分布，并且可以用于中心间的数据采集和图像重建的标准化。
