Fujishiro S, Mitsumori M, Nishimura Y, Okuno Y, Nagata Y, Hiraoka M, Sano T, Marume T, Takayama N
Department of Radiology, Faculty of Medicine, Kyoto University, Japan.
Int J Hyperthermia. 1998 Sep-Oct;14(5):495-502. doi: 10.3109/02656739809018250.
It is known that there are large temperature elevations in proximity to air bubbles during US (ultrasound) heating. The existence of tiny air bubbles in the target tissue may enhance the temperature elevation in US hyperthermia. To examine this hypothesis, phantom tissue experiments using an US contrast agent consisting of tiny air bubbles surrounded by a 5% (w/v) human albumin shell (Alb) were performed. As a phantom tissue, a 2 cm cube of beef was used. The phantom tissue was heated with or without the US contrast agent by an US hyperthermia device for 3 min. The heating device was operated at 1.5 MHz with the US intensity of 0.9 W/cm2. Physiological saline solution, iodized oil, and ethanol were used for control experiments. The effect of multiple needle punctures to the beef phantom was also examined. The temperature elevation rate (TER) was defined as the ratio of temperature elevation by heating with Alb or control materials to the temperature elevation by US heating alone. The TER of Alb was 1.7, whereas the TERs of the control materials and of the multiple needle punctures were approximately 1. The administration of Alb significantly increased the temperature in US hyperthermia. In addition, the heating efficiency of Alb was compared to the effect of an increase in the US intensity. Phantom tissue was heated at various US intensities. When the US intensity was increased from 0.9 to 1.8 W/cm2, the temperature elevated by approximately 1.7-fold. Thus, the effect of the administration of Alb was almost equivalent to the effect of increase in US power intensities from 0.9 to 1.8 W/cm2 in the present experimental settings. The results suggest that the US contrast agent can be a potential enhancer in US hyperthermia.
众所周知，在超声（US）加热过程中，气泡附近会出现大幅温度升高。目标组织中微小气泡的存在可能会增强超声热疗中的温度升高。为了验证这一假设，进行了模拟组织实验，使用了一种由微小气泡组成、周围包裹着5%（w/v）人白蛋白壳（Alb）的超声造影剂。作为模拟组织，使用了一块2厘米见方的牛肉。通过超声热疗设备对模拟组织进行加热，有或没有超声造影剂，加热3分钟。加热设备以1.5兆赫兹运行，超声强度为0.9瓦/平方厘米。使用生理盐水、碘化油和乙醇进行对照实验。还研究了对牛肉模拟组织进行多次针刺的效果。温度升高率（TER）定义为用Alb或对照材料加热引起的温度升高与仅超声加热引起的温度升高的比值。Alb的TER为1.7，而对照材料和多次针刺的TER约为1。Alb的给药显著提高了超声热疗中的温度。此外，将Alb的加热效率与超声强度增加的效果进行了比较。对模拟组织在不同的超声强度下进行加热。当超声强度从0.9瓦/平方厘米增加到1.8瓦/平方厘米时，温度升高了约1.7倍。因此，在本实验设置中，Alb给药的效果几乎等同于超声功率强度从0.9瓦/平方厘米增加到1.8瓦/平方厘米的效果。结果表明，超声造影剂可能是超声热疗中的一种潜在增强剂。
