Karstrup S, Juul N P
Billeddiagnostisk afdeling, Amtssygehuset Roskilde.
Ugeskr Laeger. 1999 May 17;161(20):2938-43.
Microbubbles of air or other gases are ideally suited as echo-enhancers because of the high difference in acoustic impedance of gas/fluid interfaces. The microbubbles are 1-7 microns in diameter and capable of surviving pulmonary passage to produce enhancement of especially the Doppler signal after intravenous injection. The main clinical role of ultrasound (US)-contrast is to enhance the Doppler signals (up to 20 dB) in inconclusive Doppler examinations. Experience with US-contrast agents comes mainly from use of the galactose based agent Levovist (Schering AG, Germany). The US-contrast agents have further properties: a) Air bubbles in the sound fields will reverberate and return sound with harmonic frequencies. This phenomenon can be used in "harmonic imaging". B) Short intense sound impulses will destroy the bubbles resulting in a mosaic of colours (stimulated acoustic emission). This phenomenon may be used in tumour diagnostics in the liver.
空气或其他气体的微泡因其气体/流体界面的声阻抗差异很大，是理想的回声增强剂。微泡直径为1 - 7微米，能够在肺循环中存活，静脉注射后能特别增强多普勒信号。超声（US）造影剂的主要临床作用是在不确定的多普勒检查中增强多普勒信号（增强可达20分贝）。超声造影剂的经验主要来自基于半乳糖的造影剂Levovist（德国先灵公司）的使用。超声造影剂还有其他特性：a）声场中的气泡会产生回声并以谐波频率返回声音。这种现象可用于“谐波成像”。B）短而强烈的声脉冲会破坏气泡，产生彩色镶嵌图（受激声发射）。这种现象可用于肝脏肿瘤诊断。
