Mayer I V, Lazarov M P, Utzinger U, Freiburghaus A U, Hess O M
Department of Internal Medicine, University Hospital, Zurich, Switzerland.
Heart Vessels. 1995;10(2):96-105. doi: 10.1007/BF01744500.
Contrast echocardiography with sonicated radiographic contrast agents has been used for the qualitative and quantitative determination of myocardial blood flow. One major problem has been the size of the microbubbles since only bubbles smaller than 8 microns are expected to pass the capillary bed and larger bubbles may obstruct the capillaries and, thus, alter myocardial blood flow. These techniques have been used for several years, but their reliability has not yet been assessed accurately. Five different methods for the production of sonicated radiographic contrast agents (methods 1-3 from the literature, and 4 and 5 from our laboratory; M1-5) were evaluated for their use in quantitative contrast echocardiography. The sonication of non-ionic X-ray contrast media was performed with a standard titanium probe (20 kHz) for methods 1-4, with variation in the sonication time and the number of sonication jets used for each method. In M5, we used bubbles that were produced by the insufflation of oxygen in the X-ray contrast agent; large (> 8 microns) bubbles were destroyed by sonication at 380 kHz (resonance method). Mean bubble size was determined by computerized videomicroscopy. The effect of bubble size on the backscatter of the ultrasonic signal was calculated for each method. Mean bubble size (+/- 1 SD) ranged between 11.5 +/- 4 microns and 16.1 +/- 14 microns for M1-M5. The best values, i.e., the smallest bubbles, were found with M4 (prepressurized contrast medium). Assuming capillary passage for bubbles smaller than 8 microns, only 14%-48% of the bubbles were smaller than 8 microns (M1-M5). The best results with regard to bubble size (< or = 8 microns) were observed with M5 (48% < or = 8 microns). In regard to the influence of bubble size on the backscatter of the ultrasonic signal, 56%-98.5% of the signal was produced by bubbles larger than 15 microns (M1-5) but the best results were obtained with M4. It is concluded that capillary-passage of sonicated microbubbles (< or = 8 microns) can be expected in only 14%-48% of the bubbles for the five different sonication techniques. More than 50% of all microbubbles produced by these techniques are larger than the expected 8 microns. These large bubbles are responsible for the backscatter of the ultrasonic signal in the vast majority of cases. Thus, the sonication of radiographic contrast agents appears to be inappropriate for the production of uniformly small microbubbles and, thus, this method is not suitable for quantitative measurements of coronary blood flow.
使用超声处理的放射性造影剂的对比超声心动图已用于心肌血流的定性和定量测定。一个主要问题是微泡的大小，因为预计只有小于8微米的气泡才能通过毛细血管床，而较大的气泡可能会阻塞毛细血管，从而改变心肌血流。这些技术已经使用了数年，但它们的可靠性尚未得到准确评估。评估了五种不同的生产超声处理放射性造影剂的方法（方法1 - 3来自文献，方法4和5来自我们实验室；M1 - 5）在定量对比超声心动图中的应用。对于方法1 - 4，使用标准钛探头（20 kHz）对非离子型X射线造影剂进行超声处理，每种方法的超声处理时间和超声喷射次数有所不同。在M5中，我们使用通过向X射线造影剂中注入氧气产生的气泡；大于8微米的大气泡通过380 kHz的超声处理（共振法）被破坏。通过计算机视频显微镜测定平均气泡大小。计算每种方法中气泡大小对超声信号背向散射的影响。M1 - M5的平均气泡大小（±1标准差）在11.5±4微米至16.1±14微米之间。发现M4（预加压造影剂）的气泡大小最佳，即最小。假设小于8微米的气泡能通过毛细血管，M1 - M5中只有14% - 至48%的气泡小于8微米。在气泡大小方面（≤8微米），M5观察到最佳结果（48%≤8微米）。关于气泡大小对超声信号背向散射的影响，56% - 98.5%的信号由大于15微米的气泡产生（M1 - 5），但M4获得了最佳结果。结论是，对于这五种不同的超声处理技术，预计只有14% - 48%的超声处理微泡（≤8微米）能够通过毛细血管。这些技术产生的所有微泡中超过50%大于预期的8微米。在绝大多数情况下，这些大气泡是超声信号背向散射的原因。因此，超声处理放射性造影剂似乎不适用于产生均匀的小微泡，因此这种方法不适用于冠状动脉血流的定量测量。
