Purpose: High-intensity transient signals (HITS) are commonly detected during cardiopulmonary bypass (CPB) . However, the clinical significance of HITS during CPB is still controversial. Micro-bubbles are reported to produce HITS of more than 400-500 Hz. We attempted to elucidate the incidence of HITS exceeding 400 Hz during CPB. Methods: The subjects were 6 patients who underwent open heart surgery using CPB. HITS were detected by TC2020, PIONEER (Nicolet /EME) with a 2.0-MHz pulsed Doppler probe at the middle cerebral artery. Transesophageal echocardiography (TEE) was undertaken during the operation. Results: The total number of HITS during CPB was 1707±1392 (n=6) . Of the total HITS, 88.1±6.8% had a frequency of more than 400 Hz. On the other hand, HITS of less than 400 Hz were frequently detected at aortic cannulation, aortic decannulation and aortic cross-clamping. HITS of more than 400 Hz were detected in cases showing cardiac or aortic micro-bubbles in TEE. Conclusion: The present findings suggest that the majority of HITS during CPB reflect micro-bubbles, and that aortic manipulation may be related to the formation of solid micro-emboli. HITS frequency analysis may be useful for differentiating between micro-bubbles and solid micro-emboli formed during CPB.
The purpose of this paper is to present our experiences using transcranial Doppler ultrasonography (TCD) in patients with pre and post ventriculoperitoneal (VP) shunt for hydrocephalus and burr hole operations in chronic subdural hematoma. By using Sonolayer α SSA-260A, Toshiba medical corporation, Japan, we performed TCD at pre operation and one week after operation in 14 patients since Feb. 1997 to Jan. 1998. There were four cases with idiopathic normal pressure hydrocephalus (NPH), NPH after subarachnoid hemorrhage (3), congenital hydrocephalus (3), NPH after traumatic brain injury (1), and chronic subdural hematoma (3) . We did TCD in all patients and evaluated the changes in mean flow velocity (MV), pulsatility index (PI), and their concurrent clinical corses. Result: The MV at pre operation was 40.1 ± 15.0 cm/s (mean±SEM), and 45.7±18.4cm/s at post operation. No significant change in MV was found between pre and post operation. (P=0.17) . The PI at preoperation was 1.09±0.05 and 1.09±0.07 at postoperation. No significant change in PI was found between pre and postoperation. (P = 0.99) . Many of cases got clinical improvement with increase in MV and decrease in PI, but some of cases have discrepancy between the TCD findings and their clinical improvement. These cases had parmanent focal brain injury in the computed tomography. TCD examinations in pre and post VP shunt or burr hole procedure are useful.
We examined the availability of B-mode ultrasonography (B-mode) for two patients who were followed up after stenting of the carotid artery, in comparison with angiography and 3D-CT angiography (3D-CTA) . The first patient was a 60-year-old man who had suffered an episode of cerebral ischemia, and the second was a 74-year-old man who had had several episodes of unconsciousness. On admission, about 75-80% focal stenosis of the carotid artery was demonstrated in both patients by angiography, 3D-CTA and B-mode ultrasonography. Stenting of the stenosed portion was done successfully in both cases. Postoperative examination (angiography, 3D-CTA and B-mode) revealed no occurrence of restenosis. B-mode appeared especially useful for revealing details in the stent. We observed a high-echoic layer inside the stent in the first case. We suggest that B-mode is an easy and non-invasive method that is useful for follow-up after stenting in the carotid artery.
It is not widely known that therapeutic ultrasound has been developed for almost as long as diagnostic ultrasound. However, recent progress in ultrasound technology and medical imaging technology has brought therapeutic ultrasound into center stage, since it has excellent therapeutic features. First, ultrasound can penetrate into the body more deeply than other forms of energy, for example microwaves and laser light. Second, its energy can be easily localized into a small region using an acoustic lens or a concave-shaped transducer. Therefore, ultrasound energy makes it possible to treat a small target inside the body without damage to surrounding normal tissue. Furthermore, mechanical, chemical and thermal effects can be chosen by selecting its frequency and intensity. Ultrasound is a promising form of energy with many potential applications in the minimally invasive treatment (MIT) field.