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High-frequency Transducer (high-frequency + transducer)
Selected AbstractsEstimation of Coronary Flow Velocity Reserve Using Transthoracic Doppler Echocardiography and Cold Pressor Test Might Be Useful for Detecting of Patients with Variant AnginaECHOCARDIOGRAPHY, Issue 4 2010Hui-Jeong Hwang M.D. Purpose: The cold pressor test (CPT) has been used to detect variant angina, but its sensitivity in predicting vasospasm is low. The aim of this study was to determine whether estimates of the coronary flow velocity reserve (CFVR) in the distal left anterior descending coronary artery (dLAD) using transthoracic echocardiography (TTE) and CPT are useful tool to predict variant angina. Methods: 65 patients (mean age = 52 ± 10 years; male:female = 41:24) who had normal coronary artery on angiography and underwent acetylcholine provocation test were enrolled and divided into the spasm group (n = 31) and the no spasm group (n = 34). During CPT, the peak (PDV) and mean diastolic flow velocity (MDV) of the dLAD were estimated using TTE with a high-frequency transducer, and electrocardiography, blood pressures, heart rate, and symptoms were monitored every 30 seconds. CPT%PDV and CPT%MDV were defined as the percentage changes in PDV and MDV during CPT, respectively. Results: CPT%PDV was 4.99 ± 23.62% in the spasm group and 52.75 ± 24.78% in the no spasm group (P < 0.001). CPT%MDV was 6.83 ± 23.81% in the spasm group and 50.22 ± 27.83% in the no spasm group (P < 0.001). CPT%PDV<31.1% had a sensitivity of 93.5% and a specificity of 82.4% in predicting variant angina (95% confidence interval [CI]: 0.939,0.979, P < 0.001). CPT%MDV<30.55% had a sensitivity of 90% and a specificity of 76.5% in predicting variant angina (95% CI: 0.884,0.950, P < 0.001). Conclusion: The measurement of changes in the coronary flow velocity of the dLAD using TTE and CPT might be useful for the estimation of endothelial dysfunction in patients with variant angina. (ECHOCARDIOGRAPHY 2010;27:435-441) [source] Increasing the vertical resolution of conventional sub-bottom profilers by parametric equalizationGEOPHYSICAL PROSPECTING, Issue 2 2002P. Cobo ABSTRACT Vertical resolution, i.e. the ability to resolve two close reflectors, is a crucial aspect of pulses used in geo-acoustic exploration of sea sub-bottoms. This paper deals with the problem of exploring the shallowest unconsolidated layers of the seafloor with conventional piezo-electric sonar pulses. Such transducers do not have a sufficiently broad transmission response to enable them to radiate short high-resolution pulses. Therefore, some kind of equalization process must be applied to broaden the transmission response. Here, inverse filtering is used to calculate the transducer driving waveform so that the subsequent acoustic pulse has a zero-phase cosine-magnitude nature. Within a specified bandwidth, this pulse has minimum length, i.e. maximum resolution. The method has been applied to compress the acoustic pulses radiated by two piezo-electric transducers. In conventional performance, these transducers radiate narrowband pulses which contain several cycles at the natural resonance frequency. Under equalized driving, both transducers emit broadband pulses, with resolving power greatly increased, at the cost of some amplitude loss. That is, the pulses radiated by both transducers have been shortened from 1 ms (low-frequency transducer) and 0.274 ms (high-frequency transducer) in conventional performance to 0.13 ms and 0.038 ms in equalized mode, with amplitude losses of 33% and 56%, respectively. The great improvement in the resolution of this technique is demonstrated by comparing the synthetic echograms that should be obtained when exploring a wedge model using zero-phase cosine-magnitude pulses with conventional ping pulses. [source] Evaluation of the hepatic artery anastomosis by intraoperative sonography with high-frequency transducer in right-lobe graft living donor liver transplantationJOURNAL OF CLINICAL ULTRASOUND, Issue 1 2010Han Song Mun MD Abstract Objective To describe the usefulness of intraoperative ultrasonography (IOUS) with high-frequency transducer in living donor liver transplantation (LDLT) using right-lobe graft (RLG). Method This retrospective study was approved by our institutional review board. We performed IOUS in 22 patients (17 men and 5 women, aged 51 ± 9.0 years) during LDLT with RLG using a Sequoia 512 scanner with an 8,12-MHz linear transducer. Hepatic artery (HA) anastomosis was identified on gray-scale US, and the diameter and percentage of stenosis of the anastomosis were measured. The HA was evaluated to detect thrombus or dissection in the region of anastomosis. Doppler study of the graft HA was also performed. Patients were divided into those with and without abnormalities, including thrombosis, dissection, and abnormal Doppler parameters (peak systolic velocity < 30 cm/s or > 2 m/s, resistance index < 0.5, and systolic acceleration time > 80 msec). Result On gray-scale and Doppler IOUS study, abnormalities were found in 10 of 22 patients. Diagnoses were anastomotic stenosis (n = 2), celiac stenosis (n = 1), compromise of HA inflow due to systemic hypotension (n = 1), HA thrombosis (n = 2), and HA dissection (n = 4). Re-anastomoses were done in 3 case (2 stenoses and 1 thrombosis). Uneventful postoperative recovery occurred in the other 7 patients without re-anastomosis. Conclusion IOUS with high-frequency transducer is a useful method to make an early diagnosis of HA complications of LDLT with RLG. © 2009 Wiley Periodicals, Inc. J Clin Ultrasound, 2010 [source] Sonographic spectrum of scrotal abnormalities in infertile menJOURNAL OF CLINICAL ULTRASOUND, Issue 8 2007Hussein S. Qublan Abstract Purpose. To use sonography to detect scrotal abnormalities in infertile men. Material and Methods. Two hundred thirty-four infertile men, including 176 oligospermic (sperm count < 10 × 106/ml), 58 azoospermic, and 150 normospermic men (control group) were evaluated prospectively for the presence of intra- and extratesticular abnormalities using high-frequency transducers and color Doppler imaging. Medical and surgical history, testicular volume, semen parameters, and hormonal levels were recorded. Results. A statistically significant increase in the prevalence of abnormal scrotal findings detected with sonography was observed in the study group compared with controls. These included variocele in 35.5% versus 16% (p < 0.01), hydrocele in 16.7% versus 8.7% (p < 0.05), testicular microlithiasis in 9.8% versus 2% (p < 0.01), epididymal enlargement in 9% versus 2.6% (p < 0.05), and epididymal cyst in 7.7% versus 2% (p < 0.05). Testicular tumor was not seen in either group. A statistically significant decrease in testicular volume, sperm concentration, normal morphology, and forward motility of the sperm was noted in the study group compared with controls (p < 0.01). Conclusion. The various intra- and extratesticular abnormalities were demonstrated in infertile men. Sonography should be used routinely in the work-up of male infertility. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2007 [source] Urachal remnants in asymptomatic children: Gray-scale and color Doppler sonographic findingsJOURNAL OF CLINICAL ULTRASOUND, Issue 4 2001Süha Süreyya Özbek MD Abstract Purpose We undertook this study to evaluate the frequency of visualization and the sonographic appearances of urachal remnants (URs) in asymptomatic children. Methods One hundred eighty-two children without any urachus-related symptoms underwent sonography of the prevesical region and urinary bladder with high-frequency transducers. Results A UR was visualized in 180 (99%) of the children. The URs had a mean length ± standard deviation of 13 ± 5 mm. Most of the URs were ovoid, and most demonstrated a moderate protrusion into the bladder cavity. The URs with a central echogenic area were larger than those without central echogenicity. In 36 (61%) of the 59 URs that were evaluated with color Doppler sonography, vascular signals were demonstrated within the lesion. The URs with internal vascular signals were significantly larger than those without internal vascular signals. Conclusions The gray-scale and color Doppler sonographic characteristics of URs seem to be related to their size and their degree of involution rather than to the age of the child. We think that URs are present in almost all children. URs should be considered normal findings if they are asymptomatic and their length is not significantly greater than 22.5 mm, the 95th percentile in our study. © 2001 John Wiley & Sons, Inc. J Clin Ultrasound 29:218,222, 2001. [source] | ||||||||||