Multi-frequency Transducer Research Articles

Detection and Characterization of Endoleaks Following Endovascular Treatment of Abdominal Aortic Aneurysms using Contrast Harmonic Imaging (CHI) with Quantitative Perfusion Analysis (TIC) Compared to CT Angiography (CTA)

To show the feasibility of the detection of endoleaks following endovascular treatment of aortic aneurysms using contrast harmonic imaging (CHI) in comparison to computed tomography angiography (CTA). 51 patients with suspected endoleaks, who underwent previous endovascular treatment for abdominal aortic aneurysm, were examined using CTA and vascular ultrasound. Biphasic CTA in all cases and digital subtraction angiography (DSA) in 8 patients were evaluated by two radiologists in consensus and served as the standard of reference. Ultrasound was performed by an experienced examiner with a multi-frequency linear transducer (2 - 4 MHz) using CHI following bolus injection of 2.4 ml of SonoVue® IV (maximum 5 ml). All images were evaluated by two observers in consensus regarding the reperfusion of the abdominal aneurysm using time intensity curve (TIC) analysis. In 30 of 51 patients, endoleaks were detected concordantly in CHI and CTA. In 20 of 51 patients, no endoleak was found in CHI and CTA/DSA. In one patient, a type II endoleak could initially only be detected in CHI and was later confirmed in follow-up examinations by CTA (sens. 99%, spec. 93%, NPV 99 %, PPV 95%). TIC analysis allowed evaluation of the perfusion dynamics of endoleaks in all patients. Significant differences were found (p < 0.05, Mann Whitney U Test) regarding the perfusion within the aneurysm when an endoleak was present (10.39 ± 4.29 dB) or not present (6.42 ± 2.86 dB). CHI with perfusion analysis allows definite detection of endoleaks, especially if contraindications for CTA are present. CHI presents an alternative for follow-up monitoring.

Triplex Doppler da artéria renal e a relação entre a ecobiometria dos rins com distância atlanto-coccígea e altura em Canis familiaris

O objetivo do trabalho foi estabelecer a relação entre a ecobiometria renal com medidas de conformação corporal como a distância atlanto-coccígea (DAC) e a altura (H) de cães adultos saudáveis, obtendo-se parâmetros de normalidade para avaliar o tamanho e volume renal, bem como estabelecer valores de referência para avaliar a perfusão sanguínea dos rins por meio do índice de resistividade (IR) e do índice de pulsatilidade (IP) do ramo principal da artéria renal. No estudo foram utilizados 22 cães adultos sem raça definida, sendo 11 machos e 11 fêmeas. Os animais foram previamente aferidos quanto a DAC e a H. Os exames ultra-sonográficos foram realizados com um aparelho HDI 4000 PHILIPS munido de um transdutor microconvexo multifreqüêncial (5-8 MHz), dispositivos Doppler Colorido e Doppler de Fluxo. Os animais foram posicionados em decúbito lateral direito ou esquerdo, de acordo com o rim a ser avaliado. Os diâmetros longitudinal (DL) e dorsoventral (DDV) dos rins foram mensurados na secção longitudinal e, o diâmetro transversal (DT) foi aferido no plano transversal. O volume (V) foi calculado automaticamente pelo software do ultra-som. Com o uso do Triplex Doppler, o IR e o IP das artérias renais direita e esquerda foram obtidos. Todos os dados foram apresentados em média ± EPM. Análises de regressão linear foram realizadas tendo o DL, DDV, DT e V como variáveis dependentes e a DAC e H como variáveis independentes. Os IR e IP dos rins direito e esquerdo foram comparados pelo teste t de Student. A DAC variou de 54-78cm para machos e 37-71cm para fêmeas e a altura variou entre 34-64 cm para os machos e 24-57cm para as fêmeas. As médias obtidas para DL, DDV, DT e V dos rins esquerdo e direito foram: 5,24±0,27cm, 3,07±0,15cm, 3,07±0,9cm, 28,01±3,4mL e 4,50±0,19cm, 2,88±0,14cm, 2,71±0,15cm, 21,27±2,6mL, respectivamente. As análises de regressão linear entre as medidas lineares e volume renal com a DAC e a H foram significativas para os interceptos e coeficientes de regressão (P&lt;0,01). Houve diferenças estatísticas quando comparado os IR e IP entre os rins direito e esquerdo (P=0,001), sendo que as médias para IR e IP dos rins esquerdo e direito foram 0,62±0,08; 1,34±0,18 e 0,70±0,06; 1,62±0,13; respectivamente. Os dados obtidos no presente trabalho podem auxiliar na avaliação do tamanho, volume e perfusão dos rins de cães adultos.

Central aponeurosis tears of the rectus femoris: practical sonographic prognosis

Objective:This study is a statistical analysis to establish whether a correlation exists between the level and degree of rectus femoris (RF) central tendon injury and the amount of time that...

Multi-frequency transmission/reception apparatus

The invention provides a multi-frequency transducer capable of obtaining desired directivity regardless of frequencies. Parallelepiped-shaped transducer elements ( 1 ) are used as transducer elements and a plurality of such transducer elements ( 1 ) are arranged in an array. The transducer elements ( 1 ) are caused to resonate using a resonant frequency in fundamental vibration mode and a resonant frequency in harmonic vibration mode determined by the dimensions (A, B) of a short edge ( 1 a ) and a long edge ( 1 b ) perpendicular to a longitudinal edge ( 1 c ) of each transducer element ( 1 ) to transmit and receive at multiple frequencies. The angle of directivity (θ) of the transducer elements is controlled by the dimension (C) of the longitudinal edge which is set to a value which does not affect resonance in either the fundamental vibration mode or the harmonic vibration mode.

Contrast-enhanced ultrasound versus MS-CT in blunt abdominal trauma

To evaluate the effectiveness of contrast-enhanced ultrasound (CEUS) in the diagnosis and characterization of hepatic, renal and splenic traumatic injuries versus conventional ultrasound (US) and multislice computed tomography (MS-CT). Between January 2005 and January 2007, 78 patients (48 males, 30 females, mean age 56 years) with blunt abdominal trauma were examined by conventional US, CEUS and MS-CT. CEUS employed a low-MI technique using 1.2 to 2.4 ml of SonoVue (Bracco, Italy) i.v. and a multifrequency transducer (2-4 MHz, Siemens, Sequoia, Acuson). CT examinations were performed on a 64 detector CT scanner (Somatom Sensation 16 or 64, Siemens Medical Systems, Forchheim, Germany) before and after administration of 120 ml intravenous contrast agent (Solutrast, Bracco, Milan, Italy) followed by 50 ml saline. The presence of hepatic, renal and splenic injuries was analyzed and the conspicuousness of findings was assessed. In 15 of the 78 patients conventional US identified solid organ injuries: 8 hepatic, 2 renal and 5 splenic injuries. CEUS identified 3 more injuries (2 hepatic and 1 splenic) that had been missed by conventional US. CEUS identified traumatic lesions in 18/78 patients. In one of the 18 patients even active bleeding could be identified by CEUS. In CEUS solid organ injuries appeared hypoechoic. MS-CT identified 18 solid organ injuries in 78 patients, corroborating the CEUS results.CEUS greatly improves the visualization and characterization of hepatic, renal and splenic injuries compared to conventional ultrasound and correlates well with MS-CT. The imaging technique detects even minor blood flow and is able to depict vascular structures in detail. At our institution it is used as an additional examination technique which supplements MS-CT in unclear cases. Owing to its bedside availability, CEUS provides a good alternative to MS-CT, especially in patients with contraindications to CT contrast agents (e.g. due to renal failure or severe allergy) and in hemodynamically compromised patients.

Evaluation of microcirculation of free flaps of the lower leg by contrast harmonic imaging (CHI) with time intensity curve (TIC) analysis

The aim of the prospective study was to evaluate the macro- and microcirculation in the center and periphery of free flaps with high resolution vascular ultrasound. Fifteen patients with free parascapular flaps after lower limb trauma were examined six months postoperative. All ultrasound investigations were performed by one experienced examiner with a multi-frequency linear transducer (5-9 MHz, Logiq 9, GE). Flow evaluation was angle-optimized using digital image technology with the color coded Doppler sonography (CCDS) with measurement of the peak systolic, peak diastolic flow velocities and the resistance index (RI). Contrast harmonic imaging (CHI) with time intensity curve (TIC) analysis was used for quantitative evaluation of the tissue perfusion. Through a peripheral cubital cannula, a first bolus injection was made of 2.4 ml Sonovue to evaluate the perfusion near the flap center and the distal part of the flap. The combined analysis of all 15 patients showed in the center and in the periphery of the flap a significant increase (p<0.01; Wilcoxon signed rank test) of the perfusion (relative units = RUs) in the period of 90-120 s after contrast medium application (center: baseline perfusion 2.23+/-0.31 RUs to 5.25+/-0.90 RUs after contrast medium; periphery: baseline perfusion 3.07+/-0.44 RUs to 5.80+/-0.57 RUs after contrast medium). The separate analysis of the non-bypass group (n=9) and bypass group (n=6) showed a clearly higher central flap perfusion after contrast medium application for the bypass group. The combined analysis of all patients showed RI-values amounting to 0.79+/-0.03. The RI-values of the bypass group were significantly higher than RI-values of the non-bypass group (p<0.05; t-test; p<0.05; Mann-Whitney rank sum test). The high-resolution ultrasound represents an ideal method for detection of the flow and patency of the bypass and the small vessels of the free flap. The patency of microvascular anastomosis as well as the perfusion and microcirculation in different flap territories and tissue layers can be investigated using dynamic contrast-enhanced ultrasound with subtraction modalities.

Microcirculation and perfusion with contrast enhanced ultrasound (CEUS) in Crohn's disease: First results with linear contrast harmonic imaging (CHI)

To evaluate a newly introduced high resolution linear transducer for vascularization and mural perfusion assessment using contrast harmonic imaging (CHI) with quantitative time intensity curve analysis (TIC) in patients with active Crohn's disease (CD). We prospectively evaluated 14 consecutive patients (7 women, 7 males, age range 19-42 years, median 28 years) with histologically proven CD having an acute episode of the disease applying contrast enhanced MRI and high resolution ultrasound. For the ultrasound we used a newly introduced high resolution linear multi-frequency transducer (6-9 MHz, Logiq 9, GE). Ultrasound was performed by an experienced radiologist applying color coded Doppler sonography (CCDS), power Doppler (PD) and contrast enhanced CHI using the 'true agent detection mode'. Additionally, 5 healthy volunteers were examined by ultrasound applying CCDS, PD and CHI. After the injection of 2.4 ml ultrasound contrast agent (SonoVue) the dynamic CHI cine sequences were recorded as digital raw data for 60 seconds. Therefore we were able to perform a quantitative perfusion analysis using TIC retrospectively. CCDS, PD and CHI with TIC were compared and analyzed. In all 14 patients MRI showed inflammatory changes in the terminal or pre-terminal ileum. Using PD and CCDS enlarged vessels surrounding the bowel wall were visualized in all patients. PD as well as CCDS diagnosed just in 9 of 14 patients augmented mural vessels. Having CHI with TIC increased mural contrast enhancement was diagnosed in all 14 patients. Patients with CD showed a maximum enhancement 36 s after injection with 9 dB (range 5.9-13.2 dB), while healthy volunteers reached the maximum level of 2.8 dB (range 2-3.8 dB) after 23 s (p<0.05). Using high resolution linear transducer mural perfusion changes in active Crohn's disease can be appreciated applying CHI with TIC. This technique could be an effective dynamic imaging modality for diagnosis and especially follow-up examination to monitor treatment in CD.

Multislice computed tomography versus contrast-enhanced ultrasound in evaluation of complex cystic renal masses using the Bosniak classification system

To assess the diagnostic performance of multislice computed tomography (MS-CT) in the classification of atypical or complex cystic renal masses using the Bosniak system in comparison to contrast-enhanced ultrasound (CEUS) and, in unclear cases, to the surgery findings.Thirty-two consecutive patients (14 women, 18 men; age range 39-72 years) with 37 atypical or complex cystic renal masses at MS-CT underwent conventional ultrasound (US) and CEUS. CEUS employed a low-MI technique using 1.6-2.4 ml SonoVue (Bracco, Italy) i.v. and a 2-4 MHz multifrequency transducer (Siemens, Sequoia, Acuson). Fourteen masses were resected, the remaining 23 lesions were followed up for periods ranging from 3 months to 2 years. Images and digital cine clips of all lesions were evaluated by blinded readers. On the basis of MS-CT appearance the lesions were assigned to the Bosniak classification. Similar criteria modified for US imaging were used to score atypical cysts at CEUS. In the Bosniak classification at MS-CT the lesions were scored as category II (n=15), IIF (n=7), III (n=8) and IV (n=7). At CEUS, masses were classified as Bosniak classification II (n=8), IIF (n=12), III (n=8) or IV (n=9). All type IV and 6/8 type III and 1/8 type IIF lesions were removed surgically. All category IV and 3/8 category III lesions of the surgical group were malignant, the one type IIF lesion was benign. All class II and IIF cysts except one were stable after a follow-up period ranging from 3 months to 2 years. In 7/37 lesions (19%) the MS-CT and CEUS scores were different, while in 30/37 (81%) they were equivalent. CEUS depicted more thin septa than MS-CT, or upgraded wall thickness, resulting in a Bosniak score upgrade from category II to IIF in 5 lesions. Two cystic renal masses could not be clearly assigned by MS-CT but were considered malignant due to the additional information from CEUS, which was confirmed by surgical removal (small cystic renal cancer).CEUS with SonoVue allows an early evaluation of atypical or complex cystic renal masses. It is an additional examination to MS-CT. Due to the dynamic examination, additional information about perfusion of the cystic septa or cystic renal cancer can be gained.

Evaluation of quantitative contrast harmonic imaging to assess malignancy of liver tumors: A prospective controlled two-center study

To establish the extent to which contrast enhancement with SonoVue in combination with quantitative evaluation of contrast-medium dynamics facilitates the detection of hepatic tumors. One hundred patients with histologically confirmed malignant or benign hepatic tumor (maximum size 5 cm) were analyzed. Contrast-enhanced ultrasound (bolus injection 2.5 mL SonoVue) was carried out with intermittent breath-holding technique using a multifrequency transducer (2.5-4 MHz). Native vascularization was analyzed with power Doppler. The contrast-enhanced dynamic ultrasound investigation was carried out with contrast harmonic imaging in true detection mode during the arterial, portal venous and late phases. Mechanical index was set at 0.15. Perfusion analysis was performed by post-processing of the raw data [time intensity curve (TIC) analysis]. The cut-off of the gray value differences between tumor and normal liver tissue was established using Receiver Operating Characteristic (ROC) analysis 64-line multi-slice computed tomography served as reference method in all cases. Magnetic resonance tomography was used additionally in 19 cases. One hundred patients with 59 malignant (43 colon, 5 breast, 2 endocrine metastases, 7 hepatocellular carcinomas and 2 kidney cancers) and 41 benign (15 hemangiomas, 7 focal nodular hyperplasias, 5 complicated cysts, 2 abscesses and 12 circumscribed fatty changes) tumors were included. The late venous phase proved to be the most sensitive for classification of the tumor type. Fifty-eight of the 59 malignant tumors were classified as true positive, and one as false negative. This resulted in a sensitivity of 98.3%. Of the 41 benign tumors, 37 were classified as true negative and 4 as false negative, which corresponds to a specificity of 90.2%. Altogether, 95.0% of the diagnoses were classified as correct on the basis of the histological classification. No investigator-dependency (P = 0.23) was noted. The results show the possibility of accurate prediction of malignancy of hepatic tumors with a positive prognostic value of 93.5% using advanced contrast-enhanced ultrasound. Contrast enhancement with SonoVue in combination with quantitative evaluation of contrast-medium dynamics is a valuable tool to discriminate hepatic tumors.

Transthoracic Coronary Flow Velocity Reserve Assessment: Comparison Between Adenosine and Dobutamine

We sought to compare coronary flow velocity reserve (CFVR) with adenosine and dobutamine in patients scheduled for noninvasive evaluation of coronary artery disease. Assessment of CFVR in the distal part of the left anterior descending coronary artery (LAD) by Doppler transthoracic echocardiography (TTE) is usually performed with adenosine in various settings. CFVR can also be determined during dobutamine stress echocardiography (DSE), but it has not been established whether TTE CFVR with dobutamine is equivalent to CFVR with adenosine. In all, 47 consecutive stable patients in sinus rhythm (28 men, 64 +/- 12 years, left ventricular ejection fraction 55 +/- 5%) were prospectively studied. Coronary flow velocity was measured in the distal part of the LAD by TTE, at rest and during continuous infusion of 0.14 mg/kg/min of adenosine over 2 minutes, and during DSE performed immediately after the adenosine test, using a multifrequency transducer, on a modified parasternal view. CFVR with adenosine was calculated as hyperemic to basal peak flow velocity. CFVR with DSE was obtained by calculating peak diastolic flow velocity divided by baseline diastolic flow velocity. Adequate recording of CFVR with adenosine and dobutamine was possible in 43 (91%) and 41 (87%) patients, respectively. CFVR was 2.5 +/- 0.7 with adenosine compared with 2.4 +/- 0.7 with dobutamine (P = .7). A good linear correlation was observed between the two tests (r = 0.81, P < .0001). In patients with dobutamine-induced wall-motion abnormalities in the LAD territory (n = 8), CFVR was similar during dobutamine and adenosine infusion (1.6 +/- 0.3 vs 1.5 +/- 0.2, respectively, P = .7). Coronary angiography was available in 12 patients (LAD stenosis: 55 +/- 10% quantitative coronary angiography, with a range from 40%-75%). The correlation between CFVR values was also good in this subgroup of patients (r = 0.87, P < .0001). TTE CFVR with dobutamine is comparable to CFVR with adenosine in patients with a wide range of LAD diseases. Dobutamine could be a good alternative to adenosine for TTE CFVR assessment, particularly in patients with a contraindication to adenosine or scheduled for DSE.

Multifrequency Transducer for Microemboli Classification and Sizing

The classification of circulating microemboli as gaseous or particulate matter is essential to establish the relevance of the detected embolic signals. Until now, Doppler techniques have failed to determine unambiguously the nature of circulating microemboli. Recently, a new approach based on the analysis of radio frequency (RF) signal and using the nonlinear characteristics of gaseous bubbles to classify emboli was investigated. The main limitation of these studies was the requirement of two separate transducers for transmission and reception. This paper presents a multi-frequency transducer with two independent transmitting elements and a separate receiving part with a wide frequency band. The transmitting elements are positioned in a concentric design and cover a frequency band between 100 and 600 kHz. The receiving part consists of a polyvinylidene fluoride layer. The new transducer has been tested in vitro using gaseous emboli. It could correctly classify and size air emboli with diameters ranging from 10 microm to 105 microm.

Evaluation of Left Anterior Descending Coronary Artery Stenosis of Intermediate Severity Using Transthoracic Coronary Flow Reserve and Dobutamine Stress Echocardiography

The physiologic significance of left anterior descending coronary artery (LAD) stenosis of intermediate angiographic severity is of clinical importance and difficult to assess. Assessment of coronary flow reserve (CFR) by Doppler transthoracic echocardiography (TTE) is a new tool and could allow rapid, noninvasive evaluation of stenosis severity in this setting. We sought to evaluate the value of CFR measurement determined by TTE, compared with dobutamine stress echocardiography (DSE), in the setting of LAD stenosis of intermediate angiographic severity. A total of 51 consecutive stable patients in sinus rhythm (33 men; age 65 +/- 12 years; left ventricular ejection fraction 59 +/- 7%) with no previous anterior myocardial infarction and with an angiographic proximal LAD stenosis of intermediate severity (56 +/- 8% quantitative coronary angioplasty) were prospectively studied. Coronary flow velocity was measured in the distal part of the LAD by TTE at rest and during continuous infusion of 0.14 mg/kg/min of adenosine over 2 minutes, using a multifrequency transducer, in the modified parasternal or 3-apical view. CFR was calculated as the ratio of hyperemic to basal mean (mean CFR) and peak (peak CFR) diastolic flow velocity. DSE was performed immediately after the adenosine test to assess ischemia in the LAD territory (percent maximum predicted heart rate = 94 +/- 8). Adequate recording of CFR was possible in 46 patients. Of the 35 patients with a CFR of 2 or more (peak CFR = 2.7 +/- 0.6), DSE was normal in 34. Of the 11 patients with a CFR less than 2 (peak CFR = 1.7 +/- 0.2), 7 had an abnormal response with DSE in the LAD territory. In this range of intermediate stenosis, there was a poor correlation between percent LAD diameter stenosis and CFR. For patients with positive DSE, CFR was 1.6 +/- 0.2 compared with 2.7 +/- 0.6 for patients with normal DSE (P < .05). The sensitivity, specificity, and the positive and negative predictive values of TTE CFR for detecting ischemia on DSE were 88%, 89%, 64%, and 97%, respectively, with an overall agreement of 89% between the two tests. Given its high negative predictive value, noninvasive CFR could be a useful aid in reaching clinical decisions promptly at the bedside in patients with moderately severe lesions of the proximal LAD.

Digitale Ultraschalldiagnostik der Unterschenkelvenenthrombose mit Harmonic Imaging und Cross-Beam-Technik

To evaluate the extent to which Tissue Harmonic Imaging (THI) and spatial averaging (Sono-CT, Cross Beam) facilitate the diagnosis of lower leg venous thrombosis. In 100 cases of lower leg venous thrombosis, the conventional B-scan, THI, and ultrasonic CT technology (Cross Beam) in examinations using a multi-frequency transducer head (9 - 14 MHz, Logiq 9, GE) were compared during follow-up studies using compression sonography over at least 6 weeks. Two independent examiners performed digital image documentation (PACS connection) without modifying the gray level parameters optimized in the B-scan. A thrombosis was considered to be proven sonographically if at least one ultrasonic modality yielded findings reproducible in follow-up checks at a comparable site in accordance with both examiners. Thromboses in the V. tibialis posterior category (97 %) and the fibular category (81 %) were found most often, followed by muscular venous thromboses (48 %). Thromboses in the V. tibialis anterior category were rare (12 %). The procedure comparison showed an advantage for ultrasonic CT technology in terms of the demarcation of thromboses of the deeper veins (sensitivity 98 %), as compared to THI (sensitivity 87 %, specificity 91 %, PPV: 99 %) and the B-scan (sensitivity 81 %). If a high-resolution linear transducer is used, THI and ultrasonic CT-Technology can facilitate the diagnosis of a lower leg venous thrombosis.

Contrast-enhanced ultrasound with Optison in percutaneous thermoablation of liver tumors

To detect vascularization of liver tumors by ultrasound enhanced with Optison and to determine whether increasing necrosis during a percutaneous thermal ablation can be visualized by this method. Twenty-two patients with non-resectable malignant liver tumors (9 patients with HCC, 13 patients with metastases) and a total number of 34 lesions underwent percutaneous radiofrequency thermoablation using a needle applicator perfused with a 0.9 % NaCl solution (Electrotome HiTT 106, Berchtold). The tumor size ranged from 2 to 8 cm with an average size of 3.6 cm. While intermittent energy was supplied during thermoablation, multi-slice CT (Volume-Zoom, Siemens) and ultrasound were obtained. Ultrasound was performed with a multi-frequency transducer (3 - 7 MHz, LOGIQ 700, GE) and 0.5 to 1 ml of Optison as contrast agent. If necessary, the injection of the contrast agent was repeated after about 30 min. The mechanical index (MI) was set low (0.2 - 0.3) to prevent bubble destruction. Ultrasound power Doppler (PD), contrast harmonic imaging (CHI) and coded harmonic angiography (CHA) as subtraction mode of harmonic imaging were applied intermittently. Only 21 of the 34 lesions showed increased intratumoral perfusion when the conventional B-Mode with PD was used. Similar to spiral CT, the tumor vascularization in the early arterial phase was only reliably visible with CHA after application of contrast agent. CHI with PD was best to detect increasing hypoperfusion of the tumors. When the energy supply was continued, hyperechoic border zones became visible around the central hypoechoic defects. The contrast between remaining tumor and surrounding liver tissue improved in CHI for up to 30 min after the bolus injection of contrast medium, considerably facilitating the evaluation of perfusion. Metal artifacts and the limited amount of contrast agent that can be safely administered interfered with monitoring the thermal ablation with spiral-CT. After an administered energy of maximal 100.000 watts, no more tumor vascularization was seen in 28 of 34 cases. Follow-up spiral-CT showed a complete necrosis in these cases. Evaluating perfusion with contrast-enhanced ultrasound may be helpful in monitoring the evolving necrosis during thermoablation of liver tumors. The more reliable assessment of the tumor necrosis enables a more targeted therapy.

Noninvasive quantitative tissue characterization and two-dimensional color-coded map of human atherosclerotic lesions using ultrasound integrated backscatter: Comparison between histology and integrated backscatter images

OBJECTIVES The purpose of the present study was to define clinicopathologically whether integrated backscatter (IB) combined with conventional two-dimensional echo (2DE) can differentiate the tissue characteristics of calcification (CL), fibrosis (FI), lipid pool (LP) with fibrous cap, intimal hyperplasia (IH) and thrombus (TH) and can construct two-dimensional tissue plaque structure in vivo. BACKGROUND It is difficult to characterize the components of plaque using conventional 2DE techniques. METHODS Integrated backscatter values of plaques were measured in the right common carotid and femoral arteries (total 24 segments) both during life and after autopsy in 12 patients (age 68 to 84 years, 10 men and two women). Integrated backscatter values were determined using a 5–12 MHz multifrequency transducer, setting the region of interests (ROIs) (11 × 11 pixels) on the echo tomography of the entire arterial wall (55 ± 10 ROI/segment) and comparing it with histologic features in the autopsied arterial specimens. RESULTS Corrected IB values obtained before death and at autopsy were significantly correlated (r = 0.93, p < 0.01). Corresponding to the histologic features, corrected IB values on the rectangle ROIs obtained during life were divided into five categories: category 1 (TH) 4 < IB ≤ 6; category 2 (media and IH or LP in the intima) 7 < IB ≤ 13; category 3 (FI) 13 < IB ≤ 18, category 4 (mixed lesion) 18 < IB ≤ 27 and category 5 (CL) 28 < IB ≤ 33. In category 2, media and intima were differentiated using conventional 2DE. Under the above procedures, color-coded maps constructed with IB-2DE obtained during life precisely reflected the histologic features of media and intima. CONCLUSIONS Integrated backscatter with 2DE represents a useful noninvasive tool for evaluating the tissue structure of human plaque.

Multifrequency and nonuniformly-spaced arrays: Effects on grating lobe amplitude

A computer simulation study on the effects of multifrequency and aperiodic ultrasonic transducer arrays has shown that both methods improve grating lobe response when compared to a periodic array of the same aperture and element spacing. The multifrequency array produces a better beam pattern than either the aperiodic or combination aperiodic/multifrequency array. Both the aperiodic and multifrequency arrays have a narrower main lobe and higher side lobe response than a periodic array with reduced element spacing and an equal number of elements.

Multifrequency and Nonuniformly-Spaced Arrays: Effects on Grating Lobe Amplitude

A computer simulation study on the effects of multifrequency and aperiodic ultrasonic transducer arrays has shown that both methods improve grating lobe response when compared to a periodic array of the same aperture and element spacing. The multifrequency array produces a better beam pattern than either the aperiodic or combination aperiodic/multifrequency array. Both the aperiodic and multifrequency arrays have a narrower main lobe and higher side lobe response than a periodic array with reduced element spacing and an equal number of elements.

Sonographic pattern of hydrocephalus among the under five children in Sokoto North Western Nigeria

Background: Hydrocephalus among children is an important medical problem in view of its neurological sequelae in the growing child. This situation is compounded by the acute shortage of neurosurgeons in third world countries like Nigeria; hence, the need for its early detection and proper management. Objective: Evaluation of the ultrasound (US) appearances in children under 5 years of age presenting with clinical signs of raised intracranial pressure suggestive of hydrocephalus. Patients and Methods: A retrospective review of transfontanelle US scans done in 64 children (39 boys and 25 girls) attending the Department of Radiology, Usmanu Danfodiyo University Teaching Hospital, Sokoto, Nigeria over a period of 2 years was carried out. The patients had a mean age of 5.0 ± 4.6 months (range: 1–60 months) at the time of their US examination. Some of the clinical indications for US scan included: Congenital hydrocephalus, encephalocele, meningomyelocele, and meningitis. All scans were performed through the anterior fontanelle using SIUI Apogee 800 PLUS scanner with a curvilinear probe using multi-frequency transducer of 2–5 MHz. Results: Fifty-two patients (81.3%) had hydrocephalus of congenital origin. Eleven cases (17.2%) had postmeningitic hydrocephalus while only 1 case (1.6%) was posthemorrhagic. Twenty-five patients (48.0%) of the congenital cases were due to cerebral aqueduct stenosis. Eleven (21.2%) of the congenital cases were from obstruction at the exit foramina of Luschka and Magendie resulting in the communicating type of hydrocephalus. Conclusion: Hydrocephalus is a known cause of neurological morbidity among infants in developing countries. Majority of the cases are congenital in origin and most commonly due to cerebral aqueduct stenosis. Transfontanelle US is cheap, affordable, nonhazardous, and more accessible than other imaging modalities. It should serve as the first-line investigation of infants with suspected hydrocephalus for early detection and monitoring of progression to determine those cases that would require shunt operation.

Technique for ultrasonic inspection of built-up drill bits: Shvartser, A. Ya., and Sokolinskaya, I.G. Automaticheskaya Swarka, 16, No. 3, p. 84 (1963)

In power ultrasonic and underwater acoustic fields, the ultrasonic treatment efficiency of vibration system can be improved significantly when vibration system is driven by the multi-frequency longitudinal transducer, and the performance of vibration system is determined by the multi-frequency characteristics of transducer. In this paper, using electromechanical equivalent circuit method, the multi-frequency characteristics of a longitudinal ultrasonic transducer with a stepped horn are studied for the ultrasonic vibration system optimal design. The expressions of the input impedance and the velocity amplification ratio of the transducer are obtained. The relationships between the electromechanical coupling coefficients, the velocity amplification of the multi-frequency transducer and the excitation position of the piezoelectric stack, the size of the stepped horn are analyzed. Combined with the finite element analysis of the transducer's key performance, the optimal design parameters of the multi-frequency transducer are given. Finally, the electromechanical properties of the multi-frequency transducer are tested experimentally, the theoretical analysis and finite element results are verified well.

An experimental study of the gain of sound focusing lenses: Tartakovskii, B.D. Akusticheski Zhurnal, 9, No. 3, p. 336 (1963)

In power ultrasonic and underwater acoustic fields, the ultrasonic treatment efficiency of vibration system can be improved significantly when vibration system is driven by the multi-frequency longitudinal transducer, and the performance of vibration system is determined by the multi-frequency characteristics of transducer. In this paper, using electromechanical equivalent circuit method, the multi-frequency characteristics of a longitudinal ultrasonic transducer with a stepped horn are studied for the ultrasonic vibration system optimal design. The expressions of the input impedance and the velocity amplification ratio of the transducer are obtained. The relationships between the electromechanical coupling coefficients, the velocity amplification of the multi-frequency transducer and the excitation position of the piezoelectric stack, the size of the stepped horn are analyzed. Combined with the finite element analysis of the transducer's key performance, the optimal design parameters of the multi-frequency transducer are given. Finally, the electromechanical properties of the multi-frequency transducer are tested experimentally, the theoretical analysis and finite element results are verified well.