993 resultados para Power Doppler ultrasound


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OBJECTIVES: Ultrasound scan in the mid-trimester of pregnancy is now a routine part of prenatal care in most European countries. The objective of this study was to evaluate the prenatal diagnosis of dysmorphic syndromes by fetal ultrasound examination. METHODS: Data from 20 registries of congenital malformations in 12 European countries were included in the study. RESULTS: There were 2454 cases with congenital heart diseases, 479 of which were recognized syndromes, including 375 chromosomal anomalies and 104 syndromes without chromosomal anomalies. Fifty-one of the 104 were detected prenatally (49.0%). One hundred and ninety-two of 1130 cases with renal anomalies were recognized syndromes, including 128 chromosomal anomalies and 64 syndromes without chromosomal anomalies; 162 of them (84.4%) were diagnosed prenatally, including 109 chromosomal anomalies and 53 non-chromosomal syndromes. Fifty-four of the 250 cases with limb defects were recognized syndromes, including 16 chromosomal syndromes and 38 syndromes without chromosomal anomalies; 21 of these 54 syndromes were diagnosed prenatally (38.9%), including 9 chromosomal syndromes. There were 243 cases of abdominal wall defects including 57 recognizable syndromes, 48 with omphalocele and 9 with gastroschisis; 48 were diagnosed prenatally (84.2%). Twenty-six of the 187 cases with diaphragmatic hernia had recognized syndromes, including 20 chromosomal aberrations and 6 syndromes without chromosomal anomalies. Twenty-two of them (84.6%) were detected prenatally. Sixty-four of 349 cases with intestinal anomalies were recognized syndromes; 24 were diagnosed prenatally (37.5%). There were 553 cases of cleft lip and palate (CL(P)) and 198 of cleft palate (CP) including 74 chromosomal anomalies and 73 recognized non-chromosomal syndromes. Prenatal diagnosis was made in 51 cases of CL(P) (53.7%) and 7 of CP (13.7%). Twenty-two of 188 anencephalic cases were syndromic and all were diagnosed prenatally. Of 290 cases with spina bifida, 18 were recognized syndromes, and of them 17 were diagnosed prenatally. All 11 syndromic encephaloceles were diagnosed prenatally. CONCLUSIONS: Around 50% of the recognized syndromes which are associated with major congenital anomalies (cardiac, renal, intestinal, limb defects, abdominal wall defects and oral clefts) can be detected prenatally by the anomaly scan. However the detection rate varies with the type of syndrome and with the different countries' policies of prenatal screening.

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The information gathered with intravascular ultrasound (IVUS) are of great value in endovascular techniques. The aim of this study was to evaluate the reliability of IVUS when measuring vessel dimensions by comparison with an established reference method. The left carotid artery was exposed in 4 pigs (45-55 kg) and two piezoelectric crystals were sutured on the adventitia in the same cross-sectional plane. The distance between them was measured either by IVUS and by sonomicrometers. The mean distance between the two crystals calculated by the sonomicrometer was 4.7+/-0.4 mm (mean systolic distance was 4.9+/-0.2 mm, mean diastolic distance was 4.6+/-0.1 mm). The mean distance between the two targets calculated by IVUS was 4. 5+/-0.2 mm (mean systolic distance was 4.6+/-0.2 mm and mean diastolic 4.4+/-0.2 mm). Regression analysis of the two series of data shows a R(2)=0.9984. IVUS measurements are an average 5% smaller than sonomicrometer measurements (3.6% up to 8.3%) and the difference is statistically significant ( p <0.05). The underestimation of IVUS measurements will affect the accuracy, and probably the long-term outcome, of endovascular procedures.

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Lector de comics para plataforma iOS para dispositivos iPad.

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BACKGROUND: The superficial femoral vein (SFV) is a well-established alternative conduit for infra-inguinal reconstructivenous hypertension after SFV harvest may however result in significant morbidity. This study reports the efficiency of SFV as conduit for infra-inguinal reconstructions and characterize the anatomic and physiologic changes in harvest limbs and their relationship to the development of venous complications. METHODS: From May 1999 through November 2003, 23 SFV were harvested from 21 patients undergoing infra-inguinal reconstructions. Bypasses were controlled by regular duplex-ultrasound. The venous morbidity was assessed by measurements of leg circumferences, strain-gauge plethysmography and quality of life, investigated by the VEINES-QOL scale. RESULTS: At a mean follow-up of 10.4 months (range 1-56), primary, secondary patency and limb salvage rates of infra-inguinal bypasses using SFV are 71.4%, 76.2% and 85.7% respectively. No patient had major venous claudication. Oedema was significantly present in nine patients. Strain-gauge plethysmography showed outflow obstruction in all patients. The VEINES-QOL assessment showed no limitation in social and domestic activity, moderate complain about leg heaviness despite presence of oedema. CONCLUSION: The SFV harvest is a reliable conduit for infra-inguinal reconstructions and results in moderate venous morbidity in terms of functional consequences and quality of life.

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Background: Few studies have used longitudinal ultrasound measurements to assess the effect of traffic-related air pollution on fetal growth.Objective: We examined the relationship between exposure to nitrogen dioxide (NO2) and aromatic hydrocarbons [benzene, toluene, ethylbenzene, m/p-xylene, and o-xylene (BTEX)] on fetal growth assessed by 1,692 ultrasound measurements among 562 pregnant women from the Sabadell cohort of the Spanish INMA (Environment and Childhood) study.Methods: We used temporally adjusted land-use regression models to estimate exposures to NO2 and BTEX. We fitted mixed-effects models to estimate longitudinal growth curves for femur length (FL), head circumference (HC), abdominal circumference (AC), biparietal diameter (BPD), and estimated fetal weight (EFW). Unconditional and conditional SD scores were calculated at 12, 20, and 32 weeks of gestation. Sensitivity analyses were performed considering time–activity patterns during pregnancy.Results: Exposure to BTEX from early pregnancy was negatively associated with growth in BPD during weeks 20–32. None of the other fetal growth parameters were associated with exposure to air pollution during pregnancy. When considering only women who spent 2 hr/day in nonresidential outdoor locations, effect estimates were stronger and statistically significant for the association between NO2 and growth in HC during weeks 12–20 and growth in AC, BPD, and EFW during weeks 20–32.Conclusions: Our results lend some support to an effect of exposure to traffic-related air pollutants from early pregnancy on fetal growth during mid-pregnancy.

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The mutual information of independent parallel Gaussian-noise channels is maximized, under an average power constraint, by independent Gaussian inputs whose power is allocated according to the waterfilling policy. In practice, discrete signalling constellations with limited peak-to-average ratios (m-PSK, m-QAM, etc) are used in lieu of the ideal Gaussian signals. This paper gives the power allocation policy that maximizes the mutual information over parallel channels with arbitrary input distributions. Such policy admits a graphical interpretation, referred to as mercury/waterfilling, which generalizes the waterfilling solution and allows retaining some of its intuition. The relationship between mutual information of Gaussian channels and nonlinear minimum mean-square error proves key to solving the power allocation problem.

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The analysis of the multiantenna capacity in the high-SNR regime has hitherto focused on the high-SNR slope (or maximum multiplexing gain), which quantifies the multiplicative increase as function of the number of antennas. This traditional characterization is unable to assess the impact of prominent channel features since, for a majority of channels, the slope equals the minimum of the number of transmit and receive antennas. Furthermore, a characterization based solely on the slope captures only the scaling but it has no notion of the power required for a certain capacity. This paper advocates a more refined characterization whereby, as function of SNRjdB, the high-SNR capacity is expanded as an affine function where the impact of channel features such as antenna correlation, unfaded components, etc, resides in the zero-order term or power offset. The power offset, for which we find insightful closed-form expressions, is shown to play a chief role for SNR levels of practical interest.

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This paper formulates power allocation policies that maximize the region of mutual informationsachievable in multiuser downlink OFDM channels. Arbitrary partitioning ofthe available tones among users and arbitrary modulation formats, possibly different forevery user, are considered. Two distinct policies are derived, respectively for slow fadingchannels tracked instantaneously by the transmitter and for fast fading channels knownonly statistically thereby. With instantaneous channel tracking, the solution adopts theform of a multiuser mercury/waterfilling procedure that generalizes the single-user mercury/waterfilling introduced in [1, 2]. With only statistical channel information, in contrast,the mercury/waterfilling interpretation is lost. For both policies, a number of limitingregimes are explored and illustrative examples are provided.

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In a MIMO layered architecture, several codewordsare transmitted from a multiplicity of antennas. Although thespectral efficiency is maximized if the rates of these codewordsare separately controlled, the feedback rate within the linkadaptation loop is reduced if they are constrained to be identical.This poses a direct tradeoff between performance andfeedback overhead. This paper provides analytical expressionsthat quantify the difference in spectral efficiency between bothapproaches for arbitrary numbers of antennas. Specifically, thecharacterization takes place in the realm of the low- and highpowerregimes via expansions that are shown to have a widerange of validity.In addition, the possibility of adjusting the transmit powerof each codeword individually is considered as an alternative tothe separate control of their rates. Power allocation, however,turns out to be inferior to rate control within the context of thisproblem.

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Introduction: Surgery represents the treatment of choice for localized renal cell neoplasia. Partial nephrectomy (PN) has widened its indications over the past two decades and has shown oncological results equivalent to radical nephrectomy for small tumors. The role of negative surgical margins has been widely debated. Intraoperative fresh frozen section analysis is shown to be unreliable, expensive, time-consuming and not well correlated to final pathology. The goal of the present study was to assess the feasibility of intraoperative ex-vivo ultrasound (US) control of resection margins and its correlation to margin status at definitive pathology in patients undergoing PN.Material and Methods: The study was carried out in our institution from February 2008 to March 2010. Patients undergoing PN for T1-T2 renal tumors were included. Ex vivo US was performed by one single senior radiologist. Considering its availability, not all consecutive eligible patients were included. PN was undertaken in a standardized technique applying the "minimal healthy tissue margin" technique. Once resected, the specimen was kept in a saline solution and ex-vivo US was performed to evaluate the whole tumor pseudocapsule.Results: Twelve patients (five women, age (mean}SD) 65}11 years) were included. Intraoperative ex-vivo US showed negative surgical margin in all cases. US duration ranged from 1 to 4 minutes, with a median time of 1 minute. Definitive histological analysis confirmed the presence of two angiomyolipoma, eight pT1a tumors, of which seven were clear cell carcinoma and one was a type II papillary tumor, one pT1b clear cell carcinoma and one pT2 chromophobe carcinoma (size 2.9}2.3 cm). Final pathology revealed R0 margins.Conclusion: Intraoperative ex-vivo US control of resection margins in patients undergoing PN is feasible, time-efficient and well correlated to definitive pathological examination with regards to margin status.