The objective of the present study was to validate one or a combination of fetal Doppler parameters in order to assess acute fetal hypoxia in an ovine model. Acute hypoxia was induced by reducing umbilical, or maternal aortic flow (approx. 70%). A CW Doppler probe was fixed on the fetal cervical skin, facing the internal carotid artery and the fetal abdominal skin adjacent to the umbilical arteries. (The angle between Doppler beam and flow vector remained constant.) A "Doptek 3000" spectrum analyser was used to measure the maximal and mean Doppler frequencies. Heart rate (HR), umbilical blood flow (UBF), carotid blood flow (CBF), umbilical RI (URI), cerebral RI (CRI) and cerebroplacental ratio (CPR = CRI/URI) were calculated in real time. A catheter was inserted into the fetal femoral artery, for blood gas (PO2, PCO2 pH) and blood pressure (BP) measurements. After 1 min of aorta compression (70% aortic flow reduction), the URI increased by 10% (P < 0.05), and the UBF decreased by 10% (P < 0.05), but the CRI decreased by 20% (P < 0.02), and the CBF did not change significantly. Fetal PO2 and CPR fell down after 1 min (59% and 38%, respectively; P < 0.001), although strong fetal heart rate decelerations were observed. The blood pressure, PCO2 and pH did not change significantly during this test. Throughout the 12 min of cord compression (70% umbilical flow reduction) the URI increased (70% to 80% P < 0.001), and the UBF decreased (approx. 60%; P < 0.001), but the CRI decreased (approx. 25%; P < 0.01), and the CBF remained constant (+/- 5%; ns). Fetal PO2 and CPR all decreased during the compression (30% to 44% and 40% to 60%, respectively; P < 0.001). HR, pH and PCO2 did not change significantly. During cord compression the blood pressure did not change significantly. In both cases, the CPR decreased significantly (P < 0.001) with the PO2 in the same direction and with a comparable amplitude (-30% to -50%). Nevertheless, the drop in CPR was greater during cord compression than during aorta compression, probably because the compression of the cord induced a central hypovolemia in addition to the hypoxia. The CPR was found to be the hemodynamic parameter that followed most closely the PO2 acute changes. The amplitude of the variations of this parameter (-30% to -50%) were quite similar to those of the PO2 during the period of acute hypoxia.(ABSTRACT TRUNCATED AT 400 WORDS)

Assessment of the fetal Po2 changes by cerebral and umbilical Doppler on lamb fetuses during acute hypoxia

Contrast-enhanced ultrasound (CEUS) represents a significant breakthrough in sonography and it is being increasingly used for the evaluation of focal liver lesions (FLLs). The unique feature of CEUS of non-invasively assessing in real-time liver perfusion throughout the vascular phase has led to a dramatic improvement in diagnostic accuracy of US in either detection or characterization of FLLs, as well as in the guidance and evaluation of response of therapeutic procedures. Currently, CEUS is included as a part of the suggested diagnostic work-up of FLLs, resulting in a better patient management and cost-effective therapy delivering. After a brief description of the basis of different CEUS techniques, contrast-enhancement patterns of different types of benign and malignant FLLs, among hepatic pseudolesions, will be described and discussed on the basis of our experience and literature data. At the same time, the most recent concepts and the use of CEUS in different clinical settings will be presented.

Focal liver lesions: contrast-enhanced ultrasound

Radiofrequency ablation (RFA) is increasingly being used as percutaneous treatment of choice for patients with early stage hepatocellular carcinoma (HCC). An accurate assessment of the RFA therapeutic response is of crucial importance, considering that a complete tumor ablation significantly increases patient survival, whereas residual unablated tumor calls for additional treatment. Imaging modalities play a pivotal role in accomplishing this task, but ultrasound (US) is not considered a reliable modality for the evaluation of the real extent of necrosis, even when color/power Doppler techniques are used. Recently, newer microbubble-based US contrast agents used in combination with grey-scale US techniques, which are very sensitive to non-linear behavior of microbubbles, have been introduced. These features have opened new prospects in liver ultrasound and may have a great impact on daily practice, including cost-effective assessment of therapeutic response of percutaneous ablative therapies. Technical evolution of CEUS focusing on findings after RFA are illustrated. These latter are detailed, cross-referenced with the literature and discussed on the basis of our personal experience. Timing of CEUS posttreatment assessment among with advantages and limitations of CEUS are also described with a perspective on further technologic refinement.

Hepatocellular cancer response to radiofrequency tumor ablation: contrast-enhanced ultrasound

The objectives were to evaluate cardiac and peripheral changes induced by microgravity with and without countermeasures (CM), to assess the peripheral response to orthostatic tests (tilt, LBNP). Inflight or HDT, we used echography and Doppler to assess the left heart function and the peripheral arteries. We studied the cardiovascular system during 1) 21-d and 25-d spaceflights without CM, 2) 14-d spaceflight with bracelets CM, 3) 28-d HDT with and without LBNP, and 4) 30-d HDT with and without Exercise+LBNP. Similar peripheral circulation changes were noticed in both astronauts and HDT subjects without CM. There was a decrease in renal, cerebral, and femoral vascular resistances and maintenance of cerebral flow at rest, and a lack of increase in lower limb vascular resistance and abnormal flow redistribution during orthostatic tests. Conversely, with CM at rest, cerebral and renal vascular resistances stayed elevated and femoral resistance decreased, but less than without countermeasures. Lower limb vascular resistance increased normally, peripheral flows were adequately redistributed during orthostatic tests, and no orthostatic intolerance was observed. This confirms the efficiency of countermeasures (LBNP, exercise, cuffs) in preserving the vasomotor tone in most peripheral areas at rest and reducing the development of orthostatic intolerance.

Regional blood flow in microgravity: adaptation and deconditioning.

Background: We describe the spectrum of contrast-enhancement patterns of benign hepatic tumors arising in fatty liver on contrast-enhanced ultrasound (US). Methods: Sixteen patients (12 women and four men) with 27 benign hepatic tumors (17 hemangiomas, eight focal nodular hyperplasias, and two hepatocellular adenomas) arising in fatty liver underwent baseline and pulse inversion US after administration of SonoVue. Two experienced radiologists evaluated baseline echogenicity and dynamic enhancement pattern of each lesion in comparison with adjacent liver parenchyma. Results: After administration of SonoVue, in the arterial phase 13 of 17 hemangiomas showed peripheral globular enhancement and one showed a rim of peripheral enhancement, followed by progressive centripetal fill-in, which was complete in 10 of 14 cases and incomplete in four. Three of 18 hemangiomas showed rapid and complete fill-in in the arterial phase. Eight of eight focal nodular hyperplasias became hyperechoic in comparison with adjacent liver parenchyma in the arterial phase and slightly hyperechoic or isoechoic in the portal venous and delayed phases. Both adenomas showed strong arterial contrast enhancement that became less intense in the portal venous and delayed phases. Conclusion: Contrast-enhanced US after administration of SonoVue enables depiction of typical contrast-enhancement patterns in most benign hepatic tumors arising in fatty liver, thus providing useful clues for characterization.

Characterization of benign hepatic tumors arising in fatty liver with SonoVue and pulse inversion US

Fifteen premature babies were controlled with ultrasound because of retrolental fibroplasia (RLFP). The typical echogram shows behind the lens echoes of medium amplitudes. The posterior part of the vitreous is acoustically clear. A diagnosis of retinoblastoma can be ruled out with great certainty and retinal detachment, if present, is manifest also with echo-opthalmography. Coast's disease, uveitism, persistent hyperplastic primary vitreous and vitreal opacities may show similar echograms as in RLFP. Biometry demonstrated microphthalmos in 36% of the cases. The slowing-down or arrest of the growth of the globe indicates the severity of RLFP. Visual axis shrinkage was never observed.

M. Veli

Papers

A-mode ultrasonography and oculometry in retrolental fibroplasia