Feasibility and clinical applications of multiple breath wash-out (MBW) testing using sulphur hexafluoride in adults with bronchial asthma.

Ventilation heterogeneity is frequent in bronchial asthma and can be assessed using multiple breath wash-out testing (MBW). Most data is available in paediatric patients and using nitrogen as a tracer gas. We aimed to evaluate sulphur hexafluoride (SF6) MBW in adult asthmatics. Spirometry, whole-body plethysmography, impulse oscillometry and SF6-MBW were prospectively performed. MBW parameters reflecting global (lung clearance index, LCI), acinar (Sacin) and conductive (Scond) ventilation heterogeneity were derived from three consecutive wash-outs. LCI was calculated for the traditional 2.5% and an earlier 5% stopping point that has the potential to reduce wash-out times. 91 asthmatics (66%) and 47 non-asthmatic controls (34%) were included in final analysis. LCI2.5 and LCI5 were higher in asthmatics (p < 0.001). Likewise, Sacin and Scond were elevated (p < 0.001 and p < 0.01). Coefficient of variation was 3.4% for LCI2.5 and 3.5% for LCI5 in asthmatics. Forty-one asthmatic patients had normal spirometry. ROC analysis revealed an AUC of 0.906 for the differentiation from non-asthmatic controls exceeding diagnostic performance of individual and conventional parameters (AUC = 0.819, p < 0.05). SF6-MBW is feasible and reproducible in adult asthmatics. Ventilation heterogeneity is increased as compared to non-asthmatic controls persisting in asthmatic patients with normal spirometry. Diagnostic performance is not affected using an earlier LCI stopping point while reducing wash-out duration considerably.

Symposium review: Uncertainties in enteric methane inventories, measurement techniques, and prediction models.

Ruminant production systems are important contributors to anthropogenic methane (CH4) emissions, but there are large uncertainties in national and global livestock CH4 inventories. Sources of uncertainty in enteric CH4 emissions include animal inventories, feed dry matter intake (DMI), ingredient and chemical composition of the diets, and CH4 emission factors. There is also significant uncertainty associated with enteric CH4 measurements. The most widely used techniques are respiration chambers, the sulfur hexafluoride (SF6) tracer technique, and the automated head-chamber system (GreenFeed; C-Lock Inc., Rapid City, SD). All 3 methods have been successfully used in a large number of experiments with dairy or beef cattle in various environmental conditions, although studies that compare techniques have reported inconsistent results. Although different types of models have been developed to predict enteric CH4 emissions, relatively simple empirical (statistical) models have been commonly used for inventory purposes because of their broad applicability and ease of use compared with more detailed empirical and process-based mechanistic models. However, extant empirical models used to predict enteric CH4 emissions suffer from narrow spatial focus, limited observations, and limitations of the statistical technique used. Therefore, prediction models must be developed from robust data sets that can only be generated through collaboration of scientists across the world. To achieve high prediction accuracy, these data sets should encompass a wide range of diets and production systems within regions and globally. Overall, enteric CH4 prediction models are based on various animal or feed characteristic inputs but are dominated by DMI in one form or another. As a result, accurate prediction of DMI is essential for accurate prediction of livestock CH4 emissions. Analysis of a large data set of individual dairy cattle data showed that simplified enteric CH4 prediction models based on DMI alone or DMI and limited feed- or animal-related inputs can predict average CH4 emission with a similar accuracy to more complex empirical models. These simplified models can be reliably used for emission inventory purposes.

A simple method to reconstruct the molar mass signal of respiratory gas to assess small airways with a double-tracer gas single-breath washout.

For the assessment of small airway diseases, a noninvasive double-tracer gas single-breath washout (DTG-SBW) with sulfur hexafluoride (SF6) and helium (He) as tracer components has been proposed. It is assumed that small airway diseases may produce typical ventilation inhomogeneities which can be detected within one single tidal breath, when using two tracer components. Characteristic parameters calculated from a relative molar mass (MM) signal of the airflow during the washout expiration phase are analyzed. The DTG-SBW signal is acquired by subtracting a reconstructed MM signal without tracer gas from the signal measured with an ultrasonic sensor during in- and exhalation of the double-tracer gas for one tidal breath. In this paper, a simple method to determine the reconstructed MM signal is presented. Measurements on subjects with and without obstructive lung diseases including the small airways have shown high reliability and reproducibility of this method.

Microbubble-Assisted Ultrasound-Induced Transient Phosphatidylserine Translocation.

Microbubble-assisted ultrasound (sonopermeabilization) results in reversible permeabilization of the plasma membrane of cells. This method is increasingly used in vivo because of its potential to deliver therapeutic molecules with limited cell damage. Nevertheless, the effects of sonopermeabilization on the plasma membrane remain not fully understood. We investigated the influence of sonopermeabilization on the transverse mobility of phospholipids, especially on phosphatidylserine (PS) externalization. We performed studies using optical imaging with Annexin V and FM1-43 probes to monitor PS externalization of rat glioma C6 cells. Sonopermeabilization induced transient membrane permeabilization, which is positively correlated with reversible PS externalization. This membrane disorganization was temporary and not associated with loss of cell viability. Sonopermeabilization did not induce PS externalization via activation of the scramblase. We hypothesize that acoustically induced membrane pores may provide a new pathway for PS migration between both membrane leaflets. During the membrane-resealing phase, PS asymmetry may be re-established by amino-phospholipid flippase activity and/or endocytosis, along with exocytosis processes.

Treatment of hepatic tumors by thermal versus mechanical effects of pulsed high intensity focused ultrasound in vivo.

The purpose of this study is to comparatively assess the thermal versus mechanical effects of pulsed high intensity focused ultrasound (HIFU) treatment on hepatic tumors in vivo. Forty-five rabbits with hepatic VX2 tumors were randomly separated into three groups (15 animals per group) before HIFU ablation. The total HIFU energy (in situ) of 1250 J was used for each tumor for three groups. In groups I and II, animals were treated with 1 MHz pulsed ultrasound at 1 Hz pulsed repetition frequency (PRF), 0.5 duty cycle (0.5 s on and 0.5 s off) and10 s duration for one spot sonication. For group II, in addition to HIFU treatment, microbubbles (SonoVue, Bracco, Milan, Italy) were injected via vein before sonication acting as a synergist. In group III, animals were treated with 1 MHz pulsed ultrasound at 10 Hz PRF, 0.1 duty cycle (0.1 s on and 0.9 s off) and 10 s duration for one sonication. The total treatment spots were calculated according to the tumor volume. Tumors were examined with contrast-enhanced computed tomography (CECT) immediately prior to and post HIFU treatment. Histopathologic assessment was performed 3 h after treatment. Our study showed that all animals tolerated the HIFU treatment well. Our data showed that mechanical HIFU could lead to controlled injury in rabbit hepatic tumors with different histological changes in comparison to thermal HIFU with or without microbubbles.

Novel methodology to perform sulfur hexafluoride (SF6)-based multiple-breath wash-in and washout in infants using current commercially available equipment.

Multiple-breath inert gas washout (MBW) is ideally suited for early detection and monitoring of serious lung disease, such as cystic fibrosis, in infants and young children. Validated commercial options for the MBW technique are limited, and suitability of nitrogen (N2)-based MBW is of concern given the detrimental effect of exposure to pure O2 on infant breathing pattern. We propose novel methodology using commercially available N2 MBW equipment to facilitate 4% sulfur hexafluoride (SF6) multiple-breath inert gas wash-in and washout suitable for the infant age range. CO2, O2, and sidestream molar mass sensor signals were used to accurately calculate SF6 concentrations. An improved dynamic method for synchronization of gas and respiratory flow was developed to take into account variations in sidestream sample flow during MBW measurement. In vitro validation of triplicate functional residual capacity (FRC) assessments was undertaken under dry ambient conditions using lung models ranging from 90 to 267 ml, with tidal volumes of 28-79 ml, and respiratory rates 20-60 per minute. The relative mean (SD, 95% confidence interval) error of triplicate FRC determinations by washout was -0.26 (1.84, -3.86 to +3.35)% and by wash-in was 0.57 (2.66, -4.66 to +5.79)%. The standard deviations [mean (SD)] of percentage error among FRC triplicates were 1.40 (1.14) and 1.38 (1.32) for washout and wash-in, respectively. The novel methodology presented achieved FRC accuracy as outlined by current MBW consensus recommendations (95% of measurements within 5% accuracy). Further clinical evaluation is required, but this new technique, using existing commercially available equipment, has exciting potential for research and clinical use.

Blood-brain barrier leakage after status epilepticus in rapamycin-treated rats I: Magnetic resonance imaging.

OBJECTIVE: The mammalian target of rapamycin (mTOR) pathway has received increasing attention as a potential antiepileptogenic target. Treatment with the mTOR inhibitor rapamycin after status epilepticus reduces the development of epilepsy in a rat model. To study whether rapamycin mediates this effect via restoration of blood-brain barrier (BBB) dysfunction, contrast-enhanced magnetic resonance imaging (CE-MRI) was used to determine BBB permeability throughout epileptogenesis. METHODS: Imaging was repeatedly performed until 6 weeks after kainic acid-induced status epilepticus in rapamycin (6 mg/kg for 6 weeks starting 4 h after SE) and vehicle-treated rats, using gadobutrol as contrast agent. Seizures were detected using video monitoring in the week following the last imaging session. RESULTS: Gadobutrol leakage was widespread and extensive in both rapamycin and vehicle-treated epileptic rats during the acute phase, with the piriform cortex and amygdala as the most affected regions. Gadobutrol leakage was higher in rapamycin-treated rats 4 and 8 days after status epilepticus compared to vehicle-treated rats. However, during the chronic epileptic phase, gadobutrol leakage was lower in rapamycin-treated epileptic rats along with a decreased seizure frequency. This was confirmed by local fluorescein staining in the brains of the same rats. Total brain volume was reduced by this rapamycin treatment regimen. SIGNIFICANCE: The initial slow recovery of BBB function in rapamycin-treated epileptic rats indicates that rapamycin does not reduce seizure activity by a gradual recovery of BBB integrity. The reduced BBB leakage during the chronic phase, however, could contribute to the decreased seizure frequency in post-status epilepticus rats treated with rapamycin. Furthermore, the data show that CE-MRI (using step-down infusion with gadobutrol) can be used as biomarker for monitoring the effect of drug therapy in rats.

Large Eddy Simulation of Air Escape through a Hospital Isolation Room Single Hinged Doorway--Validation by Using Tracer Gases and Simulated Smoke Videos.

The use of hospital isolation rooms has increased considerably in recent years due to the worldwide outbreaks of various emerging infectious diseases. However, the passage of staff through isolation room doors is suspected to be a cause of containment failure, especially in case of hinged doors. It is therefore important to minimize inadvertent contaminant airflow leakage across the doorway during such movements. To this end, it is essential to investigate the behavior of such airflows, especially the overall volume of air that can potentially leak across the doorway during door-opening and human passage. Experimental measurements using full-scale mock-ups are expensive and labour intensive. A useful alternative approach is the application of Computational Fluid Dynamics (CFD) modelling using a time-resolved Large Eddy Simulation (LES) method. In this study simulated air flow patterns are qualitatively compared with experimental ones, and the simulated total volume of air that escapes is compared with the experimentally measured volume. It is shown that the LES method is able to reproduce, at room scale, the complex transient airflows generated during door-opening/closing motions and the passage of a human figure through the doorway between two rooms. This was a basic test case that was performed in an isothermal environment without ventilation. However, the advantage of the CFD approach is that the addition of ventilation airflows and a temperature difference between the rooms is, in principle, a relatively simple task. A standard method to observe flow structures is dosing smoke into the flow. In this paper we introduce graphical methods to simulate smoke experiments by LES, making it very easy to compare the CFD simulation to the experiments. The results demonstrate that the transient CFD simulation is a promising tool to compare different isolation room scenarios without the need to construct full-scale experimental models. The CFD model is able to reproduce the complex airflows and estimate the volume of air escaping as a function of time. In this test, the calculated migrated air volume in the CFD model differed by 20% from the experimental tracer gas measurements. In the case containing only a hinged door operation, without passage, the difference was only 10%.

Recruitment of endocytosis in sonopermeabilization-mediated drug delivery: a real-time study.

Microbubbles (MBs) in combination with ultrasound (US) can enhance cell membrane permeability, and have the potential to facilitate the cellular uptake of hydrophilic molecules. However, the exact mechanism behind US- and MB-mediated intracellular delivery still remains to be fully understood. Among the proposed mechanisms are formation of transient pores and endocytosis stimulation. In our study, we investigated whether endocytosis is involved in US- and MB-mediated delivery of small molecules. Dynamic fluorescence microscopy was used to investigate the effects of endocytosis inhibitors on the pharmacokinetic parameters of US- and MB-mediated uptake of SYTOX Green, a 600 Da hydrophilic model drug. C6 rat glioma cells, together with SonoVue(®) MBs, were exposed to 1.4 MHz US waves at 0.2 MPa peak-negative pressure. Collection of the signal intensity in each individual nucleus was monitored during and after US exposure by a fibered confocal fluorescence microscope designed for real-time imaging. Exposed to US waves, C6 cells pretreated with chlorpromazine, an inhibitor of clathrin-mediated endocytosis, showed up to a 2.5-fold significant increase of the uptake time constant, and a 1.1-fold increase with genistein, an inhibitor of caveolae-mediated endocytosis. Both inhibitors slowed down the US-mediated uptake of SYTOX Green. With C6 cells and our experimental settings, these quantitative data indicate that endocytosis plays a role in sonopermeabilization-mediated delivery of small molecules with a more predominant contribution of clathrin-mediated endocytosis.

Contrast-enhanced ultrasonography to assess blood perfusion of skeletal muscles in normal dogs.

This study evaluated perfusion of skeletal muscle using contrast enhanced ultrasonography in humerus, radius, femur and tibia in normal dogs. Contrast enhanced ultrasonography for each region was performed after injecting 0.5 mL and 1 mL of contrast medium (SonoVue) in every dog. Blood perfusion was assessed quantitatively by measuring the peak intensity, time to the peak intensity and area under the curve from the time-intensity curve. Vascularization in skeletal muscle was qualitatively graded with a score of 0-3 according to the number of vascular signals. A parabolic shape of time-intensity curve was observed from muscles in normal dogs, and time to the peak intensity, the peak intensity and area under the curve of each muscle were not significantly different according to the appendicular regions examined and the dosage of contrast agent administered. This study reports that feasibility of contrast enhanced ultrasonography for assessment of the muscular perfusion in canine appendicular regions.

Interactions Between Targeted Ultrasound Contrast Agents With Anti-Human Interleukin 8 Monoclonal Antibody and Activated Endothelial Cells.

The study aimed to explore the role of interleukin 8 (IL-8) in atherosclerotic plaques and develop a new method for the evaluation of endothelial function by assessing the interactions between the injured endothelial cells and the targeted ultrasound agent that carried anti-human IL-8 monoclonal antibody. Anti-human IL-8 monoclonal antibodies were associated to the shells of SonoVue microbubbles by covalent conjugation technology. The specific interaction between the microbubbles and the normal or injured endothelial cells was observed using an inverted microscope. The microbubble adherence was quantified by calculating the ratio of the adherent microbubbles to endothelial cells. The results were compared with the control microbubbles. There were rare adherences of control microbubbles to the normal or injured endothelial cells, whereas the targeted microbubbles could adhere to endothelial cells well. Importantly, compared with the normal endothelial cells, a significantly higher number of targeted microbubbles bound to the injured endothelial cells. The ultrasound agents with anti-human IL-8 monoclonal antibody can specifically bind to the injured endothelial cell, which provides a new insight to the noninvasive detection of endothelial dysfunction using ultrasound imaging techniques.

Technical note: Can the sulfur hexafluoride tracer gas technique be used to accurately measure enteric methane production from ruminally cannulated cattle?

An experiment was conducted to determine whether using ruminally cannulated cattle affects the estimate of enteric methane (CH(4)) emissions when using the sulfur hexafluoride (SF(6)) tracer technique with samples taken from a head canister. Eleven beef cattle were surgically fitted with several types of ruminal cannula (2C, 3C, 3C+washer, 9C; Bar Diamond, Parma, ID). The 2C and 3C models (outer and inner flanges with opposite curvature) had medium to high leakage, whereas the 9C models (outer and inner flanges with the same curvature) provided minimum to moderate leakage of gas. A total of 48 cow-day measurements were conducted. For each animal, a permeation tube containing sulfur hexafluoride (SF(6)) was placed in the rumen, and a sample of air from around the nose and mouth was drawn through tubing into an evacuated canister (head canister). A second sample of air was collected from outside the rumen near the cannula into another canister (cannula canister). Background concentrations were also monitored. The methane (CH(4)) emission was estimated from the daily CH(4) and SF(6) concentrations in the head canister (uncorrected). The permeation SF(6) release rate was then partitioned based on the proportion of the SF(6) concentration measured in the head vs. the cannula canister. The CH(4) emissions at each site were calculated using the two release rates and the two CH(4):SF(6) concentration ratios. The head and cannula emissions were summed to obtain the total emission (corrected). The difference (corrected - uncorrected) in CH4 emission was attributed to the differences in CH(4):SF(6) ratio at the 2 exit locations. The proportions of CH(4) and SF(6) recovered at the head were greater (P < 0.001) for the 9C cannulas (64% and 66%) compared with the other cannulas, which were similar (P > 0.05; 2C, 6% and 4%; 3C, 17% and 15%; 3C+washer, 19% and 14%). Uncorrected CH(4) emissions were ± 10% of corrected emissions for 53% of the cow-day measurements. Only when more than 80% of the SF(6) escaped via the rumen did the difference between the uncorrected and corrected CH(4) emissions exceed 20%. We concluded that using cannulated cattle introduces more variability into the SF(6) technique used with a head canister, a technique that is already highly variable. Thus, use of cannulated animals is not recommended when using the SF(6) technique with head canister. However, if cannulated cattle are used, the cannulas need to be tight-fitting to minimize leakage, and large animal numbers are needed to overcome the additional variability.

Measurement and prediction of enteric methane emission.

The greenhouse gas (GHG) emissions from the agricultural sector account for about 25.5% of total global anthropogenic emission. While CO(2) receives the most attention as a factor relative to global warming, CH(4), N(2)O and chlorofluorocarbons (CFCs) also cause significant radiative forcing. With the relative global warming potential of 25 compared with CO(2), CH(4) is one of the most important GHGs. This article reviews the prediction models, estimation methodology and strategies for reducing enteric CH(4) emissions. Emission of CH(4) in ruminants differs among developed and developing countries, depending on factors like animal species, breed, pH of rumen fluid, ratio of acetate:propionate, methanogen population, composition of diet and amount of concentrate fed. Among the ruminant animals, cattle contribute the most towards the greenhouse effect through methane emission followed by sheep, goats and buffalos, respectively. The estimated CH(4) emission rate per cattle, buffaloe, sheep and goat in developed countries are 150.7, 137, 21.9 and 13.7 (g/animal/day) respectively. However, the estimated rates in developing countries are significantly lower at 95.9 and 13.7 (g/animal/day) per cattle and sheep, respectively. There exists a strong interest in developing new and improving the existing CH(4) prediction models to identify mitigation strategies for reducing the overall CH(4) emissions. A synthesis of the available literature suggests that the mechanistic models are superior to empirical models in accurately predicting the CH(4) emission from dairy farms. The latest development in prediction model is the integrated farm system model which is a process-based whole-farm simulation technique. Several techniques are used to quantify enteric CH(4) emissions starting from whole animal chambers to sulfur hexafluoride (SF6) tracer techniques. The latest technology developed to estimate CH(4) more accurately is the micrometeorological mass difference technique. Because the conditions under which animals are managed vary greatly by country, CH(4) emissions reduction strategies must be tailored to country-specific circumstances. Strategies that are cost effective, improve productivity, and have limited potential negative effects on livestock production hold a greater chance of being adopted by producers. It is also important to evaluate CH(4) mitigation strategies in terms of the total GHG budget and to consider the economics of various strategies. Although reductions in GHG emissions from livestock industries are seen as high priorities, strategies for reducing emissions should not reduce the economic viability of enterprises.

Vascular gene transfer and drug delivery in vitro using low-frequency ultrasound and microbubbles.

AIM: To determine the effects of ultrasound exposure in combination with a microbubble contrast agent (SonoVue) on the cellular uptake and delivery of drugs/genes into human umbilical vein endothelial cells (HUVECs) as well as their biological effects on migration. METHODS: HUVECs in suspension were exposed to pulsed ultrasound with a 10% duty cycle in combination with various concentrations of a microbubble contrast agent (SonoVue) using a digital sonifier at a frequency of 20 kHz and an intensity of 3.77 W/cm(2) on the surface of a horn tip. Cell culture inserts were used to determine the cell migration ability. RESULTS: Exposure to pulsed ultrasound resulted in enhanced green fluorescent protein (EGFP) gene transfection efficiencies ranging from 0.2% to 2%. The transfection efficiency of HUVECs was approximately 3-fold higher in the presence of SonoVue than in its absence at the effective exposure time of 6 s. For drug delivery to HUVECs using ultrasound, the delivery efficiencies of a low-molecular-weight model drug (TO-PRO-1, M(W) 645.38) were significantly higher when compared to drug delivery without ultrasound, with a maximum efficiency of approximately 34%. However, the delivery efficiencies of a high-molecular-weight model drug (Dextran-Rhodamine B, M(W) 70,000) were low, with a maximum delivery efficiency of nearly 0.5%, and gene transfection results were similarly poor. The migration ability of HUVECs exposed to ultrasound was also lower than that of the control (no exposure). CONCLUSION: The use of low-frequency and low-energy ultrasound in combination with microbubbles could be a potent physical method of increasing drug/gene delivery efficiency. This technique is a promising nonviral approach that can be used in cardiovascular disease therapy.

[Binding of targeted microbubble contrast agent to choriocarcinoma cells in vitro].

OBJECTIVE: To observe the cell binding characteristics of SonoVue microbubbles targeting choriocarcinoma cells and provide evidence for clinical ultrasonic localization of the tumor utilizing the microbubbles. METHODS: The targeted microbubbles were prepared by conjugating anti-HCG antibody with the SonoVue microbubbles and added in choriocarcinoma cells or endometrial stromal cells to compare the cell binding rate of the agents under optical microscope and with flow cytometry. RESULTS: Flow cytometry demonstrated a binding rate of 77.6% between the SonoVue microbubbles and anti-HCG antibody. Light microscopy showed that the total rosette formation rate of the choriocarcinoma cells exposed to the targeted microbubble bearing anti-HCG antibody reached (87.8-/+6.3)%, significantly higher than that of the endometrial stromal cells [(9.4-/+1.7)%, P<0.05]. The binding rate of the targeted microbubbles with the choriocarcinoma cells before and after PBS washing were (85.4-/+4.7)% and (83.1-/+3.8)% (P>0.05), respectively, suggesting strong stability of the binding. The binding rate was 81.0% according to the results of flow cytometry. CONCLUSION: The targeted microbubbles as a contrast agent can efficiently bind to the choriocarcinoma cells in vitro with a stability sufficient to resist the blood flow.

Evaluating bowel wall vascularity in Crohn's disease: a comparison of dynamic MRI and wideband harmonic imaging contrast-enhanced low MI ultrasound.

This was a prospective comparison of dynamic MRI (1.5 T) and echo-signal enhanced ultrasound in evaluating vascularization in thickened bowel walls cases of Crohn's disease. Twenty-one patients with histologically confirmed Crohn's disease and bowel wall diameters >5 mm were examined by MRI and ultrasound (US). MR sequences: T1w fl2D, T2w, FLASH T1w post-contrast media (CM) applications with fat saturation were used. Dynamic Turbo-FLASH T1w sequences were acquired in the area of maximal thickening of the ileal wall every 1.5 s post-CM application for a total duration of 1 min. US was performed after the application of 1.2 ml of echo-signal enhancer. Contrast uptake was measured by the semiquantitative score and brightness analysis in regions of interest (ROI). Clinical and laboratory findings including Crohn's disease activity indices were documented; MRI and US parameters were correlated. The length of sonographically documented lesions (122+/-75 mm) correlated significantly with the length of thickened bowel segments in MRI (128+/-76 mm; r=0.466; P=0.033). The maximum percent signal enhancement in the terminal ileum at ultrasound (217.5+/-100.1%) showed a high correlation with the findings of MRI (262+/-108%; r=0.623; P=0.003). With both methods, a plateau phase was observed. US and MRI are capable of evaluating local vascularization in the bowel wall objectively.

Is microbubble-enhanced ultrasonography sufficient for assessment of response to percutaneous treatment in patients with early hepatocellular carcinoma?

The objective of this study was to assess the efficacy of contrast-enhanced ultrasonography (CEUS) with SonoVue to evaluate the response to percutaneous treatment (ethanol injection/radiofrequency) of hepatocellular carcinoma in comparison with spiral computed tomography (CT) immediately and 1 month after treatment. Forty-one consecutive cirrhotic patients with early stage tumor (not suitable for resection) were included. Spiral CT and CEUS were performed in all patients before treatment, in the following 24 h, and 1 month later. The results of each examination were compared with the 1-month spiral CT, considered the gold standard technique. The 24-h CEUS and the 24-h spiral CT sensitivity to detect residual disease were 27% and 20%, respectively. The 24-h CEUS and the 24-h spiral CT positive predictive value of persistent vascularization detection were 75% and 66%, respectively. The 1-month CEUS detected partial responses in ten out of 11 cases (91% sensitivity, 97% specificity, 95% accuracy). Spiral CT and CEUS performed in the 24 h following treatment are slightly useful to evaluate therapeutic efficacy. The 1-month CEUS has a high diagnostic accuracy compared with spiral-CT in the usual assessment of percutaneous treatment response.

Extraction of polychlorinated biphenyl with supercritical carbon dioxide, sulfur hexafluoride and subcritical water.

In the extraction of spiked PCB from soil, three extracting fluids were investigated: supercritical carbon dioxide (CO2), supercritical sulfur hexafluoride (SF6) and subcritical water. Among the tested fluids SF6 appeared to be appropriate especially for the extraction of low polar PCB. CO2 and water were found to be suitable for the quantitative extraction of all PCB. Water was judged as the best because of its low price, good availability and environmental safety.

Intrapulmonary gas mixing and the sloping alveolar plateau in COPD patients with macroscopic emphysema.

Chronic obstructive pulmonary disease patients, especially those with emphysema, show steep slopes of the alveolar plateau (S). This study tested the hypothesis that continued gas exchange between poorly and well-ventilated lung units by means of collateral ventilation would contribute to S in these patients. Nine young volunteers, nine older volunteers and 11 patients with macroscopic emphysema performed wash-out tests with helium (He) and sulphur hexafluoride (SF6). S was determined for breaths 1-5 (range 1), and for breaths between 95% and 98% of complete wash-out (range 2). An unequal ventilation index (UVI) was defined as the ratio between the estimated mean alveolar pressure and the end tidal pressure (PET) of each tracer gas, calculated over range 2. Over the same range, a phase III ratio was calculated by dividing PET by the estimated pressure at Fowler dead space. In all groups of subjects, the S for He and SF6 were greater for range 2 than for range 1 (p< or =0.012). In the emphysema patients, the correlations between S and UVI were 0.72 for He (p=0.012) and 0.81 for SF6 (p=0.002), while the mean phase III ratios were 1.7 for He and 2.4 for SF6, much less than their theoretical maxima. It was concluded that in patients collateral ventilation may account for only a small part of the increase in the alveolar plateau slope between ranges 1 and 2, and that this increase was mainly caused by unequal ventilation in combination with sequential emptying of lung units. The degree of sequential emptying, however, was modest compared with its full potential.