Quantification of liver iron concentration with magnetic resonance imaging by combining T1-, T2-weighted spin echo sequences and a gradient echo sequence

BACKGROUND: The aim of the study was to quantify hepatic iron by MRI for practical use. METHODS: In twenty-three patients with various degrees of iron overload, measurements were carried out with a 1.5 Tesla MR unit. A combination of pulse sequences (T1, T2 and gradient echo) enabled us to quantify smaller amounts of liver iron as accurately as larger amounts of liver iron. The gradient echo sequence provided us with a good correlation when detecting smaller amounts of iron in the liver where the T1 sequence provided a good correlation when larger amounts of iron were present. RESULTS: The combination of the three sequences showed a nice correlation (r=-0. 93, P<0.001) and provided us with an accurate estimate of the liver iron content (LIC). This correlation was achieved with a LIC from the lower range of normal up to LIC of 146 mmol/kg dry weight, which seems the highest measurable liver iron content for a 1.5 Tesla MRI. Measuring in the lower range makes it possible to decide whether further invasive diagnostic investigations by a liver biopsy are indicated. CONCLUSION: MRI is a useful tool to quantify iron overload non-invasively. In cases where a liver biopsy is hazardous MRI can easily be used to obtain reliable, quantitative information about the initial LIC. Quantification by MRI could also be used for follow up of the iron content during depletion treatment by phlebotomy or iron chelation. The stronger the magnet the more sensitive the detection of concentrations up to 150 mmol/kg is. A semi-quantitative judgement will only be possible with severe iron overload over 150 mmol/kg. If such an iron excess is found, a liver biopsy should be performed to exclude cirrhosis.     

Inter-study reproducibility of 3D volume selective fast spin echo sequence for quantifying carotid artery wall volume in asymptomatic subjects

PURPOSE: To determine, in asymptomatic subjects, the inter-study reproducibility of a three-dimensional (3D) volume selective fast spin echo (FSE) cardiovascular magnetic resonance sequence for the assessment of carotid artery wall volume as a measure of atheroma burden. METHODS: Inter-study reproducibility was evaluated in 16 asymptomatic volunteers (10 male, 6 female). Both carotid arteries were scanned twice with a median inter-scan time of 5 days. The images were acquired in cross-section, and the total carotid arterial wall volume (TWV) was calculated by subtraction of the total carotid lumen volume from the total outer carotid vessel volume. RESULTS: The mean carotid T1-weighted TWV for the first and second scans was 828 and 821 mm(3), respectively (mean difference 7 mm(3), p=0.45). The standard deviation (S.D.) of the differences between the measurements was 38 mm(3) yielding an inter-study coefficient of variation of 4.6%. The time for each study was approximately 30 min. For the longitudinal evaluation of carotid atheroma burden with pharmacological intervention versus placebo, 32 subjects would enable a difference of 38 mm(3) to be detected with a significance level of 5% with 80% power. CONCLUSION: Volumetric analysis with carotid CMR in asymptomatic subjects using a 3D volume-selective FSE is time-efficient with good inter-study reproducibility, and is well suited for longitudinal studies of carotid atheroma with reasonable sample sizes.     

L wave in echo Doppler

62-Year-old female presented with progressive dyspnea NYHA class III for six months. Echocardiography showed normal left ventricular (LV) systolic function, mild biatrial enlargement, an L wave in pulse wave Doppler at mitral inflow and in M mode echocardiography across mitral valve. Tissue Doppler imaging at medial mitral annulus showed an L′ wave in mid diastole in addition to E′ and A′ wave. An L wave in pulse wave Doppler and M mode echocardiography represents continued pulmonary vein mid diastolic flow through the left atrium in to LV across mitral valve after early rapid filling. Presence of an L′ wave in these patients associated with higher E/E′ is indicative of advance diastolic dysfunction with elevated filling pressures.     

Comparison of echo 2D and echo Doppler in the evaluation of the mitral valve area

The aim of the study was to compare the degree of accuracy achieved using 2D ultrasonography and Doppler ultrasonography in measuring the mitral valve area. The complementary role of the two methods of diagnosing mitral stenosis and of assessing the severity of valvular involvement emerges from a broad review of the literature. However, in comparison to the two-dimensional technique, Doppler ultrasonography gives a greater mathematical precision and is more reproducible. Doppler ultrasonography enables the pulsatile flow to be registered, while 2D ultrasonography gives a morphological image of the valvular anatomy. "Net" surface values which are closer to real values and usually lower than those obtained using 2D ultrasonography can be deduced from the assessment of the transvalvular pressure gradient.     

Pulmonary valve echo motion in clinical practice

Examination of the pattern of pulmonary valve echo motion provides useful diagnostic information in a variety of clinical situations. This report describes the normal patterns and variations in pulmonary valve echo motion. It further discusses the applications and limitations of M-mode and cross-sectional echocardiography in detecting obstruction to right ventricular outflow at both the valvular and infundibular level; the wide ranging effects of increases in pulmonary artery pressure on the pulmonary valve echogram; and alterations in right ventricular compliance and volume which may combine to produce diastolic opening of the pulmonary valve. It is emphasized that the thin pliable pulmonary leaflets move in response to local alterations in pressure and flow. The patterns of pulmonary valve echo motion, therefore, although not specific for any particular clinical disorder, may provide valuable, indirect information concerning local pressure and flow characteristics and, as such, may prove extremely helpful when applied to a specific clinical situation.     

Spontaneous echo contrast of unexpected etiology.

Cor triatriatum sinister is a rare congenital anomaly characterized by the presence of a fibromuscular membrane dividing the left atrium into two chambers: one entering the four pulmonary veins, the other connecting to the mitral valve. The extent of the communication between the two chambers and the presence of associated lesions determine the severity of symptoms and the complications. We report the case of a 20-year-old man firstly diagnosed with obstructive cor triatriatum sinister and severe pulmonary hypertension.     

Analysis of high-frequency rotational angioplasty-induced echo contrast

During high-frequency rotational angioplasty (HFRA), myocardial contrast enhancement (echo contrast) was observed by means of two-dimensional echocardiography. In order to evaluate the echo contrast produced by HFRA, an in vitro experimental model was built using a cylinder with the HFRA catheter scanned in a water bath. The cylinder was filled with blood, mineral water, and distilled water. With a 2.5-MHz transducer, echograms were recorded and analyzed by video intensitometer, and the maximum intensity IUmax and persistence time P were calculated. Rotation frequencies of 20,000-200,000 rpm with 2.0--mm burrs and times of 10 s were tested. In another model, hyperbaric conditions for the same media were produced. The influence of debris from arterioscleroic plaque and of hematocrit on echo contrast intensity were also analyzed. The effect of HFRA on hemolysis (LDH, free hemoglobin) within 10 s and temperature were also measured. The contrast effect was transient, depending on the rotation frequency. In blood, it appeared at 20,000 rpm (IUmax at 200,000 rpm: 237 IU), in mineral water at 40,000 rpm (IUmax 165 IU), and in distilled water at 80,000 rpm (IUmax 72 IU). Persistence time was measured up to about a half-minute. Echo contrast production was reduced at 0.5 bar and fully suppressed at 2.5 bar. Debris increased contrast intensity from about 219 IU to 225 IU (at 160,000 rpm). In blood IUmax decreased from 227 IU to 97 IU by lowering the hematocrit from 44.2% to 3.6%.(ABSTRACT TRUNCATED AT 250 WORDS)     

The echo chamber effect on social media

Social media may limit the exposure to diverse perspectives and favor the formation of groups of like-minded users framing and reinforcing a shared narrative, that is, echo chambers. However, the interaction paradigms among users and feed algorithms greatly vary across social media platforms. This paper explores the key differences between the main social media platforms and how they are likely to influence information spreading and echo chambers’ formation. We perform a comparative analysis of more than 100 million pieces of content concerning several controversial topics (e.g., gun control, vaccination, abortion) from Gab, Facebook, Reddit, and Twitter. We quantify echo chambers over social media by two main ingredients: 1) homophily in the interaction networks and 2) bias in the information diffusion toward like-minded peers. Our results show that the aggregation of users in homophilic clusters dominate online interactions on Facebook and Twitter. We conclude the paper by directly comparing news consumption on Facebook and Reddit, finding higher segregation on Facebook.

Social media radically changed the mechanism by which we access information and form our opinions (1–5). We need to understand how people seek or avoid information and how those decisions affect their behavior (6), especially when the news cycle—dominated by the disintermediated diffusion of information—alters the way information is consumed and reported on. A recent study (7) limited to Twitter claimed that fake news travels faster than real news. However, a multitude of factors affects information spreading on social media platforms. Online polarization, for instance, may foster misinformation spreading (1, 8). Our attention span remains limited (9, 10), and feed algorithms might limit our selection process by suggesting contents similar to the ones we are usually exposed to (11–13). Furthermore, users show a tendency to favor information adhering to their beliefs and join groups formed around a shared narrative, that is, echo chambers (1, 14–18). We can broadly define echo chambers as environments in which the opinion, political leaning, or belief of users about a topic gets reinforced due to repeated interactions with peers or sources having similar tendencies and attitudes. Selective exposure (19) and confirmation bias (20) (i.e., the tendency to seek information adhering to preexisting opinions) may explain the emergence of echo chambers on social media (1, 17, 21, 22).According to group polarization theory (23), an echo chamber can act as a mechanism to reinforce an existing opinion within a group and, as a result, move the entire group toward more extreme positions. Echo chambers have been shown to exist in various forms of online media such as blogs (24), forums (25), and social media sites (26–28). Some studies point out echo chambers as an emerging effect of human tendencies, such as selective exposure, contagion, and group polarization (13, 23, 29–31). However, recently, the effects and the very existence of echo chambers have been questioned (2, 27, 32). This issue is also fueled by the scarcity of comparative studies on social media, especially concerning news consumption (33). In this context, the debate around echo chambers is fundamental to understanding social media’s influence on information consumption and public opinion formation. In this paper, we explore the key differences between social media platforms and how they are likely to influence the formation of echo chambers or not. As recently shown in the case of selective exposure to news outlets, studies considering multiple platforms can offer a fresh view on long-debated problems (34). Different platforms offer different interaction paradigms to users, ranging from retweets and mentions on Twitter to likes and comments in groups on Facebook, thus triggering very different social dynamics (35). We introduce an operational definition of echo chambers to provide a common methodological ground to explore how different platforms influence their formation. In particular, we operationalize the two common elements that characterize echo chambers into observables that can be quantified and empirically measured, namely, 1) the inference of the user’s leaning for a specific topic (e.g., politics, vaccines) and 2) the structure of their social interactions on the platform. Then, we use these elements to assess echo chambers’ presence by looking at two different aspects: 1) homophily in interactions concerning a specific topic and 2) bias in information diffusion from like-minded sources. We focus our analysis on multiple platforms: Facebook, Twitter, Reddit, and Gab. These platforms present similar features and functionalities (e.g., they all allow social feedback actions such as likes or upvotes) and design (e.g., Gab is similar to Twitter) but also distinctive features (e.g., Reddit is structured in communities of interest called subreddits). Reddit is one of the most visited websites worldwide (https://www.alexa.com/siteinfo/reddit.com) and is organized as a forum to collect discussions on a wide range of topics, from politics to emotional support. Gab claims to be a social platform aimed at protecting freedom of speech. However, low moderation and regulation on content has resulted in widespread hate speech. For these reasons, it has been repeatedly suspended by its service provider, and its mobile app has been banned from both App and Play stores (36). Overall, we account for the interactions of more than 1 million active users on the four platforms, for a total of more than 100 million unique pieces of content, including posts and social interactions. Our analysis shows that platforms organized around social networks and news feed algorithms, such as Facebook and Twitter, favor the emergence of echo chambers.We conclude the paper by directly comparing news consumption on Facebook and Reddit, finding higher segregation on Facebook than on Reddit.     

The stress echo prognostic gender gap.

AIMS: To investigate whether myocardial ischaemia elicitable during pharmacological stress echocardiography portends different prognosis in men and women.METHODS AND RESULTS: The study group was made by 1733 patients (941 men, 792 women) who underwent dipyridamole (n=1008) or dobutamine (n=725) stress echo for evaluation of known or suspected coronary artery disease. An ischaemic response was found in 460 patients (308 men, 152 women). Considering the whole ischaemic population, women were older (P<0.0001) and more likely to have hypertension (P=0.02) and hypercholesterolaemia (P=0.04) than men. No difference in age and risk factors was evidenced between the two sexes in the subset of 203 patients with ischaemia and suspected coronary artery disease. During follow-up (25 +/- 24 months for the ischaemic and 37 +/- 25 months for the non-ischaemic sample), there were 113 cardiac events (45 deaths and 68 infarctions) and 232 revascularizations. Revascularization rate in ischaemic population was similar in both sexes (P=0.36). Multivariate predictors of cardiac events in the whole ischaemic group were resting WMSI (HR=2.7, 95% CI 1.3--3.3;P=0.0050), female gender (HR=2.2, 95% CI 1.2--3.7;P=0.0062), age > or = l65 years (HR=1.9, 95% CI=1.0--3.6;P=0.0427), and Delta WMSI (HR=2.1, 95% CI=1.0--3.7;P=0.0447). Female gender (HR=2.7, 95% CI 1.1--6.3;P=0.0233) was the only independent prognostic predictor in patients with ischaemia and suspected coronary artery disease. Five-year infarction-free survival was 82% in men and 71% in women in the whole ischaemic population (P=0.0041) as well as in the ischaemic group with suspected coronary artery disease (CAD) (P=0.0175). In the non-ischaemic sample resting WMSI (HR=4.8), history of myocardial infarction (HR=2.5), and hypercholesterolaemia (HR=1.8) were independent predictors of outcome at multivariate analysis, whilst the gender had no prognostic importance.Conclusions: Our results show that female gender is an independent predictor of cardiac events in patients with myocardial ischaemia induced by pharmacological stress echocardiography.     

Pulmonary valve echo motion in pulmonary regurgitation.

Four cases are presented to illustrate the echo patterns of pulmonary valve motion in patients with pulmonary regurgitation caused by pulmonary hypertension, idiopathic dilatation of the pulmonary artery, or congenital absence of the pulmonary valve or in association with pulmonary stenosis. Absence of the pulmonary 'a' wave, fluttering of the e-f slope, and midsystolic closure or 'notching' of the valve were noted with pulmonary hypertension. In the case with idiopathic dilatation of the pulmonary artery a normal echo pattern of pulmonary valve motion along with distinct dilatation of the pulmonary artery at the valvular level were present. Pronounced dilatation and systolic expansion of the pulmonary artery along with dilatation of the right ventricle were seen with congenital absence of the pulmonary valve. No pulmonary valve could be demonstrated on multiple scans from the right ventricle to pulmonary artery. In Case 4 large 'a' waves (14 mm) were noted, indicating a reversal of the normal end-diastolic gradient across the valve and suggesting that pulmonary regurgitation in this case was associated with right ventricular outflow obstruction. Study of the echo pattern of pulmonary valve motion may therefore provide useful information in establishing the cause of pulmonary regurgitation.     

Two-dimensional echocardiographic echo intensity distribution by histographic analysis

To assess myocardial tissue changes, the distribution of echo intensities of two-dimensional echocardiograms was analyzed using a histogram. The materials were obtained from six normal subjects (N), 29 patients with left ventricular hypertrophy (LVH), and 12 patients one year or more after the onset of anteroseptal myocardial infarction (MI). A transducer with a central frequency of 2.3 MHz was used. Scanner receiver settings, including sensitivity-time control, were kept constant for all subjects. The parasternal long-axis image was digitized and computer-processed. The region of interest was located within the interventricular septum. The mean echo intensity and its distribution were studied. The shape of the histogram was evaluated for skewness and kurtosis. Relative echo intensity: N = 0.23 +/- 0.07 (mean +/- SD) less than LVH = 0.58 +/- 0.18 less than MI = 1.07 +/- 0.25 (p less than 0.01). Skewness: N = 1.58 +/- 0.63 greater than LVH = 0.60 +/- 0.61 greater than MI = -0.14 +/- 0.43 (p less than 0.01). Kurtosis: N = 18.0 +/- 7.3 greater than LVH = 10.5 +/- 3.3 greater than MI = 7.7 +/- 0.9 (p less than 0.01). These differences may closely relate to an increase in collagen fiber content. Consequently, analysis of the myocardial echo intensity distribution, in addition to mean echo intensities, may become a clinically useful approach for identifying myocardial tissue changes.     

Differential diagnosis of a low echo thyroid gland

Hypothyrosis as a result of inflammatory disease of the thyroid gland, often is a diagnostic problem because of the insidous onset and its lack of specific symptoms. In the rather large amount of literature about sonography of the thyroid no papers with a systematic approach to this entity are found. In a prospective study we evaluated 36 proven cases and found a characteristic sonographic pattern of the thyroid with regard to its size, contour and structure.     

Cardiac resynchronization in 2008: An echo approach

Dyssynchrony is the abnormality in timing of regional ventricular mechanical activation in patients with heart failure. Dyssynchrony is one of the principal pathophysiologic features that improves with cardiac resynchronization therapy (CRT). Several echocardiographic approaches over the past several years have been described to quantify mechanical dyssynchrony in an attempt to improve patient selection over the electrocardiographic QRS complex width, which is a surrogate for dyssynchrony. Although no ideal method exists, this article focuses on the strengths and limitations of measures of longitudinal velocity using color tissue Doppler, radial strain using speckle tracking, and interventricular mechanical delay using routine pulsed Doppler. Recent results using these methods are exciting; however, they have not yet replaced routine clinical implant criteria for CRT. Echocardiographic assessment of dyssynchrony continues to evolve, with new information being added continually, and appears to have promise for future clinical applications.