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Multi-center transferability of a breath-hold T2 technique for myocardial iron assessment.
Get PDFBackground: Cardiac iron overload is the leading cause of death in thalassemia major and is usually assessed using myocardial T2* measurements. Recently a cardiovascular magnetic resonance (CMR) breath-hold T2 sequence has been developed as a possible alternative. This cardiac T2 technique has good interstudy reproducibility, but its transferability to different centres has not yet been investigated.
Methods and Results: The breath-hold black blood spin echo T2 sequence was installed and validated on 1.5T Siemens MR scanners at 4 different centres across the world. Using this
sequence, 5–10 thalassemia patients from each centre were scanned twice locally within a week for local interstudy reproducibility (n = 34) and all were rescanned within one month at the standardization centre in London (intersite reproducibility). The local interstudy reproducibility
(coefficient of variance) and mean difference were 4.4% and -0.06 ms. The intersite reproducibility and mean difference between scanners were 5.2% and -0.07 ms.
Conclusion: The breath-hold myocardial T2 technique is transferable between Siemens scanners with good intersite and local interstudy reproducibility. This technique may have value in the diagnosis and management of patients with iron overload conditions such as thalassemia
Comparison of biventricular dimensions and function between pediatric sickle-cell disease and thalassemia major patients without cardiac iron
No full textPatients with chronic anemia develop compensatory ventricular dilation, even when maintained on chronic
transfusion regimens. It is important to characterize these effects to interpret pathological changes in cardiac
dimensions and function introduced by iron overload and sickle cell vasculopathy. Our primary goal
was to compare biventricular dimensions and function assessed by cardiovascular magnetic resonance
(CMR) in pediatric, chronically-transfused sickle-cell disease (SCD) and thalassemia major (TM) patients
who had normal cardiac iron levels. Moreover, we explored systematic sex differences in ventricular dimensions
in both populations. We identified 261 studies suitable for analysis from 64 patients with SCD (34
females) and 49 patients with TM (20 females). All demographic and CMR parameters were inversely
weighted by the number of exams. In both populations, males had larger left and right ventricular dimensions
than females, with a more marked effect observed in patients with SCD. Compared to patients with
TM, patients with SCD showed significantly greater biventricular dilation and left ventricular hypertrophy.
This difference could not be explained by different hemoglobin levels, cardiac iron overload, and systolic
blood pressure. The left ventricular (LV) ejection fraction (EF) for the males and the right ventricular (RV)
EF for both the sexes were comparable between SCD and TM groups, while females with SCD had significantly
lower LV EF than females with TM. Our results represent important baseline findings that place
changes introduced by iron overload as well as systemic and pulmonary vasculopathy in proper context
Cardiac iron overload in sickle-cell disease
No full textChronically transfused sickle cell disease (SCD) patients have lower risk of myocardial iron overload (MIO)
than comparably transfused thalassemia major (TM) patients. However, cardioprotection is incomplete. We
present the clinical characteristics of six patients who have prospectively developed MIO, to identify
potential risk factors for cardiac iron accumulation. From 2002 to 2011, cardiac, hepatic, and pancreatic iron
overload were assessed by R2 and R2* magnetic resonance imaging techniques in 201 chronic transfused
SCD patients as part of their clinical care. At the time, they developed MIO, five of six patients had been on
chronic transfusion for more than 11 years; only one was on exchange transfusion. The time to MIO was
correlated with reticulocyte and hemoglobin S percentages. All patients had qualitatively poor chelation
compliance (4600 ng/ml and liver iron concentration >22 mg/g.
Pancreatic R2* was >100 Hz in every patient studied (5/6). Cardiac iron rose proportionally to pancreas R2*,
with all patients having pancreas R2*>100 Hz when cardiac iron was present. MIO had a threshold
relationship with liver iron that was higher than observed in TM patients. In conclusion, MIO occurs in a small
percentage of chronically transfused SCD patients and is only associated with exceptionally poor control of
total body iron stores. Duration of chronic transfusion is clearly important but other factors, such as levels of
effective erythropoiesis, appear to contribute to cardiac risk. Pancreas R2* can serve as a valuable screening
tool for cardiac iron in SCD patients
Pulmonary hypertension in well-transfused thalassemia major patients
No full textThe risk for pulmonary hypertension (PH) in thalassemia major (TM) patients remains controversial. We report
echocardiography results from 60 TM patients: we evaluated the association between tricuspid regurgitation
velocities (TRV), iron stores, and serologic markers of hemolysis and arginine dysregulation.
Patientswere enrolled fromAugust 2004 untilMay 2009. All parameterswere inverselyweighted by the number
of exams.
TRVwas comparable between sexes and itwas uncorrelatedwith age. At the first exam, TR velocities at the upper
limits of normal (2.5–2.7 m/s) were observed in 8 patients. An abnormal TRV (2.9 m/s) was found in 1 patient.
Borderline increases in TRV were associated with a reduced global arginine bioavailability (R = −0.399 P =
0.005), increased anemia (hemoglobin: R=−0.219 P=0.0461), cardiac index (R=0.223 P=0.0481), and diastolic
dysfunction (E/A: R =0.289 P = 0.0088; E/E′: R= 0.223 P = 0.0453), but not hemolysis, iron overload
and systolic function evaluated by Magnetic Resonance Imaging, and splenectomy.
Well-transfused TM patients have a lower risk for PH than thalassemia intermedia patients. However, they
do have vascular stressors that raise their lifetime PH risk to levels higher than for the general population.
Consequently,we support recommendations for annual echocardiographic screening and cardiac catheterization
for persistent TRV above 3 m/s
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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