1,721,104 research outputs found
[18F]FDG-PET-CT for early monitoring of tumor response: when and why.
No full text(18)F-fluorodeoxyglucose positron emission tomography ([(18)F]FDG PET) has been recognized as a suitable tool in tumor response assessment of patients complaining with solid tumors who have undergone chemo- and radiotherapy. It offers the advantage of functional tissue characterization, which is independent from morphologic criteria allowing to differentiate disease relapse from therapy-induced fibrosis. At present, there is a growing body of evidence that PET semi-quantitative assessment of treatment-induced changes in tumor [(18)F]FDG avidity may predict early tumor response and patient outcome. Patient management might be changed. For instance, in non responder patients this novel diagnostic approach would hamper useless ''wait and watch'' attitude in implementing further options or identifying those needing additional therapeutic strategies. On the other hand, for those patients revealing promptly a favourable metabolic response a cost-sparing approach could be implemented avoiding expensive diagnostic procedures during the follow-up as well as the risk of over-treating. In any case, since even a partial metabolic response may be an indication for continuing therapy, the advantage of metabolic assessment over conventional procedures may be clinically relevant. Although a morphological assessment has been considered for long time the standard for detecting therapy response, limitations of conventional computed tomography-based evaluation in solid tumors are well-known. PET provides an independent means of assessing malignancy. However, no consensus has been achieved until now regarding the optimal timing in performing PET during or at completion of treatment
Radionuclide monitoring of left ventricular function
No full textThe development of continuous left ventricular (LV)
function–monitoring devices has allowed monitoring of
several physiologic parameters in a number of cardiovascular
disorders. This interesting application of radionuclide
angiography relates to the use of miniaturized
equipment suitable for evaluating patients during routine
activities by means of nonimaging probes. In contrast to
gamma cameras, these probes do not produce an image
of the heart, but are used specifically to record count variations
within its field of view. Because the systems are
not designed to generate images, the detectors are simpler
than a standard scintillation camera. The simplicity
in detector configuration makes the systems portable and
less expensive than gamma cameras. Several devices have been evaluated and validated
for continuous monitoring of LV function. The diagnostic
and prognostic roles of these techniques appear to be
predominant in patients with CAD. Silent myocardial
ischemia may be widely evaluated by these systems,
which allow the clinician to predict ischemic cardiac
events, perform risk stratification, and guide treatment in
patients with CAD more accurately than can be done
with exercise test results. In fact, it has been demonstrated
that adverse cardiac events are more commonly
observed during routine daily activities.
The continuous improvement in miniaturizing these
devices and the capability of online processing of data
could make this technique useful and widely acceptable,
facilitating simultaneous assessment of hemodynamic
and metabolic changes in silent LV dysfunction and continuing
to play an important role in noninvasive evaluation
of ventricular performance
The current and evolving role of FDG–PET/CT in personalized iodine-131 therapy of differentiated thyroid cancer
No full textPurpose: Several approaches have been recommended for the selection of patients with differentiated thyroid cancer amenable for postoperative radioiodine remnant ablation or repeated radioiodine treatment, though with inadequate results. 2-[18F]-fluoro-2-deoxy-d-glucose positron emission tomography is gaining consideration for predicting disease-free or survival of differentiated thyroid carcinoma patients, in particular in the peri-or post-surgery setting and for the detection of recurrence in patients with elevated or rising thyroglobulin without evidence of disease on neck ultrasound or iodine scintigraphy. This paper aims to review the role of FDG–PET/CT in tailoring iodine-131 empiric therapy for radioiodine remnant ablation and the detection of recurrence in patients with elevated thyroglobulin and negative iodine-123 scan. Methods: A literature search up to May 2017 of MEDLINE® and SCOPUS® with the Mesh terms: “PET/CT”, “iodine-131 therapy”, “differentiated thyroid cancer” and “prognosis” was performed. Thereafter, papers dealing with radioiodine remnant ablation and empiric therapy were selected. Results: Ninety papers were retrieved from the initial search and 19 considered for the review. The percentage of positive FDG–PET/CT performed at radioiodine remnant ablation or shortly after ranged from 17 to 69%, with highest values in high- and intermediate-to-high risk patients. The response rate to radioiodine remnant ablation and survival were consistently higher in negative FDG–PET/CT patients. Besides, FDG–PET/CT imaging was found to be a very accurate diagnostic tool for the detection of recurrence in patients with elevated thyroglobulin and negative iodine-123 scan, discriminating patients needing further empirical iodine-131 therapy from those who could benefit from alternative approaches. Conclusions: Although a meta-analysis was not possible due to the heterogeneity and the small population samples of the studies retrieved, the results of the present review support the use of FDG–PET/CT in tailoring iodine-131 therapy when used close to radioiodine remnant ablation and in patients amenable to iodine-131 empiric therapy
Quantitative assessment of myocardial blood flow with SPECT
No full textThe quantitative assessment of myocardial blood flow (MBF) and coronary flow reserve (CFR) may be useful for the functional evaluation of coronary artery disease, allowing judgment of its severity, tracking of disease progression, and evaluation of the anti-ischemic efficacy of therapeutic strategies. Quantitative estimates of myocardial perfusion and CFR can be derived from single-photon emission computed tomography (SPECT) myocardial perfusion images by use of equipment, tracers, and techniques that are available in most nuclear cardiology laboratories. However, this method underestimates CFR, particularly at high flow rates. The recent introduction of cardiac-dedicated gamma cameras with solid-state detectors provides very fast perfusion imaging with improved resolution, allowing fast acquisition of serial dynamic images during the first pass of a flow agent. This new technology holds great promise for MBF and CFR quantification with dynamic SPECT. Future studies will clarify the effectiveness of dynamic SPECT flow imaging
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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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