1,720,986 research outputs found
Liver Vessel Segmentation and Accurate Landmark Pairs Detection for Quantitative Liver Deformable Image Registration Verification
No full textBackground: Target Registration Error (TRE) calculated based on selected anatomical landmarks is commonly known as the only trustable way to evaluate DIR accuracy. However, manual landmark pair selection is labor intensive and subjected to observer variability. Currently, no DIR benchmark datasets are available for Liver CTs. Manually selected landmark pairs have limited DIR evaluation power due to inadequate landmarks quantity (i.e., ~5 landmark pairs per dataset1 for liver CTs) and positional accuracy. For the purpose of liver DIR verification, there is a great need to establish a large quantity of landmark pairs with good positional accuracy.Purpose: An image processing procedure was developed in this study to automatically and precisely detect landmark pairs on corresponding vessel bifurcations between pairs of intra-patient CT images. With high positional accuracy, the generated landmark pairs can be used to evaluate deformable image registration (DIR) methods quantitatively for liver CTs.
Methods: Landmark pairs were detected within the liver between pairs of contrast-enhanced CT scans for 32 patients. For each case, the liver vessel tree was automatically segmented in one image. Landmarks were automatically detected on vessel bifurcations. The corresponding landmarks in the second image were placed using a parametric DIR method (pTVreg). Manual validation was applied to reject outliers and adjust the landmarks’ positions to account for vessel segmentation uncertainty caused by the inconsistent image quality. Landmark pairs' positional accuracy of the procedure was evaluated using digital phantoms on target registration errors (TREs).
Results: On average, ~71 landmark pairs per case were detected after manual outlier rejection. The proposed procedure increased the quantity of liver landmark pairs by ~10 times compared to the reported in the literature. A fully manual spot check showed that the reported procedure performed better than or as good as human at landmark pairs positional accuracy. Measured in the digital phantoms, the mean and standard deviation of TREs were 0.67 ± 0.48 mm with 99% of landmark pairs having TREs smaller than 2mm.
Conclusion: A large number of liver landmark pairs with high positional accuracy were detected in contrasted enhanced CT image pairs using the reported method. The detected landmark pairs can be used for the quantitative evaluation of DIR methods.
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Build 5DCT by Connecting Cardiac ECG 4DCT with Respiratory 4DCT for Heart Motion Management in Stereotactic Tachycardia Radiosurgery
No full textPurpose: To develop a generic procedure to make 5DCT from ECG 4DCTs and respiratory 4DCTs of cardiac RT patients. The 5DCT, whose dimension consists of 3D volume, cardiac cycle and respiratory cycle, will be used for quantitatively evaluating respiratory and cardiac motion of the heart, and supporting cardiac RT motion management, 5D dose calculation and dosimetry motion assessment. Methods: Images of ECG 4DCTs and respiratory 4DCTs for cardiac RT patients were obtained from the clinical system with IRB approval. For each patient, ten ECG 4DCT phases were registered using the groupwise deformable image registration algorithm GroupRegNet. The results were the template ECG CT representing the accurate average heart anatomy rather than an intensity-averaged CT, and the cardiac 4D DVF (deformation vector field). The ECG CT template and ten respiratory 4DCT phases were registered together using the 2nd groupwise registration to compute the 2nd respiratory 4D DVF. The computed DVFs from two groupwise registrations connected ECG 4DCTs to respiratory 4DCTs. A 10x10 cardiorespiratory 5DCT volume was generated by warping the ECG phases using composed DVFs. The final 5DCT phases were manually evaluated by visually the checking the respiratory and cardiac motion of the heart chambers.
Results: The 5DCT generation procedure was implemented using Python and MATLAB, and was successfully applied to 4DCT images from five cardiac RT patients. The registration results were satisfactory based on visual evaluation. The quantitative evaluation and 5D dose calculation are planned for future work.
Conclusion: A practical and effective procedure was developed to assess 5D motion of the heart and generate 5DCT phases from the clinical ECG 4DCTs and respiratory 4DCTs. The generated 5DCT could be used in dose calculation to assess the effect of 5D motion of the heart chambers on dosimetry for cardiac RT treatments.
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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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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