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The impact of regional 99mTc-HMPAO single-photon-emission computed tomography (SPECT) imaging on clinician diagnostic confidence in a mixed cognitive impairment sample
No full textAIM:To assess the clinical impact of regional cerebral blood flow (rCBF) single-photon-emission computed tomography (SPECT) imaging on diagnosis and clinician diagnostic confidence in a cohort of individuals with cognitive impairment. MATERIALS AND METHODS:Forty-one clinicians who referred 79 patients for a [99mTc]-hexamethylpropyleneamine oxime (HMPAO) SPECT for cognitive complaints completed a two-part questionnaire to determine the diagnosis and diagnostic confidence (using a 0-100 visual analogue scale [VAS]) before and after imaging. SPECT images were analysed using statistical parametric mapping and interpreted semi-quantitatively. Clinicians were also asked directly for their opinion on whether the imaging contributed to their diagnostic process. RESULTS:Diagnosis changed after imaging in 44% of cases, and confidence was significantly improved (VAS score change= +26.3±22.2) after imaging in cases where the pre-imaging confidence was low (p<0.001). Clinician confidence was not significantly different (VAS score change=-6.6±25.5) after imaging when pre-imaging confidence was moderate to high. Interestingly, a proportion of clinicians with the highest confidence levels became less certain about their diagnosis following imaging results. When asked directly, 96% of clinicians stated that the imaging contributed to the diagnostic process. CONCLUSIONS:In a mixed clinical cognitive impairment cohort, perfusion SPECT is valued by referring clinicians and contributes to diagnostic decision making. Imaging is of particular value when diagnostic confidence is low prior to imagin
Analytical technique to recover the third dimension in planar imaging of inhaled aerosols: (1) impact on spatial quantification
No full textAn analytical algorithm is described for converting planar scintigraphic images of aerosol distributions in the lungs to an equivalent three-dimensional (3D) representation. The recovery of volumetric information should benefit regional quantification. The technique has been validated using simulated planar images of eleven known aerosol distributions in ten realistic lungs. Global and regional 3D parameters, such as the total activity deposition (A), the penetration index (PI) and the relative penetration index (rPI), were quantified on the planar images and on their 3D representation. Random and systematic errors of the estimation were measured. Finally, the performance of planar imaging was compared with that of single-photon emission computed tomography (SPECT). SPECT images were simulated for the same aerosol distributions in the same subjects and quantified for A, PI, and rPI. The systematic errors in A, PI and rPI obtained from planar imaging were 8.9%, 64.8%, and 54.1%, respectively, using the two-dimensional (2D) analysis; they improved significantly to 4.4%, 19.0%, and 25.5% with the 3D analysis (p < 0.01). The corresponding values for SPECT were 5.2%, 9.8%, and 15.7%, significantly better for PI and rPI (p < 0.01). The random errors of A were similar for all techniques being about 5%; those of PI and rPI measurements were significantly higher for planar imaging (?14%) than SPECT (?8%). In conclusion, 3D spatial parameters can be derived from planar imaging that are significantly more accurate in characterizing different aerosol depositions than their 2D counterpart. However, the errors remain significantly higher than with SPECT
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
Comparison of SPECT aerosol deposition data with twenty-four-hour clearance measurements
No full textThree-dimensional (3D) radionuclide imaging provides detailed information on the distribution of inhaled aerosol material within the body. Analysis of the data can provide estimates of the deposition per airway generation. Information on regional distribution of deposited aerosol can also be obtained from 24-hour clearance measurements. In this study, a nebulizer was used to deliver a radiolabeled aerosol to nine human subjects. Single photon emission computed tomography (SPECT) has been used to assess the distribution of aerosol deposition per airway generation. The deposition pattern was also estimated using measurements of the aerosol remaining in the lung 24 h after inhalation. The error in the SPECT value was assessed by simulation and that in the 24-h clearance value by repeat analysis. The mean fraction of lung deposition in the conducting airway (CADF) from SPECT was 0.21. The corresponding 24-h clearance value was 0.23. These values were not significantly different. There was a weak but non-significant correlation between the SPECT and 24-h measurements (r = 0.49). The standard error of the difference was 0.11. The corresponding errors on the SPECT and 24-h clearance measurements were 0.04 and 0.05, respectively. There was no systematic difference between the values of conducting airways deposition obtained from 24-h measurements and SPECT. However, there were random differences on individual subjects, which were larger than the estimated measurement errors
Measurement of cerebral perfusion volume and 99mTc-HMPAO uptake using SPECT in controls and patients with Alzheimer's disease
No full textMethods for quantifying the changes in brain function observed in single photon emission computed tomography (SPECT) using hexamethylenepropylene amine oxime (HMPAO) for patients with Alzheimer's disease have the potential of improving the diagnostic accuracy of the procedure and its ability to monitor response to treatment. The absolute percentage uptake of HMPAO and the cerebral perfusion volume (CPV) of the brain were assessed using SPECT in 26 patients with mild to moderate Alzheimer's disease (AD) and 24 control subjects. A subset of 15 control subjects, which was age-matched to the AD patients, was selected to allow fair statistical comparison of parameters between groups. The percentage of brain volume with reduced perfusion (R) and a volume loss index (VLI), given by R1/2/CPV, were also calculated. Eight of the control subjects were studied on a second occasion after a mean period of 6 months. There was no significant difference in percentage uptake between controls and AD patients, the mean value being 5.8%. Cerebral perfusion volume in controls was found to depend on sex (mean value in males and females being 1327 ml and 1222 ml, respectively) and on age. The volume loss index corrected for age and sex provided good discrimination between controls and AD subjects giving a sensitivity and specificity of 81% and 96%, respectively. The repeatability coefficient, the 95% confidence limit for the difference between repeat measurements, on controls was 67 ml (5%). The measurement of cerebral perfusion volume and related indices may be of value in identifying patients with early Alzheimer's disease and in following their response to treatment
A comparison of planar scintigraphy and SPECT measurement of total lung deposition of inhaled aerosol
No full textPlanar gamma camera imaging of inhaled aerosol deposition is extensively used to assess the total deposition in the lung. However, validation of the measurements is not straightforward, as gold standard measurements of lung activity against which to compare are not readily available. Quantitative SPECT imaging provides an alternative method for comparison. Four different methods for planar image quantification are compared. Two attenuation correction techniques, thickness measurement and transmission measurement, have been combined with two scatter correction techniques, reduced attenuation coefficient and line-source scatter function convolution subtraction. Each technique has been applied to 10 studies of aerosol deposition of a fine aerosol (mass median aerodynamic diameter 1.8 ?m) and 10 studies using a coarse aerosol (mass median aerodynamic diameter 6.5 ?m). The total activity in the right lung for each measurement has been compared to the value determined from SPECT imaging on the same subjects. When the thickness measurement and transmission techniques were applied with scatter compensation using a reduced attenuation coefficient, activity was systematically overestimated by 5% in both cases. The corresponding random errors (coefficient of variation) were 8.6% and 6.6%. Separate scatter correction reduced these systemic errors significantly to -1.5% and 2.7%, respectively. The random errors were not affected. All techniques provided assessment of total lung activity with an accuracy and precision that differed by less than 10% compared to the SPECT values. Planar gamma camera imaging provides a good method of assessing total lung deposition of inhaled aerosol.
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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
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