One Observer (one + observer)

Distribution by Scientific Domains


Selected Abstracts


3T versus 1.5T phased-array MRI in the presurgical work-up of patients with partial epilepsy of uncertain focus

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2009
Maeike Zijlmans MD
Abstract Purpose To study 3T compared to 1.5T phased array magnetic resonance imaging (MRI) in the presurgical work-up of patients with epilepsy with complex focus localization. Materials and Methods In all, 37 patients (>10 years) in preoperative work-up for epilepsy surgery were offered 3T in addition to 1.5T MRI if ambiguity existed about the epileptic focus. Scans were randomly reviewed by two observers, blinded for prior imaging, patient-identifying information, and each other's assessments, followed by a consensus meeting. The number of abnormal scans, detected lesions, and interobserver agreement were calculated and compared. The final consensus was compared to original scan reports. Results One observer identified 22 lesions in both 3 and 1.5T scans, while the second identified more lesions in 1.5T scans (28 vs. 20). 3T MRI had better interobserver agreement. 3T revealed more dysplasias, while 1.5T revealed more tissue loss and mesial temporal sclerosis (MTS). The final consensus yielded 29 lesions, whereas original reports identified only 17 lesions. Conclusion The 3T scans revealed different lesions compared to 1.5T. Patients can benefit most from 3T scans when a dysplasia is suspected. Reevaluation by another experienced neuroradiologist is advised in case of negative or equivocal MRIs. J. Magn. Reson. Imaging 2009;30:256,262. © 2009 Wiley-Liss, Inc. [source]


New method to census primate groups: Estimating group density of Japanese macaques by point census

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 2 2003
Goro Hanya
Abstract We devised a new method to estimate the density of primate groups in habitats that preclude the use of a line-transect census because the ground is too steep. We combined point census and group follows. From the number of groups counted at a fixed point for an hour, n, group density D was calculated: . ,, the detectability constant, was a constant when distance-dependent detectability g(y) was regressed on a half-normal model: g(y) = e -,2 and can be estimated by combining the information of group follow and point census. Using this method, we estimated the group density of Japanese macaques in Yakushima. A census area of 7 km2 was divided into 28 grid squares (500 m×500 m). One observer was positioned at a point in each grid square, and those points were censused simultaneously for 4,6 days from 0600,0700 to 1500,1600 hr. Four troops were followed for 144 hr during the point census. Distance-dependent detectability closely correlated with the half-normal model. The detectability constant varied with the time of day, but it was not influenced by troop identity or topography. Group density was calculated to be 1.48±0.61 and 0.701±0.432 groups/km2 in the disturbed and undisturbed areas, respectively (95% confidence limit). "True" group density estimated by home range data was within the confidence limit calculated by a point census in the home range of the troops for two troops, suggesting that this method was valid. This method is applicable to other species as long as at least one group can be followed, because it satisfies the fundamental assumptions of point census, and the detectability does not seem to be biased by troop or topography. Am. J. Primatol. 60:43,56, 2003. [source]


Charity Basket or Revolution: Beliefs, Experiences, and Context in Preservice Teachers' Service Learning

CURRICULUM INQUIRY, Issue 4 2000
David M. Donahue
Given what one observer calls the "vast disparity of definitions that faculty can bring to service learning,from what is basically the charity basket approach to the revolutionary," service learning can varytremendously, from reading to elderly residents of a nursing home to organizing a boycott of a sneaker company. With such diversity before teachers, what influences them in the way they design service learning? How do preservice teachers, for whom so many ideas about teaching are emerging, make such choices? Two case studies suggest that preservice teachers' beliefs, experiences, and the context where they teach play an important role related to if and how they use service learning. Beliefs and experiences are especially important because, although service learning is often presented as supporting apolitical values,empowerment and responsibility, for example,for which broad consensus exists, such values are also ambiguous and open to interpretation. Teacher educators and advocates of service learning need to acknowledge the ambiguous political nature of service and service learning. By doing so, they have an opportunity to make the political context of teaching explicit for preservice teachers. Such education in service learning for new teachers goes beyond "training" in the logistical and technical details of implementing a new pedagogy to thoughtful reflection on the value-laden act of teaching. [source]


Differentiation of intraductal papillary mucinous neoplasms from other pancreatic cystic masses: Comparison of multirow-detector CT and MR imaging using ROC analysis

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2007
Su Jin Song MD
Abstract Purpose To compare the diagnostic performance of multirow-detector computed tomography (MDCT) and magnetic resonance imaging (MRI) in the differentiation of intraductal papillary mucinous neoplasms (IPMNs) from other pancreatic cystic masses. Materials and Methods A total of 53 patients with pathologically proven pancreatic cystic lesions who had undergone MDCT and MRI were included in this study. Two radiologists analyzed the morphologic features of the lesions and graded the lesion conspicuity on each examination. The readers assigned their confidence level regarding the differentiation of IPMN from other lesions and predicting ductal communication of the lesion. The radiologists' diagnostic confidence was compared using receiver operating characteristic (ROC) analysis. Results The Az values for each observer for predicting ductal communication of the lesion and differentiating IPMN from other lesions were as follows: For MRI they were respectively 0.949 and 0.995 for reader 1, and 0.916 and 0.932 for reader 2. For MDCT they were respectively 0.790 and 0.875 for reader 1, and 0.774 and 0.850 for reader 2. In addition, for differentiating IPMNs from other lesions, MRI was significantly more accurate than MDCT (P < 0.05) for one observer, but for the other observer there was no significant difference between the two examinations (P = 0.059). For predicting ductal communication of the cystic lesions for both observers, MRI was significantly more accurate than MDCT (P < 0.05). The weighted , values indicate good agreement (, = 0.61) between observers for MDCT, and excellent agreement (, = 0.82) for MRI. Conclusion Pancreatic MRI shows better diagnostic performance than MDCT for differentiating IPMNs from other cystic lesions of the pancreas. J. Magn. Reson. Imaging 2007;26:86,93. © 2007 Wiley-Liss, Inc. [source]


Plasma Homocysteine, Fasting Insulin, and Androgen Patterns among Women with Polycystic Ovaries and Infertility

JOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 3 2001
Dr. E. Scott Sills
Abstract Objective: To measure plasma homocysteine, androgen, and insulin concentrations in women with normal and polycystic-appearing ovaries in an infertility setting. Methods: Among women referred for infertility evaluation (n = 54), homocysteine, androstenedione, DHEAS, total testosterone, fasting insulin/glucose and methyltetrahydrofolate reductase (MTHFR) polymorphism status (C677T mutation) were studied. Ovaries were examined via transvaginal sonogram by one observer and scored as either normal (n = 18) or polycystic (n = 36). Results: When polycystic ovaries were identified, mean total testosterone was significantly higher than when non-polycystic ovaries were present (p = 0.01), although no measured androgen was outside the normal reference range in either group. Average BMI was higher in the polycystic group, but the difference was not significant (p = 0.10). We observed a trend toward higher mean fasting insulin levels in women with polycystic ovaries, but this increase did not reach statistical significance (p = 0.07). Median plasma homocysteine was identical (7.0 mmol/l) in both populations, and no study subject exceeded the current recommended maximum reference value. Conclusions: In this population, the presence of polycystic ovaries was associated with higher serum androgens (especially total testosterone) although none of the measured androgens were above the normal range. While fasting insulin levels were also higher in this group, median plasma homocysteine levels were similar irrespective of ovarian morphology. Concomitant plasma homocysteine derangements in this population of young, lean patients with polycystic-appearing ovaries seem unlikely. Further studies are needed to clarify the role(s) of homocysteine in human reproductive physiology. [source]


Regression modelling of weighted , by using generalized estimating equations

JOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 1 2000
R. Gonin
In many clinical studies more than one observer may be rating a characteristic measured on an ordinal scale. For example, a study may involve a group of physicians rating a feature seen on a pathology specimen or a computer tomography scan. In clinical studies of this kind, the weighted , coefficient is a popular measure of agreement for ordinally scaled ratings. Our research stems from a study in which the severity of inflammatory skin disease was rated. The investigators wished to determine and evaluate the strength of agreement between a variable number of observers taking into account patient-specific (age and gender) as well as rater-specific (whether board certified in dermatology) characteristics. This suggested modelling , as a function of these covariates. We propose the use of generalized estimating equations to estimate the weighted , coefficient. This approach also accommodates unbalanced data which arise when some subjects are not judged by the same set of observers. Currently an estimate of overall , for a simple unbalanced data set without covariates involving more than two observers is unavailable. In the inflammatory skin disease study none of the covariates were significantly associated with ,, thus enabling the calculation of an overall weighted , for this unbalanced data set. In the second motivating example (multiple sclerosis), geographic location was significantly associated with ,. In addition we also compared the results of our method with current methods of testing for heterogeneity of weighted , coefficients across strata (geographic location) that are available for balanced data sets. [source]