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Experienced Observers (experience + observer)
Selected AbstractsComputer-aided calibration for visual estimation of vegetation coverJOURNAL OF VEGETATION SCIENCE, Issue 6 2009Åsa Gallegos Torell Abstract Question: What precision and accuracy of visual cover estimations can be achieved after repeated calibration with images of vegetation in which the true cover is known, and what factors influence the results? Methods: Digital images were created, in which the true cover of vegetation was digitally calculated. Fifteen observers made repeated estimates with immediate feedback on the true cover. The effects on precision and accuracy through time were evaluated with repeated proficiency tests. In a field trial, cover estimates, before and after calibration, were compared with point frequency data. Results: Even a short time of calibration greatly improves precision and accuracy of the estimates, and can also reduce the influence of different backgrounds, aggregation patterns and experience. Experienced observers had a stronger tendency to underestimate the cover of narrow-leaved grasses before calibration. The field trial showed positive effects of computer-based calibration on precision, in that it led to considerably less between-observer variation for one of the two species groups. Conclusions: Computer-aided calibration of vegetation cover estimation is simple, self-explanatory and time-efficient, and might possibly reduce biases and drifts in estimate levels over time. Such calibration can also reduce between-observer variation in field estimates, at least for some species. However, the effects of calibration on estimations in the field must be further evaluated, especially for multilayered vegetation. [source] Borderline nuclear change; can a subgroup be identified which is suspicious of high-grade cervical intraepithelial neoplasia, i.e. CIN 2 or worse?CYTOPATHOLOGY, Issue 5 2002J. M. Edwards Borderline nuclear change; can a subgroup be identified which is suspicious of high-grade cervical intraepithelial neoplasia, i.e. CIN 2 or worse? Only 10% of first borderline smears are associated with a histological high-grade (HG) abnormality, i.e. CIN 2,3, invasive malignancy or glandular neoplasia on subsequent investigation. The advantages of highlighting this subgroup are obvious but is this possible? From 1996 and 1997, 242 borderline smears with histological follow-up were examined by two independent experienced observers (observer 1 and 2) without prior knowledge of further investigation results. For each smear a profile of nuclear details was produced, also noting the type of cell mainly affected by the process; then the observers were asked to assess the degree of worry of HG disease for each smear i.e. whether the smear fell into group 1 borderline changes indicative of low-grade (normal, inflammatory, CIN1/HPV) disease (BL/LG) or group 2 difficult borderline smear, HG disease (CIN 2,3, invasive neoplasia or glandular neoplasia) cannot be excluded (BL/HG). Observer 1 selected a group of BL/HG with a PPV for HG disease of 38%, with observer 2 having a PPV of 50%; this compared with the overall laboratory HG disease PPV for borderline smears of 14%. Both observers found the most useful criterion to be the increase in nuclear:cytoplasmic ratio. Our results show that it is possible to separate a small group of borderline smears which should be classified as ,borderline/high grade lesion difficult to exclude' (BL/HG). Both observers had some success in arriving at this classification although their method of selecting out this group was quite different. [source] Testicular carcinoma in situ in subfertile Danish menINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 4 2007Inge A. Olesen Summary Carcinoma in situ (CIS) testis is the precursor stage for the majority of testicular germ cell tumours (TGCT). Infertility is one of the conditions known to predispose to TGCT, but based on scarce existing data, the prevalence of CIS in this risk group was estimated at only approximately 1%. To establish more objective data, we investigated retrospectively the prevalence of CIS based on testicular biopsies performed in a well-defined group of subfertile males. We included 453 patients who had testicular biopsies performed for infertility reasons during 1995,2005 at the Copenhagen University Hospital (Rigshospitalet). Biopsies were evaluated by two experienced observers independently. CIS was detected in 10 individuals, of whom three had bilateral CIS, corresponding to a prevalence of 2.2% (95% CI 1.1,4.0%). This is greater than the estimated risk of 0.45% for the age- and birth cohort-matched general Danish population. All patients with CIS testis had severe oligozoospermia (,2.06 million/mL). We confirmed that a thorough examination of men suffering from subfertility/infertility can identify those with an increased risk for testicular neoplasia and recommend performing bilateral biopsies, especially in the subpopulation of men with atrophic testicles, severe oligozoospermia and/or irregular ultrasonic pattern of their testicles. [source] Dermoscopic observation of Bowen's diseaseJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 5 2004L Bugatti ABSTRACT Background, In the literature no specific dermoscopic criteria have been described for the diagnosis of Bowen's disease (BD). Objective/aim, To assess the morphological findings of BD seen under dermoscopic observation. Methods, Clinical and dermoscopic images of 14 patients affected by BD with various amount of pigmentation were obtained by means of Heine Dermaphot. Dermoscopic images were analysed by experienced observers applying the modified pattern analysis. Results, The most frequently occurring dermoscopic features were found to be: multicomponent pattern (100%); atypical vascular structures (86.6%); absence of pigmented network (64.3%) or presence of pseudo-network (35.7%); irregular diffuse pigmentation or blotches of pigment (64.2%); irregularly distributed dots and globules (64.2%); focal/multifocal hypopigmentation (78.5%), scaly surface (64.2%) and haemorrages (26.6%). Conclusions, Dermoscopically, BD is mainly characterized by a multicomponent global pattern associated with a prominent vascular pattern (mainly dotted vessels) and a scaly surface. Although no specific dermoscopic criteria can be given for BD, epiluminescence can be a valuable aid in the diagnosis of such a mimicker lesion. [source] Fully automated analysis of colonic manometry recordingsNEUROGASTROENTEROLOGY & MOTILITY, Issue 6 2002A. M. P. De Schryver AbstractThe purpose of this study was to develop a computer program for fully automated analysis of all presently known motor patterns in human colonic motility recordings. Colonic pressure recordings obtained from 24 healthy volunteers were used. Algorithms were developed for the detection and numerical analysis of five types of pressure waves: antegrade, retrograde, simultaneous, high-amplitude and isolated pressure waves. Furthermore, periodical motor activity was quantified. Validation was performed by comparison with visual analysis by two experienced observers. Patterns recorded during day- and night-time were compared using multiple-factor analysis of variance with Bonferroni correction. Automated analysis correlated well with visual peak detection (r = 0.98, P <0.01) and detection of antegrade pressure waves (r = 0.98, P <0.01). Most motor patterns showed a diurnal variation. During the night, prevalences of antegrade (938 vs 455; P <0.05), retrograde (112 vs 81; P <0.05), high-amplitude (12.9 vs 1.3; P <0.05), isolated pressure waves (1114 vs 765; P <0.05), and periodic motor activity were decreased (7.33 vs 4.47%; P <0.05). However, when expressed as percentage of absolute numbers of pressure waves, prevalences remained constant. In conclusion, fully automated analysis of all hitherto described colonic motility patterns is feasible. During the night, overall wave prevalences markedly decreased, but the distribution over the various motor patterns was preserved. [source] Digit ratios (2D:4D) determined by computer-assisted analysis are more reliable than those using physical measurements, photocopies, and printed scansAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 3 2009Heather C. Allaway Prenatal androgens influence the second to fourth digit ratio (2D:4D) of hands with men having lower ratios than women. Numerous methods are used to assess 2D:4D including, physical measurements with calipers, and measurements made from photocopies, scanned images, digital photographs, radiographs, and scaled tubes. Although each method appears relatively reliable, agreement upon a gold standard is necessary to better explore the putative effects of prenatal androgens. Our objective was to assess the level of intra and interobserver reliability when evaluating 2D:4D using four techniques: (1) physical measurements, (2) photocopies, (3) printed scanned images, and (4) computer-assisted image analysis. Physical measurements, photocopies, and printed scanned images were measured with Vernier calipers. Scanned images were also measured with computer-based calipers. Measurements were made in 30 men and 30 women at two different time points, by three experienced observers. Intraclass correlation coefficients were used to assess the level of reliability. Intraobserver reliability was best for computer-assisted (0.957), followed by photocopies (0.939), physical measurements (0.925), and printed scans (0.842; P = 0.015). Interobserver reliability was also greatest for computer-assisted (0.892), followed by photocopies (0.858), physical measurements (0.795), and printed scans (0.761; P = 0.001). Mean 2D:4D from physical measurements were higher than all other techniques (P < 0.0001). Digit ratios determined from computer-assisted, physical measurements, and printed scans were more reliable in men than women (P = 0.009, P = 0.017, and P = 0.012, respectively). In summary, 2D:4D determined from computer-assisted analysis yielded the most accurate and consistent measurements among observers. Investigations of 2D:4D should use computer-assisted measurements over alternate methods whenever possible. Am. J. Hum. Biol., 2009. © 2009 Wiley-Liss, Inc. [source] Photoscreening for diabetic retinopathy: a comparison of image quality between film photography and digital imagingCLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 4 2004Christina MC Klais MD Abstract Purpose:,Retinal images from patients attending an urban screening centre before and after the transition from film photography to digital image acquisition were analysed for quality of image. Methods:,A total of 1946 diabetic patients, aged 12,92 years (mean 55.6 ± 14.88 years), were included in this retrospective study of retinal screening techniques. Each imaging group was subdivided into age-matched groups. In all subjects pupils were pharmacologically dilated before photography. The images were reviewed by the same three experienced observers and graded at the time of screening from grade 1 (excellent quality) to grade 4 (unreadable). Results:,Of 938 patients in the film group, 31.3% had excellent images, 38.2% good, 22.7% poor and 7.8% were unreadable. Of the 1008 patients in the digital imaging group, 25.3% had excellent images, 46.3% good, 14.6% poor and 13.8% were unreadable. A significant difference was observed in patients over 65 years of age who exhibited a threefold increase in failure rate with digital imaging (33.7% v 11.3%)(P < 0.0001). Conclusion:,In this study population a statistically significant degradation of image quality was observed in those older than 65 years following transition to digital photography. This has implications for service provision planning. [source] | ||||||||||