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At least 433 records · Page 24Linked to original sources
PubMed2005

Predictive accuracy of sexing the mandible by ramus flexure.

Loth & Henneberg (Am J Phys Anthrop 99 (1996) 473) described a single morphological indicator of sexual dimorphism, namely the presence or absence of flexure on the posterior border of the mandible, with a predictive accuracy of 90.6-99.0%. In the other studies, which have criticized mandibular ramus flexure as sex indicator in adult and fossils specimens by the same method, the accuracy of sexing was found between 59.0% and 80.4% which is well below the reported 90.6-99.0% (Am J Phys Anthrop 107 (1998) 363; Am J Phys Anthrop 111 (2000) 573; Am J Phys Anthrop 111 (2000) 429; Homo 53 (2002) 97). It was indicated that the method sexed males more reliably than females and consistency was low. In the current blind test, 120 mandibles from forensic cases were examined for the presence or absence of mandibular ramus flexure. Virtually identical results were obtained when a second observer examined the same sample of mandibles. The results were then compared to records of the same cases resulting in 85.8% accuracy for the total sample. A marked difference was observed between sexes where the ramus shape was diagnostic for 92.6% of the males but for only 60.0% of the females (p < 0.001). When mandibles with excessive tooth loss (more than two molars missing) (n = 35) were removed from the sample (in normative sample), the overall predictive value increased to 90.6% (95.6% accuracy in males and 70.6% in females). Our results confirm that there are marked differences between the sexes in the predictive accuracy and this indicator is better in mandibles without molar tooth loss as mentioned by Loth & Henneberg. They also pointed out that the tooth loss is a potential source of error. On the other hand, in this study, there were no sexing errors when mandibles which ramus shape scores -1, 0 and +1 were extracted from the normative sample as the "sex indeterminate group". This study suggests that further assessment should be made only when both rami are available for observation, and the mandible shows either bilateral flexure (+2) or bilateral non-flexure (-2). The consideration of this new categorization can also be useful when using Loth & Henneberg's method.

Adult↗
PubMed2006

Accuracy and reproducibility of a subpixel extended phase correlation method to determine micron level displacements in the heart.

Future treatment of heart disease may involve local perturbations of mechanical function, such as intramyocardial injections of angiogenic growth factors or progenitor cells. This necessitates an accurate measurement technique to determine regional heart function. We have previously developed a method to determine regional heart function using a phase correlation algorithm. However, in determining regional function over a single heartbeat it is necessary to sum displacements between many images. We have therefore incorporated a subpixel algorithm that models the result of phase correlation as a sinc function in order to increase the accuracy of our technique. This method, which we have named high density mapping (HDM), determines the subpixel displacement of 64 x 64 pixel regions from images of the heart. To determine the accuracy and precision of the technique, a high contrast image of a heart was digitally shifted 1, 2 or 3 pixels. The original and shifted images were then downsampled four times resulting in 0.25, 0.50 or 0.75 pixel shifts between the original and shifted images. The average accuracy of HDM in the digitally shifted images was 0.06 pixels, with a precision of 0.08 pixels. Effectiveness of HDM in characterization of deformation was also assessed in digitally stretched images. Error in quantification of strain was found to be less than 3.5% of the calculated strain. In an additional set of experiments, in which accuracy was determined using physical motion instead of digital shifting and downsampling, a speckle pattern was displaced by known distances using a micromanipulator, such that the displacement between the captured images was 0.5 pixels. These data demonstrated an accuracy of 0.09 pixels and a precision of 0.02 pixels. Finally, as HDM is used to determine the regional stroke work index (RSW) in beating hearts, the repeatability of using this method to compute RSW was assessed. RSW, the integral of intraventricular pressure with respect to unitless regional area, where end diastolic area was normalized to unity, was assessed in consecutive beats from four different hearts. The average standard deviation of RSW was 0.098 mmHg. Uncertainty analysis determined the maximum error of RSW to be +/-0.41 mmHg, approximately two-thirds of the measured biologic variability. These data demonstrate the ability of HDM to accurately and reproducibly measure displacement and regional function in the beating heart.

Algorithms↗
PubMed2004

Trunk use and co-contraction in cerebral palsy as regulatory mechanisms for accuracy control.

In the present study, we examined whether individuals with cerebral palsy (CP) systematically vary motion of the trunk and co-contraction in the upper limb as a function of accuracy demands. Four participants with spastic tetraparesis, four with spastic hemiparesis, and four healthy controls were asked to repeatedly move a spoon back-and-forth between two target locations. The task was externally paced. In half the trials the accuracy demands were increased by filling the spoon with water. In addition, a condition in which the trunk was fixated was examined. When the movements were controlled for speed, trunk motion hardly varied as a function of accuracy. Co-contraction in the shoulder, however, was systematically higher under high-accuracy demands. Trunk fixation yielded differential group effects on the co-contraction of the shoulder muscles. It increased in control participants, tended to decrease in hemiparetic participants, and was unaffected in tetraparetic participants. Collectively, the present findings show that the increased trunk involvement and high co-contraction levels in CP should not exclusively be regarded as disorder-related phenomena. Regulation of co-contraction in the shoulder is a general strategy to cope with variations in movement-accuracy constraints, while increased trunk involvement proves a secondary reaction to these constraints.

Adolescent↗
PubMed2006

Prediction of lung tumour position based on spirometry and on abdominal displacement: accuracy and reproducibility.

BACKGROUND AND PURPOSE: A simulation investigating the accuracy and reproducibility of a tumour motion prediction model over clinical time frames is presented. The model is formed from surrogate and tumour motion measurements, and used to predict the future position of the tumour from surrogate measurements alone. PATIENTS AND METHODS: Data were acquired from five non-small cell lung cancer patients, on 3 days. Measurements of respiratory volume by spirometry and abdominal displacement by a real-time position tracking system were acquired simultaneously with X-ray fluoroscopy measurements of superior-inferior tumour displacement. A model of tumour motion was established and used to predict future tumour position, based on surrogate input data. The calculated position was compared against true tumour motion as seen on fluoroscopy. Three different imaging strategies, pre-treatment, pre-fraction and intrafractional imaging, were employed in establishing the fitting parameters of the prediction model. The impact of each imaging strategy upon accuracy and reproducibility was quantified. RESULTS: When establishing the predictive model using pre-treatment imaging, four of five patients exhibited poor interfractional reproducibility for either surrogate in subsequent sessions. Simulating the formulation of the predictive model prior to each fraction resulted in improved interfractional reproducibility. The accuracy of the prediction model was only improved in one of five patients when intrafractional imaging was used. CONCLUSIONS: Employing a prediction model established from measurements acquired at planning resulted in localization errors. Pre-fractional imaging improved the accuracy and reproducibility of the prediction model. Intrafractional imaging was of less value, suggesting that the accuracy limit of a surrogate-based prediction model is reached with once-daily imaging.

Abdomen↗
PubMed2004

Accuracy of sonographic vascular features in differentiating different causes of cervical lymphadenopathy.

This study was undertaken to evaluate the accuracy of the power Doppler sonographic features in differentiating cervical lymphadenopathy in different diseases. We reviewed power Doppler sonograms of 270 patients with palpable neck nodes (metastases n = 101, lymphoma n = 21, tuberculosis n = 76, reactive n = 72). Confirmed diagnosis was either made by fine-needle aspiration cytology on the largest node or by excision biopsy. In each patient, the largest node was included in the study. The node was evaluated using the vascular pattern, displacement of vascularity and vascular resistance (resistance index, RI, and pulsatility index, PI). Individual groups were compared and the optimum vascular feature in the differential diagnosis was determined. Vascular pattern was more useful in differentiating reactive nodes from malignant nodes, with a sensitivity of 88% for metastases and 67% for lymphoma, and a specificity of 100%. RI with a cut-off value of 0.8 was more accurate in distinguishing metastases (RI > 0.8) from lymphoma (RI < 0.8), with an accuracy of 65% and 75%, respectively. Displacement of vascularity was helpful to differentiate tuberculous nodes (accuracy: 67%) from reactive and lymphomatous nodes (accuracy: 100% and 95%, respectively), whereas PI with a cut-off of 1.5 helped the differentiation between tuberculosis (PI < 1.5) and metastases (PI > 1.5), with an accuracy of 77% in both diseases. When appropriate criteria are used, power Doppler sonography is a valuable adjunct in the sonographic evaluation of cervical lymphadenopathy.

Diagnosis, Differential↗
PubMed2002

Low accuracy and low consistency of fourth-graders' school breakfast and school lunch recalls.

OBJECTIVE: To determine the accuracy and consistency of fourth-graders' school breakfast and school lunch recalls obtained during 24-hour recalls and compared with observed intake. DESIGN: Children were interviewed using a multiple-pass protocol at school the morning after being observed eating school breakfast and school lunch. SUBJECTS: 104 children stratified by ethnicity (African-American, white) and gender were randomly selected and interviewed up to 3 times each with 4 to 14 weeks between each interview. STATISTICAL ANALYSIS: Match, omission, and intrusion rates to determine accuracy of reporting items; arithmetic and/or absolute differences to determine accuracy for reporting amounts; total inaccuracy to determine inaccuracy for reporting items and amounts combined; intraclass correlation coefficients (ICC) to determine consistency. RESULTS: Means were 51% for omission rate, 39% for intrusion rate, and 7.1 servings for total inaccuracy. Total inaccuracy decreased significantly from the first to the third recall (P=0.006). The ICC was 0.29 for total inaccuracy and 0.15 for omission rate. For all meal components except bread/grain and beverage, there were more omissions than intrusions. Mean arithmetic and absolute differences per serving in amount reported for matches were -0.08 and 0.24, respectively. Mean amounts per serving of omissions and intrusions were 0.86 and 0.80, respectively. APPLICATIONS/CONCLUSIONS: The low accuracy and low consistency of children's recalls from this study raise concerns regarding the current uses of dietary recalls obtained from children. To improve the accuracy and consistency of children's dietary recalls, validation studies are needed to determine the best way(s) to interview children.

Child↗
PubMed1997

Impact of gender, ethnicity, meal component, and time interval between eating and reporting on accuracy of fourth-graders' self-reports of school lunch.

OBJECTIVE: To validate fourth-graders' self-reports of school lunch by comparing their reports to lunch observations, and to determine the impact on accuracy of gender, ethnicity, meal component, and time interval between eating and reporting. DESIGN: Students were randomly selected, observed eating lunch, and interviewed the same day, next day, or Monday regarding Friday's lunch. Accuracy of reporting items was determined by tallying matched foods (items reported and observed), phantom foods (items reported but not observed), and omitted foods (items not reported but observed). Accuracy of reporting amount eaten was determined by calculating absolute and arithmetic differences. SUBJECTS: Subjects were 260 students: 89 same-day, 148 next-day, and 23 Monday recalls; 59 whites (30 boys) and 201 blacks (103 boys) from four schools. STATISTICAL ANALYSES: Rates for matched, phantom, and omitted foods; analysis of variance; Friedman's nonparametric analog of analysis of variance; Student-Newman-Keuls' post hoc comparisons. RESULTS: In regard to reporting items, the respective rates for matched, phantom, and omitted foods were 84%, 5%, and 16% for same-day recalls; 68%, 13%, and 32% for next-day recalls; and 38%, 48%, and 62% for Monday recalls. Rates for omitted and phantom foods were higher for Monday recalls than for next-day recalls, which were higher than for same-day recalls (P < .05 for all). In regard to reporting amounts, analysis by gender, ethnicity, and time interval failed to yield significant main or interaction effects. When children correctly reported items eaten, they were quite accurate in reporting amounts eaten. Omitted food rates were lowest for beverage, followed by entree, and highest for miscellaneous and condiment. APPLICATIONS: Even under the best conditions (ie, reporting within 90 minutes after eating school lunch), children have difficulty accurately reporting what they have eaten. As the time interval between eating and reporting increases, accuracy decreases markedly. Techniques that improve reporting of items eaten should result in improved accuracy of reporting amounts eaten.

Analysis of Variance↗
PubMed1997

Gender differences in the accuracy of dobutamine stress echocardiography for the diagnosis of coronary artery disease.

The accuracy of dobutamine stress echocardiography (DSE) for the diagnosis of coronary artery disease (CAD) has not been yet evaluated in women. We studied the effect of gender on the accuracy of DSE for the diagnosis of CAD in 306 consecutive patients (210 men and 96 women) with limited exercise capacity and suspected myocardial ischemia who underwent coronary angiography within 3 months of DSE. There were no serious complications during DSE. Men had a higher prevalence of nonsustained ventricular tachycardia (7% vs 0.03%, p <0.05) and supraventricular tachycardia (9% vs 0.03%, p <0.05) during the test compared with women. Peak stress rate-pressure product was not different in men and women (18,140 +/- 4,187 vs 18,543 +/- 4,223). Significant CAD (> or =50% luminal diameter stenosis) was present in 171 men (81%) and in 62 women (65%, p <0.005). The sensitivity, specificity, and accuracy of ischemic pattern at DSE for the diagnosis of significant CAD were 76% (confidence interval [CI] 67 to 84), 94% (CI 89 to 99), and 82% (CI 75 to 90) in women and 73% (CI 67 to 79), 77% (CI 71 to 83), and 74% (CI 68 to 80) in men, respectively. Overall specificity was higher in women than in men (p <0.05). Regional accuracy of DSE was significantly higher in women than in men in the 3 arterial regions (84% [CI 79 to 88] vs 75% [CI 72 to 79], p <0.005). It is concluded that DSE is a safe and feasible method for the diagnosis of CAD in women. The overall specificity and the regional accuracy of DSE are higher in women than in men. Further studies are required to evaluate the functional significance of these findings and their reproducibility in different patient populations.

Cardiotonic Agents↗
PubMed1995

Accuracy of anticardiolipin antibodies in identifying a history of thrombosis among patients with systemic lupus erythematosus.

OBJECTIVE: To measure the accuracy of anticardiolipin antibodies (aCL) in identifying a history of thrombosis among patients with systemic lupus erythematosus (SLE) or the primary antiphospholipid syndrome (PAPS). PATIENTS AND METHODS: Patients with SLE or PAPS who attended our rheumatology clinic between April 1992 and March 1994 were included in a retrospective analysis of the relationship between thrombotic events and aCL. All aCL measurements were performed in the same laboratory by enzyme-linked immunosorbent assay, blinded as to the presence or absence of thrombosis. The diagnostic accuracy of IgG, IgM, and IgA aCL was quantified by means of the receiver operating characteristic area under the curve (ROC AUC) for each isotype. Stratum-specific likelihood ratios and their 95% confidence intervals were calculated to define strata with optimal discriminant power. RESULTS: During the period of study, aCL was measured in 117 patients (113 SLE and 4 PAPS), of whom 24 (20.5%) had experienced thrombotic events. The ROC AUC +/- the standard error for IgG aCL was 0.81 +/- 0.05, signifying an 81% accuracy in the identification of a history of thrombosis. In contrast, the accuracy of the IgM and IgA aCL was significantly lower (0.60 +/- 0.08 and 0.54 +/- 0.07, respectively, P < 0.05). Using stratum-specific likelihood ratios, we defined three strata in the IgG aCL scale that discriminate between patients with low, indeterminate, and high probabilities of thrombosis. For IgG aCL levels below 21.4 IgG phospholipid (GPL) U/mL, the posttest probability of thrombosis was 0.07, whereas for IgG aCL levels > or = 65.1 GPL U/mL, the posttest probability of thrombosis was 0.75. For IgG aCL values between 21.4 and 65.0 GPL U/mL, the probability of thrombosis was 0.20, equivalent to the entire cohort. CONCLUSIONS: The IgG aCL determinations perform well in the identification of thrombosis in SLE or PAPS, while the IgM and IgA aCL have poor diagnostic accuracy. These findings may have implications for management of these patients.

Adolescent↗
PubMed1997

Endosonography-guided fine-needle aspiration biopsy: diagnostic accuracy and complication assessment.

BACKGROUND & AIMS: Endosonography-guided fine-needle aspiration biopsy (EUS-FNA) permits cytological confirmation of EUS findings. A multicenter prospective evaluation of EUS-FNA for primary diagnosis, staging, and/or follow-up purposes was undertaken. METHODS: EUS-FNA was performed in 457 patients with 554 lesions. Clinical (n = 218) or histopathologic (n = 256) confirmation was available in 192 lymph nodes, 145 extraluminal masses, 115 gastrointestinal wall lesions, and 22 cystic lesions. RESULTS: EUS-FNA sensitivity, specificity, and accuracy was 92%, 93%, and 92% for lymph nodes, 88%, 95%, and 90% for extraluminal masses, and 61%, 79%, and 67% for gastrointestinal wall lesions, respectively. The sensitivity and accuracy for lymph nodes and extraluminal masses was superior to that for gastrointestinal wall lesions. When EUS-FNA was compared with EUS size criteria in lymph node evaluation, specificity (93% vs. 24%) and accuracy (92% vs. 69%) were superior, whereas sensitivity (92% vs. 86%) was similar. The accuracy of EUS-FNA in patients with previously failed biopsy procedures was 81% (73 of 90). Five nonfatal complications occurred for a rate of 0.5% (95% confidence interval, 0.1%-0.8%) in solid lesions vs. 14% (95% confidence interval, 6%-21%) in cystic lesions. CONCLUSIONS: EUS-FNA accurately and safely evaluates solid peri-intestinal lesions and improves lymph node staging accuracy.

Abdomen↗
PubMed1999

EUS compared with CT, magnetic resonance imaging, and angiography and the influence of biliary stenting on staging accuracy of ampullary neoplasms.

BACKGROUND: Computerized tomography (CT), magnetic resonance imaging (MRI), and transabdominal ultrasound frequently fail to detect ampullary lesions. Endoscopic ultrasound (EUS) is a sensitive modality for detecting and staging ampullary tumors. Accurate staging may be affected by biliary stenting, which is frequently performed in these patients with obstructive jaundice. The present study assessed the accuracy of ampullary tumor staging with multiple imaging modalities in patients with and those without endobiliary stents. METHODS: Fifty consecutive patients with ampullary neoplasms from two endosonography centers were preoperatively staged by EUS plus CT (37 patients), MRI (13 patients), or angiography (10 patients) over a 3(1/2) year period. Twenty-five of the 50 patients had a transpapillary endobiliary stent present at the time of endosonographic examination. Accuracy of EUS, CT, MRI, and angiography was assessed with the TNM classification system and compared with surgical-pathologic staging. The influence of an endobiliary stent present at the time of EUS on staging accuracy of EUS was also evaluated. RESULTS: EUS was more accurate than CT and MRI in the overall assessment of the T stage of ampullary neoplasms (EUS 78%, CT 24%, MRI 46%). No significant difference in N stage accuracy was noted between the three imaging modalities (EUS 68%, CT 59%, MRI 77%). EUS T stage accuracy was reduced from 84% to 72% in the presence of a transpapillary endobiliary stent. This was most prominent in the understaging of T2/T3 carcinomas. CONCLUSIONS: EUS is superior to CT and MRI in assessing T stage but not N stage of ampullary lesions. The presence of an endobiliary stent at EUS may result in underestimating the need for a Whipple resection because of tumor understaging.

Adult↗
PubMed1976

The concepts of sensitivity, specificity and accuracy in evaluation of electrocardiographic, vectorcardiographic and polarcardiographic criteria.

The concepts sensitivity and specificity are critically evaluated in the light of case studies drawn from electrocardiographic literature. These terms are often misused, and the meaning of these elementary statistical concepts is often misunderstood in studies on ECG, VCG and PCG criteria. Specificity figures reported in literature commonly refer to the fraction of true negatives with a negative test in normals. Limiting the test to two-group analysis and eliminating other disease categories tend to give overoptimistic values for specificity and diagnostic accuracy in general. It is pointed out that various performance indices for diagnostic accuracy depend heavily on the composition of the test groups and the fraction of test cases in each group. Sensitivity and specificity appear inadequate performance indices for evaluation of event detection schemes such as classification of ectopic beats. Alternative performance indices are considered, including the error ratio, association index, accuracy of positive test, accuracy of negative test, and overall diagnostic accuracy. Increased utilization of simple statistical tests for significance estimation in ECG criteria evaluation is suggested. The development and application of better diagnostic performance evaluation schemes based on concepts of cost of misclassification, entropy and information is encouraged.

Arrhythmias, Cardiac↗
PubMed1996

Holter triage ambulatory ECG analysis. Accuracy and time efficiency.

Triage ambulatory electrocardiographic (ECG) analysis permits relatively unskilled office workers to submit 24-hour ambulatory ECG Holter tapes to an automatic instrument (model 563, Del Mar Avionics, Irvine, CA) for interpretation. The instrument system "triages" what it is capable of automatically interpreting and rejects those tapes (with high ventricular arrhythmia density) requiring thorough analysis. Nevertheless, a trained cardiovascular technician ultimately edits what is accepted for analysis. This study examined the clinical validity of one manufacturer's triage instrumentation with regard to accuracy and time efficiency for interpreting ventricular arrhythmia. A database of 50 Holter tapes stratified for frequency of ventricular ectopic beats (VEBs) was examined by triage, conventional, and full-disclosure hand-count Holter analysis. Half of the tapes were found to be automatically analyzable by the triage method. Comparison of the VEB accuracy of triage versus conventional analysis using the full-disclosure hand count as the standard showed that triage analysis overall appeared as accurate as conventional Holter analysis but had limitations in detecting ventricular tachycardia (VT) runs. Overall sensitivity, positive predictive accuracy, and false positive rate for the triage ambulatory ECG analysis were 96, 99, and 0.9%, respectively, for isolated VEBs, 92, 93, and 7%, respectively, for ventricular couplets, and 48, 93, and 7%, respectively, for VT. Error in VT detection by triage analysis occurred on a single tape. Of the remaining 11 tapes containing VT runs, accuracy was significantly increased, with a sensitivity of 86%, positive predictive accuracy of 90%, and false positive rate of 10%. Stopwatch-recorded time efficiency was carefully logged during both triage and conventional ambulatory ECG analysis and divided into five time phases: secretarial, machine, analysis, editing, and total time. Triage analysis was significantly (P < .05) more time efficient for the machine, analysis, and total time phases and required significantly more time in the editing phases. The triage analysis was limited by the inability of the automatic methodology to detect a specific VT waveform contained on one tape. This result which caused substantial loss of sensitivity for VT, emphasizes the necessity for careful quality control and editing of all automatic Holter analysis methods.

Electrocardiography, Ambulatory↗
PubMed2003

Dimensional accuracy and surface detail reproduction of two hydrophilic vinyl polysiloxane impression materials tested under dry, moist, and wet conditions.

STATEMENT OF PROBLEM: A major limitation of vinyl polysiloxane (VPS) impression materials is their hydrophobicity. There are 2 aspects to this problem, the wettability of the polymerized impression by dental gypsum materials and the ability of the unpolymerized material to wet intraoral tissues. To address this problem, manufacturers have added surfactants and labeled the new products as hydrophilic vinyl polysiloxane. PURPOSE: The purpose of this investigation was to compare dimensional accuracy and surface detail reproduction of 2 hydrophilic VPS impression materials, when used under dry, moist, and wet conditions. MATERIALS AND METHODS: A total of 102 impressions were made of stainless steel metal dies similar to those described in American Dental Association (ADA) specification 19. The dies had 2 vertical and 3 horizontal lines inscribed on their superior surfaces. Impressions were made under dry, moist, and wet conditions. Dimensional accuracy was measured by comparing the average length of the middle horizontal line in each impression to the same line on the metal die, by use of a measuring microscope with an accuracy of 0.001 mm. A 2-way analysis of variance and least significant difference post hoc test were used to compare mean dimensional changes (alpha=.05). Surface detail reproduction was evaluated in 2 ways: (1) by use of criteria similar to ADA specification 19 for detail reproduction, continuous replication of at least 2 of the 3 horizontal lines, and (2) by use of a method developed for this study that categorized the impressions as satisfactory or unsatisfactory based on their surface characteristics: presence of pits, voids, or roughness. Pearson chi(2) (alpha=.05) was used to compare detail reproduction results. RESULTS: Conditions (dry, moist, and wet) did not cause significant adverse effects on the dimensional accuracy of either material. The mean dimensional change and SD were 0.005% +/- 0.002% or less. With both surface detail analyses, dry, moist, and wet conditions had a significant effect on the detail reproduction of both materials (P<.05). Only under dry conditions did both impression materials continuously replicate at least 2 of the 3 horizontal lines 100% of the time. Under moist conditions, 82% of the Aquasil impressions and 100% of the Reprosil impressions were judged satisfactory, while under wet conditions, only 47% Aquasil and 11% Reprosil impressions were satisfactory. With the additional surface detail characterization, only under dry conditions were impressions produced with clinically acceptable surface quality (Aquasil 77% and Reprosil 100% satisfactory). CONCLUSIONS: Dimensional accuracy of both materials tested was well within ADA standards. Best surface detail results were obtained only under dry conditions for both materials.

Analysis of Variance↗
PubMed1996

Dimensional accuracy and stability of polymethyl methacrylate reinforced with metal wire or with continuous glass fiber.

The aim of this study was to determine the dimensional accuracy and stability of denture base polymethyl methacrylate (PMMA), which was reinforced in various ways. Autopolymerizing PMMA and heat-cured PMMA were reinforced either with semicircular steel wire or with a prefabricated experimental reinforcement made of continuous E-glass fiber. Control specimens had no reinforcement. The width of each U-shaped test specimen was measured with a digital micrometer under a light microscope immediately after the test specimen was cured and when stored in water for 1, 2, 7, and 14 days. The results revealed that both the type of PMMA and the type of reinforcement affected the dimensional accuracy of the test specimens, especially after 7 and 14 days in water storage (p < 0.001). The greatest dimensional accuracy was found with the unreinforced test specimen made from autopolymerizing PMMA and with test specimens reinforced with the metal wire made from heat-cured PMMA. In terms of the width of the test specimens, the lowest dimensional accuracy was found in unreinforced and glass fiber reinforced specimens made from heat-cured PMMA. Storage in water did not affect the stability of the width (p > 0.1). The results suggest that the polymerization shrinkage of PMMA causes lower dimensional accuracy of the test specimens reinforced with glass fiber. This should be considered when glass-fiber reinforcement is used clinically.

Analysis of Variance↗
PubMed2000

Movement accuracy constraints in Parkinson's disease patients.

This study examined the hypothesis that the kinematics of movements performed by PD (Parkinson's disease) patients are differentially affected depending on whether or not the aiming movement has an accuracy constraint. The aiming movements required elbow extension in the horizontal plane on a digitizer. There were two movement conditions: (1) one having a spatial accuracy requirement in which the subjects moved to the defined target and stopped on it; and (2) one requiring the subjects to move toward the defined target without stopping precisely on it. Subjects were instructed to make their movements as fast and as accurate as possible in response to the auditory imperative signal. PD patients modified the movement speed and kinematics depending on the two accuracy conditions. However, when the accuracy constraint was imposed, movement slowness observed in the patients was much more pronounced. The most revealing result was localized to the deceleration phase, particularly as the target was approached. The patients also were found to make a higher number of acceleration zero crossings from negative to positive to reach the target, indicating that the movements were more irregular. For the patients, the first acceleration zero crossing from negative to positive occurred much earlier in the movement than that for the controls. In addition, when movement accuracy was constrained, the number of zero crossings was accentuated. These data show that when PD patients make aiming movements to a target, their deceleration phase becomes longer and more variable.

Aged↗
PubMed2005

[Measurement of head penetration on digitalized radiographs: reproducibility and accuracy].

PURPOSE OF THE STUDY: Wear of the acetabular component of total hip arthroplasty (THA) is incriminated as the cause of loosening and bone resorption. Consequently, an accurate evaluation of wear can contribute to the prediction of mechanical failure of the arthroplasty. Among the different methods proposed, digitalized imaging using a high-resolution scanner associated with data processing procedures appears to be a simple easily accessible technique. A system based on this concept has been introduced in orthopedics. To our knowledge, there has been no report on the system's reproducibility and accuracy. MATERIAL AND METHODS: Thirty-nine radiography series for THA served as the basis for the evaluation of intra- and interobserver reproducibility. We evaluated the error induced by digitalization, the error induced by digitalized measurement, the accuracy of the measurements as a function of the material constituting the bearing, the intra- and interobserver reproducibility for repeated measures of THA wear (six observers and two observations). All measurements were done after digitalization and analyzed with a specimen designed software. RESULTS: The inter and intra-observer coefficients of concordance were 0.6 and 0.58 respectively, i.e. moderate reproducibility. Depending on the prosthetic material, the error and accuracy of the system varied from 0.112 to 0.44 mm and 0.28 to 1.29 mm respectively. To obtain valid inter-observer reproducibility, the number of observers had to be limited to three (coefficient = 0.82). The type of implant had an influence on measurement error. The error was 0.342 for polyethylene cups and 0.118 for press-fit metal back cups. Likewise, for a metallic head measuring 22.2 mm, the error was 0.138 mm while for a ceramic head or metal head measuring 28 mm, the error was 0.28 mm and 0.112 mm respectively. DISCUSSION AND CONCLUSION: The accuracy and error depend directly on the type of implant. The accuracy was better for metallic heads associated with metal-backed cups. To obtain satisfactory interclass correlation, the number of observers should be three. The proposed digitalized measurement system should be relatively accurate and reproducible. Its use can be recommended for the evaluation of wear after five years of follow-up, limiting the number of observers to three.

Acetabulum↗
PubMed1988

Accuracy of and reasons for frozen sections: a correlative, retrospective study.

Previous studies on the accuracy of frozen sections (FS) were not based on the reasons for which the FS was performed. By omitting this important information, those studies reported FS accuracy of 94% to 97.4%. The current study analyzes the accuracy of FS diagnoses based on the reasons for which they were conducted. Of 482 specimens examined by FS in 1986, 41 were performed for evaluation of section margins of tumors, 29 for identification of unknown tissue, and 43 for detection of lymph node metastases. All 113 of these examinations proved to be 100% accurate. The remaining 369 FS were performed for diagnosis of an unknown pathologic process. Of these, 83.47% were precisely diagnosed; in 10.30%, the pathologic process was correctly, but not precisely, diagnosed; in 3.79%, the diagnosis was deferred; and the remaining 2.44% were incorrectly diagnosed (with no harmful consequences to the patients). By eliminating the cases of deferred diagnoses, the accuracy rate increased to 86.76%. Therefore, we suggest that the pathologist and the surgeon should not draw any conclusion from an inconclusive interpretation of FS and should proceed as though an FS had not been performed. When combining results of "precise diagnoses" with those of "correct pathologic process," the overall accuracy rate increased to 97%. The investigators conclude that FS should be used for a general diagnosis of a pathologic process rather than for an exact or precise diagnosis. Finally, we suggest that a similar survey of FS be periodically performed in every pathology department as part of its quality assurance program.

Diagnostic Errors↗