Evaluation of the precision of dimensional measurements of the mandible on panoramic radiographs

The task of objective perimetry is to scan the visual field and find an answer about the function of the visual system. Flicker-burst stimulation--a physiological sensible combination of transient and steady-state stimulation--is used to generate deterministic sinusoidal responses or visually evoked potentials (VEP's) at the visual cortex, which are derived from the electroencephalogram by a suitable electrode array. In this paper we develop a new method for the detection of VEP's. Based on the periodogram of a time-series, we test the data for the presence of hidden periodic components, which correspond to steady-state VEP's. The method is applied successfully to real data.     

Factors affecting the precision of TLD dose measurements using an automatic TLD reader

An increase in the variability of TLD dose measurements prompted a study of the precision of dose measurements with a Rialto automatic TLD reader. It was found that readings with the same chip measured using two different trays could differ by as much as 7%. In order to overcome this problem it was necessary to ensure that individual chips were correctly identified. Marking the chips with a hard graphite pencil was found to be a satisfactory method of identifying them, which, although it reduced the light output by approximately 3%, had no effect on the reproducibility of readings. Using marked chips and an individual tray for each chip, the reproducibility of a reading was reduced to a typical value of 1%. A system of quality assurance based on these findings is described.     

Effects of a new positioner on the precision of hip bone mineral density measurements

In an attempt to reduce patient positioning errors, the authors tested the use of a new hip-specific positioning tool, OsteoDyne's Hip Positioner System (HPS). The HPS is an "A" frame splint designed to abduct both legs approximately 15 degrees to hold them in full extension at the hips and knees and to lock the feet in a neutral position. Seventy volunteer women aged 35-82 years were randomly assigned in two age-matched groups (mean age 56 years). Each group underwent two consecutive femur dual X-ray absorptiometry (DXA) scans with intermediate repositioning using the HPS system and two others utilizing the standard hip positioner provided with Hologic and Lunar scanners. One technician performed all scans using a Hologic QDR 1000-Plus and Lunar DPX-Plus densitometer. One hundred and fifty volunteer women aged 50-84 years (mean age, 64 years) were recruited in a multicenter study for the assessment of precision. Each subject underwent three consecutive femur DXA scans with intermediate repositioning using the HPS system. The coefficient of variation (CV) was significantly improved at the femoral neck by the use of the HPS with 0.7 versus 1.2 with the Hologic densitometer but only moderately altered at other sites. Similar results were found with the Lunar densitometer with improvement of precision at the femoral neck, 0.8 versus 1.8 with a similar trend but no significant difference at the other regions. No statistical difference was noted between the femoral neck BMD measured with the HPS system and with the standard positioners in either group. The mean precision of data obtained on the QDR 1000+ was 0.8% (range 0.1-1.4) for the femoral neck BMD, 1.1% (range 0.1-3.0) for the trochanter BMD, 2.3% (range 0.2-5.2) for Ward's triangle BMD, and 0.8% (range 0.1-1.9) for the total femur BMD. The mean precision of data obtained on the QDR 2000 was 0.7% (range 0.1-2), 1% (range 0.1-4.9), 2.6% (range 0.3-5.7), and 0.7% (range 0.1-1.8), respectively. In conclusion, data obtained with the new OsteoDyne's HPS seem capable of reducing patient positioning errors for the hip measurement. Its use is likely to improve confidence in hip bone mineral density measurements.     

Calibration of ion-exchange HPLC measurements of glycohemoglobin: effect on interassay precision

To investigate the effect of calibration with lyophilized calibrators on the interassay precision of glycohemoglobin (glyHb) measurements, we used an ion-exchange HPLC system equipped with a Pharmacia Mono S HR 5/5 column. Calibration of analytical runs substantially increased interassay variation (CV), from 1.7% to 4.4% and from 0.9% to 3.2% for control samples with low (6.5%) and high (14%) glyHb percentages, respectively. Standardization of glyHb results, though essential for interlaboratory comparisons, should not be done at the expense of assay precision, as may occur with thoughtless use of lyophilized calibrators. We therefore recommend the use of carefully determined conversion factors for standardization of glyHb results obtained with ion-exchange HPLC systems that are capable of excellent long-term interassay precision.     

Human precision of operating a digitizing board: implications for electrocardiogram measurements

To investigate the precision achieved by human measurement on a digitizing board, 100 healthy volunteers (46 women, mean age 36 +/- 12 years) were asked to measure 15 times on artificial pattern composed of 15 points. A high precision digitizing board (programmed to the technical accuracy of +/- 50 microns) was used, and mean and maximum errors in measuring the same distance repeatedly and relocalizing the same point repeatedly were obtained for each volunteer. A median mean and maximum error of 0.2 mm and 1.0 mm were found for repeated distance measurement. When simulating QT dispersion measurement (measuring the same distance 12 times), median value of 20 ms was obtained for ECGs of 25 mm/s paper speed. The study concludes that human precision of operating a digitizing board is rather poor. A recommendation is given to use either a computer screen for manual measurement of ECGs or to provide an operator of the digitizing board with an immediate feedback of the precision and measurement stability achieved so that erroneous measurement can be actively rejected.     

Long-term precision of glomerular filtration rate measurements using 51Cr-EDTA plasma clearance

Emerging and reemerging infections are attracting greater attention from the public health and medical communities. Pathologists and other physicians are increasingly aware of the importance of the subspecialty of infectious disease pathology as a tool for diagnosis, surveillance, and research of emerging infections. In this communication, we describe the role that infectious disease pathologists have played during the last 2 years in broadening our understanding of selected emerging infections, including such examples as new variant Creutzfeldt-Jakob disease and bovine spongiform encephalopathy, leptospirosis, microsporidiosis, Ebola hemorrhagic fever, and cyclosporiasis. The significance of providing pathology services, especially the autopsy, to patients with potentially hazardous communicable diseases is discussed with the supposition that it is unethical to exclude or withhold health care from a patient based on his or her underlying disease or on risk factors for acquiring a disease. The increasing occurrence of infectious diseases imported into the United States and other nations, including human immunodeficiency virus-1 group O, dengue fever, tuberculosis, malaria, diphtheria and cholera in immigrants and travelers, and Ebola virus in nonhuman primates, emphasizes the necessity for pathologists of having competence with infectious disease pathology. It is critical that new generations of pathologists not only be trained in the subspecialty of infectious disease pathology, but that they also be willing participants in the diagnosis and investigation of infectious diseases. The lack of training programs for infectious disease pathologists, as well as the deficiency in infectious disease pathology support for ongoing and future epidemiologic investigations and research, has led to the broadening of pathology services and initiation of a dedicated section of Infectious Disease Pathology at one of the nation's premier public health institutions, the Centers for Disease Control and Prevention in Atlanta, Ga. Together with preexisting groups of medical and veterinary infectious disease pathologists at universities, the Armed Forces Institute of Pathology, the US Army Medical Research Institute of Infectious Diseases, and the National Institutes of Health, this new program will significantly strengthen the capability of the United States to respond to future challenges of emerging and reemerging infections, both in this country and abroad.     

The clinico-laboratory characteristics of pseudotuberculosis in persons with chronic opisthorchiasis

Clinical and laboratory parameters investigated in pseudotuberculosis patients with and without CO proved patients with mixed infection to be more seriously affected. They had more pronounced polymorphism of clinical symptoms, more severe intoxication, fever, hepato- and splenomegaly, longer convalescence, more frequent relapses, worse laboratory findings. Complicated course of pseudotuberculosis patients with CO may be due to hypersensitization of the body and hepatobiliary disorders resultant from parasitic invasion.     

A clinico-laboratory validation of the combined therapy of lichen ruber planus of the oral mucosa

Fifty-two patients with lichen planus were examined over the course of disease using clinical, microbiological, and histological methods. Treatment protocols aimed at normalization of microbiocenosis have been developed, based on the detected microbiological and histological changes.     

Evaluation of the accuracy and precision of lung aerosol deposition measurements from planar radionuclide imaging using simulation

Planar images of known, theoretical distributions of radioaerosol in the lung have been simulated using lung models derived from magnetic resonance studies on human subjects. Total lung activity was evaluated from the simulated images together with the absolute penetration index (PI) and a relative value expressed as a fraction of that in a simulated ventilation image. The accuracy and precision of these measurements were calculated by comparison with the true values used in the simulation. Total activity was assessed with systematic errors within 5% and precision within 6.5%. Measured PIs varied only slowly with true PI and inter-model variation masked changes between measurements on the different distributions. The relative PI reduced inter-model variation and provided significant differences between all the distributions. PI was significantly affected by misalignment of the lung region of interest. The conducting airways deposition fraction (CADF) used in the simulation correlated linearly with the fractional activity in a central lung region, allowing CADF to be estimated with a precision of 21%.     

A study of the precision of confocal, ratiometric, Fura-2-based [Ca2+] measurements

Increased ammonia has been considered a key factor in the pathogenesis of hepatic encephalopathy. The high concentration of ammonia interferes with oxidative metabolism in the brain through an inhibitory effect on the tricarboxylic acid cycle (TCA). Inhibition of the TCA cycle may result in depletion of ATP. Due to the involvement of astrocytes in brain detoxification of ammonia, these cells are good candidates for studying ammonia's effect on energy stores in the brain. C6-glioma cells, which have altered glycolytic rates, may show greater sensitivity to the toxicity of ammonium chloride than astrocytes. To study the effect of ammonium chloride on energy storage of both astrocytes and C6-glioma, we observed the acute and chronic effects of NH4Cl (7.5 or 15 mM) on the metabolism of isolated astrocytes and C6-glioma cells. Primary astrocytes were isolated from the cerebral hemispheres of 1-2 day old Sprague-Dawley rats, and C6-glioma cells were purchased from the American Type Culture Collection (ATCC). Following treatment of the cells with ammonia, glucose, lactate, glutamate, ATP, and PCr were assayed. Our data showed that at 15 min following treatment with NH4Cl, there were no significant differences in the concentration of metabolites measured in astrocytes. However, following 15 min of treatment with NH4Cl, the concentration of some metabolites, for example, ATP and lactate, changed significantly in C6-glioma cells. We have shown that 24 h of treatment was sufficient time to see significant biochemical changes but not morphological changes in either cell type. Simultaneous biochemical and morphological changes were observed 48 h following treatment in C6-glioma cells and at 9-10 days following treatment in primary astrocytes. In primary astrocytes at 24 h following treatment, glucose utilization increased. This high utilization of glucose was in accordance with the increase in lactate and glutamate production and the decrease in ATP and PCr formation. In C6-glioma cells the utilization of glucose increased but this high utilization of glucose was consistent with a significant decrease in the concentration of lactate, glutamate and ATP.     

Specific determination of PAH and its N-acetyl metabolite by HPLC increases the accuracy and precision of PAH clearance measurements

Alpha2-adrenergic receptors (alpha2-ARs) in vascular smooth muscle cells are known to mediate vasoconstriction; however, it is unknown which of the 3 subtypes of alpha2-AR (alpha2A, alpha2B, or alpha2C) is expressed in vascular tissue. We have used subtype-specific probes in in situ hybridization and RNase protection assays to analyze the expression of alpha2-AR in the thoracic aorta of New Zealand White (NZW) and Watanabe heritable hyperlipidemic (WHHL) rabbits, a model for atherosclerosis. We found that the alpha2A-AR mRNA was in endothelial and smooth muscle cells in both NZW and WHHL aorta. In addition, the shoulders and subendothelial regions of the atherosclerotic lesions in WHHL aorta showed abundant expression of alpha2A-AR mRNA. Antibodies to macrophage (RAM-11) and smooth muscle cell (HHF-35) antigens were used to localize macrophage and smooth muscle cells in aortic sections from WHHL rabbits. The expression of alpha2A-AR mRNA within the lesions of WHHL rabbits correlated with the presence of infiltrating macrophages. We discuss the potential role of alpha2A-ARs in macrophage function and in promoting atherosclerosis.     

PMSM的高精度感应电势状态观测器与位置估计

提出了永磁同步电动机考虑参数变化时精确的感应电势关系式新模型,建立了微分型和非微分型两种高精度感应电势观测器,证明了感应电势观测器的稳定性和收敛性,分析了参数变动对位置估计的影响.针对无位置传感器矢量控制系统,以内埋式永磁同步电动机为例进行了仿真实验研究,结果表明设计的感应电势状态观测器具有优良的性能.     

Clinical precision of the Rinne test

The precision of the Rinne test at 128-2048 Hz was studied in 100 ears with confirmed conductive pathologies. The number of negative (diagnostic) Rinnes decreased significantly with fall in frequency. While there were significantly more negative than positive Rinnes at 128 and 256 Hz, there were significantly more positive results at higher frequencies; indicating that the Rinne is not reliably diagnostic above 256 Hz. However, the possibility of vibrotactile responses must be remembered with low frequency tuning forks. Also, conductive lesions manifested as high tone air-bone gaps will not be identified with low frequency Rinne tests. Air-bone gaps of 25 to 40 dB, depending on frequency, are necessary for the Rinne to identify the presence of conductive components in most cases. Gaps of 25-30 dB for 128 Hz; 35-40 dB for 256 Hz; 55-60 dB for 512 Hz; and 45-50 dB for 1024 Hz, are necessary for the Rinne to meet a 75% correct detection criterion. The 2o48 Hz Rinne does not attain even chance detection. The Rinne test cannot be validly employed as a criterion against which other measures can be evaluated.     

Carbon dioxide and oxygen partial pressure measurements in the cerebrospinal fluid in a conventional blood gas analyzer: analysis of bias and precision

An immobilization device was constructed for Fractionated Stereotactic Radiotherapy (FSRT) based on registration of the teeth and facial bones in a single thermoplastic mask system, along with a custom hardened foam pillow for posterior head immobilization relative to the mask. The unit interfaces mechanically with all of our current radiosurgery equipment and can be used with any standard stereotactic planning system. After initial trials to design a reproducible radiographic localization test, we performed a series of daily AP and Lateral port films on 3 patients over five isocenters. Seventy-nine films were reviewed and the maximum deviation in anatomical projection in both sagittal and coronal planes was less than 2 mm, with over 60% of films showing no distinguishable deviations from initial port films. Ninety-three percent of the test films showed a repositioning accuracy of less than 1 mm for all tested structures. We have developed an accurate, non-invasive means of repeat head immobilization that, when properly constructed, can facilitate precise fractionated stereotactic radiation therapy with patient comfort, ease of construction and long term stability.     

Standardizing the physical properties of precision alloys

The standardization of the physical properties of precision alloys to ensure their reliable operation in electronic, electrical-engineering, and radio equipment is considered.