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At least 487 records · Page 27Linked to original sources
PubMed1992

An evaluation of cusum analysis and control charts applied to quantitative gamma-camera uniformity parameters for automated quality control.

Gamma-camera uniformity is often monitored for quality control of performance. Many parameters can be derived from computer analysis of the image of a uniform (flood) source to obtain quantitative measures of uniformity. However, it is not clear which best reflect changes in uniformity, or how action levels should be set. The latter are essential for an automated analysis. To compare the various parameters and assess two techniques used for their analysis, a series of technetium-99m flood images were obtained consecutively. After establishing a baseline from repeated images, uniformity was degraded by offsetting the pulse height analyser (PHA) window by a small amount. Nine non-uniformity parameters were calculated for each flood image, including the Department of Health and Social Security (DHSS) and National Electrical Manufacturers Association (NEMA) integral and differential uniformities, the uniformity index and the percentage of pixels more than 5% from the mean. All parameters were calculated for both central field-of-view (CFOV) and useful field-of-view (UFOV). Eighty such trials were carried out on two gamma-cameras. The PHA offsets ranged from 1-10 keV. The two techniques used for analysis were the control chart and cusum analysis. Decision levels were set for each parameter, as multiples of SD for the control charts or by varying the dimensions of a truncated V-mask for cusum analysis. Receiver operating characteristic (ROC) curves were then used for an objective comparison of the parameters and of the analysis techniques. The area under the ROC curve was used to rank the parameters in order of sensitivity to change in uniformity.(ABSTRACT TRUNCATED AT 250 WORDS)

Gamma Cameras↗
PubMed1990

A quality-control phantom for digitization of radiographs.

Quality control is fundamental to the clinical application of digital radiography. A 14 x 17-in phantom radiograph was designed to test digital image quality by measurement of five parameters: high-contrast spatial resolution, low-contrast discrimination, linearity of gray-scale response, high-frequency noise, and geometric distortion. The phantom was used to evaluate the AT&T-Philips CommView picture archival and communications system (AT&T Bell Laboratories, West Long Branch, NJ; Philips Medical Systems, Shelton, CT). High-contrast resolution was found to be greater along the diagonal axis of the system than along either the horizontal or vertical axis. Problems with low-contrast discrimination and linearity of gray-scale response were identified. This phantom provides a simple tool for daily quality assurance testing and an objective standard for comparison of image quality between different digital radiography systems.

Quality Control↗
PubMed1993

Quality control review for radiotherapy of small breast cancer: analysis of 708 patients in the GBSG I trial. German Breast Study Group (GBSG).

Within six years between November 1983 and December 1989 the German Breast Cancer Study Group (GBSG) conducted a prospective multicenter trial on the treatment of pT1 pN0 M0 breast carcinoma. Out of 1036 eligible patients from 69 hospitals, a total of 733 underwent breast preservation surgery and postoperative radiotherapy. A detailed quality control (QC) screening of 708 available radiotherapy records was performed by the radiotherapy reference center. The following quality control scoring system was used for all radiotherapy variables: Radiotherapy treatment "completely according to study protocol" (QC score = 0); "acceptable protocol deviations" (QC score = 1); "unacceptable protocol violations" (QC score = 2); the "overall QC score" was the worst judgement for any single quality control criterion, while the "total QC score" was the summation of all single quality control scores (range: 0 to 14). 292 (41.2%) patients were treated per protocol; 290 (41.0%) had acceptable protocol deviations; and 126 (17.8%) had unacceptable protocol violations. 107 (84.9%) single violations, 15 (11.9%) combinations of two, three (2.4%) combinations of three, and one (0.8%) combination of four unacceptable violations were observed. 564 (79.4%) patients achieved a total QC score of < or = 2, 124 (17.5%) of 3 to 5, and 20 (2.8%) of > or = 6. The criterion "radiotherapy treatment duration" had the highest rate of protocol violations, 67/708 (9.5%); other quality control criteria with protocol violations were "radiotherapy reference dose" (27 = 3.8%), "radiotherapy treatment initiation" (15 = 2.1%) and "other protocol violations" (33 = 4.7%). No protocol violations were observed for the criterion "target volume coverage". The protocol compliance improved slightly during the conduct of the study. Institutional differences in protocol compliance were observed depending upon the accrual rate, the institutional treatment preference and between academic and non-academic hospitals. After a short median follow-up of 48 months, differences in protocol compliance, i.e. protocol violations, have not resulted in a reduced disease-free survival; however, the final prognostic evaluation of the quality control review may require longer follow-up and eventually different treatment endpoints to be analyzed.

Breast Neoplasms↗
PubMed2001

Quality control of diphtheria tetanus acellular pertussis combined (DTaP) vaccines in Japan.

Diphtheria tetanus acellular pertussis combined (DTaP) vaccines have been successfully used in Japan by controlling their potencies and toxicities with animal models. In accordance with the recent practical introduction of DTaP vaccines of various formulations, a question has been raised in other nations as to the efficacy of a quality control system based on animal tests and standard preparations. The World Health Organization issued its guidelines on the production and quality control of acellular pertussis vaccines in 1998 along with the concept of quality control by ensuring that production lots were consistent with clinical trial lots, rather than by comparing them with standard preparations in traditional laboratory tests. However, because it is not feasible to evaluate the combined use of vaccines from different manufacturers in a clinical study, the alternative trend of quality control may give rise to a difficulty in rationalizing the practical immunizations to use vaccines of different brands in a mixed consequence. A standardized national regulation system to ensure the equivalence of approved products would be essential for such an immunization practice. The success of the Japanese DTaP vaccination suggests the possibility of an effective quality control of DTaP vaccines by means of standardized test systems.

Animals↗
PubMed1992

[4-years experience with quality control of decentralized reflectometry blood glucose measurement in the Vienna-Lainz hospital].

Since 1987 a quality control programme for ward-based blood glucose assays has been established in Lainz Hospital, Vienna. In 1991 following a decision to standardise the type of reflectometer used in the ward, 62 Reflolux IIS reflectance meters (Boehringer Mannheim) were assessed in a quality control consisting of 4 ring trials a year (blood glucose determination in two "unknown" samples) and in daily measurements of control solutions of known glucose concentrations. Experience with this quality control procedure is reported in this presentation of the relevant results of the ring trials. The most frequent errors in performing the test are discussed and the importance of instructing and training the nursing staff in the proper use and maintenance of the meters is pointed out.

Austria↗
PubMed2005

Interobserver agreement for colposcopy quality control using digitized colposcopic images during the ALTS trial.

OBJECTIVE: To estimate interobserver agreement among colposcopy quality control reviewers viewing digitized cervical images during the Atypical Squamous Cells of Undetermined Significance/Low-Grade Squamous Intraepithelial Lesion Triage Study (ALTS). MATERIALS AND METHODS: Three colposcopy quality control reviewers independently examined modem-transferred digitized colposcopic images from subjects examined at four clinical centers. Reviewers indicated colposcopic impression, Reid colposcopic index scores, lesion size, and the technical quality of the image. Rates of agreement were evaluated using the kappa statistic and McNemar and Bowker tests of symmetry. RESULTS: Regarding colposcopic impressions, the average weighted kappa for pairs of initial reviewers was 0.36 (95% confidence interval, 0.33-0.39). kappa scores with respect to Reid colposcopic index, cervical image quality, and lesion size ranged from 0.23 to 0.28, 0.18 to 0.27, and 0.33 to 0.42, respectively. CONCLUSIONS: Fair rates of agreement and poor to fair kappa scores among ALTS colposcopy quality control reviewers were noted for colposcopic impression, Reid colposcopic index scores, image quality, and lesion size. Great latitude exists in the interpretation of digitized cervical images. Poor image quality partially may explain these suboptimal results.

Cervix Uteri↗
PubMed1984

Internal quality control of hormone determinations by RIA. Detection of clinically significant analytical errors of serum thyroxine determination.

An internal quality control system by which clinically significant analytical errors can be detected with high probability was developed for serum thyroxine (T4) determination by RIA. The mean concentration of the quality control samples (C1, C2, and C3) were 40.0, 101.8, and 156.7 nmol/l, and their total standard deviations (st) 2.5, 4.1, and 7.1 nmol/l, respectively, in stable analytical performance of the T4 assay. From the clinical point of view it was accepted that the results of C1 varied from 30 to 50 nmol/l at the most. When expressed in standard deviations, the same size of error was accepted for C2 and C3. It followed that the quality control system had to detect a systematic shift of 2.43st (delta SEc) and a 2.08 times increase in random error (delta REc) in order that the quality goals could be reached. With three control samples the combination of rules, 1: 3s/CS1: (1.0s; 2.7s), which was chosen for manual quality control, detected the delta SEc with about an 80% probability and the delta REc with about a 30% probability. The probability of false rejections was less than 1%. The probability of detecting the delta SEc was considered acceptable, but to detect the delta REc with a higher probability, the within-assay variation of each run was calculated from the results of duplicate patient samples. Although the whole run was not rejected because of systematic and/or random errors, individual samples were reanalysed if the results of their duplicate determinations differed from the criteria stated.(ABSTRACT TRUNCATED AT 250 WORDS)

False Negative Reactions↗
PubMed1992

MIC and disk diffusion quality control guidelines for Neisseria gonorrhoeae susceptibility tests of cefdinir, cefetamet, CI-960, fleroxacin, lomefloxacin, and temafloxacin.

Cefdinir (FK482), cefetamet (Ro 15-8074), CI-960, fleroxacin, lomefloxacin, and temafloxacin have potent activities against Neisseria gonorrhoeae. They were tested in a multilaboratory study to establish quality control guidelines. Quality control ranges for N. gonorrhoeae ATCC 49226 were determined by using multiple GC agar lots, three disk lots, and a number of test replicates consistent with the M23-T guidelines of the National Committee for Clinical Laboratory Standards. The MIC ranges included 2 to 4 log2 dilution steps. The recommended inhibition zone diameter ranges were generally 7 to 8 mm and included greater than or equal to 91.3% of all recorded study results.

Anti-Infective Agents↗
PubMed1998

Multivariate approach to quality control in clinical chemistry.

When monitoring analyzer performance in the clinical setting, laboratories are required to test multiple concentrations of control material on a daily basis. Because of the nature of laboratory testing, there is the potential for correlation between the concentrations of control material being monitored. Although traditional clinical quality-control approaches make an underlying assumption of independence with respect to the control concentrations, this will not always be the case. The presence of correlation in some circumstances suggests the use of a new approach for evaluating clinical laboratory monitoring data: the multivariate control chart. Such a chart (the chi2 chart) is evaluated and compared with traditional quality-control approaches used in the laboratory setting. Results indicate that the multivariate approach provides an attractive alternative to many traditional methods of quality assurance when control concentrations are correlated.

Chemistry, Clinical↗
PubMed1983

Quality control of acid phosphatase assay improved by direct reconstitution of lyophilized control materials with citric acid.

Current quality control of assays of acid phosphatase (EC 3.1.3.2) with thymolphthalein substrate is inadequate when certain control-suppliers' instructions are followed for reconstituting and stabilizing human lyophilized control material. If such materials are reconstituted with a citric acid solution, then stored frozen, control vial-to-vial variability is minimized, as are losses of activity in freshly reconstituted controls and losses during room-temperature storage of the control material. Effects of pH of the reconstituting solution on the acid phosphatase activity of human lyophilized controls are also discussed.

Acid Phosphatase↗
PubMed1978

The need for quality control in the developing countries.

In the developing countries there is a need for greater activity in the quality control of vaccines used in immunization programmes. The establishment of a quality control facility can give assistance not only in the checking of vaccines at the time of release, but also in monitoring the efficacy of the cold chain. Furthermore, the antibody responses of the local child population to the vaccines can be measured. Quality control should be established before vaccine manufacturer, therefore, and the economics of importing vaccine in the bulk concentrated form with dilution, blending and filling locally is worthy of consideration.

Antibodies↗
PubMed2001

Quality control of transmembrane domain assembly in the tetraspanin CD82.

Retention of misfolded proteins in the endoplasmic reticulum (ER) is a primary mechanism of quality control. To discover whether quality control can monitor assembly inside the hydrophobic ER membrane, we characterized the folding and transport of the tetraspanin glycoprotein CD82. Truncated forms of CD82 that are missing one or more transmembrane segments remain in the ER. A construct (TM 2-4) that is missing the first transmembrane segment remains in the ER, even though its extracellular domain, which is facing the ER lumen, has folded to the native structure. Transport to the cell surface is restored by co-expressing the missing segment (TM 1) as a separate polypeptide. Prior to leaving the ER, CD82 transiently associates with the membrane-bound chaperone calnexin but not with its soluble homolog calreticulin. TM 2-4, in contrast, remains in a prolonged interaction with calnexin that is partially reversed by co-expressing TM 1. These findings establish a simple system to study transmembrane domain assembly, show that ER quality control can directly monitor assembly inside the lipid bilayer and suggest that calnexin may play a role in this process.

Animals↗
PubMed2006

[Current problems in the quality controll of pharmaceutical preparations manufactured in pharmacies I. Identification tests].

Quality controll has fundamental importance in drug safety. During the last 15 years the regulatory changes resulted many problems in the quality controll of pharmaceutical preparations manufactured in pharmacys. The issue of Formulae Normales (FoNo VII.) and the 8th Hungarian Pharmacopoeia raises further questions. Our intentions to show the results have been achived in the area of elaborating new analytical prescriptions (identification and assay) which are crucial due to the obsolescence of previously used prescriptions.

Hungary↗
PubMed1997

Immunocytochemical staining of effusions; an external quality control study in The Netherlands.

In The Netherlands an external quality control study of immunocytochemical (IC) staining of effusions was initiated, consisting of three test rounds. The 12 participating laboratories received samples of malignant effusions (runs 1, 2 and 3), and five unstained control specimens prepared from the same material in runs 2 and 3. The laboratories used their own protocols to prepare and stain the samples ('in-house' specimens). Two persons viewed and scored the slides following preset criteria concerning number and morphology of diagnostic cells, background staining and staining specificity. Better scoring results were found for control specimens, compared with 'in-house' specimens, primarily caused by cell loss in the latter. This finding underlines the view that high quality IC needs well organized processing and staining procedures, and warrants external quality control systems.

Breast Neoplasms↗