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PURPOSE: To implement in software the procedures described in AAPM Task Group 150's draft recommendations for image receptor performance testing, and to evaluate the effectiveness and practicality of these procedures. METHODS: Images of flat fields were acquired using digital x-ray image receptors at 6 cooperating institutions. Four flat field images obtained with each detector spanned a range of input detector air kerma. Software based on AAPM TG150's draft report processed the test images and generated results. Image receptor response and several measures of non-uniformity were evaluated. Images were divided into 10 mm square regions, after eliminating 10 mm borders. For each region, signal (mean), noise (standard deviation) and SNR were calculated. Characteristic signal, noise and SNR were calculated based on average values from all regions. Local non-uniformity for signal (SLN), noise (NLN) and SNR (SNRLN) were expressed as the maximum ratio of the absolute difference between each region's value and its 4 nearest neighbors, to the respective characteristic value. Global non-uniformity (SGN, NGN, SNRGN) were expressed similarly but differences between maximum and minimum values obtained from the regions were used (without comparison to local neighbors). RESULTS: TG150 tests discriminated between good and poorly performing detectors. Improper detector calibration was detectable, with noise non-uniformity proving to be a more sensitive measure than signal or SNR non-uniformity. Detector rotation relative to calibration conditions produced a greater change in signal non-uniformity than the other measures. Image receptor structured noise was characterized by an increase in noise non-uniformity with incident air kerma. CONCLUSIONS: AAPM TG150's proposed approach to image receptor testing was implemented and evaluated. The approach appears to be an effective and practical one for routine quality assurance testing of digital radiographic image receptors.

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PURPOSE: Anomalous pixels may be defined as those pixels whose exposure response relationship is deviant from the typical, expected or calibrated response. A group of anomalous pixels may Result in visible correlated artifacts. Here we demonstrate an approach to identify anomalous pixels and correlated artifacts using flat-field images. METHODS: Using manufacturer specific calibration geometry, sets of four flat-field images per detector were obtained with varying input air kerma values (0.5 to 160 µGy) from 9 digital detectors at 6 institutions. Images obtained before and after calibration, with both proper and improper gain maps and structured artifacts were additionally acquired with some detectors. Image analysis methodology under consideration by AAPM Task Group 150 was used.After eliminating 10mm borders, images were divided into square regions (100mm2 ). Anomalous pixels were identified as pixels within each region with valuesabove or below ±3 standard deviations (SD) relative to the mean value of the region. If these pixels were identified in all four images comprising a set, then they were reported as anomalous. Line artifacts were identified as rows and columns with cumulative profile values that were above or below ±3 SD with respect to the mean value of neighboring profiles in the set of four flat-field mages. Results were verified with visual inspection of the images. RESULTS: For four sets of images, the algorithm did not identify any anomalous pixels, and none were spotted on visible inspection as well, while for five sets of images the identified anomalous pixels matched visual inspection results. Anomalous pixel detection failed in regions with an unusually large number of defects and structured noise, since those regions exhibited relatively large SD. Line artifacts consistent with visual analysis were identified correctly when present. CONCLUSIONS: A practical approach to identify anomalous pixels and correlated artifacts from flat-field images is demonstrated.

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Distemper virus causes a disease affecting minks with respiratory, gastrointestinal, neurological and skin symptoms and showing high morbidity and mortality, mainly among puppies. It is controlled through immunization, using vaccines that are supplied for mink use. The aim of this work was to determine the seroneutralization titer against the distemper virus at a mink farm in Argentina. The antibody kinetics obtained after vaccination in 27 adult animals, as well as the duration of colostrum-transferred antibodies in 10 puppies were determined. All vaccinated adult minks showed protective titers up to at least 3 months after vaccination, and 37.5% significantly reduced their antibody levels, 12 months after vaccination. Only 20% of the puppies showed protective levels of colostrum-transferred antibodies at the age of 7 weeks, while non-detectable levels of antibodies were found when puppies reached 11 weeks old. Vaccination performed in these puppies at the age of 13 weeks, elicited protective seroneutralization titers. These results show that vaccination induces a satisfactory humoral immune response in our environment, and support the convenience of vaccinating dams annually before the beginning of the breeding season. The vaccination plan in puppies is also discussed.

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BACKGROUND: Major surgical procedures are performed with increasing frequency in elderly persons, but the impact of age on resource use and outcomes is uncertain. OBJECTIVE: To evaluate the influence of age on perioperative cardiac and noncardiac complications and length of stay in patients undergoing noncardiac surgery. DESIGN: Prospective cohort study. SETTING: Urban academic medical center. PATIENTS: Consecutive sample of 4315 patients 50 years of age or older who underwent nonemergent major noncardiac procedures. MEASUREMENTS: Major perioperative complications (cardiac and noncardiac), in-hospital mortality, and length of stay. RESULTS: Major perioperative complications occurred in 4.3% (44 of 1015) of patients 59 years of age or younger, 5.7% (93 of 1646) of patients 60 to 69 years of age, 9.6% (129 of 1341) of patients 70 to 79 years of age, and 12.5% (39 of 313) of patients 80 years of age or older (P < 0.001). In-hospital mortality was significantly higher in patients 80 years of age or older than in those younger than 80 years of age (0.7% vs. 2.6%, respectively). Multivariate analyses indicated an increased odds ratio for perioperative complications or in-hospital mortality in patients 70 to 79 years of age (1.8 [95% CI, 1.2 to 2.7]) and those 80 years of age or older (OR, 2.1 [CI, 1.2 to 3.6]) compared with patients 50 to 59 years of age. Patients 80 years of age or older stayed an average of 1 day more in the hospital, after adjustment for other clinical data (P = 0.001). CONCLUSIONS: Elderly patients had a higher rate of major perioperative complications and mortality after noncardiac surgery and a longer length of stay, but even in patients 80 years of age or older, mortality was low.

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OBJECTIVES: In a study of access to medical care, the authors analyzed the relationship between factors influencing demand, local unmet needs, and the availability of physicians in a rural California community. METHODS: The California Department of Health Services screened 1,697 (90%) of children aged 1 to 12 years in McFarland, CA. The relation of demand to unmet needs was examined using multiple logistic regression. Factors influencing demand for medical care were: ability to pay (income, health insurance) desire to purchase care (ethnicity, education, perceived need), and incidental costs (transportation, child care, etc). Questions from the Hispanic Health and Nutrition Survey were reconstrued to fit the demand model. Local need and demand for physicians was compared with state levels to assess whether sufficient physicians were available. RESULTS: Eighty-six percent of the children were of Mexican ancestry. Factors influencing demand were linked with specific unmet needs. Although unmet needs were high, demand was low; 46% of all families were below the poverty level. Although four primary care physicians were needed, only one could be supported in the private sector because of low demand. CONCLUSIONS: Advantages to the demand model are: (1) it shows why medical services are underused and lacking in low-income areas although need is high, (2) it permits an economic rationale for extra services for poor diverse populations, (3) it estimates the amount of resources lacking to assure adequate levels of care, (4) it shows why facilitated access is needed for certain groups.

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