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Assessment of image quality in dental radiography, part 1: phantom validity.

OBJECTIVE: The purpose of this study was to describe and validate an image-quality phantom to be used in dental radiography for comparison of film and digitally acquired images. STUDY DESIGN: An aluminum block of 12 steps, with 7 holes in each step, was covered by acrylic blocks. This phantom was radiographed with Kodak Ultra-speed and Ektaspeed Plus films at 70, 65, and 60 kVp with the whole exposure range available. All together, 50 dental films were randomly sequenced and presented to 7 observers. The average number of perceptible holes from all steps was plotted against exposure for each tube voltage and film type, generating a modified perceptibility curve. The tentative optimum exposure level was determined from perceptibility curves in each experimental condition and compared with that determined by means of the standard aluminum stepwedge and the preset time of the x-ray machine. The density range of this phantom at the optimum exposure was compared with that of clinical dental radiographs. Validity of the phantom was evaluated according to the optimum exposure level from the modified perceptibility curves and the overall density range. Finally, the average maximum numbers of perceptible holes at the tentative optimum exposure level were compared for each tube voltage and film type. The statistical test used was a 2-way factorial analysis of variance. RESULTS: The exposure at the perceptibility curve peak approximated that obtained by means of the standard aluminum step-wedge and the time preset by the manufacturer. The overall density range at the perceptibility curve peak covered the clinical density range for each tube voltage and film type. There were no statistically significant differences between film types or among tube voltages. CONCLUSIONS: The x-ray attenuation range for this phantom seemed to approximate clinical conditions. In addition, differences in image quality could be quantitatively evaluated by means of the number of the holes seen in the phantom.

Absorptiometry, Photon↗

Rapid epidemiological assessment of health status in displaced populations--an evolution toward standardized minimum, essential data sets.

Rapid epidemiological assessment (REA) has evolved over the past 30 years into an essential tool of disaster management. Small area survey and sampling methods are the major application. While REA is protocol driven, needs assessment of displaced populations remains highly non-standardized. The United Nations and other international organizations continue to call for the development of standardized instruments for post-disaster needs assessment. This study examines REA protocols from leading agencies in humanitarian health assistance across an evaluation criteria of best-practice attributes. Analysis of inconsistencies and deficits leads to the derivation of a Minimum Essential Data Set (MEDS) proposed for use by relief agencies in post-disaster REA of health status in displaced populations. This data set lends itself to initial assessment, ongoing monitoring, and evaluation of relief efforts. It is expected that the task of rapid epidemiological assessment, and more generally, the professional practice of post-disaster health coordination, will be enhanced by development, acceptance, and use of standardized Minimum Essential Data Sets (MEDS).

Benchmarking↗

Technology insight: Photodynamic therapy for cholangiocarcinoma.

Cholangiocarcinoma is, in most cases, rapidly fatal. Curative resection can only be offered to approximately 10% of patients. Even after seemingly curative resection, recurrence frequently occurs. Adjuvant chemotherapy and/or radiotherapy do not reduce the recurrence rate after resection. In the palliative setting, endoscopic or percutaneous biliary drainage is performed to relieve jaundice; however, poor results have been obtained in patients with tumors involving the intrahepatic bile ducts. Biliary drainage alleviates jaundice, but there is no evidence that it prolongs life. Palliative chemotherapy and/or radiotherapy have not been proven to prolong life and relieve jaundice. Photodynamic therapy (PDT) is a relatively new local, minimally invasive procedure that can be used to treat cholangiocarcinoma. PDT uses the physical properties of light-absorbing molecules, so-called photosensitizers, which accumulate within proliferating cells. Activation of the photosensitizer by a non-thermal laser leads to selective photochemical destruction of tumors. In a randomized trial of patients with nonresectable cholangiocarcinoma, PDT prolonged survival time, improved cholestasis and quality of life considerably, and had a favorable side-effect profile. A second randomized trial confirmed the beneficial effect of PDT. For the time being, PDT is recommended for patients with nonresectable disease. The role of PDT before and after surgical resection needs to be assessed.

Bile Duct Neoplasms↗

A guide for diagnostic evaluations.

Accurate diagnostic tests have a key role in patient management and the control of most infectious diseases. Unfortunately, in many developing countries, clinical care is often critically compromised by the lack of regulatory controls on the quality of these tests. The information available on the performance of a diagnostic test can be biased or flawed because of failings in the design of the studies which assessed the performance characteristics of the test. As a result, diagnostic tests are sold and used in much of the developing world without evidence of effectiveness. Misdiagnosis leading to failure to treat a serious infection or wasting expensive treatment on people who are not infected remains a serious obstacle to health.

Communicable Diseases↗

Principles of recruitment and retention in clinical trials.

Efficient and effective recruitment and retention of participants is the largest single component of the study workload and forms an essential component in the conduct of clinical trials. In this paper, we present five principles to guide the processes of both recruitment and retention. These principles include the selection of an appropriate population to adequately answer the research question, followed by the establishment of a sampling process that accurately represents that population. Creation of systematic and effective recruitment mechanisms should be supported by implementation of follow-up mechanisms that promote participant retention. Finally, all activities related to recruitment and retention must be conducted within the framework of ethics and privacy regulations. Adherence to these principles will assist the researcher in achieving the goals of the study within the available resources.

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