Comparison Euromet.EM-K8 of DC Voltage Ratio: Results
Twenty National Metrology Institutes have participated in the European DC voltage ratio key comparison (EUROMET.EM-K8). The results for the voltage ratios 1000V/10V and 100V/10V are reported
A Simple Build-Up Method for the DC Voltage Scale of a Source
We report on the performance of a simple method, known as the reference step method, to build up the dc voltage scale of a source. The key advantages of this method are that it relies on equipment that is readily available in most high-level laboratories and can be fully automated. The Type A uncertainties achieved by this approach can be less than 0.1 <formula formulatype="inline"><tex Notation="TeX">$\mu{\rm V/V}$</tex></formula>. This performance is achieved because of the excellent differential linearity of the DVM used in the method. We have validated the overall accuracy of the method by directly comparing this approach with more traditional resistive divider techniques and have established that the expanded uncertainty is better than 0.2 <formula formulatype="inline"><tex Notation="TeX"> $\mu{\rm V/V}$</tex></formula> up to 1000 V, limited only by the performance of the instruments used.
The effect of collimation on image quality and radiation safety in digital radiography of small animals
Collimating the primary x-ray beam to the specific area of anatomic interest has traditionally been strongly recommended to produce high quality radiographic images, even though some small animal patients can fit their entire torso on a single radiographic casette or detector. However, modern digital radiography may allow for whole-body projections for these patients at similar quality to specific collimated projections. Lateral and ventrodorsal projections of 31 small dogs were obtained to evaluate the effect of collimation on the quality of the resulting digital radiograph. Each projection was performed using both a collimated and whole-body technique. Scatter radiation was detected during each exposure as well to determine the effect of collimation on radiation safety for veterinary personnel. The resulting images were cropped to portray only the thorax, and were evaluated by five radiologists blinded to the procedure used for each image. Visual grading characteristics analysis was performed. An overall trend towards higher image quality was found in the collimated approach compared to the whole-body, but in most cases this change was not significant. Overall image quality for the ventrodorsal images was found to be significantly better in the collimated approach compared to the whole-body. Evaluation of image histograms suggests that the application of digital processing and the look-up table differs between them, and this may account for a large portion of any quality difference. Over twice as much scatter radiation was detected during the whole-body images as during the collimated images. Overall image quality was rated as adequate to high for almost all images with both approaches. Adequate collimation remains recommended to provide the highest quality images with the lowest exposure to veterinary personnel.