Temporal Changes In Response Research Articles

Suitability of laser stimulated TLD arrays as patient dose monitors in high dose x-ray imaging.

Skin entrance doses of patients undergoing interventional x-ray procedures are capable of causing skin damage and should be monitored routinely. Single TLD chips are not suitable because the location of maximum skin exposure cannot be predicted. Most photographic films are too sensitive at diagnostic x-ray energies for dosimetry, exhibit temporal changes in response, and require special packaging by the user. We have investigated the suitability of laser heated MgB4O7 TLDs in a polyimide binder in the range of 0.2-20 Gy. These are available in radioluscent arrays up to 30 x 30 cm for direct measurement of patient skin dose. Dose response was compared with a calibrated ion chamber dosimeter. Exposures were made at 60, 90, and 120 kVp, at low (fluoroscopy) and high (DSA) dose rates, and at different beam incidence angles. Longitudinal reproducibility and response to temperature changes during exposure were also checked. The dose response is linear below approximately 6 Gy where the slope starts to increase 2% per Gy. Errors were less than +/- 2% over a 0-80 degrees range of beam incidence angles; less than +/- 3% for both dose rate variations and kVp differences between 70 and 120 kVp. The response was unaffected by temperature changes between 20 and 37 degrees C. Reproducibility is current +/- 7%. MgB4O7 TLD arrays are suitable for patient dosimetry in high dose fluoroscopy procedures if appropriate calibrations are used. Uncertainty in skin dose measurement is less than 10%, which is substantially better than film dosimetry.

Effects of misclassification and temporal change of response in food frequency on risk ratio.

Misclassification and temporal changes of food consumption frequencies were estimated under the statistical models with some assumptions, and their effects on risk ratios were evaluated. Food frequencies of 27 items in 214 subjects were doubly measured by a questionnaire with 2 weeks interval, and those in 326 subjects were measured in 1989, 1993 and 1994. Median of probabilities of misclassification in responses among 27 food items was estimated to be 0.12. Medians of proportions of persons whose responses in 1989 were different from those after 5 years, were calculated to be 35% with misclassification and 27% without misclassification. For the true risk ratio of 3, medians of the risk ratios of dietary habits during 5 years, based on food frequencies measured at 1989, were observed to be 2.2 in case of responses with misclassification, and 1.7 in case of responses with misclassification and temporal changes. These suggested that the risk ratios of food frequencies would be seriously affected by misclassification and temporal changes in responses.

Cognitive factors affecting taste intensity judgments

The mean sensory response is often considered to represent the perceived intensity for a stimulus on the specified attribute. However, a momentary judgment is the outcome of a number of physical, physiological, and psychological processes. Four types of cognitive variables are discussed, that can affect the outcomes of an intensity scaling experiment. First of all, the role of cognitive algebra and concept formation in tasks varying with regard to the number of stimuli to be compared, and with regard to the type and number of response scales used, is discussed. Subsequently, the effects of stimulus set characteristics on context and sequence effects are reviewed. Thirdly, temporal changes in responses during the time course of an experimental session are related to fatiguing and learning. Finally, the role of subjects' expectations is discussed.