Precision of measurements with arbitrary confidence levels when samples are counted equal to or longer than blanks by computer codes.

Past computer solutions for confidence intervals, both in paired counting and when the sample is counted an integer number of times more than the blank, are extended to computing the precision of the measurement. The blank count and the contribution of the sample to the gross count are assumed to be Poisson distributed. While the standard deviation and the probability density function of the net count are readily computed, the name and properties of the probability density function are unknown. Hence, the uncertainty of the net count is unknown. However, both the upper and lower confidence limits, at a given confidence level, can be computed. In general, the difference between the upper limit and the observed net count is greater than the difference between the observed net count and the lower confidence limit. So the bound on the uncertainty is taken to be the difference between the upper confidence limit and the observed net count. Then the precision can be taken to be the bound on the uncertainty divided by the observed net count (relative bound on the uncertainty).

Improved confidence intervals when the sample is counted an integer times longer than the blank.

Past computer solutions for confidence intervals in paired counting are extended to the case where the ratio of the sample count time to the blank count time is taken to be an integer, IRR. Previously, confidence intervals have been named Neyman-Pearson confidence intervals; more correctly they should have been named Neyman confidence intervals or simply confidence intervals. The technique utilized mimics a technique used by Pearson and Hartley to tabulate confidence intervals for the expected value of the discrete Poisson and Binomial distributions. The blank count and the contribution of the sample to the gross count are assumed to be Poisson distributed. The expected value of the blank count, in the sample count time, is assumed known. The net count, OC, is taken to be the gross count minus the product of IRR with the blank count. The probability density function (PDF) for the net count can be determined in a straightforward manner.

Measurements should not be recorded as less than MDA: an extension.

Sometimes the results of measurements in radioactivity are reported as "less than the minimum detectable activity." Over the years there have been articles informing the reader that it is incorrect to express the results of measurements as less than the minimum detectable activity. A very brief review of past comments on expressing the results of measurements precedes a discussion of why measurements should not be reported as less than the minimum detectable activity. The decision level is the value of the net count above which a measurement process is claimed to have detected activity; it is determined so that the probability of detecting activity, when there is no activity in the sample, is less than or equal to the desired error of the first kind. This article extends previous work restricted to paired counting, where the blank and sample were counted for the same amount of time, to blank count times greater than or equal to the sample count times.

Facts and controversies about radiation exposure, part 2: low-level exposures and cancer risk.

In this 2-part article, the authors address the need to put in perspective the risks of radiation exposure in the rapidly changing field of radiology, considering the current state of knowledge of effects at low levels. The article is based on the content of the refresher course RC 516 presented at the Radiological Society of North America's 2005 annual meeting. In part 1, the authors presented a brief review of epidemiologic studies, a discussion of typical radiation doses experienced in medicine by both patients and professionals, and the description of practical approaches to reduce unnecessary exposures. Part 2 addresses a special concern for the unborn and discusses advisory and regulatory cancer risk estimates based mainly on epidemiologic studies. The limitations of epidemiologic studies at low-level exposures and recent new findings in radiobiology, some of which are summarized, challenge the notion that any amount of radiation causes adverse effects.

Factors associated with adherence to recommendations for screening mammography among American Indian women in Colorado.

OBJECTIVE: To compare adherence to screening mammography recommendations of American Indian and non-Hispanic White women in the Denver, Colorado, area. DESIGN/SETTING/PARTICIPANTS: This study retrospectively examined adherence patterns in 229 American Indian and 60,197 non-Hispanic White women > or = 40 years and older, with at least one screening mammogram in the Colorado Mammography Project (CMAP), from January 1, 1999, to December 31, 2003. The CMAP was a prospective study of women receiving mammograms at participating clinics around Denver. MAIN OUTCOME MEASURES: Using logistic mixed models, we defined two dependent variables as annual and biennial adherence from the intervals between screening mammograms for each woman. RESULTS: Biennial adherence was substantially higher than annual adherence for both American Indian and non-Hispanic White women in our analyses. American Indian women were less likely than non-Hispanic White women to adhere to biennial recommendations in multivariate models controlling for age, family history of breast cancer, and economic status (zip code): odds ratio (OR) .4 and 95% confidence interval (CI) .2-.6. The association between American Indian race/ethnicity and annual adherence was similar, although not as strong (OR .5, 95% CI .3-.8). CONCLUSIONS: American Indian women in the CMAP cohort were less likely than non-Hispanic White women to adhere to recommendations for screening mammography, both annually and biennially. Additional research is needed to explore the effect of biennial screening and other barriers among American Indian women.

Radon treatment controversy.

In spite of long traditions, treatments utilizing radon-rich air or water have not been unequivocally embraced by modern medicine. The objective of this work is to examine factors that contribute to this continuing controversy. While the exact mechanism of radon's effect on human body is not completely understood, recent advances in radiobiology offer new insights into biochemical processes occurring at low-level exposures to ionizing radiation. Medical evidence and patients' testimonials regarding effectiveness of radon spa treatments of various ailments, most notably rheumatoid arthritis are accumulating worldwide. They challenge the premise of the Linear-No-Threshold (LNT) theory that the dose-effect response is the same per unit dose regardless of the total dose. Historically, such inference overshadowed scientific inquiries into the low-dose region and lead to a popular belief that no amount of radiation can be good. Fortunately, the LNT theory, which lacks any scientific basis, did not remain unchallenged. As the reviewed literature suggests, a paradigm shift, reflected in the consideration of hormetic effects at low-doses, is gaining momentum in the scientific community worldwide. The impetus comes from significant evidence of adaptive and stimulatory effects of low-levels of radiation on human immune system.

Facts and controversies about radiation exposure, part 1: controlling unnecessary radiation exposures.

In this 2-part article, the authors address the need to put in perspective the risks of radiation exposure in the rapidly changing field of radiology, considering the current state of knowledge of effects at low levels. The article is based on the content of the refresher course RC 516 presented at the Radiological Society of North America's 2005 annual meeting. After a brief review of epidemiologic studies, part 1 contains a discussion of typical radiation doses experienced in medicine, by both patients and professionals, and it concludes with a description of practical approaches to reduce unnecessary exposures. Part 2 of the article addresses a special concern for the unborn and discusses advisory and regulatory cancer risk estimates based mainly on epidemiologic studies. The limitations of epidemiologic studies at low-level exposures and recent new findings in radiobiology, some of which are summarized, challenge the notion that any amount of radiation causes adverse effects.

Radiation exposure in rheumatology practice.

BACKGROUND: Patients encountered in rheumatology practice often have concerns about radiation exposure from the imaging procedures used to diagnose and monitor their diseases. However, such imaging procedures normally deliver radiation doses that are associated with only a low level of risk. OBJECTIVES: To review and quantify the radiation doses delivered by the various imaging procedures commonly ordered in a rheumatology practice and to compare those doses with background radiation exposure in the United States. METHODS: The authors reviewed and compiled literature on radiation exposure from background radiation and diagnostic imaging procedures. The review included a Medline search through December 2003. RESULTS: Radiation doses from medical imaging procedures are so low that they do not have a clinically significant effect on mortality rates. In comparison to our normal daily exposures from naturally occurring background radiation and daily activities, the exposures from medical procedures are quite small. Moreover, the International Commission for Radiological Protection (ICRP) recommends that dose limits should not be applied to medical exposures in nonpregnant patients. Rather, the ICRP recommends that the medical exposure be justified and the protection be optimized so that the dose to the patient is as low as is compatible with the medical purpose. CONCLUSIONS AND RELEVANCE: Appropriate care of patients within the rheumatology practice frequently necessitates the use of imaging procedures that utilize ionizing radiation, such as radiographs, computed tomography scans, and bone densitometry. If ordered prudently, the benefits of these imaging procedures supersede the risks imposed by their radiation exposures.

Disparities in adherence to recommended followup on screening mammography: interaction of sociodemographic factors.

OBJECTIVE: The objective of this study was to examine disparities in adherence to screening mammography and, specifically, to investigate whether race/ethnicity, education, age, health insurance, and family history of breast cancer (FHBC), as unique factors and in interactions, influence adherence to recommended follow up on screening mammography. DESIGN: The study involved retrieval and analyses of data collected by the Colorado Mammography Project (CMAP) for 167,232 diverse (82.8% White, 3.4% Black, 11% Hispanic, 1.6% Asian, 0.6% Native American, and 0.6% "other") screening participants during the 1990-1997 study period. METHODS: Subjects' first mammograms captured by CMAP were tracked in the database to identify women who received follow-up recommendations, women who adhered within 12 months and those that did not. Analyses included comparisons of adherence rates among women with various sociodemographic characteristics. RESULTS: Of the 17,358 women who received follow-up recommendations, 80.7% adhered. Overall, non-White women in each of the racial/ethnic groups were less likely to adhere to recommendations than were White women (P<.05). Also less likely to adhere were the younger, less educated, uninsured/underinsured, and women who reported not having FHBC. CONCLUSION: Race/ethnicity appeared to interact with age, education, health insurance, and FHBC to influence the probability of adherence, suggesting the need to explore further cultural, psychosocial, and situational factors.