ABSTRACT
Optimisation must be carried out on all medical radiological units to ensure doses are as low as reasonably practicable, consistent with the intended purpose. To achieve this, population doses must be estimated and diagnostic reference levels (DRLs) set. For mammography examinations, mean glandular doses (MGDs) are calculated for this purpose. The average MGD per unit is compared to the national mammography DRL, which is applicable to compressed breast thicknesses (CBTs) of 50-60 mm for oblique (OB) views only and set using data from screening units. It is the purpose of this work to assess planar MGDs across Scotland and set DRLs based on data collected from all screening and symptomatic units across Scotland, considering craniocaudal (CC) and OB views and a wider range of CBTs. Data from the most recent dose audit (spanning 2015-2017) for 67 mammography x-ray units were collated and analysed (26 195 images). No large differences between MGD of CC and OB views were found when considering specific CBT ranges (median difference 2.6%). There was, however, a significant difference between screening and symptomatic data (19%). As expected, MGD increased with CBT and there were significant differences in MGD between manufacturers. From the data analysed, Scottish DRLs were set based on 95th percentile values for digital mammography units for three CBT ranges (30-49, 50-60 and 61-80 mm): 1.3, 1.8 and 2.6 mGy respectively. These values consider OB and CC views collectively. Fifth percentile values are quoted to highlight units at greater risk of insufficient image quality. These MGD values, together with image quality assessments, will facilitate optimisation across Scotland. Results show that use of different CBT ranges and inclusion of CC views increases the number of images included in dose audit data analysis from approximately 12%-92%, which is substantially more representative of the population.
Subject(s)
Diagnostic Reference Levels , Mammography , Breast/diagnostic imaging , Radiation Dosage , ScotlandABSTRACT
This study compared the age-specific incidence, postdiagnostic survival, and mortality for cardiovascular disease (CVD) in two cohorts of people aged 65 years and older. All subjects were members of a large prepaid health maintenance organization. The influence of changes in CVD risk factors on these rates also was evaluated. Trends in prevalence, incidence, postdiagnostic survival, and mortality for CVD were examined in both cohorts in 1971 and 1980. Myocardial infarction (MI), angina pectoris, stroke, and congestive heart failure (CHF) were included as CVD outcomes in this analysis. Nine-year prospective data on these diagnoses were abstracted from medical records and computerized hospitalization records for both cohorts. Age-sex-adjusted cardiovascular mortality was lower for both sexes by approximately 20% in the 1980 cohort. Overall survival did not change, whereas cancer mortality increased by 76% in women and 36% in men. With the exception of stroke, there was no increase in age-adjusted or age-specific prevalence. In men, the age-adjusted prevalence of stroke in men was 24% higher in the 1980 cohort. Age-adjusted 9-year incidence of MI, angina pectoris, stroke, and CHF did not change between cohorts in either sex Postdiagnostic, age-adjusted mortality for men with incident stroke was 24% lower in the 1980 cohort, and Postdiagnostic, age-adjusted mortality for men with incident angina was 35% lower in the 1980 cohort. Adjustment for risk factors measured at or before baseline had little influence on cohort differences in CVD incidence or duration of survival after CVD diagnosis. This study confirms other research showing a decline in CVD mortality over the past 20 years. These findings suggest that prevalent angina pectoris is increasing in men, and that survival with stroke and with angina is improving in men. Later diagnosis of incident CHF in men suggests that prevention and early detection may be postponing the development of more serious disease.
