Investigation into possible causes of blurring in mammograms
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KeywordsCancer Research Rhodium Full Text Compression Force Longe Exposure
Technical recalls cause unnecessary anxiety to the women concerned and an increased workload for the screening unit. A review of technical recalls at Bolton Breast Unit found that over 90% were due to blurred images. This study aimed to identify causes of blurring and to reduce the number of technically inadequate films. X-rays were taken using static IGE DMR & 800T units and Kodak Min-R 2000 film/screen combination. Exposure factors (kVp, mAs, target & filter) were selected automatically, using 'Standard' mode. Two groups of films were examined; group 1 (n = 45) were identified as blurred at reporting stage and group 2 (n = 45) were technically adequate films selected randomly.
Analysis showed that the mean compression force applied was 10 dN and 13 dN for the blurred and adequate films, respectively, which is a significant difference (P < 0.01). The breast thickness and mAs were significantly higher in the blurred group (P < 0.01). With the 800T unit, the rhodium filter was selected for 90% of blurred films compared to 36% of adequate films. Inadequate compression in the blurred group (which would result in greater breast thickness, longer exposures and earlier selection of rhodium target/filter) is suspected. A minimum compression force has been recommended at the unit.