Blurred digital mammography images: an analysis of technical recall and observer detection performance.

OBJECTIVE: Blurred images in full-field digital mammography are a problem in the UK Breast Screening Programme. Technical recalls may be due to blurring not being seen on lower resolution monitors used for review. This study assesses the visual detection of blurring on a 2.3-MP monitor and a 5-MP report grade monitor and proposes an observer standard for the visual detection of blurring on a 5-MP reporting grade monitor. METHODS: 28 observers assessed 120 images for blurring; 20 images had no blurring present, whereas 100 images had blurring imposed through mathematical simulation at 0.2, 0.4, 0.6, 0.8 and 1.0 mm levels of motion. Technical recall rate for both monitors and angular size at each level of motion were calculated. χ2 tests were used to test whether significant differences in blurring detection existed between 2.3- and 5-MP monitors. RESULTS: The technical recall rate for 2.3- and 5-MP monitors are 20.3% and 9.1%, respectively. The angular size for 0.2- to 1-mm motion varied from 55 to 275 arc s. The minimum amount of motion for visual detection of blurring in this study is 0.4 mm. For 0.2-mm simulated motion, there was no significant difference [χ2 (1, N = 1095) = 1.61, p = 0.20] in blurring detection between the 2.3- and 5-MP monitors. CONCLUSION: According to this study, monitors ≤2.3 MP are not suitable for technical review of full-field digital mammography images for the detection of blur. Advances in knowledge: This research proposes the first observer standard for the visual detection of blurring.

Analysis of motion during the breast clamping phase of mammography.

OBJECTIVE: To measure paddle motion during the clamping phase of a breast phantom for a range of machine/paddle combinations. METHODS: A deformable breast phantom was used to simulate a female breast. 12 mammography machines from three manufacturers with 22 flexible and 20 fixed paddles were evaluated. Vertical motion at the paddle was measured using two calibrated linear potentiometers. For each paddle, the motion in millimetres was recorded every 0.5 s for 40 s, while the phantom was compressed with 80 N. Independent t-tests were used to determine differences in paddle motion between flexible and fixed, small and large, GE Senographe Essential (General Electric Medical Systems, Milwaukee, WI) and Hologic Selenia Dimensions paddles (Hologic, Bedford, MA). Paddle tilt in the medial-lateral plane for each machine/paddle combination was calculated. RESULTS: All machine/paddle combinations demonstrate highest levels of motion during the first 10 s of the clamping phase. The least motion is 0.17 ± 0.05 mm/10 s (n = 20) and the most motion is 0.51 ± 0.15 mm/10 s (n = 80). There is a statistical difference in paddle motion between fixed and flexible (p < 0.001), GE Senographe Essential and Hologic Selenia Dimensions paddles (p < 0.001). Paddle tilt in the medial-lateral plane is independent of time and varied from 0.04 ° to 0.69 °. CONCLUSION: All machine/paddle combinations exhibited motion and tilting, and the extent varied with machine and paddle sizes and types. ADVANCES IN KNOWLEDGE: This research suggests that image blurring will likely be clinically insignificant 4 s or more after the clamping phase commences.

A mammography image set for research purposes using BI-RADS density classification.

PURPOSE: Breast density categorization consistency is important when performing research, and minimization of interoperator and intraoperator variability is essential. This research aimed to validate a set of mammography images for visual breast density estimation to achieve consistency in future research projects and to determine observer performance. METHODS: Using the Breast Imaging Reporting and Data System (BI-RADS) as the visual grading scale, 50 mammography images were scored for density grade by 8 observers. RESULTS: Six of 8 observers achieved near-complete intraobserver agreement (kappa > 0.81). Strong agreement among observers (kappa = 0.61-0.8) was found in 10 of 28 paired observation episodes on the first iteration and 12 of 28 on the second. No observers demonstrated a delta variance above 1. Fleiss' kappa was used to evaluate concordance among all observers on the first and second iterations (first iteration, 0.64; second iteration, 0.56). DISCUSSION: This research illustrates the difficulties of comparing observer visual performance scores because differences can exist when studies are repeated by and among individuals. CONCLUSION: We confirmed that the 50 images were suitable for research purposes. Some variability existed among observers; however, overall density classification agreement was strong. Future research should include repeating this study with digitally acquired images.