Soft-copy reading in digital mammography of mass: diagnostic performance of a 5-megapixel cathode ray tube monitor versus a 3-megapixel liquid crystal display monitor in a diagnostic setting

Abstract

Background: Liquid crystal display (LCD) monitors and cathode ray tube (CRT) monitors are currently the two most common types used in digital mammography systems. The appropriate selection of a monitor is very important and requires balancing the monitor's performance and its cost. A previous study of soft-copy reading in digital mammography of microcalcifications showed that 3-megapixel (M) LCD monitors were similar in diagnostic performance to 5M CRT monitors in a diagnostic setting. Purpose: To compare 5M CRT monitors with 3M LCD monitors for soft-copy reading of digital mammography of a mass in a diagnostic setting. Material and Methods: Seventy mass lesions having undergone either breast biopsies or definitive surgery (46 malignant and 24 benign) and 30 normal cases were recruited into the study. The median size of the lesions was 16 mm (range 7–20 mm). The digital mammograms in the 100-case set were assigned to two blocks, block A (50 cases) and block B (50 cases), for 5M CRT and 3M LCD monitors. A single radiologist read all 100 cases with both types of monitors, starting with the images in block A on the 5M CRT monitors and then the images in block B on the 3M LCD monitors. The radiologist analyzed the soft-copy images on 5M CRT and 3M LCD monitors with 5 months between the interpretations to reduce the effects of learning and memory. Again, the reader started with the images in block A on the 3M LCD monitors and then read the images in block B on the 5M CRT monitors. A five-point rating scale for the probability of malignancy was used for interpreting the soft-copy mammograms. The mass descriptor was scored on a six-point scale. Breast density was scored on a four-point scale. The positive predictive value (PPV) and negative predictive value (NPV) were calculated based on the criteria of the Breast Imaging Reporting and Data System. The interpretation time was also measured. Results: No significant difference was observed in the probability of malignancy ( P=1), mass descriptor ( P=0.317), and breast density ( P=0.739). The PPV and NPV of soft-copy reading on the 5M CRT monitors were 91% (42/46) and 94% (51/54), respectively, identical to the results using 3M LCD monitors. The total interpretation time averaged 62 s for the 5M CRT monitors and 60 s for the 3M LCD monitors ( P<0.0001). Conclusion: Soft-copy reading of a digital mammography of mass with 3M LCD monitors was similar in diagnostic performance to 5M CRT monitors in this study. On the basis of the results of this and a previous study, 3M LCD monitors can replace 5M CRT monitors without any loss in the ability to diagnose digital mammograms.