Channelized Hotelling observer assessing microcalcification detectability on 2D mammography: a first application to study the impact of tube voltage

Abstract

This work was aimed to assess the detectability of microcalcifications as a function of tube voltage in 2D mammography using an in-house developed Channelized Hotelling Observer (CHO). The images of a 3D structured phantom, containing acrylic beads of different diameters in water and inserted signals (microcalcifications, spiculated and non-spiculated mass models) were assessed. Images had been acquired on a Siemens Mammomat Inspiration system at 5 different tube voltage levels (28-32 kVp) under AEC setting. The detectability of microcalcifications was analyzed in terms of percentage correctly detected signals (PC) as well as diameter threshold (dtr), using the CHO and human observers. Two Laguerre-Gauss and 8 Gabor channels were included in the two-layers CHO. The model and human observer results were retrieved from a 4-alternative forced choice (4-AFC) study. At 28 kVp and 32 kVp, the diameter thresholds dtr of microcalcifications together with their 95% confidence intervals (CI95) were 0.114 [0.110-0.118] mm and 0.119 [0.116-0.122] mm for the CHO, and 0.110 [0.093-0.127] mm and 0.123 [0.111-0.134] mm for the human observers. The Pearson correlation (r) between the PC values of model and human observer was more than 0.934. The in-house developed CHO and the human observer scores correlated very well for the application on 2D digital mammography acquired with different tube voltages. The overlapping range of CI95 of the dtr for the tested kVp shows that the tube voltage setting does not significantly affect the detectability of microcalcifications neither by the CHO nor by the human observers.