Luminance and contrast performance of liquid crystal displays for mammographic applications

Abstract

Liquid crystal displays (LCDs) are gradually replacing cathode-ray tubes (CRTs) as the primary means of electronic display of digital radiographs. The transition from CRT to LCD is fueled by advantages of the LCD technology such as enhanced maximum luminance and smaller form factor. This transition is expected to extend to digital mammography as well. The purpose of this study was to report the on-axis luminance and contrast performance of five medical-grade LCDs in terms of compliance with the DICOM grayscale display function (GSDF) and AAPM TG18 guidelines. The display devices included two 3 Mpx monochrome LCDs (Planar Dome C3, and NDS 20.8″ Nova), two 5 Mpx monochrome LCDs (NDS 21.3″ Nova, and Totoku ME511L), and one 9 Mpx color LCD (IBM T221). The on-axis luminance values were measured at all 8-bit driving levels using the TG18-LN test patterns and a baffled luminance meter and the results averaged. The luminance data were analyzed according to the AAPM TG18 methodology. The measured Lmin, Lmax, mean ΔJND/Δp, and maximum local deviation in ΔJND/Δp from GSDF, κ256 ranged within 0.43-0.87 cd/m2, 263-715 cd/m2, 2.15-2.72, and 0.79-1.46 intervals, respectively. While the values varied notably between different devices, all devices conformed to the TG18 criteria for primary class displays in terms of on-axis luminance response, and thus judged suitable for mammographic applications from on-axis luminance standpoint. Notwithstanding the findings, other factors such as matrix size, angular response, and color functionality should further be taken into consideration.