Author: Weiyuan Wang 👨🔬
Affiliation: University of Oklahoma Health Sciences Center 🌍
Purpose:
This study investigates the variability between popular light meters by measuring mammography review workstation monitors using three calibrated light meters.
Methods:
Three calibrated light meters—Radcal AGLS, Unfors/Raysafe X2 Light Sensor, and Spectra Cine SC-850—were used to measure the eighteen TG18-LN patterns (TG18-LN01 to TG18-LN18) on a Barco MDMG-5221 dual-monitor review workstation for mammography. Measurements were taken sequentially for each pattern to minimize monitor stability effects. All light meters had unexpired calibrations. Additionally, the Barco built-in light meter, with an unknown calibration status, was also included for comparison. Luminance values from different light meters were plotted against the TG18-LN patterns for both monitors. DICOM GSDF compliance (contrast response) curves were calculated using the luminance measurements from the different light meters.
Results:
The SC-850 recorded the highest luminance values, followed by Barco, Raysafe, and Radcal. The most significant luminance difference was observed for the TG18-LN04 pattern on the right monitor, where the SC-850 reading was 63% higher than the Radcal reading. On average, SC-850 measured over 30% higher luminance than Radcal, and Raysafe measured over 15% higher than Radcal. The Barco built-in light meter's contrast response curve had a maximum error of 2.46%, passing the 10% compliance threshold. However, the contrast response curves from all three calibrated light meters failed the test, with maximum errors of 25% for SC-850, 32% for Raysafe, and 49% for Radcal.
Conclusion:
Significant differences exist in luminance measurements among calibrated light meters. While the Barco built-in light meters passed the compliance test for the monitors, all three calibrated light meters failed, with the maximum error reaching 49%, exceeding the 10% limit. The findings underscore the need for improved calibration methods and third-party evaluations to ensure accurate and stable light meter performance, which is crucial for maintaining diagnostic quality in medical imaging.