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Updated: Aug 5, 2026
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Published on: July 22, 2022
Impact of Exposure Settings Variations on Contrast and Spatial Resolution in CMOS and Direct-Conversion CMOS
Daniela Pita de Melo1, Luiz Eduardo Marinho-Vieira2, Caroline Hoang3
1College of Dentistry, University of Saskatchewan (USASK), Saskatoon, SK, Canada.
Objective:
To evaluate the impact of exposure setting variations on contrast and spatial resolution (SR) in CMOS and direct-conversion CMOS (DC-CMOS) intraoral sensors.
Methods:
Ten images of a DDQA phantom were acquired for each assessed condition using three sensors (CMOS-I, CMOS-S, DC-CMOS) and two X-ray units (HH: handheld; WM: wall-mounted). HH was set at 60kVp/2.5mA, and WM was set at 60kVp/7mA and 70kVp/7mA. Each combined sensor-x-ray unit condition was exposed at 0.02, 0.04, 0.05, 0.08, 0.10, 0.16, 0.20, 0.25, 0.32, 0.40, 0.50, 0.63, 0.80, and 1.00s. One observer selected 2 × 2 mm ROIs from the third and fifth steps of the DDQA step-wedge and measured their mean gray values using Fiji macro. Contrast was calculated by subtracting the mean gray value of the third step from the fifth step for each group. SR was determined by identifying the line pair with the highest value, in which five peaks and four valleys were distinguishable. Descriptive statistics were calculated for SR and three-way ANOVA and Tukey's post-hoc tests for contrast (α = 0.05).
Results:
Across all exposure parameters, CMOS-I exhibited the highest mean contrast, followed by DC-CMOS and CMOS-S (p < 0.001). HH yielded the highest mean contrast, which was significantly greater than WM (p < 0.001). CMOS-S exhibited the highest SR, and DC-CMOS the lowest, although SR remained constant for DC-CMOS across all exposure times.
Conclusion:
Sensor type, x-ray unit, and exposure time influenced image contrast and spatial resolution, while variations in kVp had minimal impact on these image quality parameters.
