Restor Dent Endod.  2013 Aug;38(3):146-153.

The effects of image acquisition control of digital X-ray system on radiodensity quantification

• Seong WJ
• Kim HC
• Jeong S
• Heo Y
• Song WB
• Ahmad M

Abstract

OBJECTIVES
Aluminum step wedge (ASW) equivalent radiodensity (eRD) has been used to quantify restorative material's radiodensity. The aim of this study was to evaluate the effects of image acquisition control (IAC) of a digital X-ray system on the radiodensity quantification under different exposure time settings.
MATERIALS AND METHODS
Three 1-mm thick restorative material samples with various opacities were prepared. Samples were radiographed alongside an ASW using one of three digital radiographic modes (linear mapping (L), nonlinear mapping (N), and nonlinear mapping and automatic exposure control activated (E)) under 3 exposure time settings (underexposure, normal-exposure, and overexposure). The ASW eRD of restorative materials, attenuation coefficients and contrasts of ASW, and the correlation coefficient of linear relationship between logarithms of gray-scale value and thicknesses of ASW were compared under 9 conditions.
RESULTS
The ASW eRD measurements of restorative materials by three digital radiographic modes were statistically different (p = 0.049) but clinically similar. The relationship between logarithms of background corrected grey scale value and thickness of ASW was highly linear but attenuation coefficients and contrasts varied significantly among 3 radiographic modes. Varying exposure times did not affect ASW eRD significantly.
CONCLUSIONS
Even though different digital radiographic modes induced large variation on attenuation of coefficient and contrast of ASW, E mode improved diagnostic quality of the image significantly under the under-exposure condition by improving contrasts, while maintaining ASW eRDs of restorative materials similar. Under the condition of this study, underexposure time may be acceptable clinically with digital X-ray system using automatic gain control that reduces radiation exposure for patient.

Keyword

Aluminum step wedge equivalent radiodensity; Digital radiographic mode; Digital radiography; Image acquisition control; Image quality

MeSH Terms

Aluminum
Humans
Radiographic Image Enhancement
Aluminum

Figure

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  Figure 1 Aluminum step wedge and brass housing used in this study.

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  Figure 2 Radiographic images of ASW and 3 restorative material samples under 9 different conditions (3 radiographic modes ×3 exposure time settings).

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  Figure 3 Plots for ASW attenuation coefficient (slope) determination. X-axis denotes the ASW thickness (mm) and Y-axis denotes logarithm of background (unexposed) corrected grey scale value (LN(g-G)) for digital sensor (L, N, E modes). Square, round, and triangle lines indicate underexposure, normal exposure, and overexposure time settings, respectively.

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