Analysis of the reproducibility of the gray values and noise of a direct digital radiography system

Marcelo Lupion Poleti,Ana Lúcia Alvares Capelozza,Izabel Regina Fischer Rubira-Bullen,Thais Maria Freire Fernandes,Renata Cordeiro Teixeira

doi:10.1590/1807-3107bor-2015.vol29.0062

Marcelo Lupion Poleti, Ana Lúcia Alvares Capelozza + Show 3 more

Open Access

https://doi.org/10.1590/1807-3107bor-2015.vol29.0062

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Abstract

The aim of this study was to evaluate the reproducibility of the gray values and noise of a direct digital radiography system (Visualix eHD) for various exposure times and analyzed regions. To obtain radiographic images in a standardized manner, the digital sensor of the system and a stepwedge were positioned in a phantom at a focus-film distance of 30 cm in a dental device at 70 kV, 7 mA and 2.2 mm filtration. Ten consecutive repetitions of X-ray imaging were performed at each exposure time (0.05, 0.07, 0.09 and 0.13 s). Gray values were analyzed using ImageJ software in five regions of interest (ROIs): alveolar bone (AB), soft tissue (ST) and three steps of the stepwedge (S1, S2 and S3). The results showed that both the variability of the gray values and the noise were statistically greater (p < 0.05) in the most radiolucent region (ST). Only the noise was affected by the exposure time. In conclusion, the reproducibility of the gray values and the noise of the Visualix eHD system can vary in specific areas with different radiolucency.

Highlights

The technique of digital radiography is similar to that of conventional radiology; a computer is substituted for the chemical processing phase
The image visualization programs used in digital radiography systems have various post-processing resources, enabling the user to alter brightness and contrast, rotate and amplify or reduce the image, invert the gray scale, apply pseudocolors to different gray tones, perform linear and angular measurements and quantify gray values in a region of interest (ROI).[5,6,7,8,9,10,11]
There were no significant differences between mean gray values evaluated for analyzed ROIs and exposure times (p > 0.05)

Summary

Introduction

The technique of digital radiography is similar to that of conventional (analogic) radiology; a computer is substituted for the chemical processing phase. This substitution is advantageous because it eliminates technical errors inherent in chemical processing. Damante et al.[10] developed a protocol for radiographic diagnosis and follow-up studies of simple bone cysts based on gray values. Ferreira Junior et al.[11] performed a study using gray values for the diagnosis of simple bone cysts and

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