Reproducibility of pixel values for two photostimulable phosphor plates in consecutive standardized scannings

Abstract

ABSTRACT:The objective of the present study was to determine the reproducibility of the pixel values obtained with the Digora system (Soredex, Finland). Exposures were standardized, with variation in exposure and scanning time of two photostimulable phosphor plates containing a stepwedge image. The smallest variation in pixel values ranged from 50 to 75%, with the widest variations being observed in less dense steps. A signifi cant difference in pixel values was observed in terms of X-ray exposure and scanning times and between the two plates themselves (ANOVA, p < 0.01). Using the present methodology, the reproducibility of pixel values was not satisfactory for the tested white photostimulable plates. This wide variation in digitalization might be infl uenced by the amount of X-rays that sensitized the plates. It may be important to establish the reproducibility of the pixel values in quantitative studies using digital image. DESCRIPTORS:Radiography, dental, digital; Reproducibility of results. RESUMO:O objetivo do presente trabalho foi determinar a reprodutibilidade dos valores de "pixels" obtidos com o sistema Digora (Soredex, Finlândia). As exposições foram padronizadas, com variação no tempo de exposição e leitura de duas placas de fósforo fotoestimuláveis contendo a imagem de um penetrômetro. A menor variação nos valores de "pixels" foi de 50 a 75%, sendo as maiores variações oriundas nas faixas mais claras. Uma diferença signifi cante nos valores de "pixels" foi observada em relação ao tempo de exposição e leitura das placas e entre as duas placas (ANOVA, p < 0,01). Utilizando a presente metodologia, a reprodutibilidade dos valores de "pixels" das placas testadas do sistema Digora não foi satisfatória. Essa grande variação na digitalização pode ter sido infl uenciada pela quantidade de Raios X que sensibilizou as placas. Isso pode ser importante para estabelecer a reprodutibilidade dos valores de "pixels" em estudos quantitativos usando imagem digital. DESCRITORES:Radiografi a dentária digital; Reprodutibilidade dos resultados.

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

“…Thus, when an X-ray beam penetrates an analyzed region, the presence of soft and hard tissues in this trajectory influences the gray values. In this study, the highest gray values were observed in the most radiopaque regions (AB and S3), and the lowest values were observed in the most radiolucent regions (ST and S1) 5,8,16,17 (Table 1).…”

“…5 According to Pietrobelli et al 18 attenuation occurs when the photon signal crosses an element, chemical component or solution, spontaneously reducing the intensity through atomic interactions and leading to the absorption and dissipation of photons. Thus, when an X-ray beam penetrates an analyzed region, the presence of soft and hard tissues in this trajectory influences the gray values.…”

“…The highest difference corresponds to the mean gray value minus the lowest gray value or the highest gray value minus the mean gray value in the ROI on each image. 5 The mean, highest and lowest gray values were obtained after ten consecutive scannings of the sensor for each of the four exposure times and for each of the five regions. The noise was calculated in the ROI of the images.…”

“…1,2,3,4,5,6 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 Damante et al 10 developed a protocol for radiographic diagnosis and follow-up studies of simple bone cysts based on gray values. The authors evaluated ten patients and concluded that it is possible to apply a non-interventional follow-up protocol that avoids unnecessary surgery of these lesions.…”

“…1,3,4,5,6,7,9,12,13,14,15,16,17 However, the current literature does not include studies of the reproducibility of gray values and noise associated with the Visualix eHD system when using gray values analysis to diagnose and track lesions. 8,10,11,12 Therefore, the objective of this study was to evaluate the reproducibility of the gray values and noise associated with the Visualix eHD system when varying the exposure times and the regions analyzed.…”