Effects of Image Compression on Linear Measurements of Digital Panoramic Radiographs

Abstract This study aimed to evaluate the accuracy of panoramic radiographs obtained by digital system based on charge coupled device (CCD) and a phosphor storage plate (PSP) system with two different file formats, JPEG irreversible type and BMP. Linear measurements of artificial bony defects were made in dry mandibles with a digital caliper. Measures of digital panoramic radiographs were taken in ImageJ(r) software. Each measurement was performed twice by an experienced examiner. The intra-rater agreement was considered very strong (Pearson's correlation coefficient of 0.97). There was no significant difference between the linear measurements of dry mandibles, considered the gold standard, in relation to measurements obtained from digital radiographs (p=0.47). The error of these measures for the CCD was 1.04 mm (9.97%) for JPEG images and 1.03 mm (9.99%) for those with BMP format. For the PSP images, these values were 1.48 mm (14.94%) and 1.43 mm (14.43%), respectively. Although there was no statistical difference between the images with JPEG and BMP format, for both digital systems (p=1.00 for CCD and p=0.98 for PSP system), errors made on radiographs obtained by PSP system were significantly higher than those of CCD (p<0.05). The size of the files saved in JPEG was also significantly lower (p=0.005) compared with the files saved in BMP. It may be concluded that the digital radiographs, both saved in JPEG and BMP formats, are accurate, regardless the used digital system, and JPEG images are more suitable for teleradiology.

Resumo Este estudo teve como objetivo avaliar a acurácia de radiografias panorâmicas digitais obtidas por sistema digital baseado em dispositivo acoplador de carga (DAC) e por sistema de placa de fósforo (PF) com duas diferentes extensões de arquivo (JPEG e BMP, sendo o primeiro do tipo compactador irreversível). Medidas lineares de defeitos ósseos foram realizadas em mandíbulas secas com paquímetro digital. As medidas correspondentes nas radiografias panorâmicas digitais foram realizadas no software ImageJ(r). As medidas foram realizadas duas vezes por um examinador. A concordância intraexaminador foi considerada muito forte (coeficiente de correlação de Pearson de 0,97). Não houve diferença significante entre as medidas lineares das mandíbulas secas, consideradas padrão-ouro, em relação às medidas obtidas das radiografias digitais (p=0,47). Os erros absolutos e relativos dessas medidas para o DAC foram de 1,04 mm (9,97%) para as imagens JPEG e de 1,03 mm (9,99%) para aquelas com extensão BMP. Para o sistema digital com PF esses valores foram de 1,48 mm (14,94%) e 1,43 mm (14,43%), respectivamente. Apesar de não ter havido diferença estatística entre as imagens com extensão JPEG e BMP, para ambos os sistemas digitais (p=1,00 para DAC e p=0,98 para a PF), os erros das medidas realizadas nas radiografias obtidas pelo sistema de PF foram significativamente maiores que os erros do DAC (p<0,05). O tamanho dos arquivos salvos em JPEG também foram significativamente menores (p=0,005) em comparação com os arquivos salvos em BMP. Pode-se concluir que as radiografias digitais tanto com extensão JPEG quanto BMP são acuradas, independente do sistema digital utilizado e as imagens salvas em JPEG são mais indicadas em telerradiologia.

Association between radiographic features and cell proliferation in keratocystic odontogenic tumor / Asociación entre las características radiográficas y la proliferación celular en el tumor odontogénico queratoquístico

The radiographic features of an intraosseous lesion are usually associated with the biological behavior of the tumor. In view of the fact that the growth and behavior of keratocystic odontogenic tumors (KCOT) is mainly associated with the proliferation of the cystic epithelium, the objective of the present study was to evaluate the relationship between cell proliferation markers and radiographic features of this tumor. Thirty-seven radiographs of KCOT obtained from 30 patients were scanned and evaluated on a monitor. Sections were submitted to immunohistochemistry for Ki-67, p63, and p53 proteins on an EnVision system. Thirty-one KCOTs were observed in the posterior of the mandible, and the unilocular aspect was predominant (n= 26). Nineteen KCOTs distorted the mandibular canal and 11 displaced teeth. Satellite cysts were associated with a multilocular aspect (P= 0.016). p53 was in KCOTS with diffuse margins (p=0.049), p63 with NBCCS (p=0.049) KOT and higher KI-67 positive cells was observed in KCOTs presenting distortion of the mandibular canal (p=0.042). The distribution of Ki-67, p63, and p53 positive cells was similar between KCOTs with uni- and multilocular aspects. The results of the present study suggest that cell proliferation in KCOT contributes to the radiographic features of this tumor.

Las características radiográficas de una lesión intraósea se asocian generalmente con el comportamiento biológico del tumor. Debido a esto, el crecimiento y comportamiento de los tumores odontogénicos queratoquísticos se asocian principalmente con la proliferación del epitelio quístico. El objetivo del estudio fue evaluar la relación entre los marcadores de proliferación celular y las características radiológicas de este tumor. Se escanearon y evaluaron 37 radiografías de tumores odontogénicos queratoquísticos obtenidos de 30 pacientes y las secciones de sus biopsias fueron sometidas a evaluación inmunohistoquímica para las proteíneas Ki-67, p63 y p53 en un sistema Envision. Se observaron 31 tumores odontogénicos queratoquísticos en el área posterior de la mandíbula, con predominio del aspecto unilocular (n= 26). Diecinueve tumores odontogénicos queratoquísticos distorsionaron el canal mandibular y se observaron 11 dientes desplazados. Los quistes satélites se asociaron con el aspecto multilocular (P= 0,016). La distribución de células positivas para Ki-67, p63 y p53 fue similar entre tumores odontogénicos queratoquísticos con aspectos uniformes y multiloculares, y no estaban relacionadod con la distorsión del canal mandibular (P>0,05) o con el desplazamiento del diente (P>0,05). Los resultados del presente estudio sugieren que la proliferación celular en tumores odontogénicos queratoquísticos contribuye a las características radiográficas de este tumor.