Characterization of Tympanic Cavity Volume in Newborns using Computerized Tomography Scanning/ Caracterizacion del Volumen de la Cavidad Timpanica en Recien Nacidos usando Tomografia Computadorizada

This study reports tympanic cavity (TC) volume in newborns, which was missing in the literature. Ex vivo histology and computerized tomography (CT) scans were performed on temporal bone and data were analyzed in part using software developed in house. CT images with a slice thickness of 0.5 mm were obtained from 5 newborn cadavers and analyzed independently by two expert researchers. The border of the TC was delineated manually and measurement of area of interest was calculated on masked images. Then, the area measurements from all sections were added to estimate the total volume. The agreements between the histological and CT findings were then compared for accuracy, repeatability and reliability. The Dice and Jaccard similarity coefficient measures were used as a statistical validation metric to evaluate the assessor's performance in manual volume segmentation. Good assessor agreement was observed with average Dice values above 0.8 indicating that consistent and reliable volume measurements were feasible. The proposed protocol was shown to be accurate in calculating the TC volume, and thus can be used for computer-assisted presurgical planning or for diagnosing structural alterations in TC. KEY WORDS: Computerized tomography; Tympanic cavity; Tympanic cavity volume; Similarity index. El objetivo fue determinar el volumen de la cavidad timpanica (CT) en recien nacidos, informacion no encontrada en la literatura. Se realizaron escaners a traves de tomografia computadorizada (TC) y estudios histologicos en el hueso temporal; los datos se analizaron utilizando un software desarrollado en nuestra institucion. Se obtuvieron imagenes de secciones de TC, de 0,5 mm de grosor, a partir de 5 cadaveres de recien nacidos, los que fueron analizados de forma independiente por dos investigadores expertos. El margen de los cortes de TC fue delineado manualmente y la medicion del area de interes se estimo sobre imagenes ocultas. Despues, se anadieron las mediciones de area de todas las secciones para estimar el volumen total. Las concordancias entre el estudio histologico y los hallazgos de la TC se compararon en cuanto a precision, repetibilidad y confiabilidad. Se utilizaron las medidas de coeficiente de similitud de Jaccard y Dice como metrica de validacion estadistica para evaluar el desempeno del asesor en la medicion manual del volumen. Se observo una buena correlacion del evaluador con los valores medios de Dice, por encima de 0,8 indicando que es factible obtener