Ultralow-dose CT of the petrous bone using iterative reconstruction technique, tin filter and high resolution detectors allows an adequate assessment of the petrous bone structures

To assess image quality and radiation dose in computed tomography (CT) studies of the petrous bone done with a scanner using a tin filter, high-resolution detectors, and iterative reconstruction, and to compare versus in studies done with another scanner without a tin filter using filtered back projection reconstruction. Thirty two patients (group 1) were acquired with an ultra-low dose CT (32-MDCT, 130kV, tin filter and iterative reconstruction). Images and radiation doses were compared to 36 patients (group 2) acquired in a 16-MDCT (120kV and filtered back-projection). Muscle density, bone density, and background noise were measured. Signal-to-noise ratio (SNR) was calculated. To assess image quality, two independent radiologists subjectively evaluated the visualization of the different structures of the middle and inner ear (0=not visualized, 3=perfectly identified and delimited). Interobserver agreement was calculated. Effective dose at different anatomical levels with the dose-length product was recorded. In the quantitative analysis, there were no significant differences in image noise between the two groups. In the qualitative analysis, a similar or slightly lower subjective score was obtained in the delimitation of different structures of the ossicular chain and cochlea in the 32-MDCT, compared to 16-MDCT, with statistically significant differences. Mean effective dose (±standard deviation) was 0.16±0.04mSv for the 32-MDCT and 1.25±0.30mSv for the 16-MDCT. The use of scanners with tin filters, high-resolution detectors, and iterative reconstruction allows to obtain images with adequate quality for the evaluation of the petrous bone structures with ultralow doses of radiation (0.16±0.04mSv). Valorar la calidad de imagen y la dosis de radiación en tomografía computarizada (TC) de peñascos adquiridos con una TC multidetector (TCMD) con filtro de estaño, detectores de alta resolución y reconstrucción iterativa, comparándola con otro equipo sin filtro de estaño y con reconstrucción por retroproyección filtrada. Se incluyeron retrospectivamente 32 pacientes con TC de peñascos, realizadas con dosis ultrabaja en una 32-TCMD (130kV con filtro de estaño y reconstrucción iterativa). Se compararon con 36 estudios realizados en una 16-TCMD (120kV y retroproyección filtrada). Se cuantificó la densidad muscular, ósea y el ruido de fondo, y se calculó la relación señal/ruido. Para valorar la calidad de imagen, dos radiólogos evaluaron de forma subjetiva e independ