Noise reduction and image quality in ultra-high resolution computed tomography of the temporal bone using advanced modeled iterative reconstruction.

BACKGROUND: The novel advanced modeled iterative reconstruction (ADMIRE) algorithm in ultra-high-resolution (UHR) computed tomography (CT) of the temporal bone has not yet been systematically evaluated.

PURPOSE: To assess the potential of ADMIRE in temporal bone UHR CT.

MATERIAL AND METHODS: Forty-four patients who underwent UHR CT of the temporal bone using z-axis UHR protocol were retrospectively selected for analysis. Images were reconstructed using filtered back projection (FBP) and ADMIRE with multiple strength levels. Regions of interest were drawn in the posterior fossa and petrous bone. The average density (in Hounsfield units [HU]) and the image noise (standard deviation of density values) were extracted. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were then calculated. Additionally, a subjective qualitative analysis was performed using a five-point Likert scale. The potential dose reduction was extrapolated from objective analysis and confirmed in an additional phantom study.

RESULTS: The image noise was significantly lower, and the SNR and CNR were significantly higher in ADMIRE reconstructions levels A2-A5 than in FBP ( P < 0.001, respectively). Subjective image quality was significantly higher in ADMIRE levels A2-A5 than in FBP ( P < 0.001) and it was rated best in ADMIRE level A3. Confirmed by the results from the phantom study, a dose reduction of at least 40% was feasible while maintaining image quality.

CONCLUSIONS: The ADMIRE reconstruction algorithm significantly improves image quality and reduces noise on temporal bone UHR CT scans. Thus, it allows for substantial dose reduction.