Motion compensation for cone-beam CT using Fourier consistency conditions.

In cone-beam CT, involuntary patient motion and inaccurate or irreproducible scanner motion substantially degrades image quality. To avoid artifacts this motion needs to be estimated and compensated during image reconstruction. In previous work we showed that Fourier consistency conditions (FCC) can be used in fan-beam CT to estimate motion in the sinogram domain. This work extends the FCC to [Formula: see text] cone-beam CT. We derive an efficient cost function to compensate for [Formula: see text] motion using [Formula: see text] detector translations. The extended FCC method have been tested with five translational motion patterns, using a challenging numerical phantom. We evaluated the root-mean-square-error and the structural-similarity-index between motion corrected and motion-free reconstructions. Additionally, we computed the mean-absolute-difference (MAD) between the estimated and the ground-truth motion. The practical applicability of the method is demonstrated by application to respiratory motion estimation in rotational angiography, but also to motion correction for weight-bearing imaging of knees. Where the latter makes use of a specifically modified FCC version which is robust to axial truncation. The results show a great reduction of motion artifacts. Accurate estimation results were achieved with a maximum MAD value of 708 µm and 1184 µm for motion along the vertical and horizontal detector direction, respectively. The image quality of reconstructions obtained with the proposed method is close to that of motion corrected reconstructions based on the ground-truth motion. Simulations using noise-free and noisy data demonstrate that FCC are robust to noise. Even high-frequency motion was accurately estimated leading to a considerable reduction of streaking artifacts. The method is purely image-based and therefore independent of any auxiliary data.

An evaluation of different steam disinfection protocols for cystic fibrosis nebulizers.

BACKGROUND: Contamination is a key element in cystic fibrosis. For this reason, nebulizer hygiene is an important, but complex and time-consuming task for cystic fibrosis patients. The aim of this study was to compare different steam disinfection and drying protocols. METHODS: One hundred nebulizer parts were inoculated with cystic fibrosis-related bacteria in high concentrations (Burkholderia multivorans 3.9 × 10(10)/ml, Staphylococcus aureus 8.9 × 10(8/)ml and Pseudomonas aeruginosa 2.1 × 10(9)/ml). Tubes with Mycobacterium abscessus complex were additionally tested. Six steam disinfectors were compared. Different methods of drying were examined. RESULTS: All tested bacteria were efficiently killed by the different steam disinfectors tested. The risk of contamination depended on the method of drying. CONCLUSIONS: Steam disinfection is a safe disinfection method. It is better to leave the nebulizers wet after steam disinfection than to manipulate them by active drying, which seems to be a source of recontamination.