Abstract
We propose a method for registration of 3D fetal brain ultrasound with a reconstructed magnetic resonance fetal brain volume. This method, for the first time, allows the alignment of models of the fetal brain built from magnetic resonance images with 3D fetal brain ultrasound, opening possibilities to develop new, prior information based image analysis methods for 3D fetal neurosonography. The reconstructed magnetic resonance volume is first segmented using a probabilistic atlas and a pseudo ultrasound image volume is simulated from the segmentation. This pseudo ultrasound image is then affinely aligned with clinical ultrasound fetal brain volumes using a robust block-matching approach that can deal with intensity artefacts and missing features in the ultrasound images. A qualitative and quantitative evaluation demonstrates good performance of the method for our application, in comparison with other tested approaches. The intensity average of 27 ultrasound images co-aligned with the pseudo ultrasound template shows good correlation with anatomy of the fetal brain as seen in the reconstructed magnetic resonance image.
Highlights
In this paper we propose a method for the alignment of fetal brain 3D US and magnetic resonance (MR) images, which will in future allow us to explore the idea, that models of brain anatomy build from more complete MR images of fetal brain can be exploited to serve as prior knowledge for automatic image analysis of fetal brain 3D US or to assist in making clinical diagnosis from 3D fetal neurosonography
In the second paper (Kuklisova-Murgasova et al, 2012a) we described creation of pseudo US images at earlier gestational age (GA) and improved robustness of the method by introducing robust block-matching algorithm (Ourselin et al, 2001), which employs local normalised cross-correlation (NCC) as a similarity measure to deal with intensity and contrast variation and robust least trimmed squares to remove outliers produced by incorrectly matched blocks, which is helpful in situations when the corresponding features in US image is missing
Registrations of all 27 US images of the younger subjects with the MR image of 23 weeks GA, as well as registrations of 7 US images of GA 29 weeks with MRI of 28 GA were visually inspected and we found that visually reasonable alignment was achieved in all cases
Summary
Fetal ultrasound (US) is the imaging modality of choice in clinical practice for assessing fetal development. Traditional methods for assessment of fetal brain development rely on qualitative evaluation and manual measurements performed on 2D US scans, where a pre-defined plane is manually selected by the sonographer, and several 2D measurements are taken to assess the size of the fetal head and some brain structures (ISUOG, 2007). If a brain abnormality is suspected, fetal magnetic resonance (MR) imaging is often performed to confirm the finding. US does not always depict sufficient information about the structures within the fetal brain, largely due to acoustic shadows caused by the fetal skull, while MR imaging is unaffected by the presence of bone (Pugash et al, 2008). 3D fetal neurosonography is currently one of the most active research fields in obstetric imaging Provides evidence that in prospective studies fetal brain structures and anomalies can be visualised correctly in 90% of the cases by experienced operators with 3D US (Gandolfi Colleoni et al, 2012). 3D fetal neurosonography is currently one of the most active research fields in obstetric imaging
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