How to assess the reliability of cerebral microbleed rating?

Hugo J. Kuijf, Susanne J. van Veluw, Max A. Viergever, Koen L. Vincken, Geert Jan Biessels

Interest in cerebral microbleeds has grown rapidly over the past years. The need for sensitive and reliable detection of microbleeds has spurred the development of new MR sequences and standardized visual rating scales (Cordonnier et al., 2009; Gregoire et al., 2009). The value of these rating scales is currently assessed by measuring the inter-rater agreement, which is commonly determined using Cohen’s kappa coefficient (κ) or the intraclass correlation coefficient (ICC). With the recent increase of MR scanner field strength to 3T and even 7T, the sensitivity of microbleed detection has grown significantly, whence often multiple microbleeds are found in a single subject. As a result of this, researchers no longer solely focus on the absence or presence of microbleeds, but aim at determining their exact count and location as well.

Our concern is that, with this shift of focus, the measures that are in use to validate the reliability of microbleed ratings are no longer up-to-date. If the interest is confined to the presence or absence of microbleeds, the inter-rater agreement can be adequately assessed using κ. However, with multiple microbleeds in an individual subject, determining the inter-rater agreement using a measure that does not consider the number and location of the microbleeds appears inadequate. In other words, raters who agree on the presence or absence of microbleeds in an individual subject might disagree on their count or distribution.

DOI: 10.3389/fnagi.2013.00057

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Registration of brain CT images to an MRI template for the purpose of lesion-symptom mapping

H.J. Kuijf, J.M. Biesbroek, M.A. Viergever, G.J. Biessels, K.L. Vincken

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Lesion-symptom mapping is a valuable tool for exploring the relation between brain structure and function. In order to perform lesion-symptom mapping, lesion delineations made on different brain CT images need to be transformed to a standardized coordinate system. The preferred choice for this is the MNI152 template image that is based on T1-weighted MR images. This requires a multi-modal registration procedure to transform lesion delineations for each CT image to the MNI152 template image. A two-step registration procedure was implemented, using lesion-masking and contrast stretching to correctly align the soft tissue of the CT image to the MNI152 template image. The results were used to transform the lesion delineations to the template. The quality of the registration was assessed by an expert human observer. Of the 86 CT images, the registration was highly successful in 71 cases (83%). Slight manual adjustments of the lesion delineations in the standard coordinate system were required to make unsuccessful cases suitable for a lesion-symptom mapping study.

DOI: 10.1007/978-3-319-02126-3_12