Automated Detection of Regions of Interest for Brain Perfusion MR Images

Abstract

Background. Images with abnormal brain anatomy produce problems for automatic segmentation techniques, and as a result poor ROI detection affects both quantitative measurements and visual assessment of perfusion data. Objective. This paper presents a new approach for fully automated and relatively accurate ROI detection from dynamic susceptibility contrast perfusion magnetic resonance and can therefore be applied excellently in the perfusion analysis. Methods. In the proposed approach the segmentation output is a binary mask of perfusion ROI that has zero values for air pixels, pixels that represent non-brain tissues, and cerebrospinal fluid pixels. The process of binary mask producing starts with extracting low intensity pixels by thresholding, which subsequently correspond to zero values of the mask. Optimal low-threshold value is solved by obtaining intensity pixels information from the approximate anatomical brain location. Holes filling algorithm and binary region growing algorithm are used to remove falsely detected regions and produce region of only brain tissues. Further, CSF pixels extraction is provided by thresholding of high intensity pixels from region of only brain tissues. Each time-point image of the perfusion sequence is used for adjustment of CSF pixels location. Results. The segmentation results were compared with the manual segmentation performed by experienced radiologists, considered as the reference standard for evaluation of proposed approach. On average of 120 images the segmentation results have a good agreement with the reference standard with a Dice Index of 0.9576 ± 0.013 (sensitivity and specificity are 0.9931 ± 0.0053 and 0.9730 ± 0.0111 respectively). All detected perfusion ROIs were deemed by two experienced radiologists as satisfactory enough for clinical use. Conclusions. The results show that proposed approach is suitable to be used for perfusion ROI detection from DSC head scans. Segmentation tool based on the proposed approach can be implemented as a part of any automatic brain image processing system for clinical use.

Analysis of Effectiveness of Thresholding in Perfusion Roi Detection on T2-Weighted MR Images With Abnormal Brain Anatomy

“…The third algorithm to be used for the analysis is also threshold-based and uses approximate anatomical brain location (AABL) as image region for threshold value calculation [19]. The image processing by applying threshold value detected in AABL region is a type of global thresholding.…”

Impact of perfusion ROI detection to the quality of CBV perfusion map

“…background and foreground. In the case of DSC perfusion data, the preprocessing step should exclude low intensity pixels (air pixels and pixels that represent non-brain tissues) and high intensity pixels (pixels that represent regions filled with cerebrospinal fluid) as background [12]. Therefore, the thresholding should be bidirectional and should provide a binary mask M x y ( , ) for processed image as follows:…”