A Post-Processing Technique to Remove Extra-Cerebral Signals from Three-Dimensional Time-of-Flight MR Brain Images

Three-dimensional time-of-flight MR angiography is routinely used for detecting cerebral vascular disorders in clinical practice. This technique is inherited with high signals of subcutaneous and bone-marrow fat tissues, and they can contaminate the visual perception of vascular structures on the maximum intensity projected views. Because cortical bones have low signals on three-dimensional time-of-flight MR images, the inner table of a skull bone can serve as a natural anatomical boundary between the brain surface and skull bone. This study presents an automatic post-processing technique based on automatic thresholding, morphological operation, and region growing techniques to extract the brain pixels using this boundary. The subsequent maximum intensity projections of brain pixels achieve a better display of cerebral vascular structures. This technique is mostly useful for imaging slices covering the upper cerebral hemisphere, where bone structure forms a good brain boundary.