Fig. 1.

Typical image and lesion processing pipeline for lesion-symptom mapping studies. Lesion-symptom mapping studies essentially require three image and lesion processing steps to prepare lesion maps. Examples are shown for three common imaging sequences: FLAIR, DWI, and CT. First, the lesion must be delineated on the original scan data (lesion segmentation). This can be done manually, or (semi-)automatically using computer algorithms. Next, the scan and corresponding lesion map are transformed to fit the size and shape of a brain template (spatial normalization). An intermediate registration step to an age-specific template is often used to improve registration accuracy. Finally, the resulting lesion map is projected onto the brain template. This result is compared to the original scan, to determine whether lesion registration was successful. Main criteria are that the key anatomical landmarks of the transformed scan and template should correspond and that the registered lesion map accurately represents the original lesion regarding location, size, and shape. The final lesion map can be used for group comparisons, unrestricted by type and format of the raw imaging data. Abbreviations: CT, computed tomography; DWI, diffusion-weighted imaging; FLAIR, fluid attenuated inversion recovery.