Preoperative localization of intracranial lesions on MR.

Intraoperative identification of small or diffusely infiltrative subcortical lesions may be difficult. The apparent position of an abnormality demonstrated on higher CT sections may be particularly misleading. Lesions seen in the center of the image may be located in the frontal or parietal lobes, depending on the angulation of the plane of the section. Surgical exploration of these lesions is aided considerably by preoperative localization. The procedure is usually performed by using CT in the coronal or axial plane. However, in many cases, coronal planes may be difficult or impossible to obtain on CT. Several localization methods have been described. Most refer the position of the lesion to the skull landmarks or to devices placed externally on the scalp. The proposed method allows for simple and accurate localization of the intracranial process on MR.