Scalp Localization of Supratentorial Lesions Demonstrated by Computerized Tomography

Abstract

Two methods of correlating a supratentorial lesion seen on a computerized tomographic (CT) scan with its scalp location are described. The head is positioned at any angle and the lesion is imaged. The axial plane imaged is identified on the scalp with the aid of the gantry light of the EMI 1005U scanner or with the alignment light and gantry laser of the GE 8800 scanner. On the CT image the coronal and sagittal planes of the lesion are constructed and extended until the calvarium is intersected. One of two methods is used to relate the lesion to the scalp. With Method 1 a circumferential measurement around the scalp on the CT image is made from the anterior or posterior midline to the points of intersection of the coronal and sagittal planes of the lesion with the calvarium. A magnification factor is used to convert these distances into units appropriate for scalp measurements. The corresponding distances are then measured circumferentially on the scalp in the axial plane and marked. With Method 2 a measurement is made along the y-axis to the coronal plane and along the x-axis to the sagittal plane of the lesion. A magnification factor is used to convert these distances into units appropriate for scalp measurements. These distances are then measured on the scalp in the axial plane with a standard x-ray caliper along parallel coordinates to the x- or y-axis and marked. With either method the coronal and sagittal planes of the lesion are then outlined on the scalp by connecting appropriate points corresponding to these planes over the top of the head, either perpendicular or parallel to the midline. In this manner the axial, coronal, and sagittal planes, as they relate to the lesion, are identified. These points of reference are used to make a scalp incision or to place a burr hole for biopsy. (Neurosurgery, 6: 164-175, 1980)