A headholder system is described for use in the correlation of images obtained with positron computed tomography (PCT) and other neuroradiological imaging modalities. Methods are described for defining brain anatomy from PCT images by the use of projection schemes from tomographic data. Cross-correlation of images between positron CT and standard lateral skull films, X-ray computed tomography (XCT), and two-dimensional rectilinear positron images are discussed. Such methods allow for improved reproducibility of head positioning and more precise cortical localization necessary in studies of normal brain function as well as in neuropathological conditions.