Figure 2-2. CT myelogram and MRI of the lumbosacral spine. Sagittal (A) and axial (B–C) CT images of the lumbosacral spine obtained after the intrathecal administration of radiopaque contrast material. The vertebral bodies are separated by intervertebral discs and the spinous processes are seen posteriorly. Contrast contained within the thecal sac appears white. The conus medullaris terminates at the L2 vertebral level (A–B) and the nerve roots of the cauda equina are clearly seen within the posterior thecal sac (A–C). Sagittal (D) and axial (E–F) T2-weighted MRI of the lumbosacral spine shows hyperintense CSF surrounding the conus medullaris, which terminates at the L1 vertebral level (A–B). The nerve roots of the cauda equina are seen within the posterior thecal sac (A–C). In C and F, traversing nerve roots within the lateral recess of the spinal canal are seen.
Figure 2-3. Normal brain MRI. A. Axial T2-weighted MRI at the level of the lenticular nuclei. Gray matter appears brighter than white matter. CSF within the ventricles and cortical sulci is very bright. The caudate nuclei, putamen, and thalamus appear brighter than the internal capsule.
B. Axial T2-weighted MRI at the level of the pons. Subcutaneous fat and calvarial marrow appear relatively bright. CSF within the fourth ventricle and prepontine cistern, endolymph within the cochlea and semicircular canals, and ocular vitreous fluid appears very bright. Signal is absent (i.e., a “flow void”) within the basilar artery. C. Midline sagittal T1-weighted MRI of the brain. Note that white matter appears brighter than gray matter and the corpus callosum is well defined. The pons, medulla, and cervicomedullary junction are well delineated, and the pituitary gland is demonstrated with a normal posterior pituitary bright spot. The cerebral aqueduct is seen between the ventral midbrain and the tectum. The clivus and upper cervical vertebrae are noted as well. D. Axial T2-weighted fluid-attenuated inversion recovery (FLAIR) MRI of the brain at the same level as in A. Note that the hyperintense fluid signal from CSF is now suppressed, and the differentiation between brighter gray matter and darker white matter is accentuated.
Figure 2-4. Intracranial and cervical angiography. A. Oblique CT angiogram of the neck showing the carotid bifurcation and the cervical segments of the internal and external carotid arteries. Note the slightly dilated carotid bulb at the initial segment of the internal carotid artery. A small focus of calcified atherosclerosis is noted near the origin of the external carotid artery. Note that the external carotid artery has multiple branches within the neck. B. Coronal MR angiogram of the neck showing the aortic arch, the origins and cervical courses of the carotid and vertebral arteries, and the vertebrobasilar junction. The sigmoid sinuses and internal jugular veins are faintly visible. C–D. Sagittal dynamic CT angiography of the head. Bony and soft tissue structures as well as brain parenchyma have been digitally subtracted. The image C was acquired during the arterial phase; the carotid and basilar termini and the anterior cerebral arteries are enhanced. Venous phase imaging (D) shows enhancement of the superior and inferior sagittal sinuses, straight sinus, vein of Galen, internal cerebral veins, basal veins of Rosenthal, and the transverse and sigmoid sinuses.