Lesions and pseudolesions of the cavernous sinus and petrous apex.

Endoscopic surgery using an expanded endonasal approach now allows surgical access to an increasing range of parasellar, suprasellar, clivus, and petrous apex lesions. Accurate preoperative planning requires proper interpretation of CT and MRI results. It is essential to identify important anatomic landmarks and to recognize the appearance of common lesions and pseudolesions. Postoperative imaging must evaluate for residual tumors and identify iatrogenic conditions.

Imaging of neurologic disorders associated with pregnancy and the postpartum period.

Diverse pathologic conditions affect the central nervous system (CNS) and pituitary gland during pregnancy and the puerperium. Some are specific to the physiologic process of reproduction (eg, eclampsia, postpartum cerebral angiopathy, Sheehan syndrome, lymphocytic adenohypophysitis). Others are nonspecific but occur more often in pregnant women (eg, cerebral infarction, dural venous thrombosis, pituitary apoplexy). Recognition of the characteristic imaging findings in eclampsia, for example, may allow exclusion of other disorders. Even when imaging changes are nonspecific, knowledge of those entities associated with pregnancy and awareness of the increased likelihood of certain diseases in pregnancy will allow a more informed differential diagnosis. Differentiation of primary nonaneurysmal subarachnoid hemorrhage (SAH) from aneurysmal SAH is an example. Moreover, earlier use of imaging will result in fewer delayed diagnoses. For example, magnetic resonance venography allows early diagnosis of cerebral venous thrombosis. Even when the imaging changes are less specific, knowledge of likely possibilities will lead to more appropriate earlier use of imaging. For example, the stimulatory effects of pregnancy on prolactinoma, meningioma, hemangioblastoma, vestibular schwannoma, and metastatic tumors such as breast cancer and choriocarcinoma suggest the early use of CNS imaging to avoid the consequences of a delayed diagnosis.

Contrast-enhanced MR angiography at 1.5 T after implantation of platinum stents: in vitro and in vivo comparison with conventional stent designs.

OBJECTIVE: The objective of our study was to evaluate the in vitro and in vivo 3D contrast-enhanced MR angiography characteristics of a new platinum-based balloon-expandable stent system and compare this system with a variety of competing metallic stents. MATERIALS AND METHODS: All experiments were performed on 1.5-T scanners. In vitro experiments were performed using 10 stents implanted into a custom-built phantom. Different orientations of the stents along the magnetic field and multiple flip angles were examined. In addition, 19 patients underwent contrast-enhanced MR angiography after the implantation of 36 stents, including four patients with six platinum stents. Angiographic correlation was available for all 19 patients, and luminal patency and stent-induced artifacts were assessed quantitatively. RESULTS: Of the tested balloon-expandable stents, only the platinum-based stents created artifact causing luminal narrowing of 30% or less. All other balloon-expandable stents induced larger artifacts that resulted in higher degrees of narrowing. Thus, if patent, the platinum-based stents allow significant in-stent stenosis to be ruled out reliably. Selected nitinol- or tantalum-based self-expandable stents also are suitable in this regard. CONCLUSION: Of the tested devices, platinum-based stents are the only type of currently available balloon-expandable stent that creates 30% or less artifact-induced apparent stenosis and thus are suitable for MR angiography.