Cerebral venous thrombus signal intensity and susceptibility effects on gradient recalled-echo MR imaging.

BACKGROUND AND PURPOSE: Cerebral venous thrombus (CVT) signal intensity is variable on MR imaging, and the appearance of CVT on gradient recalled-echo (GRE) sequences has been incompletely assessed. This study was performed to evaluate the GRE imaging appearance of CVT in different stages of thrombus evolution and its relationship to signal intensity on other MR pulse sequences. MATERIALS AND METHODS: The clinical and MR imaging findings in 18 patients with CVT and GRE imaging were reviewed. Sixty-nine thrombosed venous segments were evaluated, and the signal intensity of thrombus relative to gray matter was determined. The degree of thrombus susceptibility effect (SE) was assessed and related to time of imaging after onset of symptoms (clinical thrombus age) and appearance on other pulse sequences. Segments were classified as SE+ (demonstrating susceptibility effect) or SE- (no susceptibility effect). RESULTS: Thirty-six venous segments exhibited visible SE. SE+ segments had a clinical thrombus age that was less than that in SE- segments (8.1 versus 24.6 days, P=.003). Sixty-three percent (23/36) of SE+ segments exhibited hypointensity on T2-weighted images (T2WI) versus 12% (4/33) of SE- segments (P<.001). Twenty-nine of 32 (90.6%) segments with clinical thrombus age of 0-7 days were SE+, versus 7 of 30 (23.3%) segments with a thrombus age of 8 days or greater. CONCLUSION: SEs from CVT can be detected with GRE imaging and are most prevalent in patients with hypointense thrombus on T2WI within 7 days after the symptom onset. This correlates with the paramagnetic effects of deoxyhemoglobin in acute stage thrombus. GRE imaging may be useful in detecting thrombus in this stage when difficult to detect on other pulse sequences.

Cerebrovascular trauma.

Cerebrovascular trauma includes a wide variety of injuries, including dissections, traumatic aneurysms, arteriovenous fistulas, and vascular occlusions. These entities, which are often underdiagnosed, can produce devastating neurologic complications. This article reviews the clinical and radiographic presentations of vascular trauma to increase awareness of these injuries and improve our ability to detect and treat them.

Glioma resection in a shared-resource magnetic resonance operating room after optimal image-guided frameless stereotactic resection.

OBJECTIVE: We describe a shared-resource intraoperative magnetic resonance imaging (MRI) design that allocates time for both surgical procedures and routine diagnostic imaging. We investigated the safety and efficacy of this design as applied to the detection of residual glioma immediately after an optimal image-guided frameless stereotactic resection (IGFSR). METHODS: Based on the twin operating rooms (ORs) concept, we installed a commercially available Hitachi AIRIS II, 0.3-tesla, vertical field, open MRI unit in its own specially designed OR (designated the magnetic resonance OR) immediately adjacent to a conventional neurosurgical OR. Between May 1998 and October 1999, this facility was used for both routine diagnostic imaging (969 diagnostic scans) and surgical procedures (50 craniotomies for tumor resection, 27 transsphenoidal explorations, and 5 biopsies). Our study group, from which prospective data were collected, consisted of 40 of these patients who had glioma (World Health Organization Grades II-IV). These 40 patients first underwent optimal IGFSRs in the adjacent conventional OR, where resection continued until the surgeon believed that all of the accessible tumor had been removed. Patients were then transferred to the magnetic resonance OR to check the completeness of the resection. If accessible residual tumor was observed, then a biopsy and an additional resection were performed. To validate intraoperative MRI findings, early postoperative MRI using a 1.5-tesla magnet was performed. RESULTS: Intraoperative images that were suitable for interpretation were obtained for all 40 patients after optimal IGFSRs. In 19 patients (47%), intraoperative MRI studies confirmed that adequate resection had been achieved after IGFSR alone. Intraoperative MRI studies showed accessible residual tumors in the remaining 21 patients (53%), all of whom underwent additional resections. Early postoperative MRI studies were obtained in 39 patients, confirming that the desired final extent of resection had been achieved in all of these patients. One patient developed a superficial wound infection, and no hazardous equipment or instrumentation problems occurred. CONCLUSION: Use of an intraoperative MRI facility that permits both diagnostic imaging and surgical procedures is safe and may represent a more cost-effective approach than dedicated intraoperative units for some hospital centers. Although we clearly demonstrate an improvement in volumetric glioma resection as compared with IGFSR alone, further study is required to determine the impact of this approach on patient survival.

Intraoperative magnetic resonance imaging to determine the extent of resection of pituitary macroadenomas during transsphenoidal microsurgery.

OBJECTIVE: Well-established surgical goals for pituitary macroadenomas include gross total resection for noninvasive tumors and debulking with optic chiasm decompression for invasive tumors. In this report, we examine the safety, reliability, and outcome of intraoperative magnetic resonance imaging (iMRI) used to assess the extent of resection, and thus the achievement of preoperative surgical goals, during transsphenoidal microneurosurgery. METHODS: Our magnetic resonance operating room contains a Hitachi AIRIS II 0.3-T, vertical-field open magnet (Hitachi Medical Systems America, Inc., Twinsburg, OH). A motorized scanner tabletop moves the patient between the imaging and operative positions. For transsphenoidal surgery, the patient is positioned directly on the scanner tabletop so that the surgical field is located between 1.2 and 1.6 m from the magnet isocenter. At this location, the magnetic field strength is low (<20 G), thus permitting the use of many conventional surgical instruments. Thirty consecutive patients with pituitary macroadenomas underwent tumor resection in our magnetic resonance operating room by use of a standard transsphenoidal approach. After initial resection, the patient was advanced into the scanner for imaging. If residual tumor was demonstrated and deemed surgically accessible, the patient underwent immediate re-exploration. RESULTS: iMRI was performed successfully in all 30 patients. In one patient, iMRI was used to clarify the significance of hemorrhage from the sellar region and resulted in immediate conversion of the procedure to a craniotomy. In the remaining 29 patients, initial iMRI demonstrated that the endpoint for extent of resection had been achieved in only 10 patients (34%) after an initial resection attempt, whereas 19 patients (66%) still had unacceptable residual tumor. All 19 of these latter patients underwent re-exploration. Ultimately, re-exploration resulted in the achievement of the planned endpoint for extent of resection in all of the 29 completed transsphenoidal explorations. Operative time was extended in all cases by at least 20 minutes. CONCLUSION: iMRI can be used to safely, reliably, and objectively assess the extent of resection of pituitary macroadenomas during the transsphenoidal approach. The surgeon is frequently surprised by the extent of residual tumor after an initial resection attempt and finds the intraoperative images useful for guiding further resection.

Routine CT evaluation of acute stroke.

Although new imaging techniques such as MR perfusion/diffusion and xenon CT have shown considerable promise in the detection of early brain ischemia, noncontrast CT remains the primary imaging test for the evaluation of acute stroke. It is fast, reliable, readily available, and continues to be used for all major stroke therapy trials. Despite its limitations, CT is an accurate method of screening patients prior to thrombolytic therapy.

Angiography in the evaluation of head and neck trauma.

Cerebrovascular trauma is a heterogeneous group of injuries including arterial dissections, traumatic aneurysms, arteriovenous fistulas, and venous occlusions. Detection of vascular trauma may be difficult because of variations in clinical presentation; however, in recent years, increased awareness and understanding of these injuries has improved the ability to detect and subsequently treat many lesions. Despite advances in other imaging modalities, angiography remains the primary radiographic tool used in the evaluation of traumatic vascular lesions.