Intraoperative imaging of the brain

The development of computed imaging techniques has revolutionized contemporary neurosurgical procedures. In a 20-year interval, intraoperative imaging was used in more than 4,000 patients at our center. The selection of the appropriate intraoperative imaging tool was dependent on the neurosurgical procedure performed. In our dedicated operating room suite, intraoperative fluoroscopic imaging was used during transsphenoidal, spinal, and functional procedures, e.g. to treat percutaneous trigeminal neuralgia. A dedicated intraoperative computed tomography scanner was first available in 1981 and was used in more than 1,500 stereotactic or image-guided procedures. During radiosurgical procedures with the Gamma Knife (n = 1,560) a variety of intraoperative imaging tools (MRI, CT, angiography, and digital subtraction angiography) were used to define the target. The output of these imaging tools is currently transferred via fiberoptic ethernet to a wide variety of computer workstations designed to facilitate surgical or radiation dose planning. In addition, intraoperative imaging became increasingly important during vascular neurosurgery. Because of its superior patient accessibility and instrument compatibility. CT is likely to remain the most important imaging tool for conventional intraoperative image-guided stereotactic surgery. In contrast, intraoperative MRI proved to be the superior imaging tool for radiosurgery.     

Assignment of the human skeletal muscle alpha actin gene (ACTA1) to 1q42 by fluorescence in situ hybridisation

Intraoperative computerized tomographic (CT) scan findings in two cases during resection of glial tumor are described. These intraoperative CT images were obtained by an exclusively developed operating CT scanner system for use in the operating room. Repeated intraoperative CT scans taken during tumor removal showed shift of the brain including central structures and displacement of the cortical subarachnoid space in both cases. With contrast medium, the edge of the surrounding brain after resection was enhanced and a round enhanced area was observed in distant white matter. The distant enhancement, which we call 'remote enhancement', probably suggests damage to the blood-brain barrier due to surgical manoeuvre.     

Intraoperative magnetic resonance imaging with the magnetom open scanner: concepts, neurosurgical indications, and procedures: a preliminary report

OBJECTIVE: Intraoperative magnetic resonance imaging (MRI) is now available with the General Electric MRI system for dedicated intraoperative use. Alternatively, non-dedicated MRI systems require fewer specific adaptations of instrumentation and surgical techniques. In this report, clinical experiences with such a system are presented. METHODS: All patients were surgically treated in a "twin operating theater," consisting of a conventional operating theater with complete neuronavigation equipment (StealthStation and MKM), which allowed surgery with magnetically incompatible instruments, conventional instrumentation and operating microscope, and a radiofrequency-shielded operating room designed for use with an intraoperative MRI scanner (Magnetom Open; Siemens AG, Erlangen, Germany). The Magnetom Open is a 0.2-T MRI scanner with a resistive magnet and specific adaptations that are necessary to integrate the scanner into the surgical environment. The operating theaters lie close together, and patients can be intraoperatively transported from one room to the other. This retrospective analysis includes 55 patients with cerebral lesions, all of whom were surgically treated between March 1996 and September 1997. RESULTS: Thirty-one patients with supratentorial tumors were surgically treated (with navigational guidance) in the conventional operating room, with intraoperative MRI for resection control. For 5 of these 31 patients, intraoperative resection control revealed significant tumor remnants, which led to further tumor resection guided by the information provided by intraoperative MRI. Intraoperative MRI resection control was performed in 18 transsphenoidal operations. In cases with suspected tumor remnants, the surgeon reexplored the sellar region; additional tumor tissue was removed in three of five cases. Follow-up scans were obtained for all patients 1 week and 2 to 3 months after surgery. For 14 of the 18 patients, the images obtained intraoperatively were comparable to those obtained after 2 to 3 months. Intraoperative MRI was also used for six patients undergoing temporal lobe resections for treatment of pharmacoresistant seizures. For these patients, the extent of neocortical and mesial resection was tailored to fit the preoperative findings of morphological and electrophysiological alterations, as well as intraoperative electrocorticographic findings. CONCLUSION: Intraoperative MRI with the Magnetom Open provides considerable additional information to optimize resection during surgical treatment of supratentorial tumors, pituitary adenomas, and epilepsy. The twin operating theater is a true alternative to a dedicated MRI system. Additional efforts are necessary to improve patient transportation time and instrument guidance within the scanner.     

Psychosocial consequences of weight cycling

PURPOSE: To perform stereotactic radiation therapy (SRT) without cranially fixated stereotactic frames, we developed a dual computed tomography (CT) linear accelerator (linac) treatment unit. METHODS AND MATERIALS: This unit is composed of a linac, CT, and motorized table. The linac and CT are set up at opposite ends of the table, which is suitable for both machines. The gantry axis of the linac is coaxial with that of the CT scanner. Thus, the center of the target detected with the CT can be matched easily with the gantry axis of the linac by rotating the table. Positioning is confirmed with the CT for each treatment session. Positioning and treatment errors with this unit were examined by phantom studies. Between August and December 1994, 8 patients with 11 lesions of primary or metastatic brain tumors received SRT with this unit. All lesions were treated with 24 Gy in three fractions to 30 Gy in 10 fractions to the 80% isodose line, with or without conventional external beam radiation therapy. RESULTS: Phantom studies revealed that treatment errors with this unit were within 1 mm after careful positioning. The position was easily maintained using two tiny metallic balls as vertical and horizontal marks. Motion of patients was negligible using a conventional heat-flexible head mold and dental impression. The overall time for a multiple noncoplanar arcs treatment for a single isocenter was less than 1 h on the initial treatment day and usually less than 20 min on subsequent days. Treatment was outpatient-based and well tolerated with no acute toxicities. Satisfactory responses have been documented. CONCLUSION: Using this treatment unit, multiple fractionated SRT is performed easily and precisely without cranially fixated stereotactic frames.     

Carotid artery balloon test occlusion: combined clinical evaluation and xenon-enhanced computed tomographic cerebral blood flow evaluation without patient transfer or balloon reinflation: technical note

OBJECTIVE: Clinical evaluation was combined with xenon-enhanced computed tomographic (CT) cerebral blood flow (CBF) evaluation during carotid artery balloon test occlusion (BTO), without patient transfer from the angiography suite to the CT scanner or balloon reinflation. TECHNIQUE: Thirteen patients underwent carotid artery BTO. Placement of temporary occlusion balloons was performed with patients positioned on the CT scanner table. If neurological testing revealed no changes within 10 minutes after balloon inflation, patients were positioned within the CT scanner gantry for xenon-enhanced CT CBF evaluation. CBF evaluations were begun 12 to 15 minutes after balloon inflation and required 8 minutes for completion. After completion of CBF evaluation, neurological testing continued during 30 minutes of arterial occlusion. RESULTS: One patient did not tolerate BTO, with the development of reversible hemiparesis. Reliable CBF data were not obtained because of patient motion in one case. Eleven patients clinically tolerated BTO and completed CBF evaluation. For five patients, xenon-enhanced CT scanning revealed no regions with CBF of less than 30 ml/100 g/min. For four patients, xenon-enhanced CT scanning revealed small regions with CBF of less than 30 ml/100 g/min within the anterior frontal lobe on the occluded side. For two patients, ipsilateral CBF decreased dramatically during BTO, with CBF in many regions of less than 30 ml/100 g/min and in some of less than 20 ml/100 g/min. CONCLUSION: Xenon-enhanced CT CBF evaluation can be combined with clinical testing during BTO without patient transfer, balloon reinflation, or increases in the duration of the procedure. We recognize that the value of CBF evaluation during BTO remains to be proven; our technique does, however, eliminate abbreviated clinical neurological evaluation, patient transfer, and balloon reinflation, which were previously associated with the use of xenon-enhanced CT CBF evaluation during carotid artery BTO.     

Image quality in dynamic CT: a clinical discussion

Modern state-of-the-art computed tomographic (CT) scanners emphasize three capabilities: image quality, dynamic scan capability, and a high-resolution thin-section technique. Image quality is fundamental and dependent on optimum performance and the interrelationship of all system components. Variables that affect the performance of the scanner include x-ray tube output and rate of heat dissipation; quantum detection efficiency; electronic noise in the acquisition system; speed, accuracy, and integration of mechanical motion in the gantry and table; and the algorithm used for image reconstruction. System design must allow for dynamic scan operation, either in the single-scan or cluster mode, with short interscan or intergroup delays or, as more recently developed, with helical acquisition. Dynamic scanning is frequently used for nonneurologic applications, including diagnosis of vascular and perivascular diseases and multifocal organ disease, particularly hepatic disease. Efficient operation depends on rapid reconstruction and display capability. Modern systems have been engineered to provide flexible modes of operation, particularly in dynamic scanning, and rapid on-line review and analysis, all of which serve to improve the quality of images produced with dynamic CT scanning.     

The technical design and performance of ultrafast computed tomography

The ultrafast radiograph CT scanner utilizes a scanning electron beam and semicircular tungsten targets to produce a moving radiograph source about the patient, thus eliminating mechanical motion within the gantry. This design allows scan times as short as 50 or 100 ms, as well as two levels of image resolution. The short scan time reduces the effects of motion blurring and artifacts and provides the ability to obtain high-quality images of dynamic processes and rapidly moving organs. When utilized in the SS (high-resolution) mode, the UFCT scanner provides contiguous image acquisition through a patient volume at rapid speeds, yet maintains image quality comparable with conventional CT scanners. This technology provides extremely short exposure times, rapid acquisition of multiple slices, continuous scanning without concern for anode heat storage and dissipation, and the ability to image moving organs or flowing contrast media. Many clinical applications exist that exploit these unique features.     

Interactive intraoperative localization using an infrared-based system

We discuss new methods of localizing and treating brain lesions for both the conventional method of a base-ring fixed to the patient's skull (referred to as frame-based procedures) and the new method of frameless procedures (no base ring). Frame-based procedures are used for finding a precise instrument position during neurosurgical procedures, such as stereotactic biopsy of deep-seated lesions, placing electrodes for functional stereotaxis or catheters with radioactive seeds for brachytherapy, or even the placement of a stereotactic retractor or endoscope for removal or internal decompression of lesions. In such procedures, the intraoperative image localization of instruments becomes useful as it tracks instruments as they travel through the preplanned trajectory. Additional intraoperative digitization of surgical instruments, e.g., bipolar suction, biopsy forceps, microscope, ultrasound probe, etc, can be achieved during the stereotactic resection of eloquent areas or deep intracranial lesions by adding an infrared-based system. Frameless procedures broaden the range of surgical approaches, image guidance planning, and operative procedures, since no ring is attached to the patient's head which might interfere with the surgical approach, and offers logistic advantages in scheduling diagnostic studies. Frameless diagnostic studies employ anatomical markers and/or surface matching techniques for data registration in the computer software surgical preplanning program. This simplifies scheduling of the procedures since the image study does not need to be acquired the same day as surgery. Frameless diagnostic studies allow for the use of more than one type of imaging data for planning and optimization of surgical procedures, and greatly improve patient tolerance and comfort during these procedures and during surgery, as compared with frame-based procedures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Preoperative diagnosis of the thoracic aortic aneurysm by three-dimensional CT angiography

Serial eight patients with thoracic aortic aneurysms were evaluated by a newly developed three-dimensional CT angiography (3D-CT) from December 1992 to January 1993. The patients include 3 aortic dissections, 3 aortic arch aneurysms, one descending aortic aneurysm and one thoracoabdominal aortic aneurysm. The surgical treatment was performed after the evaluation of 3D-CT, and the operative findings were compared to the three-dimensional images reconstructed by 3D-CT in all patients. Three-dimensional displays were achieved using the unique method of data collection of the helical (spiral) scanner with continuous tube rotation and continuous table feed. A intravenous contrast material was used to image the thoracic aorta and major aortic branches with the single-breath-hold technique. Two and three-dimensional images reconstructed by 3D-CT were displayed within 10-20 minutes after the scanning. These three-dimensional images of the aortic lesions could be displayed in any angle we chose. Three-dimensional structures of the thoracic aorta and major aortic branches were clearly visualized and easily recognized by 3D-CT. These images were similar to the intraoperative findings and were quite useful to determine the operative procedure. The successful repair of thoracic aortic aneurysm was achieved in all cases. 3D-CT is a new and attractive modality to assess the vascular system. Although our experience is limited, 3D-CT may be a useful and powerful diagnostic method for the surgical treatment of thoracic aortic aneurysm.     

In vitro study of cytotoxicity of quinolones on rabbit tenocytes

During the week of October 15-24, 1995 a team of 65 medical, anaesthesiology, surgical, nursing and paramedical personnel travelled to Guatemala City, Guatemala to perform cardiac surgery on children with complex congenital and acquired valvular heart disease. During this mission 42 patients had their lesions surgically repaired. Cardiopulmonary bypass was required in 36 cases. There were no anaesthetic or surgical deaths. All six patients who did not require cardiopulmonary bypass were extubated in the operating room. Of the patients who required cardiopulmonary bypass, 23 were extubated in the operating room (64%). There was no intraoperative anaesthetic morbidity nor postoperative respiratory complications. No patients was reintubated after planned extubation. Cardiac surgery in paediatric age patients can safely be performed in developing countries if close attention is paid to proper patient selection and one maintains the standards of care practised in developed countries.     

CT of head trauma

The advent of CT in the early 1970s revolutionized the diagnosis and management of head trauma patients. CT remains to be the imaging modality of choice in the evaluation of patients with acute head trauma. High resolution CT is excellent for evaluating facial and skull fractures. Neurosurgically significant lesions such as epidural hematomas, subdural hematomas, or depressed skull fractures are already detected by CT. The early detection of extra-axial hematomas made possible by the increased availability of CT, results in early surgical interventions with marked improvement in morbidity and mortality in head trauma patients.     

Development of a frameless and armless stereotactic neuronavigation system with ultrasonographic registration

OBJECTIVE: We have developed a frameless stereotactic neuronavigation system that allows navigation during neurosurgical procedures through an image formed from integrating ultrasonography and preoperative magnetic resonance (MR) imaging and/or x-ray computed tomography. METHODS: The system consists of a ultrasound imaging scanner, a workstation with an image capture board, and an ultrasonic tracking sensor with a 5-MHz ultrasonographic transducer. The ultrasonic tracking sensor measures the position and orientation of the ultrasonographic transducer. The oblique plane of the MR/computed tomographic image corresponding to the ultrasound image is then displayed on the workstation monitor. A three-dimensional computer graphic representation of the integrated image is also reported as a preliminary test. For the patient-image registration, the coordinates of digitized and imaged markers on a specifically developed reference frame are used. The reference frame is noninvasive because it is not bolted but only fastened to the patient's head with silicon. RESULTS: Based on the findings from the clinical application of the system in three cases, the system was advantageous because of the surgical procedures could be controlled by intraoperative ultrasonography as well as by preoperative MR/computed tomographic images. Missing parts in the ultrasonogram were supplemented with preoperative MR/computed tomographic images. At other times, spatial positioning and visualization by ultrasonography were useful for identifying anatomical objects in the image. CONCLUSION: This preliminary study of the frameless integration of ultrasonography into stereotactic space demonstrated its clinical usefulness. We believe that the concept of pre- and intraoperative image-guided surgery presented here will find increasing use in the future.     

Luteotropic effect of pregnant mare serum gonadotropin in cattle

The ability to accurately assess tumor size and orientation to surrounding vital structures is an important consideration during preoperative evaluation. The authors report on nine children with solid tumors (hepatoblastoma [1], neuroblastoma [2], adrenal cortical carcinoma [2], liver adenoma [1], primitive neuroectodermal tumor [PNET] [1], and stage V Wilms' tumor [2]) for whom tumor resectability was questioned because of the tumors' close proximity to major blood vessels (noted through conventional radiographic imaging). The children had scanning with spiral volumetric acquisition computerized tomography, (CT) which obtains images during continuous rotation of the x-ray source while the patient moves at a constant velocity through the gantry. This technique is rapid (18 to 30 seconds), and is similar with respect to radiation exposure; little or no sedation is required, and the contrast dose is lower than that of conventional CT. Three-dimensional reconstruction of spiral CT imaging provided useful information that allowed successful resection in all nine cases. The authors suggest that spiral CT may become an important imaging modality in the preoperative evaluation of pediatric solid tumors and that further evaluation of this new methodology is warranted.     

Fulminant hepatitis complicated by small intestine infection and massive hemorrhage

OBJECT: The purpose of this study was to evaluate the efficacy of noninvasive preoperative functional imaging data used in an interactive fashion in the operating room. The authors describe a method of registering preoperative functional magnetic resonance (fMR) imaging localization of sensorimotor cortex with a frameless stereotactic surgical navigation device. METHODS: The day before surgery, patients underwent blood oxygen level-dependent fMR imaging while performing a finger-tapping motor paradigm. Immediately afterward an anatomical stereotactic MR image was acquired. Raw fMR imaging data were analyzed offline at a separate workstation, and the resulting functional maps were registered to a high-resolution anatomical scan. The fused functional-anatomical images were then downloaded onto a surgical navigation computer via an ethernet connection. At surgery, the brain was exposed in the standard fashion, and the sensorimotor cortex was identified by direct cortical stimulation, the use of somatosensory evoked potentials, or both. This localization was then compared with that predicted by the registered fMR study. Thirteen procedures were performed in 12 patients. The mean registration error was 2.2 mm. The predicted location of motor and/or sensory cortex matched that found on intraoperative mapping in all 12 patients tested. Maximal tumor resection was accomplished in each case and no new permanent neurological deficits resulted. CONCLUSIONS: Compared with conventional brain mapping techniques, fMR image-guided surgery may allow for smaller brain exposures, localization of the language cortex with the patient under general anesthesia, and the mapping of multiple functional sites. The scanning equipment used in this method may be more readily available than for other functional imaging techniques such as positron emission tomography or magnetoencephalography.     

The genomic organization of the genes for human lipopolysaccharide binding protein (LBP) and bactericidal permeability increasing protein (BPI) is highly conserved

PURPOSE: The authors evaluated computed tomographic (CT) virtual colography for the detection of simulated polyps under ideal conditions, as well as the effects on lesion conspicuity of (a) collimation, (b) table pitch, and (c) orientation of the colon lumen with respect to the gantry. MATERIALS AND METHODS: Pig colon was resected and cleansed, and polyps with diameters of 3, 7, and 10 mm were created. Each specimen was scanned with collimation of 5 and 7 mm and table pitch of 1.0, 1.6, and 2.0 at angles of 0 degrees, 45 degrees, and 90 degrees to the gantry. The initial two-dimensional (2D) images were reconstructed at 1-mm intervals (2D reconstructions), from which three-dimensional (3D) virtual colography images were generated. Polyp conspicuity on the initial and reconstructed 2D images and the 3D reconstructions was evaluated on a three-point scale: 0 = polyp not depicted, 1 = polyp faintly depicted, and 2 = polyp clearly depicted. RESULTS: The 10-mm-diameter polyp was clearly depicted (grade 2 conspicuity) on every initial and reconstructed 2D image and 3D reconstruction without regard to collimation, table pitch, or angle to the gantry. The 7-mm-diameter polyp was clearly depicted (grade 2 conspicuity) on every initial and reconstructed 2D image, but conspicuity on 3D reconstructions varied as the imaging parameters varied. The 3-mm-diameter polyp was faintly depicted (grade 1 conspicuity) on the initial and reconstructed 2D images and 3D reconstructions, but conspicuity varied on the 3D reconstructions as the imaging parameters varied. CONCLUSION: CT virtual colography helped detection of small mucosal polyps regardless of the angle of the colon lumen to the gantry at which they were obtained.     

A study of interrater reliability when using videofluoroscopy as an assessment of swallowing

PURPOSE: To evaluate the possible role of intraoperative cerebral emboli in the origin of perioperative stroke during major head and neck surgical procedures. MATERIALS AND METHODS: Eleven patients undergoing major head and neck surgery that involved direct manipulation of the carotid sheath were the participants in this study. Transcranial Doppler (TCD) ultrasound was used intraoperatively to detect possible cerebral emboli. The presence or absence of intraoperative cerebral emboli in each patient was assessed by the presence or absence of typical embolic signal patterns within the TCD waveform. RESULTS: No intraoperative cerebral emboli were noted in the series, nor did any patient have a postoperative stroke. CONCLUSIONS: No intraoperative cerebral emboli were noted by using TCD ultrasound for embolus monitoring in patients undergoing major head and neck surgery involving carotid sheath manipulation. This detection system is easily used in appropriate head and neck cases and allows real-time, noninvasive intraoperative monitoring.     

Prediction of surgical resectability in patients with hepatic colorectal metastases

OBJECTIVE: To evaluate the efficacy of two distinct imaging techniques to predict, before operation, unresectability compared with standard computed tomographic scan (CT). SUMMARY BACKGROUND: Accurate preoperative identification of the number, size, and location of hepatic lesions is crucial in planning hepatic resection for colorectal hepatic metastases. Although infusion-enhanced CT is the standard, its limitations are the imaging of relatively isodense and/or small (< 1 cm) lesions. The increased sensitivity of CT arterial portography (CTAP) may be offset by false-positive results caused by benign lesions and flow artifacts. METHODS: Fifty-eight selected patients considered to be eligible for resection by standard CT had laparotomy. Before operation and in addition to CT, all patients had CT arterial portography and hepatic artery perfusion scintigraphy (HAPS) using radiolabeled macroaggregated albumin. Early studies showed an increased sensitivity for detecting small lesions using the invasive CTAP. Similarly, the HAPS study has detected malignant lesions not observed by standard CT. RESULTS: Of 58 patients having laparotomy, 40 were resectable by either lobectomy (22) or trisegmentectomy (1) and the rest by single or multiple wedge resections. Eighteen patients could not be resected because of combined intra- and extrahepatic disease or the number and location of metastases. Standard CT detected 64% of all lesions (12% of lesions less than 1 cm). Unresectability was accurately predicted by CTAP and HAPS in 16 (88%) and 15 (83%), respectively, of the 18 patients considered ineligible for resection at laparotomy. Of the 40 patients who had resection for possible cure, CTAP and HAPS falsely predicted unresectability in 6 of 40 patients (15%) and in 10 of 40 patients (25%), respectively. The positive predictive value for unresectability of CTAP and HAPS was 73% and 60%, respectively. False-positive lesions after CTAP included hemangiomas, cysts, granulomas, and flow artifacts. False-positive HAPS lesions included patients in whom no tumor was found at surgery but with some identified by intraoperative ultrasound, blind biopsy, and blind resection. CONCLUSIONS: False-positive results by HAPS and CTAP may limit the ability of these tests to accurately predict unresectability before operation and may deny patients the chance for surgical resection. The HAPS study does, however, detect small lesions not seen by CT or CTAP. Standard CT, although less sensitive, followed by surgery and intraoperative ultrasound, does not necessarily preclude patients who could be resected.     

Antiaggregatory effects of picotamide in long-term treatment: a 2-year, double-blind placebo-controlled trial

With faster CT scanners, asymmetric/heterogeneous enhancement (ASHE) of the internal jugular veins (IJVs) is frequently encountered in the absence of pathology. We investigated the frequency, side, pattern and significance of ASHE in 200 patients with various head and neck lesions. Non-ionic contrast medium (300 mgI/ml) was infused into a forearm vein (right, n = 100); left, n = 100). Forty seconds after contrast medium injection, contiguous 5-mm-thick sections were obtained craniocaudally from the skull base to the aortic arch. CT machines with two different scanning cycle times (3 s, n = 100; 2 s, n = 100) were used. ASHE of the IJVs was observed in 51 patients (25.5%); the patient group receiving a right-sided injection with a 2-s scan cycle machine, showing a higher frequency (44%). ASHE was divided into four patterns: homogeneous low density, focal low density, heterogenous opacification and fluid-fluid level formation. ASHE was frequently observed in routine contrast-enhanced CT of the head and neck. Frequency of ASHE increased when the scanning cycle was shorter. We should be aware of this phenomenon to avoid its misinterpretation as venous thrombosis or other pathology.     

Effect of chronic hypoxia on adrenoceptor responses of ovine foetal umbilical vessels

OBJECTIVE: To evaluate the relevance of hypometabolism in the hippocampal head to the pathophysiology of memory impairment. BACKGROUND: Neurofunctional imaging studies with an image reslicing technique provided by using software suggest that dysfunction of the amygdalohippocampal system causes memory impairment. However, metabolic and morphologic profiles of the whole hippocampal formation have not been evaluated in detail. METHODS: By tilting the gantry of a high-resolution PET scanner in a plane parallel to the hippocampal longitudinal axis determined beforehand by MRI, we performed quantitative measurement of glucose metabolism in the subdivisions of the hippocampal formation (head, body, tail) in 10 patients of normal intelligence with pure amnesia, in eight patients with AD, and in eight normal subjects. RESULTS: Although the volumes of the amygdala and hippocampal formation in pure amnesics were not different significantly from those of normal subjects, glucose metabolism in the head of the hippocampus was significantly lower in pure amnesics. In patients with AD, marked hypometabolism was found extending to the amygdala, the hippocampal head, and the parietotemporal cortex, along with amygdalohippocampal atrophy. CONCLUSION: Hippocampal head dysfunction plays an important role in memory impairment in amnesic patients. Further metabolic impairment over the amygdalohippocampal system and the surrounding association cortex reflects the pathophysiology of AD.     

BrainLab VectorVision Neuronavigation System: technology and clinical experiences in 131 cases

OBJECTIVE: The BrainLab VectorVision neuronavigation system was used in 131 cases of different brain pathological conditions. The neuronavigation system was used without problems in 125 cases. These cases included 114 microsurgical operations, 4 endoscopic procedures, 4 frameless stereotactic biopsies, and 3 catheter placements. METHODS: The BrainLab VectorVision neuronavigation system is an intraoperative, image-guided, frameless, localization system. The system consists of a computer workstation for registration of images and physical spaces, an intraoperative localization device, and a computer image display. The system provides real-time responses regarding the locations of surgical instruments. VectorVision is based on passive reflections of infrared flashes. Universal adapters with reflective markers for surgical instruments, endoscopes, and the operating microscope are used. RESULTS: In six cases, the system could not be used because of system failure or mishandling. In 125 neurosurgical cases, the neuronavigation system was useful, with a target-localizing accuracy of 4+/-1.4 mm (mean+/-standard deviation). For small cerebral lesions, we never performed an exploration with negative results. CONCLUSION: The BrainLab neuronavigation system has been shown to be very helpful and user-friendly for routine neurosurgical interventions. Its advantage lies in its mobility, based on wireless reflective adapters for surgical instruments, endoscopes, and the operating microscope.