Biomedical subjects

A Nabavi

Publications and source records attributed to A Nabavi.

13 recordsLinked to original sources

PubMed2001

Intraoperative diffusion imaging on a 0.5 Tesla interventional scanner.

Intraoperative line scan diffusion imaging (LSDI) on a 0.5 Tesla interventional MRI was performed during neurosurgery in three patients. Diffusion trace images were obtained in acute ischemic cases. Scan time per slice was 46 seconds and 94 seconds, respectively, for diffusion tensor images. Diagnosis of acutely developed vascular occlusion was confirmed with follow-up scans. White matter tracts were displayed with the principal eigenvectors and provided guidance for the tumor surgery. In all cases, the diagnostic utility of LSDI was established. J. Magn. Reson. Imaging 2001;13:115-119.

Adult↗

PubMed2001

Intra-operative MR guidance during trans-sphenoidal pituitary resection: preliminary results.

The use of intra-operative MR image guidance has the potential to improve the precision, extent, and safety of trans-sphenoidal pituitary resections. The trans-sphenoidal approach to pituitary surgery has been performed for some time (1--3). Until now these surgeries have relied on direct visualization without the aid of image guidance. An open-bore configuration 0.5T SIGNA SP MR system (GE Medical Systems, Milwaukee, Wisconsin) has been used to provide image guidance for seventeen trans-sphenoidal pituitary adenoma resections (4). The intra-operative MRI system allowed the radiologist to successfully direct the surgeon toward the sella turcica while avoiding the cavernous sinus, optic chiasm and other critical structures. Imaging performed during the surgery monitored the extent of resection and allowed for removal of tumor beyond the surgeon's view in seven cases. Dynamic MR imaging was used to distinguish residual tumor from normal gland and postoperative changes, permitting more precise tumor localization. A heme-sensitive long TE gradient echo sequence was used to find the presence of hemorrhagic debris. All patients tolerated the procedure well without significant complications. J. Magn. Reson. Imaging 2001;13:136-141.

Adenoma↗

PubMed2001

Motion robust imaging for continuous intraoperative MRI.

The sensitivity of MR imaging to motion and susceptibility normally requires that the physician using intraoperative MRI cease surgical activity while image data sets are acquired. We demonstrate that line scan imaging allows the physician to continue operating without the delays caused by imaging. Consequently, patient anesthesia, surgery, and operating room time can be reduced. J. Magn. Reson. Imaging 2001;13:158-161.

Brain↗

PubMed2001

Integration of interventional MRI with computer-assisted surgery.

Interventional MRI (IMRI) has entered into a new stage in which computer-based techniques play an increasing role in planning, monitoring, and controlling the procedures. The use of interactive imaging, navigational image guidance techniques, and image processing methods is demonstrated in various applications. The integration of intraoperative MRI guidance and computer-assisted surgery will greatly accelerate the clinical utility of image-guided therapy in general and interventional MRI in particular. J. Magn. Reson. Imaging 2001;13:69-77.

Humans↗

PubMed2001

Automated segmentation of MR images of brain tumors.

An automated brain tumor segmentation method was developed and validated against manual segmentation with three-dimensional magnetic resonance images in 20 patients with meningiomas and low-grade gliomas. The automated method (operator time, 5-10 minutes) allowed rapid identification of brain and tumor tissue with an accuracy and reproducibility comparable to those of manual segmentation (operator time, 3-5 hours), making automated segmentation practical for low-grade gliomas and meningiomas.

Brain↗

PubMed2000

[Neuronavigation in the region of the skull base].

Neuronavigation (computer-aided surgery planning and performance) has proven to be helpful in performing neurosurgical operations. The experiences of our department gained on more than 500 patients operated upon will be presented, with special focus on more than 100 operations for lesions on the skull base. Navigation is one of several modern surgical tools, its value cannot be defined without observing other improvements e.g. in the area of preoperative diagnostics, intraoperative monitoring, microsurgical instruments and microsurgical approaches.

Adenoma↗

PubMed1999

Craniotomy for tumor treatment in an intraoperative magnetic resonance imaging unit.

OBJECTIVE: The complex three-dimensional anatomic features of the brain and its vulnerability to surgical intervention make the surgical treatment of intracranial tumors challenging. We evaluated the surgical treatment of supratentorial tumors using intraoperative magnetic resonance imaging (MRI), which provides real-time guidance, allows localization of intracranial tumors and their margins, and facilitates continuous assessment of surgical progress. METHODS: Sixty patients underwent craniotomies for tumor treatment in the General Electric intraoperative MRI unit at the Brigham and Women's Hospital (Boston, MA) during a 1-year period. The patients selected were those with intracranial tumors that were considered difficult to resect because of their locations or previous incomplete operations. Twenty-nine low-grade and 19 high-grade gliomas, 8 metastatic lesions, 2 meningiomas, 1 pineoblastoma, and 1 astroblastoma were resected. RESULTS: Tumors were accurately localized and targeted, and the extent of resection, as well as any intraoperative complications, could be immediately assessed during surgery. Marked brain shifting occurred during the procedures, and repeated intraoperative imaging allowed surgical accommodation for this shifting. In more than one-third of the cases, intraoperative imaging showed residual tumor when resection appeared complete on the basis of surgical observation alone. CONCLUSION: Intraoperative MRI is a revolutionary tool for the surgical treatment of brain tumors, providing observation of the procedure as it is being performed. With intraoperative MRI, tumor resection is safer, the extent of resection can be directly evaluated, and intraoperative complications can be noted if they occur. Outcomes after resection depend on minimizing injury to normal brain tissue and achieving maximal tumor resection. The use of intraoperative MRI directly affects these factors.

Adult↗

PubMed1998

[Interhemispheric subdural hematoma].

The interhemispheric subdural hematoma (ISH) is a special subdural hematoma with regard to both location and symptomatology. The most widely described clinical signs and symptoms associated with an ISH are a lucid interval and the falx syndrome. The latter is featured by a contralateral hemiparesis that is accentuated in the lower extremity but spares the face. Minor head trauma or a preexisting coagulation disorder are also often found. Nonsurgical treatment should be chosen in patients with little neurologic dysfunction and a stable clinical course. Patients with progressive neurologic deterioration and focal neurologic deficits should be operated on without delay. This article provides a review of 99 published cases of ISH and adds 3 cases to the existing literature.

Cerebral Cortex↗

PubMed1998

Intracranial cavernomas: indications for and results of surgery.

Between April 1991 and April 1997, 46 patients were treated in our department presenting with intracranial cavernomas. Initial symptoms were focal seizures, bleeding episodes, and/or headaches. Mean age was 41 year (range 9 to 68 years). There were 24 female and 22 male patients. Computed tomography and magnetic resonance imaging were performed in order to establish the diagnosis, angiography was only indicated when the hemorrhaged area was so close to the subarachnoid space in the vicinity of the basal cisterns that an aneurysm had to be ruled out. Aggressive indication for surgery also in brainstem cavernomas was based on the natural history of the lesion, since the majority of patients presenting with intracranial bleeding had suffered several (up to six) episodes of previous hemorrhages. Patients' clinical status upon admission and accessibility of the cavernoma were taken into account for planning the operation. The operative planning and approach were greatly facilitated by using a neuronavigational device and intraoperative electrophysiological monitoring particularly in cavernomas located in the brainstem, thalamus, and medulla oblongata. Surgical removal of the lesions resulted in a new permanent neurological deficit only in two patients (4%). These data show that patients benefit from modern neurosurgical techniques in contrast to conservative approach in this disease of rather prolonged natural course.

Adolescent↗

PubMed1996

[Perimesencephalic subarachnoid hemorrhage--an independent clinical picture of non-aneurysmatic subarachnoid hemorrhage with a benign course].

Two hundred seventy-three Patients with acute SAH were treated within the last 46 months (1.4.1991 to 31.1.1995). Diagnosis was made upon visible SAH on CT-scans or bloody spinal tap regardless of a negative CT-scan. These patients harbored 194 aneurysms, 25 AVM and cavernomas. Within the same time-period we treated 27 Patients without SAH but harboring vascular malformations (17 aneurysms, 10 AVM and cavernomas). In 30 patients (11%) no bleeding source was detectable. Fourteen of these patients (5.1%) had blood concentrated within the perimesencephalic cisterns on the CT-scans. On admission all of these 14 patients (8 men, 6 female, aged 30 to 63 years) were awake and without mentionable neurological deficit, equalling Hunt & Hess grade 1 (11 patients) and 2 (3 patients). Neither the initial nor control angiography revealed a vascular malformation as a bleeding source. MRI-scans performed for 11 patients did not reveal further etiological clues. During a follow-up interval of 3 to 48 months, none of these patients suffered a rebleeding. Vasospasm was not or only slightly present, no ischemia leading to neurological deficit. GOS reached 5 and Karnofsky-scale was 100 for all of these patients. We conclude that the perimesencephalic SAH is a homogeneous entity with a different natural course than the common aneurysmatic SAH. Probably leakage within the capillary or venous circulation causes this form of SAH with a benign clinical course. Further experience is required to determine whether control angiography is mandatory in these patents with a distinct CT appearance.

Adult↗

PubMed1995

[Neuronavigation. Computer-assisted surgery in neurosurgery].

Computers in Neurosurgery were limited to diagnostics, planning stereotactic procedures, Radiosurgery and Radiation therapy. The possibility of intra-operative localisation only evolved since the mid 80's with the advent of more powerful computers. The computer adds more precision to microneurosurgical procedures, allowing neuronavigation in interaction with the computer. Diverse neuronavigationsystems are described in the literature [7-9, 11, 13]. We are working with the "ISG Viewing Wand" since april 1994. 113 operations were planed and executed aided by this system. We report on our experiences, the advantages and limitations of this system.

Adult↗

PubMed1993

[Muscle anomalies of the upper extremity as an atavistic cause of peripheral nerve disorder].

We report on 2 patients with anomalous muscles of the upper extremity causing symptoms of peripheral nerve entrapment. Our first case clinically showed a lesion of the R. dorsalis manus of nervus ulnaris produced by an accessory muscle belly at the dorsum of the hand to be identified as an extensor indicis brevis muscle. The second case presented a carpal-tunnel-syndrome, tunnel into the palm. Phylogenetically and ontogenetically these muscles are classified as atavistic. We demonstrate the homologies of the upper extremity of fishes, amphibians, reptiles, lower mammals and man, which show an upward migration of the muscle masses from the hand to the forearm. By that means the upper extremity gains additionally to the power of the reptiles paw the functionality and free motility of the human hand.

Adult↗

PubMedDate not supplied

Three-dimensional optical flow method for measurement of volumetric brain deformation from intraoperative MR images.

A three-dimensional optical flow method to measure volumetric brain deformation from sequential intraoperative MR images and preliminary clinical results from five cases are reported. Intraoperative MR images were scanned before and after dura opening, twice during tumor resection, and immediately after dura closure. The maximum cortical surface shift measured was 11 mm and subsurface shift was 4 mm. The computed deformation field was most satisfactory when the skin was segmented and removed from the images before the optical flow computation.

Adult↗