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Oliver Ganslandt

Publications and source records attributed to Oliver Ganslandt.

18 recordsLinked to original sources
PubMed2005

1.5 T: intraoperative imaging beyond standard anatomic imaging.

Intraoperative high-field MRI with integrated microscope-based neuronavigation is a safe and reliable technique providing immediate intraoperative quality control. Major indications are pituitary tumor, glioma, and epilepsy surgery. Intraoperative high-field MRI provides intraoperative anatomic images at high quality that are up to the standard of pre- and postoperative neuroradiologic imaging. Compared with previous low-field MRI systems used for intraoperative imaging, not only is the image quality is clearly superior but the imaging spectrum is much wider and the intraoperative work flow is improved. Furthermore, high-field MRI offers various modalities beyond standard anatomic imaging, such as magnetic resonance spectroscopy, diffusion tensor imaging, and functional MRI.

Brain Diseases↗
PubMed2005

Preoperative and intraoperative diffusion tensor imaging-based fiber tracking in glioma surgery.

OBJECTIVE: To investigate the intraoperative displacement of major white matter tracts during glioma resection by comparing preoperative and intraoperative diffusion tensor imaging-based fiber tracking. METHODS: In 37 patients undergoing glioma surgery, preoperative and intraoperative diffusion tensor imaging was performed with a 1.5-T magnetic resonance scanner applying an echo-planar imaging sequence with six diffusion directions. For three-dimensional tractography, we implemented a knowledge-based multiple-region-of-interest approach applying user-defined seed regions in the color-coded maps of fractional anisotropy. Tracking was initiated in both the retrograde and orthograde directions according to the direction of the principal eigenvector in each voxel of the region of interest. The tractography results were also assigned color, applying the convention used in color-coded fractional anisotropy maps. RESULTS: Preoperative and intraoperative fiber tracking was technically feasible in all patients. Fiber tract visualization gave a quick and intuitive overview of the displaced course of white matter tracts in three-dimensional space. Comparison of preoperative and intraoperative tractography depicted a marked shifting of major white matter tracts during glioma removal. Maximum white matter tract shifting ranged from -8 to +15 mm (+2.7 +/- 6.0 mm; mean +/- standard deviation); in 29.7%, an inward and in 62.2%, an outward shifting was detected. CONCLUSION: Comparing preoperative and intraoperative fiber tracking visualizes a marked shifting and deformation of major white matter tracts because of tumor removal. This shifting emphasizes the need for an intraoperative update of navigation systems during resection of deep-seated tumor portions near eloquent brain areas. Fiber tracking is a method not only for preoperative neurosurgical visualization but also for further intraoperative planning.

Adolescent↗
PubMed2004

Intraoperative diffusion-tensor MR imaging: shifting of white matter tracts during neurosurgical procedures--initial experience.

PURPOSE: To prospectively evaluate the location of white matter tracts with diffusion-tensor imaging (DTI) during neurosurgical procedures. MATERIALS AND METHODS: Ethical committee approval and signed informed consent were obtained. A 1.5-T magnetic resonance imager with an adapted rotating surgical table that is placed in a radiofrequency-shielded operating theater was used for pre- and intraoperative imaging. DTI was performed by applying an echo-planar imaging sequence with six diffusion directions in 38 patients (20 female patients, 18 male patients; age range, 7-77 years; mean age, 45.6 years) who were undergoing surgery (35 craniotomy and three burr hole procedures). Color-encoded maps of fractional anisotropy were generated by depicting white matter tracts. A rigid registration algorithm was used to compare pre- and intraoperative images. RESULTS: Intraoperative DTI was technically feasible in all patients, and no major image distortions occurred in the areas of interest. Pre- and intraoperative color-encoded maps of fractional anisotropy could be registered; these maps depicted marked and highly variable shifting of white matter tracts during neurosurgical procedures. In the 27 patients who underwent brain tumor resection, white matter tract shifting ranged from an inward shift of 8 mm to an outward shift of 15 mm (mean shift +/- standard deviation, outward shift of 2.5 mm +/- 5.8). In 16 (59%) of 27 patients, outward shifting was detected; in eight (30%), inward shifting was detected. In eight patients who underwent temporal lobe resections for drug-resistant epilepsy, shifting was only inward and ranged from 2 to 14 mm (9 mm +/- 3.3). In two of the three patients who underwent burr hole procedures, outward shifting occurred. CONCLUSION: Intraoperative DTI can depict shifting of major white matter tracts that is caused by surgical intervention.

Adolescent↗
PubMed2004

Intraoperative high-field-strength MR imaging: implementation and experience in 200 patients.

PURPOSE: To review the initial clinical experience with intraoperative high-field-strength magnetic resonance (MR) imaging of brain lesions in 200 patients. MATERIALS AND METHODS: Two hundred patients (mean age, 46.1 years; range, 7-84 years), most of whom had glioma or pituitary adenoma, were examined with a 1.5-T MR imager equipped with a rotating operating table and located in a radiofrequency-shielded operating theater. A navigation microscope placed inside the 0.5-mT zone and used in combination with a ceiling-mounted navigation system enabled integrated microscope-based neuronavigation. The extent of resection depicted at intraoperative imaging, the surgical consequences of intraoperative imaging, and the clinical practicability of the operating room setup were analyzed. RESULTS: Seventy-seven resections with a transsphenoidal approach, 100 craniotomies, and 23 burr-hole procedures were performed. In 55 (27.5%) of 200 patients, intraoperative MR imaging had immediate surgical consequences (eg, extension of resection in 39% of patients with pituitary adenoma or glioma). In 108 patients the navigation system was used, and for 37 of those patients, functional imaging data were integrated into the navigation system. There was nearly no difference in quality between pre- and intraoperative images. Intraoperative workflow with intraoperative patient transport for imaging was straightforward, and imaging in most cases began less than 2 minutes after sterile covering of the surgical site. No complications resulted from high-field-strength MR imaging. CONCLUSION: The high-field-strength MR imager was successfully adapted for intraoperative use with the integrated neuronavigation system. Intraoperative MR imaging provided valuable information that allowed intraoperative modification of the surgical strategy.

Adenoma↗
PubMed2004

Strategies for brain shift evaluation.

For the analysis of the brain shift phenomenon different strategies were applied. In 32 glioma cases pre- and intraoperative MR datasets were acquired in order to evaluate the maximum displacement of the brain surface and the deep tumor margin. After rigid registration using the software of the neuronavigation system, a direct comparison was made with 2D- and 3D visualizations. As a result, a great variability of the brain shift was observed ranging up to 24 mm for cortical displacement and exceeding 3 mm for the deep tumor margin in 66% of all cases. Following intraoperative imaging the neuronavigation system was updated in eight cases providing reliable guidance. For a more comprehensive analysis a voxel-based nonlinear registration was applied. Aiming at improved speed of alignment we performed all interpolation operations with 3D texture mapping based on OpenGL functions supported in graphics hardware. Further acceleration was achieved with an adaptive refinement of the underlying control point grid focusing on the main deformation areas. For a quick overview the registered datasets were evaluated with different 3D visualization approaches. Finally, the results were compared to the initial measurements contributing to a better understanding of the brain shift phenomenon. Overall, the experiments clearly demonstrate that deformations of the brain surface and deeper brain structures are uncorrelated.

Brain Neoplasms↗
PubMed2004

Improved delineation of brain tumors: an automated method for segmentation based on pathologic changes of 1H-MRSI metabolites in gliomas.

In this study, we developed a method to improve the delineation of intrinsic brain tumors based on the changes in metabolism due to tumor infiltration. Proton magnetic resonance spectroscopic imaging ((1)H-MRSI) with a nominal voxel size of 0.45 cm(3) was used to investigate the spatial distribution of choline-containing compounds (Cho), creatine (Cr) and N-acetyl-aspartate (NAA) in brain tumors and normal brain. Ten patients with untreated gliomas were examined on a 1.5 T clinical scanner using a MRSI sequence with PRESS volume preselection. Metabolic maps of Cho, Cr, NAA and Cho/NAA ratios were calculated. Tumors were automatically segmented in the Cho/NAA images based on the assumption of Gaussian distribution of Cho/NAA values in normal brain using a limit for normal brain tissue of the mean + three times the standard deviation. Based on this threshold, an area was calculated which was delineated as pathologic tissue. This area was then compared to areas of hyperintense signal caused by the tumor in T2-weighted MRI, which were determined by a region growing algorithm in combination with visual inspection by two experienced clinicians. The area that was abnormal on (1)H-MRSI exceeded the area delineated via T2 signal changes in the tumor (mean difference 24%) in all cases. For verification of higher sensitivity of our spectroscopic imaging strategy we developed a method for coregistration of MRI and MRSI data sets. Integration of the biochemical information into a frameless stereotactic system allowed biopsy sampling from the brain areas that showed normal T2-weighted signal but abnormal (1)H-MRSI changes. The histological findings showed tumor infiltration ranging from about 4-17% in areas differentiated from normal tissue by (1)H-MRSI only. We conclude that high spatial resolution (1)H-MRSI (nominal voxel size = 0.45 cm(3)) in combination with our segmentation algorithm can improve delineation of tumor borders compared to routine MRI tumor diagnosis.

Adult↗
PubMed2004

Volumetric assessment of glioma removal by intraoperative high-field magnetic resonance imaging.

OBJECTIVE: To investigate the contribution of high-field intraoperative magnetic resonance imaging (iMRI) for further reduction of tumor volume in glioma surgery. METHODS: From April 2002 to June 2003, 182 neurosurgical procedures were performed with a 1.5-T magnetic resonance system. Among patients who underwent these procedures, 47 patients with gliomas (14 with World Health Organization Grade I or II glioma, and 33 with World Health Organization Grade III or IV glioma) who underwent craniotomy were investigated retrospectively. Completeness of tumor resection and volumetric analysis were assessed with intraoperative imaging data. RESULTS: Surgical procedures were influenced by iMRI in 36.2% of operations, and surgery was continued to remove residual tumor. Additional further resection significantly reduced the percentage of final tumor volume compared with first iMRI scan (6.9% +/- 10.3% versus 21.4% +/- 13.8%; P < 0.001). Percentages of final tumor volume also were significantly reduced in both low-grade (10.3% +/- 11.5% versus 25.8% +/- 16.3%; P < 0.05) and high-grade gliomas (5.4% +/- 9.9% versus 19.5% +/- 13.0%; P < 0.001). Complete resection was achieved finally in 36.2% of all patients (low-grade, 57.1%; high-grade, 27.3%). Among the 17 patients in whom complete tumor resection was achieved, 7 complete resections (41.2%) were attributable to further tumor removal after iMRI. We did not encounter unexpected events attributable to high-field iMRI, and standard neurosurgical equipment could be used safely. CONCLUSION: Despite extended resections, introduction of high-field iMRI in conjunction with functional navigation did not translate into an increased risk of postoperative deficits. The use of high-field iMRI increased radicality in glioma surgery without additional morbidity.

Adolescent↗
PubMed2004

Integration of biochemical images of a tumor into frameless stereotaxy achieved using a magnetic resonance imaging/magnetic resonance spectroscopy hybrid data set.

OBJECT: It is often difficult to delineate the extent of invasion of high- and low-grade gliomas into normal brain tissue by using conventional T1- and T2-weighted magnetic resonance (MR) imaging. Knowledge of the relationship between the tumor infiltration zone and normal brain, however, is one of the prerequisites for performing as radical a tumor resection as possible. Proton MR spectroscopy allows noninvasive measurements of the concentrations and spatial distributions of brain metabolites and, therefore, may provide biochemical information in vivo, that is useful in distinguishing pathological from normal areas of the brain. The authors have developed a method to use the properties of MR spectroscopy to investigate intraoperatively pathological changes in the spatial distribution of choline (Cho)-containing compounds, total creatine, and N-acetylaspartate (NAA) in brain tumors with the aid of frameless stereotaxy. METHODS: Maps of the Cho/NAA ratio were calculated and automatic segmentation of the tumors was performed. Spectroscopic images of the segmented tumor were matched to an anatomical three-dimensional (3D) MR imaging set by applying a fully automated mutual-information algorithm. The resulting 3D MR image can be used subsequently for neurosurgical planning, transfer to a frameless stereotactic system, and display in the navigation microscope during surgery leading to 1H-MR spectroscopy-guided navigation. CONCLUSIONS: This method may allow better intraoperative identification of tumor border zones based on metabolic changes due to tumor infiltration.

Brain Neoplasms↗
PubMed2003

[Fractionated stereotactically guided radiotherapy for pharmacoresistant epilepsy].

AIM: This prospective study evaluated the efficiency of fractionated stereotactically guided radiotherapy as a treatment of pharmacoresistant temporal lobe epilepsy. PATIENTS AND METHODS: Inclusion criteria were patients aged between 17 and 65 years with one-sided temporally located focus, without sufficient epilepsy control by antiepileptic drugs or neurosurgery. Between 1997 and 1999, two groups of six patients each were treated with 21 Gy (7 times 3 Gy) and 30 Gy (15 times 2 Gy). Study end points were seizure frequency, intensity, seizure length and neuropsychological parameters. RESULTS: All patients experienced a marked reduction in seizure frequency. The mean reduction of seizures was 37% (range 9-77%, i. e. seizures reduced from a monthly mean number of 11.75 to 7.52) at 18 months following radiation treatment and 46% (23-94%, i. e. 0.2-23 seizures per month) during the whole follow-up time. Seizure length was reduced in five out of eleven patients and intensity of seizures in seven out of eleven patients. CONCLUSION: Radiotherapy was identified as safe and effective for pharmacoresistant epilepsy since a very good reduction of seizure frequency was observed. It is no substitute for regular use of antiepileptic drugs, but means an appropriate alternative for patients with contraindication against neurosurgery or insufficient seizure reduction after neurosurgery.

Adolescent↗
PubMed2003

Anesthesia during high-field intraoperative magnetic resonance imaging experience with 80 consecutive cases.

Intraoperative magnetic resonance imaging (MRI) has been used for years to update neuronavigation and for intraoperative resection control. For this purpose, low-field (0.1-0.2 T) MR scanners have been installed in the operating room, which, in contrast to machines using higher magnetic field strength, allowed the use of standard anesthetic and surgical equipment. However, these low-field MR systems provided only minor image quality and a limited battery of MR sequences, excluding functional MRI, diffusion-weighted MRI, or MR angiography and spectroscopy. Based on these advantages, a concept using high-field MRI (1.5 T) with intraoperative functional neuronavigational guidance has been developed that required adaptation of the anesthetic regimen to working in the close vicinity to the strong magnetic field. In this paper the authors present their experience with the first 80 consecutive patients who received anesthesia in a specially designed radio frequency-shielded operating room equipped with a high-field (1.5 T) MR scanner. We describe the MR-compatible anesthesia equipment used including ventilator, monitoring, and syringe pumps, which allow standard neuroanesthesia in this new and challenging environment. This equipment provides the use of total intravenous anesthesia with propofol and remifentanil allowing rapid extubation and neurologic examination following surgery. In addition, extended intraoperative monitoring including EEG monitoring required for intracranial surgery is possible. Moreover, problems and dangers related to the effects of the strong magnetic field are discussed.

Adolescent↗
PubMed2003

Intraoperative low-field magnetic resonance imaging in pediatric neurosurgery.

BACKGROUND: Since the mid-1990s, the feasibility and indications of intraoperative magnetic resonance (MR) imaging have been investigated by different groups. The majority of examinations were carried out in adults. The aim of this study was to summarize our experience of over 5 years of intraoperative MR imaging in pediatric neurosurgery. METHODS: For scanning, we used a 0.2-Tesla Magnetom Open, which was placed in a radiofrequency-shielded twin operating theater, allowing surgery with standard instruments and additional neuronavigational guidance either in an adjacent operating room or directly in the radiofrequency cabin on the extended MR table, at the 5-G line. RESULTS: In total, 330 patients were investigated, among them 33 children who were younger than 17 years. We found four main indications for intraoperative MR imaging: the evaluation of cyst drainage (n = 9), of the extent of resection in epilepsy surgery (n = 6) and of the removal of pituitary tumors (n = 6) and gliomas and other brain tumors (n = 12). Intraoperative MR imaging allowed us to evaluate the extent of the resection or to monitor catheter placements and consecutive cyst alterations in all cases. In 2 tumor cases and 3 catheter placements, intraoperative imaging resulted in a modification of the surgical strategy. CONCLUSIONS: Intraoperative low-field MR imaging is a safe procedure; we did not encounter an increased morbidity in the children investigated. It serves as intraoperative quality control documenting the effects of surgery, e.g. the extent of a resection, which can then be compared to the treatment plan. Besides its most essential application in brain tumors, it also proved to be particularly helpful in children undergoing complicated catheter placements for cyst drainage, as well as in pituitary and epilepsy surgery.

Adolescent↗
PubMed2003

Limited benefit of intraoperative low-field magnetic resonance imaging in craniopharyngioma surgery.

OBJECTIVE: To investigate the benefit of intraoperative low-field magnetic resonance imaging (MRI) in craniopharyngioma surgery. METHODS: We used a 0.2-T Magnetom Open scanner (Siemens Medical Solutions, Erlangen, Germany) that was located in a radiofrequency-shielded operating theater for intraoperative MRI. The head of the patient was placed in the fringe field of the scanner, so that standard microinstruments could be used. In transsphenoidal surgery, T1-weighted coronal and sagittal images were acquired. In transcranial surgery, a three-dimensional, gradient echo, T1-weighted, fast low-angle shot sequence was measured, thus allowing multiplanar reformatting. RESULTS: A total of 21 surgical procedures in craniopharyngioma patients were investigated. In 10 patients, a bifrontal-translaminar approach was used; in 6 patients, the craniopharyngioma was removed via a transsphenoidal approach; and in 5 patients, intraoperative MRI was used to monitor cyst puncture and aspiration. In the craniotomy group, intraoperative imaging depicted a clear tumor remnant in one patient, which was subsequently removed. In another patient, an area of contrast enhancement was interpreted as artifact; however, postoperative follow-up at 3 months was suspicious for a minor remnant. Two of the eight patients with complete removal developed a recurrence during the follow-up period. In the group of patients who underwent primary transsphenoidal surgery (n = 4), complete removal was estimated by the surgeon in three cases. Intraoperative imaging depicted a remaining tumor in one case, leading to further tumor removal; however, follow-up revealed recurrent cysts. CONCLUSION: Intraoperative low-field MRI allows an ultraearly evaluation of the extent of tumor removal in craniopharyngioma surgery in most cases. Imaging showing an incomplete resection offers the chance for further tumor removal during the same operation. However, intraoperative low-field MRI depicting a complete resection does not exclude craniopharyngioma recurrence.

Adolescent↗
PubMed2003

Remote computing environment compensating for brain shift.

OBJECTIVE: Anatomical and functional image data become invalid during an operation due to brain shift. Compensation is achieved by using intraoperative imaging to update anatomical information. To accelerate the registration and visualization of pre- and intraoperative image data, the presented work focuses on remote computing capabilities. The underlying framework efficiently combines local desktop computers and remote high-end graphics workstations exploiting expensive hardware. METHODS: By performing all computations on the remote computer, the MR volumes are rigidly aligned via voxel-based registration. Using graphics hardware for acceleration, all interpolation operations are performed with 3D texture-mapping hardware. A new approach then transforms functional markers from preoperative measurements to the intraoperative situation using an automatic tracking algorithm to identify corresponding sulci. Communicating Java viewers are suggested for analyzing the results interactively on a local computer, with all calculations being performed exclusively on the remote computer. RESULTS: The suggested approach was successfully applied in 5 cases using MR data containing functional markers of MEG and fMRI measurements identifying eloquent brain areas. Remote large-scale graphics hardware was thereby efficiently made available for fast registration and interactive direct volume rendering in neurosurgery. CONCLUSION: Overall, the presented framework demonstrates efficient access of expensive high-end hardware remotely controlled by thin clients, and further emphasizes the need to compensate for brain shift in functional neuronavigation.

Brain↗
PubMed2002

Low-field magnetic resonance imaging for intraoperative use in neurosurgery: a 5-year experience.

The aim of this study was to evaluate the feasibility and point out the indications of intraoperative MR imaging in neurosurgical procedures. The MR imaging was performed using a 0.2-T scanner which was located in a radiofrequency-shielded operating theater. Three major setups for intraoperative imaging were possible: inside the scanner; at the 5-Gauss line; or in an adjacent operating theater. Additionally, in lesions adjacent to eloquent brain areas microscope- and pointer-based neuronavigation with integrated functional data was applied. Three hundred ten patients were investigated in the previous 5 years, among them gliomas ( n=95), pituitary tumors ( n=81), and 39 non-lesional cases in whom resective or disconnective epilepsy surgery was carried out. We did not observe any adverse effects due to intraoperative MR imaging. Image quality was sufficient to evaluate the extent of the tumor resection in the majority of cases. The main indications for intraoperative MR imaging were the evaluation of the extent of a resection in glioma, ventricular tumor, pituitary tumor, and in epilepsy surgery. Intraoperative MR imaging offers the possibility of further tumor removal during the same surgical procedure in case of tumor remnants, increasing the rate of complete tumor removal. Furthermore, the effects of brain shift, which would lead to inaccurate neuronavigation, can be compensated for by an update of the neuronavigation system with intraoperative MR image data.

Adult↗
PubMed2002

Use of intraoperative magnetic resonance imaging in tailored temporal lobe surgeries for epilepsy.

PURPOSE: We investigated whether intraoperative magnetic resonance imaging (MRI) was able to assess immediately the extent of a tailored temporal lobe resection for epilepsy in comparison to delayed postoperative MRI. The recently proposed concept of an individually tailored procedure, preserving tissue not involved in seizures, leads to a variety of differently shaped resections. METHODS: For intraoperative imaging we used a Magnetom Open 0.2 Tesla scanner. Fifty-eight patients undergoing temporal lobe resections for pharmacoresistant epilepsy were investigated. Half of these were nonlesional. All patients had delayed postoperative follow-up scans, which were compared with the intraoperative, postresection images. RESULTS: In 49 (84%) of 58 cases, intraoperative MRI depicted the resection cavity identical to delayed postoperative studies. Complete resection of the visible lesion was primarily proved in 23 of the 29 cases. In two patients with lesions and in one nonlesional case, the resection was extended after intraoperative imaging, thus increasing the rate of total resections in gliomas from 73 to 87%. In four patients, an extension into eloquent areas did not allow complete removal. In the nonlesional cases (n = 29), the extent of tailored temporal resections also could be exactly documented intraoperatively. CONCLUSIONS: Intraoperative MRI allowed a reliable evaluation of the localization and extent of resection in epilepsy surgery within the operative procedure. Furthermore, it provided the possibility of an image-based correction of an initially incomplete resection, particularly in lesional cases. In the majority of patients, the intraoperative images would have been able to replace delayed postoperative MRI. However, in 16%, there were postoperative changes in the resection volume.

Adolescent↗
PubMed2002

Co-registration of function and anatomy in frameless stereotaxy by contour fitting.

We investigated a co-registration algorithm using a contour-fitting procedure to integrate functional data from magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) for frameless stereotaxy. In fMRI the shape of the head was reconstructed from anatomical images, in MEG it was scanned using an electromagnetic sensor position indicator. Functional information was transferred to the 3D-MR image set used for frameless stereotaxy by fitting the digitized (MEG) and reconstructed head shape (fMRI) to the 3D-MR images. The mean residual error of the contour fit was 2.3 mm for the MEG and 1.3 mm for the fMRI registration. According to computer simulations, the achievable transformation error is 0.75 and 0.5 mm, respectively. This method enables independent recording of functional and anatomical measurements with a co-registration accuracy better than 2 mm.

Brain↗