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A Muacevic

Publications and source records attributed to A Muacevic.

At least 19 recordsLinked to original sources
PubMed2006

Functional outcome after gamma knife treatment in vestibular schwannoma.

Radiosurgery (RS) is a noninvasive, ambulatory special neurosurgical procedure for the treatment of vestibular schwannoma (VS). We treated 123 patients with unilateral schwannomas between 1994 and 2000 at the gamma knife (GK) center in Munich using a primary stereotactic procedure. These patients were followed up until June 2004 in respect to audiological, neurological, neurootological and radiological features before and after radiosurgical intervention. The actual tumor control rate of 8.2 years (mean) after GK surgery for all patients and a single treatment was calculated to be 96.7%. The impairment of hearing was on average 18% after GK, ranking from 0% gain of hearing loss up to 90%. Facial nerve function, graded according to the House-Brackmann scale, deteriorated in none of the patients; 5.8% reported a trigeminal neuralgia. Tinnitus developed in 4.1% of the patients after RS; 13.3% had vertigo for the first time after the treatment, age apparently being a predisposing factor. Radiosurgical treatment for VS is an alternative to microsurgery (MS). It is associated with a lower rate of facial and trigeminal neuropathy, postoperative complications and hospital stay. The hearing preservation rate is equivalent to MS.

Adult↗
PubMed2005

Quality assurance in stereotactic radiosurgery/radiotherapy according to DIN 6875-1.

The new DIN ('Deutsche Industrie-Norm') 6875-1, which is currently being finalised, deals with quality assurance (QA) criteria and tests methods for linear accelerator and Gamma Knife stereotactic radiosurgery/radiotherapy including treatment planning, stereotactic frame and stereotactic imaging and a system test to check the whole chain of uncertainties. Our existing QA program, based on dedicated phantoms and test procedures, has been refined to fulfill the demands of this new DIN. The radiological and mechanical isocentre corresponded within 0.2 mm and the measured 50% isodose lines were in agreement with the calculated ones within less than 0.5 mm. The measured absorbed dose was within 3%. The resultant output factors measured for the 14-, 8- and 4-mm collimator helmet were 0.9870 +/- 0.0086, 0.9578 +/- 0.0057 and 0.8741 +/- 0.0202, respectively. For 170 consecutive tests, the mean geometrical accuracy was 0.48 +/- 0.23 mm. Besides QA phantoms and analysis software developed in-house, the use of commercially available tools facilitated the QA according to the DIN 6875-1 with which our results complied.

Quality Control↗
PubMed2005

Image guided interstitial laser thermotherapy: a canine model evaluated by magnetic resonance imaging and quantitative autoradiography.

OBJECTIVE: To determine the applicability and safety of a new canine model suitable for correlative magnetic resonance imaging (MRI) studies and morphological/pathophysiological examination over time after interstitial laser thermotherapy (ILTT) in brain tissue. MATERIAL AND METHODS: A laser fibre (Diode Laser 830 nm) with an integrated temperature feedback system was inserted into the right frontal white matter in 18 dogs using frameless navigation technique. MRI thermometry (phase mapping i.e. chemical shift of the proton resonance frequency) during interstitial heating was compared to simultaneously recorded interstitial fiberoptic temperature readings on the border of the lesion. To study brain capillary function in response to ILTT over time quantitative autoradiography was performed investigating the unidirectional blood-to-tissue transport of carbon-14-labelled alpha amino-isobutyric acid (transfer constant K of AIB) 12, 36 hours, 7, 14 days, 4 weeks and 3 months after ILTT. RESULTS: All laser procedures were well tolerated, laser and temperature fibres could be adequately placed in the right frontal lobe in all animals. In 5 animals MRI-based temperature quantification correlated strongly to invasive temperature measurements. In the remaining animals the temperature fibre was located in the area of susceptibility artifacts, therefore, no temperature correlation was possible. The laser lesions consisted of a central area of calcified necrosis which was surrounded by an area of reactive brain tissue with increased permeability. Quantitative autoradiography indicated a thin and spherical blood brain barrier lesion. The magnitude of K of AIB increased from 12 hours to 14 days after ILTT and decreased thereafter. The mean value of K of AIB was 19 times (2 times) that of normal white matter (cortex), respectively. CONCLUSION: ILTT causes transient, highly localised areas of increased capillary permeability surrounding the laser lesion. Phase contrast imaging for MRI thermomonitoring can currently not be used for reliable temperature readings in vivo. The suggested new canine model proved to be safe, accurate, easy to use, and provides clinical, radiographic, pathological and physiological correlations.

Aminoisobutyric Acids↗
PubMed2004

Special indications in gamma knife surgery.

Pilocytic astrocytoma (PA) represent a rare indication for Gamma Knife Surgery. Mostly small remnants after surgical debulking are treated. The prognosis depends on specific variants of biological and clinical criteria. In this regard we differentiated two groups of tumors; the so-called 'typical' tumors with a histological grading of WHO Grade I, no prior fractionated radiotherapy and no cystic component and the so called 'atypical' tumors with either a malignant transformation, previous fractionated radiotherapy and/or cystic components. The outcome after GKS was much more favourable for typical PA than for atypical. In typical cases a high tumor control with a very low risk of side effects can be achieved.

Adolescent↗
PubMed2004

Clinical quality standards for gamma knife radiosurgery--the Munich protocol.

The clinical quality standards for outpatient gamma knife radiosurgery as developed in the German Gamma Knife Center Munich during the last ten years are described. The following aspects have been taken into account: appropriate patient selection, standardised treatment cycle, acquisition of high-quality stereotactic MR images, the integrated therapeutic concept, dose conformity and dose level, patient follow-up, quality control and scientific data analysis. Particular emphasis has been put on the importance of the interdisciplinary treatment concept by subspecialised experts. The results of the Munich concept in consideration of the described quality standards verifies that gamma knife radiosurgery is a safe and effective treatment option for well selected indications.

Ambulatory Surgical Procedures↗
PubMed2004

Gamma knife radiosurgery for nonfunctioning pituitary adenomas.

The efficacy of gamma knife radiosurgery (GKS) for non-functioning pituitary adenomas (NPAs) has been assessed. Sixty patients with NPA were treated by GKS. Complete neurological and endocrinological follow-up information was available for 51 patients. Follow-up examinations included stereotactic magnetic resonance imaging for sequential measurements of the NPA volume. The median dose to the tumor margin was 16.5 Gy (range 11-20 Gy). The mean prescription isodose was 50% (range 45-75%). All patients underwent surgery for NPA before GKS. Fractionated radiotherapy was not applied. Median follow up after GKS was 21,7 months. Actuarial recurrence-free survival was 95% after three years with respect to a single GKS and 100% for patients who underwent repeated GKS. No neurological side effects were detected. Two patients developed new partial pituitary insufficiency after radiosurgery. Postoperative GKS for residual or recurrent small fragments of NPAs is an effective and safe treatment option. The follow-up examination for NPAs should include tumor volumetric analysis.

Actuarial Analysis↗
PubMed2004

Results of outpatient gamma knife radiosurgery for primary therapy of acoustic neuromas.

Stereotactic radiosurgery (SRS) has been recognized as a non-invasive alternative to surgery for the treatment of acoustic neuromas. Purpose of the current study was to define the impact of outpatient gamma knife radiosurgery (GKS) for patients with unilateral sporadic acoustic neuromas treated within ten years. Follow-up images were analyzed using tumor volume measurements. 219 patients with sporadic acoustic neuromas were treated by GKS as primary therapy. Patients with NF-2 tumors were excluded. Patients were eligible for GKS up to a size limit of 12.5 cm3. The median follow up time was 6 years after radiosurgery. The local tumor control rate was high (97%). Cranial nerve morbidities were comparably low. 10% of the patients developed hearing loss after radiosurgery and one patient experienced a transient facial neuropathy (0.5%). Transient trigeminal neuropathy developed in 12 patients (5%) and was found to be dependent on the tumor size before treatment. Outpatient gamma knife radiosurgery is a safe and effective treatment method for selected patients with sporadic vestibular schwannomas.

Ambulatory Surgical Procedures↗
PubMed2004

[MRI-assisted thermometry for regional hyperthermia and interstitial laser thermotherapy].

PURPOSE: To demonstrate the potential of quantitative MRI-assisted thermometry for the treatment of tumor patients with regional hyperthermia (RHT) and interstitial laser thermotherapy (ILTT). METHODS: Two patients and seven tissue samples were investigated using the T1-relaxation time and the chemical shift of the proton resonance frequency (PRF) as temperature sensitive MRI-parameters at 0.2 and 1.5 T. Thermotherapy was applied using either a dedicated MRI-hyperthermia hybrid system or a temperature controlled laser with 830 nm. RESULTS: Both patients were treated successfully showing clinical benefit. T1 and PRF are depending on the applied thermotherapy method and on the MR-system suitable for MRI-assisted thermometry. The clinical application based on phantom results is not necessarily adequate. CONCLUSION: Clinical application and phantom experiments of RHT and ILTT show the potential of MRI-assisted thermometry for further improvement of both minimal invasive thermotherapy methods. Further investigations concerning optimization of the MRI-techniques, the influence of perfusion or the determination of threshold values are necessary.

Adult↗
PubMed2004

Stereotactic radiosurgery without radiation therapy providing high local tumor control of multiple brain metastases from renal cell carcinoma.

The aim of this study was to analyse treatment effects after stereotactic radiosurgery (SRS) without whole brain radiation therapy (WBRT) as primary treatment for patients harboring brain metastases of renal cell carcinoma (RCC). During an 8-year period, 85 patients with 376 brain metastases from RCC underwent 134 outpatient SRS procedures. 65 % of all patients had multiple brain metastases. The median tumor volume was 1.2 cm (3) (range: 0.1 - 14.2 cm (3)). Mean prescribed tumor dose was 21.2 (+/- 3.2) Gy. Local/distant tumor recurrences were treated by additional SRS in cases of stable systemic disease. Overall median survival was 11.1 months after SRS. The local tumor control rate after SRS was 94 %. Most patients (78 %) died because of systemically progressing cancer. A KPS > 70 and RTOG class I were related to prolonged survival time. Patients of the RTOG groups I, II and III survived for 24.2 months, 9.2 months and 7.5 months, respectively. There was no permanent morbidity after SRS. 11 patients (12.9 %) showed transient radiogenic complications and 3 patients (3.5 %) died because of intratumoral bleedings after SRS. Stereotactic radiosurgery alone achieves excellent local tumor control rates for patients with small brain metastases from renal cell carcinoma.

Adult↗
PubMed2003

[Significance of stereotactic biopsy for the management of WHO grade II supratentorial glioma].

OBJECTIVE: The aim of this prospective study was to compare the diagnostic value of magnetic resonance imaging (MRI) and stereotactic biopsy in patients harboring WHO grade II gliomas. METHODS: Stereotactic biopsy was performed in 62 adult patients with low-signal, nonenhancing, space-occupying lesions on T1 MR imaging between 1998 and 2001. The results of histological analysis were compared to the preoperative imaging diagnoses. Any adverse perioperative sequel was considered as morbidity. Applied treatment strategies are described. RESULTS: Transient perioperative morbidity for the stereotactic approach was 4.8% (three patients), and there was no mortality or permanent morbidity. In four patients, neoplastic lesions could be excluded (gliosis: three patients, encephalitis: one), and WHO grade III gliomas were seen in five patients (14.8.% false positive rate of neurodiagnostic imaging). The diagnostic reliability of stereotactic biopsy was 96.8%. The following treatment strategies were initiated: microsurgery (17 patients), interstitial radiosurgery (12 patients), combination of microsurgery and interstitial radiosurgery (21 patients), external beam irradiation (six patients),and chemotherapy (two patients). Four patients were initially not treated. CONCLUSIONS: Diagnostic neuroimaging is not sufficient for the planning of rational treatment strategies in patients harboring WHO grade II gliomas. Frame-based stereotactic biopsy is a prerequisite for individualized treatment strategies.

Adult↗
PubMed2003

Neuronavigation based on CT angiography for surgery of intracranial aneurysms: primary experience with unruptured aneurysms.

Several reports have demonstrated the use of three-dimensional (3D) computed tomographic angiography (CTA) for preoperative planning in patients with intracranial aneurysms. Until now, there are no reports on the potential role of navigation systems in combination with CTA in aneurysm surgery. In the present study we report our experience with neuronavigation based on CTA in 16 patients with unruptured anterior circulation aneurysms for 1) planning craniotomy; 2) guided approach to the aneurysm; and 3) 3D presentation of the aneurysm and adjacent arteries in correct orientation. The reconstructed CTA images were analyzed preoperatively with regard to diameter of aneurysm neck and dome as well as projection and possible daughter aneurysms, and these parameters were compared with the intraoperative findings. In addition the accuracy of the navigator to locate the aneurysm neck was measured intraoperatively. Navigated approach planning resulted in variable keyhole craniotomies for the 7 middle cerebral artery aneurysms, but did not result in deviation from small standard craniotomies for the internal carotid and anterior communicating artery aneurysms. Precision of the indication of the navigator with regard to the aneurysm neck ranged from < 1 mm to 4 mm. Intraoperative assessment confirmed the CTA data with regard to aneurysm size and projection in all, and definition of daughter aneurysms and adjacent arteries in most cases. The computer assisted approach allowed a smaller, exactly placed craniotomy primarily in MCA aneurysms. 3D presentation of the aneurysms and the adjacent arteries in correct orientation facilitated identification and dissection the aneurysms. Current navigation systems are not precise enough to allow "blind" aneurysm clipping by placing a real clip on the virtual aneurysm neck.

Adult↗
PubMed2001

[Brain protective interstitial laser thermotherapy. Therapy of brain tumors without secondary damage].

The purpose of interstitial radiosurgery is to deliver a necrotizing dose of heat to an accurately defined focal area without damaging adjacent healthy brain tissue. To achieve this, heat at a temperature of 60-100 degrees C is applied via a laser fiber placed stereotactically in the center of the tumor. With the aid of thermosensitive magnetic resonance imaging (MRI), not only can the heat distribution within and around the tumor be measured during treatment, but also the extent of the lesion produced assessed. Interstitial laser thermotherapy (ILTT) performed under MRI monitoring, could become an important interdisciplinary minimally invasive treatment option for patients with brain tumors. Experimental data on the biological effects of interstitial laser therapy on normal brain tissue are not yet available, and only preliminary clinical studies investigating the effects of laser energy on brain tumors have so far been carried out. This overview presents a description of our own initial results, discusses the present state of our knowledge and current possibilities and limitations of this new treatment modality.

Brain↗
PubMed2001

The risk of haemorrhage after image guided stereotactic biopsy of intra-axial brain tumours--a prospective study.

OBJECTIVE: To analyze prospectively the frequency and the risk of symptomatic and asymptomatic haemorrhage after image guided stereotactic biopsy of intra-axial brain tumours. METHODS: The study was conducted within a time frame of 24 months (April 1998-April 2000). 326 patients (150 males, 176 females; mean age 56.8 years) were included and 345 computerized tomography (CT)-guided stereotactic biopsies were performed/supervised by a specialized stereotactic neurosurgeon. A modified Riechert Stereotaxy System and a workstation for multiplanar trajectory planning were used in all patients. Serial biopsies (median, 5 samples) were done with small forceps (diameter 1 mm), smear preparations of the biopsy specimens were intra-operatively examined. Frequency, size, and location of any detectable bleeding were analyzed by post-biopsy CT-scan investigation. For risk estimation, logistic regression analysis was performed. The chi-square statistic was used for comparative analysis of the study results with available data from the literature. RESULTS: A conclusive tissue diagnosis could be achieved in 98%. Overall treatment morbidity was 3.1%. There was no mortality. Haemorrhage related morbidity was 0.9%. Age, Karnofsky score, mass effect of the tumour, tumour histology, tumour location and the number of specimens taken did not have any prognostic significance. The clinically silent bleeding rate was 9.6% and more often seen in patients with high grade gliomas (p = 0.03). Both the silent and non-silent bleeding rate were significantly lower as compared to available prospective data in the literature (p < 0.01). CONCLUSION: Using multiplanar image guided trajectory planning, small biopsy forceps and intra-operative smear preparations the risk of major haemorrhage related morbidity after stereotactic brain tumour biopsy is extremely low (<1%) in experienced hands.

Adolescent↗
PubMed2000

[When the computer is assisting the surgeon... Navigation systems will also find small brain metastases].

Intra-operative localization systems are increasingly being used in cranial and spinal surgery as orientation aids for the surgeon. The latest of these systems operates without the need for a mechanical or an electrical link between the surgical wound and the computer workstation in the operating room. Since both emission and detection of infrared light are handled by a special camera system, the use of such aids means maximum flexibility for the surgeon. Thus, in contrast to conventional systems, no additional electric cables or mechanical devices that may interfere with the surgeon's freedom of movement, are present. This overview article provides a short description of the technology, and discusses the experience gained with, and the results obtained in, 142 cranial and spinal neurosurgical procedures performed with the aid of the new neuro-navigation system.

Brain Neoplasms↗
PubMed2000

Accuracy and clinical applicability of a passive marker based frameless neuronavigation system.

A passive marker system permits the inclusion of an unlimited number of instruments and other devices during frameless stereotaxy. The aim of this study was to evaluate the accuracy and clinical applicability of a passive marker based frameless image guided system (VectorVision; BrainLab, Heimstetten, Germany) developed for surgical planning and intraoperative image guidance. The system was first applied to a plastic phantom to determine the accuracy of the system by measuring the difference between the actual probe position and its analogous position on the monitor screen. The navigational device was subsequently applied to 40 procedures for brain tumours and cavernomas. The mean error value between the image on the monitor screen and the real location in the phantom and the clinical study was 1.45 mm (+/-0.99) and 4.05 mm (+/-3.62), respectively. Many different instruments could be employed as pointing devices. It was helpful in minimising the size of the craniotomy. An average lengthening of the surgical procedure of 20 minutes was experienced. The neuronavigation system proved to be a useful surgical tool to approach and detect lesions larger than 5 mm in diameter. The passive marker technology is intuitive and enables the surgeon to use his or her own instruments at any time as a pointing device, thus avoiding further costs for specially designed surgical equipment.

Adult↗
PubMed1999

Image-guided endoscopic ventriculostomy with a new frameless armless neuronavigation system.

OBJECTIVE: Complications resulting from imprecise placement of the ventriculoscope and reduced visibility through the endoscopic lens under certain conditions during third ventriculostomy have been reported in the literature. The following is a report of our first experience with image-guided endoscopic ventriculostomy. MATERIALS AND METHODS: Between September 1996 and October 1997, 11 patients diagnosed with aqueduct stenosis were found to be eligible for image-guided neuroendoscopy. The image-guided system (BrainLab, Heimstetten, Germany) links a freehand probe, tracked by a passive-marker sensor system, to a virtual computer image space. A 4-mm rigid ventriculoscope (Storz Instruments GMBH, Tuttlingen, Germany) was used. RESULTS: Eight patients improved clinically directly after surgery, two patients stabilized, and one patient improved only after insertion of an additional ventriculo-peritoneal shunt. The computer- calculated registration accuracy ranged from 1. 1 to 3.1 mm (median 1.4 mm) using 3-mm computed tomographic slices. The accuracy of the tool tip calibration for the endoscope was in the range of 0.35-0.9 mm (mean = 0.47 +/- 0.21). The described technique provided maximal flexibility for the surgeon and helped in performing a safe and accurate endoscopical procedure. CONCLUSIONS: Although not all cases of ventriculostomy require additional image guidance, we found the technique to be helpful in patients with atypical or large ventricles, in cases where orientation became difficult owing to bloody or blurry cerebrospinal fluid, and in patients with small foramina of Monroe, where the entrance angle of the endoscope needs precise definition for an atraumatic procedure to be performed.

Adolescent↗