Robert Wolff

Laser surface scanning for patient registration in intracranial image-guided surgery

OBJECTIVE To report our clinical experience with a new laser scanning-based technique of surface registration. We performed a prospective study to measure the calculated registration error and the application accuracy of laser surface registration for intracranial image-guided surgery in the clinical setting. METHODS Thirty-four consecutive patients with different intracranial diseases were scheduled for intracranial image-guided surgery by use of a passive infrared surgical navigation system. Surface registration was performed by use of a Class I laser device that emits a visible laser beam. The Polaris camera system (Northern Digital, Waterloo, ON, Canada) detects the skin reflections of the laser, which the software uses to generate a virtual three-dimensional matrix of the anatomy of each patient. An advanced surface-matching algorithm then matches this virtual three-dimensional matrix to the three-dimensional magnetic resonance therapy data set. Registration error as calculated by the computer was noted. Application accuracy was assessed by use of the localization error for three distant anatomic landmarks. RESULTS Laser surface registration was successful in all patients. For the surgical field, application accuracy was 2.4 ± 1.7 mm (range, 1–9 mm). Application accuracy was higher for the surgical field of frontally located lesions (mean, 1.8 ± 0.8 mm; n = 13) as compared with temporal, parietal, occipital, and infratentorial lesions (mean, 2.8 ± 2.1 mm; n = 21). CONCLUSION Laser scanning for surface registration is an accurate, robust, and easy-to-use method of patient registration for image-guided surgery.

Thirty years' experience with Gamma Knife surgery for metastases to the brain

OBJECT The aim of this study was to analyze factors influencing survival time and patterns of distant recurrences after Gamma Knife surgery (GKS) for metastases to the brain. METHODS Information was available for 1855 of 1921 patients who underwent GKS for single or multiple cerebral metastases at 4 different institutions during different time periods between 1975 and 2007. The total number of Gamma Knife treatments administered was 2448, an average of 1.32 treatments per patient. The median survival time was analyzed, related to patient and treatment parameters, and compared with published data following conventional fractionated whole-brain irradiation. RESULTS Twenty-five patients survived for longer than 10 years after GKS, and 23 are still alive. Age and primary tumor control were strongly related to survival time. Patients with single metastases had a longer survival than those with multiple metastases, but there was no difference in survival between patients with single and multiple metastases who had controlled primary disease. There were no significant differences in median survival time between patients with 2, 3-4, 5-8, or >8 metastases. The 5-year survival rate was 6% for the whole patient population, and 9% for patients with controlled primary disease. New hematogenous spread was a more significant problem than micrometastases in patients with longer survival. CONCLUSIONS Patient age and primary tumor control are more important factors in predicting median survival time than number of metastases to the brain. Long-term survivors are more common than previously assumed.

Subacute Stereotactic Aspiration of Haematomas within the Basal Ganglia Reduces Occurrence of Complications in the Course of Haemorrhagic Stroke in Non-Comatose Patients

Background and Purpose: Medical complications occurring after stroke of both ischaemic and haemorrhagic origin are frequent and constitute an important problem. The strongest factor predicting the occurrence of complications is known to be the initial neurological impairment level. The aim of this study was to examine whether subacute stereotactic aspiration of haematomas within the basal ganglia is suitable to reduce the occurrence of complications in the course of haemorrhagic stroke in non-comatose patients. Methods: Following rigorous selection criteria, 56 consecutive non-comatose patients were treated by subacute stereotactic evacuation of the haematomas. Glasgow Coma Scale (GCS) scores after initiation of treatment, medical complications, mortality and length of in-patient stay before discharge for further rehabilitative treatment were recorded for each patient and were compared with the results obtained in a comparable group of 39 patients treated purely medically in another hospital. Results: The level of consciousness improved markedly after stereotactic surgery, and GCS scores were significantly higher than those after pure medical treatment (p < 0.0001). In comparison with medical patients, complications were considerably fewer in the surgical group, and thus peri-ictal morbidity and mortality were significantly lower. Length of necessary treatment in the intensive care unit as well as total in-patient stay in the acute care facility were significantly reduced. Conclusions: Improving alertness, subacute stereotactic aspiration of deep-seated haematomas decreases occurrence of medical complications in the course of haemorrhagic stroke. Recovery can be accelerated, and patients are earlier suitable for further rehabilitative treatment.

Analyzing 3-tesla magnetic resonance imaging units for implementation in radiosurgery

OBJECT The limiting factor affecting accuracy during gamma knife surgery is image quality. The new generation of magnetic resonance (MR) imaging units with field strength up to 3 teslas promise superior image quality for anatomical resolution and contrast. There are, however, questions about chemical shifts or susceptibility effects, which are the subject of this paper. METHODS The 3-tesla MR imaging unit (Siemens Trio) was analyzed and compared with a 1-tesla unit (Siemens Magnetom Expert) and to a 1.5-tesla unit (Philips Gyroscan). Evaluation of the magnitude of error was performed within transverse slices in two orientations (axial/coronal) by using a cylindrical phantom with an embedded grid. Deviations were determined for 21 targets in a slab phantom with known geometrical positions within the stereotactic frame. Distortions caused by chemical shift and/or susceptibility effects were analyzed in a head phantom. Inhouse software was used for data analyses. The mean deviation was less than 0.3 mm in axial and less than 0.4 mm in coronal orientations. For the known targets the maximum deviation was 1.16 mm. By optimizing these parameters in the protocol these inaccuracies could be reduced to less than 1.1 mm. Due to inhomogeneities a shift in the z direction of up to 1.5 mm was observed for a dataset, which was shown to be compressed by 1.2 mm. CONCLUSIONS The 3-tesla imaging unit showed superior anatomical contrast and resolution in comparison with the established 1-tesla and 1.5-tesla units; however, due to the high field strength the field within the head coil is very sensitive to inhomogeneities and therefore 3-tesla imaging data will have be handled with care.

Multiple target aspiration technique for subacute stereotactic aspiration of hematomas within the basal ganglia

BACKGROUND Stereotactic surgery for deep-seated intracerebral hematomas as a minimally invasive procedure has gained wide acceptance, but debate continues to be controversial concerning the issue of how to aspirate a sufficient proportion of the hematoma with minimized risk for the patient. The objective of this paper is to present a modified stereotactic aspiration technique which complies saliently with both demands. METHODS The multiple target aspiration technique was used in a series of 64 consecutive patients with spontaneous hematomas within the basal ganglia. The results obtained with this technique were evaluated with particular regard to degree of aspiration and rate of recurrent hemorrhage and were compared with results achieved with stereotactic techniques utilizing physical fragmentation or chemical lysis of the clots. RESULTS Using this technique, it was feasible in one single surgical procedure to aspirate more than 80% of the hematoma volume in 73.4% of the patients. Mean degree of aspiration was 88.8%, and rebleeding occurred only once (1.6%). These results compare favorably with those achieved with application of intricate stereotactic techniques. CONCLUSION The multiple target aspiration technique performed in the subacute stage is a rapid and simple method for stereotactic removal of deep-seated hematomas and combines a high success rate with very low risk of recurrent hemorrhage.

Automated Fiducial Marker Detection for Patient Registration in Image-Guided Neurosurgery

Objective: The registration of applied fiducial markers within the preoperative data is often left to the surgeon, who has to identify and tag the center of each marker. This is both time-consuming and a potential source of error. For this reason, the development of an automated procedure was desirable. In this study, we have investigated the accuracy of a software algorithm for detecting fiducial markers within the navigation data set. The influence of adjustable values for accuracy and threshold on the sensitivity and specificity of the detection process, as well as the time gain, was investigated. Patients and Methods: One hundred MP-RAGE MRI data sets of patients with different pathologies who were scheduled for image-guided surgery were used in this study. A total of 591 applied fiducial markers were to be detected using the algorithm of the software VVPlanning 1.3 (BrainLAB, Heimstetten, Germany) on a Pentium II standard PC. The size value of a marker in the y-direction is called “accuracy” and depends on the slice thickness. “Threshold” describes the gray level above which the algorithm starts searching for pixel clusters. The threshold value was changed stepwise on the basis of a constant “accuracy” value. The “ccuracy” value was changed on the basis of that threshold value at which all markers were detected correctly. Results: The time needed for automatic detection varied between 12 s and 25 s. An optimum value for adjustable marker size was found to be 1.1 mm, with 8 undetected markers (1.35%) and 7 additionally detected structures (1.18%) out of 591. The mean gray level (Threshold) for all data sets above which marker detection was correct was 248.9. The automatic detection of markers was good for higher gray levels, with 11 missed markers (1.86%). Starting the algorithm at lower gray levels led to a decreased incidence of missed markers (0.17%), but increased the incidence of additionally detected structures to 27.92%. Conclusion: The automatic marker-detection algorithm is a robust, fast and objective instrument for reliable fiducial marker registration when used with optimum settings for both threshold and accuracy.

Basal ganglia haematomas in non-comatose patients: subacute stereotactic aspiration improves long-term outcome in comparison to purely medical treatment

This study examined whether subacute stereotactic evacuation of basal ganglia haematomas in primarily non-comatose patients is suitable to improve the ultimate outcome of this subgroup of stroke patients. Applying rigorous selection criteria, 56 consecutive non-comatose patients with ganglionic haematomas were treated stereotactically, and 1-year outcomes employing four outcome parameters commonly used to assess outcome were compared with those of 39 similar patients who were treated purely medically. No survival benefit was found in long-term follow-up for either surgical or conservative treatment (total mortality 16.1% vs 28.2%; P=0.121). Among survivors, however, outcome was significantly better in surgical patients. Compared with medical patients, the median Glasgow Outcome Scale score was 1 point higher (P<0.0001) in surgical patients, and the median European Stroke Scale score improvement from baseline to 1-year score was significantly better (P<0.0001). Accordingly, the median Barthel Index score was significantly higher (P=0.002), and the median Modified Rankin Scale score was 1 point lower (P<0.0001). We conclude that primarily non-comatose patients with basal ganglia haematomas can ultimately profit from this form of minimally invasive treatment.

Glioblastoma Multiforme of the Brain Stem in a Patient with Aquired Immunodeficiency Syndrome

Summary. Glioblastoma of the brain stem is rare and there is no description of such a lesion in patients suffering from aquired immunodeficiency syndrome. The majority of intracerebral mass lesions are due either to toxoplasmosis or primary central nervous system lymphomas so that it is usually not included in the differential diagnosis of enhancing lesions of the central nervous system in these patients. A 31-year-old human immunodeficiency virus (HIV) infected man presented with a four months history of slowly progressive deterioration of brainstem associated symptoms despite antitoxoplasmic therapy. Magnetic resonance imaging revealed a large ring enhancing lesion in the brainstem. Clinical and neuroradiolagical data could not establish a proper diagnosis and a stereotactic serial biopsy was undertaken. Histological examination of the specimen showed a glioblastoma multiforme (GBM) as the first reported case of GBM located in the brainstem in an aquired immunodeficiency syndrome (AIDS) patient. Patient management and effectiveness of stereotactic serial biopsy are discussed.

Palliative Occipito-Cervical Stabilization in Patients with Malignant Tumors of the Occipito-Cervical Junction and the Upper Cervical Spine

Summary.Summary. Background: Occipital-cervical stability may be impaired in patients with primary malignant or metastatic tumors of the cranio-cervical junction and the upper cervical spine. The purpose of this study was to evaluate occipital-cervical fixation with prebended titanium-loops and sublaminar wiring in order to achieve a rigid and safe stabilisation of the occipito-cervical region in this group of patients. Method: 20 patients with severe impairment of occipito-cervical stability due to primary malignant or metastatic cervical bone involvement were included in this study. For palliation of symptoms, resulting from destructive instability, a stabilization procedure using Ransford Loops with sublaminar cable fixation was used in these patients as a palliative therapeutic concept. Findings: Pain which was the major symptom in all patients treated, showed good and immediate response to the stabilization procedures. All 20 patients were either pain free or had good improvement with less intake of analgesic drugs. Signs of spinal cord compression like spasticity and quadraparesis were less likely to improve after surgery. However in 3 of 5 patients neurological function improved after surgery whereas in 2 patients no improvement was achieved. Interpretation: In all patients with impaired occipito-cervical stability due to primary malignant or metastatic tumors of the occipito-cervical junction and the upper cervical spine, immediate stabilization resulting in an improvement of pain was achieved. Occipito-cervical stabilization using contoured Ransford loops is a promising palliative therapeutic concept in this group of patients.

Pertreatment radiation induced oedema causing acute hydrocephalus after radiosurgery for multiple cerebellar metastases.

Summary¶Background. Most complications of radiosurgery occur after 6–12 months and some long term complications up to after 5–10 years. Although severe, immediate side effects are rare, we report a patient who shows that this possibility should be taken into account when large volumes are treated especially in the posterior fossa.Case report. A patient was treated with radiosurgery for multiple brain metastases, of which 5 were located in the posterior fossa. Deterioration occurred, radiosurgery was halted abortion and CT showed acute hydrocephalus caused by a significant edema in the posterior fossa, not present in an MR examination performed some 6 hours earlier. After intubation and external ventricular CSF drainage, a permanent shunt was inserted, the edema resolved, and the patient recovered to her pretreatment condition within 10 days. The remaining metastases were treated during the first session and MR images showed the hydrocephalus resolved when all the radiated tumors had significantly decreased in size.Interpretation. Care should be taken when treating with radiosurgery patients posterior fossa metastases and signs of compressed CSF pathways. Exceptionally, an acute radiation induced edema could result in a block of the CSF pathways, necessitating a surgical intervention. Prophylactic shunt insertion or hospitalization the night following the treatment should be considered.