Christos Trantakis

Intraoperative MRI to guide the resection of primary supratentorial glioblastoma multiforme—a quantitative radiological analysis

Patients with supratentorial high-grade glioma underwent surgery within a vertically open 0.5-T magnetic resonance (MR) system to evaluate the efficacy of intraoperative MR guidance in achieving gross-total resection. For 31 patients, preoperative clinical data and MR findings were consistent with the putative diagnosis of a high-grade glioma, in 23 cases in eloquent regions. Tumor resections were carried out within a 0.5-T MR SIGNA SP/i (GE Medical Systems, USA). The resection of the lesion was carried out using fully MR compatible neurosurgical equipment and was stopped at the point when the operation was considered complete by the surgeon viewing the operation field with the microscope. We repeated imaging to determine the residual tumor volume only visible with MRI. Areas of tissue that were abnormal on these images were localized in the bed of resection by using interactive MR guidance. The procedure of resection, imaging control and interactive image guidance was repeated where necessary. Almost all tissue with abnormal characteristics was resected, with the exception of tissue localized in eloquent brain areas. The diagnosis of glioblastoma was confirmed in all 31 cases. When comparing the tumor volume before resection and at the point where the neurosurgeon would otherwise have terminated surgery (“first control”), residual tumor tissue was detectable in 29/31 patients; the mean residual tumor volume was 30.7±24%. After repeated resections under interactive image guidance the mean residual tumor volume was 15.1%. At this step we found tumor remnants only in 20/31 patients. The perioperative morbidity (12.9%) was low. Twenty-seven patients underwent sufficient postoperative radiotherapy. We found a significant difference (logrankp=0.0037) in the mean survival times of the two groups with complete resection (n=10, median survival time 537 days) and incomplete resection (n=17, median survival time 237 days). The resection of primary glioblastoma multiforme under intraoperative MR guidance as demonstrated is a possibility to achieve a more complete removal of the tumor than with conventional techniques. In our small but homogeneous patient group we found an increase in the median survival time in patients with MRI for complete tumor resection, and the overall surgical morbidity was low.

Open MRI-Guided Neurosurgery

Summary Objectives. A number of different image-guided surgical techniques have been developed during the past decade. None of these methods can provide the surgeon with information about the dynamic changes that occur intra-operatively. Material and Method. The first vertical open 0.5 T MRI-scanner for intra-operative MRI-guided neurosurgery in Germany was installed at the University of Leipzig during the summer 1996. Since autumn 1996 a number of surgical procedures including biopsies (n=31), craniotomies (n=32), transsphenoidal procedures (n=8) and interstitial lasertherapies (n=3) have been performed using intra-operative MR image guidance. Results. The development of MR-compatible and MR-safe non-magnetic instruments and components had to be solved. Specific surgical instruments were developed to perform biopsies, craniotomies, microsurgical tumour resections and transsphenoidal procedures in the 0.5-T open MRI. Several components required adaptation including the head holder, the stereotactic navigation device, the high speed drill, the suction unit, the ultrasonic aspirator, the bipolar coagulation, the laser probe and the surgical microscope. All these newly developed technical features enable the neurosurgeon to perform a large number of surgical procedures under direct control and guidance of intra-operative MR imaging. In contrast to frame-based for framless navigation systems, intra-operative MRI provides accurate and immediate information during the progress of surgery. These intra-operative images allow definitive localization and targeting of the lesions and accommodate anatomical changes that may occur during surgery. Conclusion. Intra-operative MRI is helpful for navigation as well as determining of tumour margins to achieve a complete and safe resection of intracranial lesions. Complications related to the surgical procedure are reduced and the risk of neurological deterioration due to tumour removal and postoperative complications is minimized. It can be concluded that the intra-operative application of interventional MRI technology may represent a major step forward in the field of neurosurgery.

The navigation-controlled drill in temporal bone surgery: a feasibility study.

Background: This study examines the feasibility of a navigation‐controlled (NC) drill for surgery on the petrosal bone in an experimental environment. According to the principle of NC, the drill is to be switched off automatically once the borders of the workspace are exceeded during a mastoidectomy.

Evaluation of a navigation system for ENT with surgical efficiency criteria

The aim of this study is the evaluation of a navigation system (NaviBase) for ENT surgery. For this purpose, a new methodology for the evaluation of surgical and ergonomic system properties has been developed. The practicability of the evaluation instruments will be examined using the example of the overall assessment of the system in comparison with the current surgical standard and with other systems using clinical efficiency criteria. The evaluation is based on 102 ENT surgical applications; of these, 89 were functional endoscopic sinus surgeries (FESS). The evaluation of surgical and ergonomic performance factors was performed by seven ENT surgeons. To evaluate surgical system properties, the Level of Quality (LOQ) in 89 cases of the FESS was determined. It compares the existing information of the surgeon with that of the navigation system on a scale of 0 to 100 and with a mean value of 50 and places it in a relationship to the clinical impact. The intraoperative change of the planned surgical strategy (Change of Surgical Strategy) was documented. The ergonomic factors of the system with the categories of Overall Confidence (Trust), awareness of the situation (Situation Awareness), influence on the operating team, requirements for specific skills (Skill Set Requirement), and cognitive load (Workload Shift) were recorded for all surgical procedures as Level of Reliance (LOR). In the evaluation of the surgical system properties, an average evaluation of the quality of the information, as an LOQ of 63.59, resulted. Every second application of the navigation system (47.9%), on average, led to a change in the surgical strategy. An extension/enhancement of the indication of the endonasal approach through the use of the navigation system was shown in 7 of 102 (6.8%) cases. The completion of the resection in the FESS was rated by 74% of group I and 11% of group II as better in comparison with the standard approach. Total confidence shows a positive evaluation of 3.35 in the LOR. To supplement the evaluation of the navigation system, the technical parameters were included. The maximum deviation, Amax, of the displayed position of the reference value amounted to 1.93 mm. The average deviation was at 1.29 mm with an SD above all values, sd, of 0.29. The subsequent economic evaluation resulted in an effective average extra expenditure of time of 1.35 minutes per case. The overall evaluation of the system imparts application‐relevant information beyond the technical details and permits comparability between different assistance systems.

Investigation of time-dependency of intracranial brain shift and its relation to the extent of tumor removal using intra-operative MRI

Abstract The object of the paper is to investigate intra-operative brainshift and its relation to the extent of tumor removal. Repeated T1w 3D datasets were acquired at different time points intra-operatively (T0; T1; T2... Tx) using a vertical open 0.5T MR scanner in six patients with intracranial tumor. An offline analysis with initial linear registration, intensity adjustment and finally nonlinear registration of the first versus subsequent time points (T0/T1; T0/T2... T0/Tx) was performed, yielding a 3D displacement vector field that describes the brainshift. Brainshift was analysed qualitatively and quantitatively. A semi-automatic segmentation technique was used for calculation of the tumor size and the size of tumor remnants. Semi-automatic segmentation was reliable in all but two cases. Segmentation was difficult and unreliable in astrocytomas grade II. The shift basically followed gravity. The major shift reached levels up to 25 mm. Significant shift was observed at the first time point (T0). Intra-operative brainshift can be analysed qualitatively and also captured quantitatively. Neuronavigation that is based on pre-operatively acquired datasets is associated with a significant risk of surgical morbidity at a very early time point. Parallelisation on a workstation cluster may reduce computation time so that information about the displacement can facilitate updated navigation.

RECORDING OF SURGICAL PROCESSES: A STUDY COMPARING SENIOR AND JUNIOR NEUROSURGEONS DURING LUMBAR DISC HERNIATION SURGERY

BACKGROUND: Evaluating surgical practice in the operating room is difficult, and its assessment is largely subjective. OBJECTIVE: Recording of standardized spine surgery processes was conducted to ascertain whether any significant differences in surgical practice could be observed between senior and junior neurosurgeons. METHODS: Twenty-four procedures of lumbar discectomies were consecutively recorded by a senior neurosurgeon. In 12 cases, surgery was entirely performed by a senior neurosurgeon with the aid of a resident, and in the 12 remaining cases, surgery was performed by a resident with the aid of a senior neurosurgeon. The data recorded were general parameters (operating time for the whole procedure and for each step), and general and specific parameters of the surgeons activities (number of manual gestures, number and duration of actions performed, use of the instruments, and use of interventions on anatomic structures). The Mann-Whitney U test was used for comparison between the 2 groups of neurosurgeons. RESULTS: The operating time was statistically lower for the group of senior surgeons. The seniors statistically demonstrated greater economy in time and in gestures during the closure step, for sewing and for the use of scissors, needle holders, and forceps. The senior surgeons statistically worked for a shorter time on the skin and used fewer manual gestures on the thoracolumbalis fascia. The number of changes in microscope position was also statistically lower for this group. CONCLUSION: There is a relationship between surgical practice, as determined by a method of objective measurement using observation software, and surgical experience: gesture economy evolves with seniority.

Advanced approach for intraoperative MRI guidance and potential benefit for neurosurgical applications.

To present an advanced approach for intraoperative image guidance in an open 0.5 T MRI and to evaluate its effectiveness for neurosurgical interventions by comparison with a dynamic scan‐guided localization technique.

Iterative neuronavigation using 3D ultrasound. A feasibility study.

Abstract Intra-operative ultrasound (iUS) can generate 2D images in real-time as well as near real-time 3D datasets of the current situation during an intervention. Tracked ultrasound can locate the images in 3D space and relate them to patient, devices, and pre-operative planning data. Therefore, tracked US is an efficient means for controlling the validity of pre-operative planning, recognition of changes (brain shift) during the intervention, replanning of the operational path due to situational changes (iterative navigation), and finally, controlling the results (residual tumor). This paper describes a neuronavigation system exploiting this potential of interventional tracked US for permanent control of intervention progress and iterative adaptation of the planned procedure to the current situation.

Open MRI-guided microsurgery of intracranial tumours in or near eloquent brain areas

Summary Objectives. Preservation of brain function while maximizing resection is the main aim of brain tumour surgery. The purpose of this study was to evaluate the efficacy of intra-operative magnetic resonance imaging to preserve brain function in patients with tumours in or near eloquent brain areas. Methods and Material. Between August 1997 and January 1999 fifty-eight craniotomies for intracranial tumours or vascular malformations have been performed at the University of Leipzig using a 0.5 T superconducting MR system “SIGNA SP” (General Electric Medical Systems, USA). In 32 of these patients (15 male/17 female) with intracranial tumours, located in or near eloquent brain areas (sensorimotor cortex/speech center), 34 craniotomies were performed using the image guidance of the interventional MRI. Results. Using intra-operative MRI criteria, complete tumour removal could be achieved in 28 (82%) of 34 procedures. In 3 patients only subtotal tumour removal was possible, because the residual tumour was not visible on the intra-operative MR images, but could be identified on early diagnostic follow-up MR-scans. In 3 patients, incomplete tumour resection was performed in order to avoid neurological impairment. In these patients intra-operative MR-images revealed residual tissue abnormalities involving or encroaching on deep brain structures or motor/language cortex. Pre-operative neurological status was unchanged in 24 patients (70%), worsened in 4 patients (12%) and improved in 6 patients (18%). Conclusions. Intra-operative MRI is helpful for navigation as well as to demonstrate the tumour margins to achieve a complete and safe resection of intracranial lesions located in or near eloquent brain areas. It enables an image based functional monitoring of the brain which is critical for motor, sensory or language function. Complications related to the surgical procedure are reduced and the risk of neurological deterioration due to tumour removal and postoperative complications is minimized.

Fundamentals of Force Feedback and Application to a Surgery Simulator

Force feedback increases the effectiveness of virtual-reality surgery training systems. An overview of the fundamentals of applying force feedback is presented. An impedance control technique and data processing methods for stability preservation are illustrated. A flexible interface for general force-feedback applications has been developed. This interface is capable of controlling several different force-feedback hardware systems, including the SensAble PHANTOM, the Laparoscopic Impulse Engines from Immersion, and the VS-One virtual endoscopic surgery trainer. The findings are evaluated using the main simulation system, KISMET, and the modeling tools KISMO and VESUV. Within the scope of a cooperative project called HapticIO (funded by the German Ministry of Education and Research [BMBF]), new haptic devices have been designed for virtual neuroendoscopy and laparoscopy. The concept and implementations presented in this paper have been found to be flexible, stable and suitable for universal use. The impedance method, combined with the open-loop feed-forward control technique, is well suited and appropriate for the task.