J.-P. Schneider

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.

MR-guided percutaneous core biopsy of small breast lesions: first experience with a vertically open 0.5T scanner.

The growing use of highly sensitive but only moderate specific breast MRI requires the development of both minimal‐invasive as well as precise biopsy systems. The aim of the study was to prove the accuracy and feasibility of a biopsy procedure carried out in prone position in a vertically opened MR imager.

Laser-induced thermotherapy of neoplastic lesions in the brain – underlying tissue alterations, MRI-monitoring and clinical applicability

SummaryLaser-induced thermotherapy (LITT) is a minimally invasive neurosurgical approach to the stereotactic treatment of brain tumors in poorly accessible regions. Its clinical applicability has been shown in several experimental and clinical studies under on-line monitoring by magnetic resonance imaging (MRI). This review characterizes LITT as an alternative neurosurgical approach with specific focus on the typical histological alterations and ultrastructural cellular changes following laser irradiation in the central nervous system. The spatial and temporal pattern of these changes is discussed in their relevance to the neurosurgical treatment of neoplastic lesions using LITT.

Preliminary experience with interactive guided brain biopsies using a vertically opened 0.5-T MR system.

Abstract. The purpose of our study was to evaluate the feasibility and accuracy of brain biopsies performed within a vertically opened MR system. We worked with the interventional 0.5-T MR “SIGNA SP” (General Electric Medical Systems, Milwaukee, Wis.) with an integrated tracking device “Flashpoint Position Encoder” (Image Guided Technologies, USA). As a holding device for this instrument we constructed a special frame. The whole system allows an exact adjustment of an optimum biopsy direction and guidance of the biopsy in a non-stereotactic, interactive mode in near real-time. As biopsy tools we used MR-compatible aspiration and specially made side-cut needles (Daum, Germany; E-Z-EM, USA). We performed a prospective diagnostic brain biopsy study in 18 patients. Guidance of the needle was carried out using gradient-echo single-slice technique. The sample was taken after controlling the exact position of the needle tip on spin-echo images. In 12 cases an exact neuropathological diagnosis was possible. In 6 cases of negative biopsy (4 aspiration biopsies) the samples were not representative. Our results demonstrate the feasibility of interactive MR-guided minimally invasive brain biopsies in an open MR system. The best results were achieved using cut needles for biopsies of contrast-enhancing lesions visible on T1-weighted gradient-echo guidance sequence.

Open MRI-Guided Microsurgery of Intracranial Tumours. Preliminary Experience Using a Vertical Open MRI-Scanner

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. The development of open configurated MRI-scanners leads to new perspectives in the intra-operative management and resection control of intracranial tumours. Material and Method. Using a vertical open 0.5 T MRI-scanner for intra-operative MR image guided neurosurgery, forty-four patients (20 female/24 male) with different intracranial tumours have been operated on since August 1997. The patients ranged in age from 20 to 70 years (mean±standard deviation=47.2±15.9 ys). Results. In 36 (82%) of 44 patients the tumours were completely removed with the aid of MR image-guidance. In 8 cases (18%) complete removal was not achieved. Postoperatively 6 (14%) of 44 patients developed neurological deficits which were transient in 5 cases (paresis, dysphasia). In these patients the tumours were located in or near eloquent brain areas (sensorimotor cortex/speech center). 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 foreward in the field of neurosurgery.

Transnasal and transsphenoidal MRI‐guided biopsies of petroclival tumors

Magnetic resonance imaging (MRI) allows excellent tissue characterization in the area of the petroclival region and can depict lesions not visualized with ultrasound or computed tomography (CT). The aim of this study was to demonstrate the clinical feasibility and utility of an interactive MR‐guidance system to target and biopsy tumors in the petroclival region. MRI‐guided biopsies of 10 patients with tumors in the clivus and petrous apex were performed in an open 0.5‐T MR system. Lesions were targeted through a transsphenoidal or transnasal approach. Imaging during biopsies was achieved by a combination of standard and interactive mode. T1‐weighted spin‐echo, T2‐weighted fast spin‐echo (FSE), and three‐dimensional T1‐weighted gradient‐echo (GRE) scans (standard mode) were selected to provide optimal tissue characterization for both the lesion and surrounding structures and varied according to the anatomic site. For interactive imaging, T1‐weighted GRE and T2‐weighted FSE sequences were used. We performed MRI‐guided transsphenoidal biopsies in 10 patients who had lesions identified by CT (n = 5) and/or MRI (n = 10). The indications for biopsies were to differentiate between suspected malignant processes (n = 4 ) and benign processes (n = 6). Lesions adjacent to structures like the internal carotid artery were accurately targeted in particular. All biopsies were performed successfully and were the basis for selection of further treatment. No complications occurred during the procedures. An open MR system allows interactive control of biopsies in the area of the petroclival region, providing maximum patient safety and diagnostic accuracy not possible in other systems. The advantages of MRI tissue characterization are combined with an interactive, one‐step method of localization and targeting, as well as tissue sampling. J. Magn. Reson. Imaging 2001;13:3–11.

Intraoperatives Erscheinungsbild des Resektionsbereichs bei Hirntumoroperationen in einem offenen 0,5-T-MRT

ZusammenfassungBei der intraoperativen Kontrolle von Hirntumorresektionen in offenen MRT-Geräten kann es zu operativ induzierten Veränderungen, insbesondere Rand-enhancement-Zonen, kommen. Diese können Tumorreste vortäuschen, so daß die Radikalität des Eingriffs unterschätzt wird oder nicht tumortragende Hirnareale entfernt werden. Ergebnisse und Diskussion: Anhand von 42 in einem offenen 0,5-T-MRT (Signa SP, GE) vorgenommenen, biopsiekontrollierten Hirntumoroperationen werden Erscheinungsbild und Entstehungsweise der Randveränderungen analysiert. Bei den häufig vorzufindenden Rand-enhancement-Zonen handelt es sich um eine Überlagerung von präformierten Tumorrandreaktionen mit Mikrokontusionen. Die Ausbildung dieser Veränderungen braucht eine Mindestzeit von 10–15 min. Die ständige Analyse der die Tumorresektion begleitenden MRT-Kontrollen durch den Operateur und einen mit der Problematik vertrauten Radiologen gestattet in der Regel die Differenzierung der operativ induzierten Veränderungen und erhöht damit die Sicherheit des Eingriffs.SummaryDuring MRI-controlled resection of brain tumors using an open MRI system, operation-induced alterations may occur, especially enhancement of the resection cavity wall. This may simulate tumor areas, resulting in false assessment of the resection or resection of non-tumorous areas. Based on 42 MRI- and biopsy-controlled brain tumor resections in an 0.5 T open MRI (Signa SP, GE), the appearance and origin of operation-induced reactions are analyzed. In our opinion, there is a superposition of preformed peritumoral reactions by operation-induced microcontusions. The beginning of the cavity wall enhancement needs at least 10–15 min. MRI-controlled analysis of the intraoperative steps by the neurosurgeon and neuroradiologist allows discrimination of operation-induced reactions from tumor areas and leads to safe operation.

Anästhesiologisch-technische Probleme bei Eingriffen im offenen MRT: Erfahrungen nach 104 Narkosen

Unter Beachtung der technischen und klinischen Besonderheiten ist es auch in einem offenen MRT möglich, die allgemein anerkannten anästhesiologischen Standards zu gewährleisten und gleichzeitig akzeptable Bedingungen für den Operateur zu schaffen. Mit dem Einsatz MR-kompatibler Geräte reduziert sich das Auftreten technischer Probleme auf ein geringes Maß.Durch die eingeschränkte Beurteilbarkeit des EKG, die diskontinuierliche Blutdruckmessung und die erschwerte Durchführung von Notfallmaßnahmen ist bei Risikopatienten (nach unserer Erfahrung bei Patienten ab ASA III) im Konsens mit den operativen Fachgebieten eine strenge Überprüfung der Indikationsstellung für einen Eingriff im oMRT erforderlich.Aufgrund der geschilderten Rahmenbedingungen kann dieses Verfahren bisher nur für elektive Eingriffe empfohlen werden.Danksagung: Wir danken Herrn Dipl. Phys. S. Lieberenz für die fachliche Beratung zu technischen Problemen.

Technological and logistic problems and first clinical results of an interventional 0.5-T MRI system used by various medical specialities

SummaryMultidisciplinary usage of a MRI system with a superconducting 0.5-T magnet (Signa SP, General Electric) with a vertical gap suited for diagnostic and therapeutic interventions raises complex problems. The MR equipment, including a special localizing system and the instruments for diagnostic and therapeutic interventions, is described. Before putting the system into operation tests were necessary to check MR compatibility of various materials and instruments and to build some auxiliary equipment. We report on the coordinating activities of the radiologist in the context of MR use by different medical specialities. Within the course of 12 months, 428 examinations/interventions of different kinds were carried out, among them 75 functional examinations of the spine or of joints, 31 diagnostic biopsies, 23 cerebral biopsies, and 23 operations. The special design of the Signa SP allows the whole scale of functional examinations, up to complete neurosurgical interventions, in the sitting position and under nearly real-time imaging control.ZusammenfassungDie Problematik der multidisziplinären Nutzung eines für diagnostische und therapeutische Interventionen geeigneten, vertikal geöffneten MRT-Systems mit supraleitendem 0,5-Tesla-Magneten („Signa SP“, General Electric) umfaßt mehrere Komplexe, die im Zusammenhang dargestellt werden müssen. Das Gerät, einschließlich des systemimmanenten speziellen Lokalisationssystems und das notwendige Equipment für diagnostische und therapeutische Eingriffe werden vorgestellt. Vor Inbetriebnahme des Systems waren Testuntersuchungen verschiedener Materialien und Instrumente bezüglich ihrer MR-Kompatibilität nötig, außerdem mußten verschiedene Zusatzgeräte im Eigenbau hergestellt werden. Es wird über die koordinative Funktion des Radiologen im Rahmen der multidisziplinären Nutzung berichtet. In einem Zeitraum von ca. 12 Monaten wurden bisher an diesem Gerät 428 Untersuchungen/Interventionen verschiedenster Art am Patienten durchgeführt, darunter 75 funktionelle Untersuchungen der Wirbelsäulen oder Gelenke, 31 diagnostische Biopsien, 23 Hirnbiopsien und 23 Operationen. Die spezielle Konfiguration des „Signa SP“ ermöglicht unter nahezu Echtzeit-Bildgebungskontrolle die ganze Palette von funktionellen Untersuchungen im Sitzen bis hin zum kompletten neurochirurgischen Eingriff.