Intraoperative computed tomography for complex craniocervical operations and spinal tumor resections

Does Intraoperative Computed Tomography Scanning in Maxillofacial Trauma Surgery Affect the Revision Rate?

PURPOSE

The purpose of this study was to determine how intraoperative computed tomography affects the intraoperative revision rate and consequently the post-operative, secondary corrective surgery in maxillofacial trauma surgeries.

PATIENTS AND METHODS

A retrospective study composed of patients with facial fractures was conducted in Prince Sultan Military Medical City in Riyadh, Saudi Arabia. The predictor variables were age, gender, site of facial fracture, type of treatment, number of scans per patient, and discharge time. The primary outcome variable was immediate intraoperative revision rate. Secondary outcome variable was total scanning time (recorded from the moment surgery was halted until it was resumed after image acquisition). Descriptive statistics were used; numerical data presented as mean ± SD and categorical variables as frequency (%).

RESULTS

A total of 22 patients underwent 25 intraoperative scans while undergoing different maxillofacial surgeries. Eleven (50%) required intraoperative revisions after the scans, and 3 (13.6%) cases had another intraoperative scan after revision. Eighteen were men and 4 were women. The mean age was 30 years and age range was 19 to 76. Cases were categorized by fracture location and treatment preformed. The mean scanning time was 18.9 ± 4.6 minutes. The highest rate of revisions was seen in zygomaticomaxillary complex fractures (63.6%), they were also the only cases that required a second intraoperative scan after revision to confirm final reduction. No complications were seen postoperatively, and all patients recovered uneventfully. None of the patients required a secondary corrective surgery. All patients were discharged on the following day, except 1 case which was admitted under another service.

CONCLUSIONS

The use of intraoperative computed tomography imaging in treating maxillofacial fractures results in a higher rate of intraoperative revisions, which in turn leads to more accurate fracture reduction and consequently reduces the possibility of a postoperative, secondary corrective surgery.

Endoscopic endonasal odontoid resection with real-time intraoperative image-guided computed tomography: report of 4 cases

The authors present 4 cases in which they used intraoperative CT (iCT) scanning to provide real-time image guidance during endonasal odontoid resection. While intraoperative CT has previously been used as a confirmatory test after resection, to the authors' knowledge this is the first time it has been used to provide real-time image guidance during endonasal odontoid resection. The operating room setup, as well as the advantages and pitfalls of this approach, are discussed. A mobile intraoperative CT scanner was used in conjunction with real-time craniospinal neuronavigation in 4 patients who underwent endoscopic endonasal odontoidectomy for basilar invagination. All patients underwent a successful decompression. In 3 of the 4 patients, real-time intraoperative CT image guidance was instrumental in achieving a comprehensive decompression. In 3 (75%) cases in which the right nostril was the predominant working channel, there was a tendency for asymmetrical decompression toward the right side, meaning that residual bone was seen on the left, which was subsequently removed prior to completion of the surgery. Endoscopic endonasal odontoid resection with real-time intraoperative image-guided CT scanning is feasible and provides accurate intraoperative localization of pathology, thereby increasing the chance of a complete odontoidectomy. For right-handed surgeons operating predominantly through the right nostril, special attention should be paid to the contralateral side of the resection, where there is often a tendency for residual pathology.

Intraoperative computed tomography guidance to confirm decompression following endoscopic endonasal approach for cervicomedullary compression

Introduction Cervicomedullary compression often requires an anterior approach to address the compressive vector. In certain cases an endoscopic endonasal approach (EEA) is ideal for decompression. It is essential that an adequate decompression be achieved and verified before the patient leaves the operating room. The purpose of this study was to evaluate the use intraoperative computed tomography (IO-CT) in assessing the adequacy of decompression. Methods A retrospective chart review revealed 11 cases of EEA odontoid resection IO-CT verification of decompression. Operative reports and review of imaging was used to determine if further decompression was performed following the intraoperative scan. Results Out of 11 EEA cases, 4 (36%) patients showed evidence of residual compression following an initial IO-CT. Further operative decompression was undertaken following the first scan in all cases. A second intraoperative scan was then used to confirm complete decompression. No patient left the operating room with residual compression. Discussion IO-CT provided valuable utility in 36% of the cases after the initial resection was incomplete. The standard fluoroscopic guidance may not provide adequate resolution and enhanced utility like IO-CT.

Intraoperative 3-dimensional imaging (O-arm) for assessment of pedicle screw position: Does it prevent unacceptable screw placement?

Background

Pedicle screws are biomechanically superior over other spinal fixation devices. When improperly positioned, they lose this advantage and put adjacent structures at risk. Accurate placement is therefore critical. Postoperative computed tomography (CT) scans are the imaging gold standard and have shown malposition rates ranging from 2% to 41%. The O-arm (Medtronic Navigation, Louisville, Colorado) is an intraoperative CT scanner that may allow intervention for malpositioned screws while patients are still in the operating room. However, this has not yet been shown in clinical studies. The primary objective of this study was to assess the usefulness of the O-arm for evaluating pedicle screw position by answering the following question: What is the rate of intraoperative pedicle screw revision brought about by O-arm imaging information? A secondary question was also addressed: What is the rate of unacceptable thoracic and lumbar pedicle screw placement as assessed by intraoperative O-arm imaging?

Methods

This is a case series of consecutive patients who have undergone spine surgery for which an intraoperative 3-dimensional (3D) CT scan was used to assess pedicle screw position. The study comprised 602 pedicle screws (235 thoracic and 367 lumbar/sacral) placed in 76 patients, and intraoperative 3D (O-arm) imaging was obtained to assess screw position. Action taken at the time of surgery based on imaging information was noted. An independent review of all scans was also conducted, and all screws were graded as either optimal (no breach), acceptable (breach ≤2 mm), or unacceptable (breach >2 mm). The rate of pedicle screw revision, as detected by intraoperative 3D CT scan, was determined.

Results

On the basis of 3D imaging information, 17 of 602 screws (2.8%) in 14 of 76 cases (18.4%) were revised at the time of surgery. On independent review of multiplanar images, 11 screws (1.8%) were found to be unacceptable, 32 (5.3%) were acceptable, and 559 (92.9%) were optimal. All unacceptable screws were revised to an optimal or acceptable position, and an additional 6 acceptable screws were revised to an optimal position. Thus, by the end of the cases, none of the 602 pedicle screws in the 76 surgical procedures was in an unacceptable position.

Conclusion

The new-generation intraoperative 3D imaging system (O-arm) is a useful tool that allows more accurate assessment of pedicle screw position than plain radiographs or fluoroscopy alone. It prompted intraoperative repositioning of 2.8% of pedicle screws in our series. Most importantly, it allowed identification and revision of all unacceptably placed pedicle screws without the need for reoperation.

A prospective study on the use of intraoperative computed tomography (iCT) for image-guided placement of thoracic pedicle screws

BACKGROUND

Placement of thoracic pedicle screws is a technically demanding procedure. The risk of thoracic pedicle breaches range from 6.5 to 41%. Current image guidance systems consist of computer based systems utilizing preoperative CT scans or 2D/3D intraoperative fluoroscopy.

OBJECTIVE

The aim of this prospective study was to evaluate the clinical feasibility and accuracy of a new intraoperative CT (iCT) based image guidance system for thoracic pedicle screw instrumentation.

METHODS

We prospectively studied the use of iCT for the first 43 consecutive cases for which thoracic pedicle screws were inserted as part of the instrumentation for spinal fusion between April 2008 and July 2011. In every case, a post-instrumentation intraoperative check CT was done before wound closure to assess accuracy of implant placement. Outcomes were analysed with regards to the incidence of pedicle wall violations detected on intraoperative check CT imaging, and the rate of immediate intraoperative revision of misplaced screws. Pedicle violations were graded according to an established classification system.

RESULTS

A total of 261 thoracic pedicle screws (T1-T12) were inserted in 43 patients (age range 13-83). Mean follow-up was 12 months. There were 7 (2.7%) pedicle violations detected on the intraoperative check CT. Out of the seven, three were grade I (< 2 mm), two were grade II (2-4 mm) and rest two were grade III (> 4 mm) violations. Only four of the screws (1.5%) that breached the pedicle wall by more than 2 mm were immediately revised before wound closure.

CONCLUSION

The iCT based spinal neuronavigation system allowed for highly safe and accurate placement (97.3%) of thoracic pedicle screws in our institution with no neurovascular injury reported.

Accuracy of image-guided pedicle screw placement using intraoperative computed tomography-based navigation with automated referencing. Part II: thoracolumbar spine

BACKGROUND

Image-guided spinal instrumentation may reduce complications in spinal instrumentation.

OBJECTIVE

To assess accuracy, time efficiency, and staff radiation exposure during thoracolumbar screw instrumentation guided by intraoperative computed tomography (iCT)-based neuronavigation (iCT-N).

METHODS

In 55 patients treated for idiopathic and degenerative deformities, 826 screws were inserted in the thoracic (T2-T12; n = 243) and lumbosacral (L1-S1; n = 545) spine, as well as ilium (n = 38) guided by iCT-N. Up to 17 segments were instrumented following a single automated registration sequence with the dynamic reference arc (DRA) uniformly attached to L5. Accuracy of iCT-N was assessed by calculating angular deviations between individual navigated tool trajectories and final implant positions. Final screw positions were also graded according to established classification systems. Clinical and radiological outcome was assessed at 12 to 14 months.

RESULTS

Additional intraoperative fluoroscopy was unnecessary, eliminating staff radiation exposure. Unisegmental K-wire insertion required 4.6 ± 2.9 minutes. Of the thoracic pedicle screws 98.4% were assigned grades I to III according to the Heary classification, with 1.6% grade IV placement. In the lumbar spine, 94.4% of screws were completely contained (Gertzbein classification grade 0), 4.6% displayed minor pedicle breaches <2 mm (grade 1), and 1% of lumbar screws deviated by >2 to <4 mm (grade 2). The accuracy of iCT-N progressively deteriorates with increasing distance from the DRA, but allows safe instrumentation of up to 12 segments.

CONCLUSION

iCT-N using automated referencing allows for safe, highly accurate multilevel instrumentation of the entire thoracolumbosacral spine and ilium, rendering additional intraoperative imaging dispensable. In addition, automated registration is time-efficient and significantly reduces the need for re-registration in multilevel surgery.

Accuracy of Image-Guided Pedicle Screw Placement Using Intraoperative Computed Tomography-Based Navigation With Automated Referencing, Part I: Cervicothoracic Spine

BACKGROUND:

Image-guided spinal instrumentation reduces the incidence of implant misplacement.

OBJECTIVE:

To assess the accuracy of intraoperative computed tomography (iCT)-based neuronavigation (iCT-N).

METHODS:

In 35 patients (age range, 18-87 years), a total of 248 pedicle screws were placed in the cervical (C1-C7) and upper and midthoracic (T1-T8) spine. An automated iCT registration sequence was used for multisegmental instrumentation, with the reference frame fixed to either a Mayfield head clamp and/or the most distal spinous process within the instrumentation. Pediculation was performed with navigated drill guides or Jamshidi cannulas. The angular deviation between navigated tool trajectory and final implant positions (evaluated on postinstrumentation iCT or postoperative CT scans) was calculated to assess the accuracy of iCT-N. Final screw positions were also graded according to established classification systems. Mean follow-up was 16.7 months.

RESULTS:

Clinically significant screw misplacement or iCT-N failure mandating conversion to conventional technique did not occur. A total of 71.4% of patients self-rated their outcome as excellent or good at 12 months; 99.3% of cervical screws were compliant with Neo classification grades 0 and 1 (grade 2, 0.7%), and neurovascular injury did not occur. In addition, 97.8% of thoracic pedicle screws were assigned grades I to III of the Heary classification, with 2.2% grade IV placement. Accuracy of iCT-N progressively deteriorated with increasing distance from the spinal reference clamp but allowed safe instrumentation of up to 10 segments.

CONCLUSION:

Image-guided spinal instrumentation using iCT-N with automated referencing allows safe, highly accurate multilevel instrumentation of the cervical and upper and midthoracic spine. In addition, iCT-N significantly reduces the need for reregistration in multilevel surgery.

Intraoperative computed tomography image-guided navigation for posterior thoracolumbar spinal instrumentation in spinal deformity surgery

OBJECT

Placement of thoracolumbar pedicle screws in spinal deformity surgery has a reported inaccuracy rate as high as 30%. At present, image-guided navigation systems designed to improve instrumentation accuracy typically use intraoperative fluoroscopy or preoperative CT scans. The authors report the prospective evaluation of the accuracy of posterior thoracolumbar spinal instrumentation using a new intraoperative CT operative suite with an integrated image guidance system. They compare the accuracy of thoracolumbar pedicle screw placement using intraoperative CT image guidance with instrumentation placement utilizing fluoroscopy.

METHODS

Between December 2007 and July 2008, 12 patients underwent posterior spinal instrumentation for spinal deformity correction using intraoperative CT-based image guidance. An intraoperative CT scan of the sterile surgical field was obtained after decompression and before instrumentation. Instrumentation was placed, and a postinstrumentation CT scan was obtained before wound closure to assess the accuracy of instrumentation placement and the potential need for revision. The accuracy of pedicle screw placement was later reviewed and recorded by independent observers. A comparison group of 14 patients who underwent thoracolumbar instrumentation utilizing fluoroscopy and postoperative CT scanning during the same time period was evaluated and included in this analysis.

RESULTS

In the intraoperative CT-based image guidance group, a total of 164 thoracolumbar pedicle screws were placed. Two screws were found to have breached the pedicle wall (1.2%). Neither screw was deemed to need revision due to misplacement. In the comparison group, 211 pedicle screws were placed. Postoperative CT scanning revealed that 11 screws (5.2%) had breached the pedicle. One patient in the fluoroscopy group awoke with a radiculopathy attributed to a misplaced screw, which required revision. The difference in accuracy was statistically significant (p = 0.031).

CONCLUSIONS

Intraoperative CT-based image guidance for placement of thoracolumbar instrumentation has an accuracy that exceeds reported rates with other image guidance systems, such as virtual fluoroscopy and 3D isocentric C-arm-based stereotactic systems. Furthermore, with the use of intraoperative CT scanning, a postinstrumentation CT scan allows the surgeon to evaluate the accuracy of instrumentation before wound closure and revise as appropriate.

The prevalence of wrong level surgery among spine surgeons

STUDY DESIGN

A questionnaire study.

OBJECTIVE

To evaluate the prevalence of wrong level surgery among spine surgeons and their use of preventive measures to avoid its occurrence.

SUMMARY OF BACKGROUND DATA

Wrong site surgery fails to improve the patient's symptoms and has medical, emotional, social, and legal implications. Organizations such as the North American Spine Society and the Joint Commission on Accreditation of Healthcare Organizations have established guidelines to prevent wrong site surgery. Spine surgeons' compliance with these guidelines and the prevalence of wrong-level spine surgery have not been investigated previously.

METHODS

All members of the American Academy of Neurologic Surgeons (n = 3505) were sent an anonymous, 30-question survey with a self-addressed stamped envelope.

RESULTS

A total of 415 (12%) surgeons responded. Sixty-four surgeons (15%) reported that, at least once, they had prepared the incorrect spine level, but noticed the mistake before making the incision. Two hundred seven (50%) reported that they had done 1 or more wrong level surgeries during their career. From an estimated 1,300,000 spine procedures, 418 wrong level spine operations had been performed, with a prevalence of 1 in 3110 procedures. The majority of the incorrect level procedures were performed on the lumbar region (71%), followed by the cervical (21%), and the thoracic (8%) regions. One wrong level surgery led to permanent disability, and 73 cases resulted in legal action or monetary settlement to the patient (17%).

CONCLUSION

There is a high prevalence of wrong level surgery among spine surgeons; 1 of every 2 spine surgeons may perform a wrong level surgery during his or her career. Although all spine surgeons surveyed report using at least 1 preventive action, the following measures are highly recommended but inconsistently adopted: direct preoperative communication with the patient by the surgeon, marking of the intended site, and the use of intraoperative verification radiograph.

Clinical indications and perspectives for intraoperative cone-beam computed tomography in oral and maxillofacial surgery

OBJECTIVES

Intraoperative cone-beam computerized tomography (CBCT) imaging has been introduced in oral and maxillofacial surgery. Using midfacial fractures as the pioneer model, this study describes the spectrum of further promising clinical indications for intraoperative CBCT and a clinical combination with intraoperative navigation.

STUDY DESIGN

One hundred seventy-nine patients admitted for surgical treatment of the facial skeleton were included in the study. Intraoperatively, 3-dimensional images were generated with the mobile CBCT scanner Arcadis Orbic 3D, obtained from Siemens Medical Solutions, in a variety of indications.

RESULTS

The acquisition of the data sets was uncomplicated, and image quality was sufficient to assess the postoperative result in all cases. In the example of a facial gunshot injury, a navigation system for intraoperative localization of the metal foreign bodies was used.

Intraoperative imaging of zygomaticomaxillary complex fractures using a 3D C-arm system

After preclinical studies and evaluation of radiation exposures, intraoperative three-dimensional (3D) C-arm based imaging is now available for the facial skeleton. Fourteen patients admitted for surgical treatment of zygomaticomaxillary complex (ZMC) fractures were included in the study. Preoperative diagnostics and surgical treatment were performed as usual. Intraoperatively, after open reduction, a cone-beam computed tomography (CBCT) dataset was generated using the SIREMOBIL Iso-C3D (Siemens Medical Solutions, Erlangen, Germany). After DICOM-import in eFilm Workstation axial, coronal and sagittal reconstructions were evaluated by five examiners with the help of six defined criteria. In our study, secondary reconstructions were available after 6 min, excluding the time needed for the evaluation of the images. Especially the positioning of the isocentre of the SIREMOBIL Iso-C3D proved to be uncomplicated. Because of the size of the datasets, assessment of the symmetry of the malar projection proved difficult. Best scoring results were found regarding the visualization of the fragment position, bony anchorage of the screws and the fitting of the plates. Remarkable was the low level of metal artefacts in primary and secondary reconstructions. In conclusion, our results demonstrate intraoperative CBCT using the SIREMOBIL Iso-C3D suitable for assessment of postoperative results following ZMC reduction.

Intraoperative magnetic resonance imaging at 0.12 T: is it enough?

Low magnetic field strength MRI provides the anatomic information needed for intracranial procedures in which intraoperative imaging is needed. Stereotactic accuracy is proven. The distinct advantage of this technologic approach is that it allows the neurosurgical team to operate an iMRI system with minimal disruption to the OR routine. Technical improvements are likely to increase the power and versatility of low field strength iMRI. Logic dictates that ergonomics and economics will make this the iMRI technique desired by most neurosurgeons.

Technology improvements for image-guided and minimally invasive spine procedures

This paper reports on technology developments aimed at improving the state of the art for image-guided minimally invasive spine procedures. Back pain is a major health problem with serious economic consequences. Minimally invasive procedures to treat back pain are rapidly growing in popularity due to improvements in technique and the substantially reduced trauma to the patient versus open spinal surgery. Image guidance is an enabling technology for minimally invasive procedures, but technical problems remain that may limit the wider applicability of these techniques. The paper begins with a discussion of low back pain and the potential shortcomings of open back surgery. The advantages of minimally invasive procedures are enumerated, followed by a list of technical problems that must be overcome to enable the more widespread dissemination of these techniques. The technical problems include improved intraoperative imaging, fusion of images from multiple modalities, the visualization of oblique paths, percutaneous spine tracking, mechanical instrument guidance, and software architectures for technology integration. Technical developments to address some of these problems are discussed next. The discussion includes intraoperative computerized tomography (CT) imaging, magnetic resonance imaging (MRI)/CT image registration, three-dimensional (3-D) visualization, optical localization, and robotics for percutaneous instrument placement. Finally, the paper concludes by presenting several representative clinical applications: biopsy, vertebroplasty, nerve and facet blocks, and shunt placement. The program presented here is a first step to developing the physician-assist systems of the future, which will incorporate visualization, tracking, and robotics to enable the precision placement and manipulation of instruments with minimal trauma to the patient.

Reliability of Three-dimensional Fluoroscopy For Detecting Pedicle Screw Violations in the Thoracic and Lumbar Spine

OBJECTIVE

Thoracic and lumbar pedicle screws have become popular because of their biomechanical superiority over other methods of spinal fixation. However, the safety and efficacy of transpedicular screws depend on their proper placement. Recent advances in imaging have resulted in the ability to acquire three-dimensional (3-D) axial images of the spine during surgery, and this study was undertaken to assess the reliability of this technology to detect pedicle violations.

METHODS

Pedicle screws were placed in six human cadaver spines from T1 to S1 using standard techniques. Intentional pedicle violations were created in 74 of 216 pedicles, and violations were graded on a four-point scale (range, 0-3). Radiographic images were then obtained using a conventional spiral computed tomographic scanner and the Siremobil Iso-C 3D (Siemens Medical Solutions, Erlangen, Germany) 3-D fluoroscopy unit. An independent neuroradiologist then graded pedicle violations as ascertained by the two imaging modalities.

RESULTS

Using direct inspection of the pedicles as the "gold standard," the overall sensitivity and specificity for detecting pedicle violations were 0.716 and 0.789, respectively, with 3-D fluoroscopy. The overall sensitivity and specificity for detecting pedicle violations were 0.608 and 0.937, respectively, with conventional computed tomography. All Grade 2 pedicle violations were detected in the thoracic spine by both modalities, and all Grade 3 violations were detected by both modalities.

CONCLUSION

Axial images obtained with 3-D fluoroscopy demonstrate a higher sensitivity but lower specificity than conventional computed tomographic scanning for assessing pedicle violations. By providing real-time intraoperative imaging, 3-D fluoroscopy may enhance the safety of thoracic transpedicular instrumentation.

Wrong disc space level surgery: medicolegal implications

BACKGROUND

Operating the wrong disc level for herniated disc disease is a rarely reported complication. However, it is considered by many a breach in the standard of care. It is not unusual for litigation to result. Sixty-nine cases of wrong disc space level surgery were identified; 68 cases were the subject of lawsuits.

METHODS

Sixty-five lawsuit outcomes were published in a national monthly newsletter of malpractice cases, Medical Malpractice Verdicts, Settlements and Experts. Two cases came from medicolegal review, one case from a news article, and one case for which no claim was made.

RESULTS

Thirty-seven cases were settled. A plaintiff verdict was rendered in 18 cases and a defense verdict in 13 cases (42% of the cases that were decided by a jury).

CONCLUSIONS

The authors summarize steps to reduce the incidence of this misadventure. The authors recommend that the patient be advised of this potential and the patient be informed of the risk factors when special circumstances exist.

Radio-guided brain tumorectomy using a gamma detecting probe and a mobile solid-state gamma camera

BACKGROUND

We herein report a technique to distinguish brain tumors from normal brain tissue during surgery using a gamma probe and a solid-state mobile gamma camera after (99m)Tc-hexakis-2-methoxy-isobutyl-isonitrile ((99m)Tc-MIBI) is administered to patients immediately before operation.

METHODS

We examined 13 patients with brain tumors. Before the operation, (99m)Tc-MIBI single photon emission computed tomography (SPECT) was performed to assess accumulation in the tumors. On the day of the operation, (99m)Tc-MIBI was administered intravenously and craniotomy for tumor resection was performed. During the operation, the tumor was localized with a gamma probe and preremoval scintigraphy images were taken with a mobile gamma camera. After tumor resection was completed, residual tumors were confirmed using it again. We compared accumulation found in the preoperative SPECT images and intraoperative scintigraphy images, performed a histologic examination of adjacent tissues, and measured the dose the personnel was exposed to per operation.

RESULTS

In all patients, tumors were confirmed by a gamma probe and scintigraphy during the operation. Intraoperative accumulation in tumors was significantly related to accumulation found in the preoperative (99m)Tc-MIBI SPECT images. In 9 out of 13 patients, accumulation disappeared in the postremoval scintigraphy images, and no tumor tissue was found by histologic examination. Residual tumor tissue was found in 4 patients. Average exposure of the personnel per operation was 22.9 +/- 4.0 microSv.

CONCLUSION

Resection of brain tumors with a gamma probe and a mobile gamma camera was very useful since the area to be removed was easily identified and residual tumors could be detected.

Functional neuronavigation and intraoperative MRI

Our concept of computer assisted surgery is based on the combination of intraoperative magnetic resonance (MR) imaging with microscope-based neuronavigation, providing anatomical and functional guidance simultaneously. Intraoperative imaging evaluates the extent of a resection, while the additional use of functional neuronavigation, which displays the position of eloquent brain areas in the operative field, prevents increasing neurological deficits, which would otherwise result from extended resections. Up to mid 2001 we performed intraoperative MR imaging using a low-field 0.2 Tesla scanner in 330 patients. The main indications were the evaluation of the extent of resection in gliomas, pituitary tumours, and in epilepsy surgery. Intraoperative MR imaging proved to serve as intraoperative quality control with the possibility of an immediate modification of the surgical strategy, i.e. extension of the resection. Integrated use of functional neuronavigation prevented increased neurological deficits. Compared to routine pre- or postoperative imaging being performed with high-Tesla machines, intraoperative image quality and sequence spectrum could not compete. This led to the development of the concept to adapt a high-field MR scanner to the operating environment, preserving the benefits of using standard microsurgical equipment and microscope-based neuronavigational guidance with integrated functional data, which was successfully implemented by April 2002. Up to the end of 2002, 95 patients were investigated with the new setup. Improved image quality, intraoperative workflow, as well as enhanced sophisticated intraoperative imaging possibilities are the major benefits of the high-field setup.

Glioma surgery evaluated by intraoperative low-field magnetic resonance imaging

OBJECTIVE

To give an overview on intraoperative magnetic resonance (MR) imaging in glioma surgery.

MATERIAL AND METHODS

MR imaging was performed using a 0.2T scanner, located in a radiofrequency-shielded operating theatre. Two setups were used: surgery either in a neighbouring operating theatre, or directly at the 5G line. Additionally, in gliomas adjacent to eloquent brain areas microscope- or pointer-based neuronavigation with integrated functional data was applied. 106 gliomas were among the 330 patients investigated in the last 5 years.

RESULTS

We did not observe complications attributable to intraoperative MR imaging. Image quality was sufficient to evaluate the extent of the tumour resection in the majority of cases. Intraoperative imaging revealed remaining tumour in 63%. In a total of 26% patients further tumour could be removed due to the results of intraoperative imaging, increasing the rate of complete tumour removal especially in the low-grade tumours. The additional use of functional neuronavigation prevented an increased morbidity.

CONCLUSION

Intraoperative MR imaging offers the possibility of further tumour removal during the same surgical procedure in case of tumour remnants, increasing the rate of complete tumour removal. The effects of brain shift can be compensated for using intraoperative image data for updating.

Intraoperative computerized tomography for improved accuracy of spinal navigation in pedicle screw placement of the thoracic spine

We report on our experiences with the use of intraoperative CT imaging in surgery of the thoracic spine and on our results of pedicle screw insertion using spinal navigation and implantable fiducial markers. For our operations we used the Tomoscan M-EG and the EasyGuideSpine (Philips Medical Systems). During the operation the patient was positioned on the mobile CT table. Following dorsal preparation, small titanium screws were implanted in the vertebrae so as to serve as fiducial markers. Image data were obtained by performing a spiral CT scan. Ventilation was suspended for the duration of the CT scan. Screw insertion as well as vertebral biopsies were performed using spinal navigation. Intraoperative CT scans were obtained to confirm the position of the implants and to assess the amount of bony decompression as well as the realignment. Since 1998, 112 patients with various disorders of the thoracic spine have been operated on using the described technique. 365 screws were inserted in the area of T1 to T12. There were 23 (6.3%) misplacements of pedicle screws. In 42 cases (11.5%) we observed a minimal lateral perforation (<2 mm) of the pedicle wall. No neurological, cardiovascular, or pulmonary injury occurred. Intraoperative CT imaging influenced surgical decisions as well as the final result of surgery. Despite the use of intraoperative imaging and accurate spinal navigation, pedicle screw placement in the thoracic spine remains extremely challenging.

CT-guided neurosurgery: preliminary experience

BACKGROUND

With the possibility of CT systems becoming more handy and sophisticated, intraoperative CT was introduced in a few neurosurgical Centres with better results in lesion removal and surgical outcome.

METHOD

At our Institution a mobile CT scanner was recently used for intraoperative evaluation (Philips Tomoscan M). For 27 tumour resections performed with a neuronavigation system, and 23 deep brain electrode positioning examinations, an intraoperative CT was employed. In addition the CT scanner was used in the recovery room for a postoperative control in 198 patients.

FINDINGS

Our preliminary experience used for a real time evaluation of the treated patients, permitted to verify an incomplete removal in 23/27 cases. Evaluation of stereotactic electrode position in relation to the planned target was also possible and demonstrated a correct position in 21 cases.

INTERPRETATION

Intraoperative CT scan is a useful system that permits to modify neuronavigation planning and is able to give information to the surgeon for better tumour removal, rule out possible hemorrhagic complications, and suitable deep brain electrode positioning.

Intraoperative magnetic resonance imaging: impact on brain tumor surgery

BACKGROUND

Refinements in the imaging of intracranial tumors assist neurosurgeons in maximizing resections in a safe manner. Intraoperative magnetic resonance imaging (iMRI) represents a recent addition to their therapeutic armamentaria.

METHODS

The authors reviewed the development of iMRI and describe their experience with iMRI-guided resection of intracranial tumors in 112 patients. The PoleStar N-10 iMRI system was used in this series.

RESULTS

Intraoperative imaging resulted in additional tumor removal in 40 (36%) of the patients. In another 35 (31%), imaging confirmed that the goals of surgery had been attained so potentially harmful dissection in and around the brain was avoided. For patients with lesions of the skull base, iMRI was possible in all but 2 patients who had a large body habitus. There was a decrease in length of hospital stay for patients who had surgery with iMRI. Lesion location did not play a role in this change. Brain tumor surgery was affected in 67% of patients. A potential for cost savings with iMRI was demonstrated.

CONCLUSIONS

Intraoperative imaging with MRI is the latest evolution in the increasing precision of neurosurgery. The advantages of this technology will make it a ubiquitous feature in the neurosurgical operating room.

Intraoperative cervical epidurography: a simple modality for assessing the adequacy of decompression during anterior cervical procedures. Technical note

OBJECT

Intraoperative cervical epidurography (ICE) was used during anterior cervical procedures to assess the success of bone resection and indicate the need for immediate correction in the event of inadequate decompression.

METHODS

The adequacy of decompression was assessed by the operating neurosurgeon who performed ICE after anterior microdiscectomy with exposure of the dura mater. If the decompression was deemed inadequate, additional bone was removed using a high-speed drill. Epidurography was conducted after each subsequent decompression until adequate bone removal was achieved. This was undertaken in 39 patients undergoing anterior cervical procedures. Nine patients underwent corpectomy, 21 one-level, and nine two-level discectomy. The ICE revealed insufficient resections requiring additional bone removal in 14 (36%) of the 39 patients.

CONCLUSIONS

The goal of ICE is to ensure adequate decompression, and if such has not been achieved, to allow for additional immediate bone excision. Furthermore, ICE provides additional real-time control of the position of cages and screws to avoid dural tear or spinal cord compression. Because of this immediate feedback, the success rate of anterior cervical procedures can be improved. The advantages of this modality include real-time assessment, low cost, simplicity, and speed.

Skin markers for surgical planning for intradural lesions of the thoracic spine. Technical note

BACKGROUND

Preparation for surgery for thoracic intraspinal lesions commonly involves rather difficult X-ray procedures in the operating room. The object of this report is to inform neurosurgeons about a modified technique for preoperative surface localization of intraspinal thoracic pathology.

METHODS

Adhesive, disposable radiographic skin markers placed at the presumed level of an intraspinal lesion are visualized along with the lesion on sagittal magnetic resonance scans of the thoracic spine.

RESULTS

The lesion and the skin markers were clearly identified within the same field of view. The lesion itself rather than the vertebral body becomes the reference point for localization.

CONCLUSION

Preoperative imaging with adhesive skin markers facilitates positioning and draping for surgery for thoracic intraspinal lesions. It may even replace intra-operative X-ray procedures in selected cases.

Intraoperative magnetic resonance imaging for skull base surgery

OBJECTIVES/HYPOTHESIS

Skull base surgery has evolved over the past several decades. Major improvements in the imaging of skull base pathology led to better target localization and better surgical planning. The objectives of this study were to assess the use of intraoperative magnetic resonance (MR) imaging in the management of a series of patients with skull base pathology. We hypothesized that high-quality intraoperative MR imaging would have an impact on surgery in this patient group.

STUDY DESIGN

Prospective, non-randomized, cohort study.

METHODS

Thirty-one patients with skull base lesions underwent surgery in a 1.5-Tesla intraoperative MR suite. The concepts of a moving magnet, high magnetic field strength, and radiofrequency coil design are presented.

RESULTS

Eleven of 31 patients had the course of surgery significantly altered by the information acquired from the images obtained during surgery.

CONCLUSIONS

Intraoperative MR imaging is a valuable adjunct to skull base surgery. One third of patients had altered surgery as a result of this adjunct. Intraoperative MR imaging is of particular value in the treatment of pituitary adenomas and benign skull base tumors.

Image-guided robotic delivery system for precise placement of therapeutic agents

The effectiveness of conventional solid tumor treatment is limited by the systemic toxicity and lack of specificity of chemotherapeutic agents. Present treatment modalities are frequently insufficient to eliminate competent cancer cells without exceeding the limits of toxicity to normal tissue. The coming generation of cancer therapeutics depends on the precise targeting and sustained release of antitumor agents to overcome these limitations. We are developing an image-guided, robotic system for precise intratumoral placement of anticancer drugs and sustained release devices to advance this new treatment paradigm. The robotic system will use intraoperatively obtained computed tomographic (CT) images from a mobile CT scanner for guidance. The concept is to track patient anatomy and localize instruments using currently available optical tracking technology. Tracking will also be used to register patient anatomy with the images. The physician can then use the registered image to select an appropriate tumor target and entry location and to plan the instrument path. This path will then be transmitted to the robot, which orients and drives the instrument to the desired target under physician control. Achievement of the target is confirmed via intraoperative CT. This system will provide instrument guidance that is precise, direct, and controllable. Error due to poor target visualization and hand unsteadiness should be reduced greatly. The basic components of the system (robot, mobile CT, tracking) have been demonstrated in our laboratory, and the integration of the components is in progress. In future work, we plan to fuse preoperative PET imaging with intraoperative CT to allow functional as well as anatomic image guidance.

Cranial surgery navigation aided by a compact intraoperative magnetic resonance imager

OBJECT

In this article the authors report on a novel, compact device for magnetic resonance (MR) imaging that has been developed for use in a standard neurosurgical operating room.

METHODS

The device includes a permanent magnet with a field strength of 0.12 tesla. The poles of the magnet are vertically aligned, with a gap of 25 cm. When not in use the magnet is stored in a shielded cage in a corner of the operating room; it is easily moved into position and attaches to a regular operating table. The magnet is raised for imaging when needed and may be lowered to allow surgery to proceed unencumbered. Surgical navigation with optical and/or magnetic probes is incorporated into the system. Twenty-five patients have undergone removal of intracranial lesions with the aid of this device. Operations included craniotomy for tumor or other lesion in 18 patients and transsphenoidal resection of tumor in seven. The number of scans ranged from two to five per surgery (average 3.4); image quality was excellent in 45%, adequate in 43%, and poor in 12%. In four patients MR imaging revealed additional tumor that was then resected; in five others visual examination of the operative field was inconclusive but complete tumor removal was confirmed on MR imaging. In 21 patients early postoperative diagnostic MR studies corroborated the findings on the final intraoperative MR image. Using a water-covered phantom, the accuracy of the navigational tools was assessed; 120 data points were measured. The accuracy of the magnetic probe averaged 1.3 mm and 2.1 mm in the coronal and axial planes, respectively; the optical probe accuracy was 2.1 mm and 1.8 mm in those planes.

CONCLUSIONS

This device provides high-quality intraoperative imaging and accurate surgical navigation with minimal disruption in a standard neurosurgical operating room.