iCT Scan Research Articles

Microscope-Based Augmented Reality with Intraoperative Computed Tomography-Based Navigation for Resection of Skull Base Meningiomas in Consecutive Series of 39 Patients.

Simple SummaryThe aim of surgery for skull base meningiomas is maximal resection with minimal damage to the involved cranial nerves and cerebral vessels. Compared to non-skull base meningiomas, these lesions show a reduced rate of gross total resection (GTR). Therefore, the use of technologies for improved orientation in the surgical field, such as neuronavigation and augmented reality (AR), is of interest. We confirmed in a consecutive series of 39 patients who underwent surgery for skull base meningiomas that automatic registration with intraoperative computed tomography (iCT) showed high registration accuracy and that microscope-based AR largely facilitated the resection by increasing surgical precision and providing improved intraoperative orientation by visualizing the tumor and the critical neurovascular structures in the operative microscope. No injuries to critical neurovascular structures occurred. There were 26 patients (66.6%) who underwent GTR. Additionally, 33 out of 35 patients who lived to follow-up could ambulate.Background: The aim of surgery for skull base meningiomas is maximal resection with minimal damage to the involved cranial nerves and cerebral vessels; thus, implementation of technologies for improved orientation in the surgical field, such as neuronavigation and augmented reality (AR), is of interest. Methods: Included in the study were 39 consecutive patients (13 male, 26 female, mean age 64.08 ± 13.5 years) who underwent surgery for skull base meningiomas using microscope-based AR and automatic patient registration using intraoperative computed tomography (iCT). Results: Most common were olfactory meningiomas (6), cavernous sinus (6) and clinoidal (6) meningiomas, meningiomas of the medial (5) and lateral (5) sphenoid wing and meningiomas of the sphenoidal plane (5), followed by suprasellar (4), falcine (1) and middle fossa (1) meningiomas. There were 26 patients (66.6%) who underwent gross total resection (GTR) of the meningioma. Automatic registration applying iCT resulted in high accuracy (target registration error, 0.82 ± 0.37 mm). The effective radiation dose of the registration iCT scans was 0.58 ± 1.05 mSv. AR facilitated orientation in the resection of skull base meningiomas with encasement of cerebral vessels and compression of the optic chiasm, as well as in reoperations, increasing surgeon comfort. No injuries to critical neurovascular structures occurred. Out of 35 patients who lived to follow-up, 33 could ambulate at their last presentation. Conclusion: A microscope-based AR facilitates surgical orientation for resection of skull base meningiomas. Registration accuracy is very high using automatic registration with intraoperative imaging.

In Reply to the Letter to the Editor Regarding “Cytotoxicity and Effect of Topical Application of Tranexamic Acid on Human Fibroblast in Spine Surgery”

The literature on the use of intraoperative computed tomography (iCT) is sparse. We provide our experience of the usefulness of iCT in extent of resection in large and giant pituitary adenomas.A retrospective review was performed of cases using the endonasal endoscopic technique in which iCT was used. Demographic factors, number of scans, and impact on the extent of resection are reported, with visual acuity and field changes. Tumors were graded according to the Hardy classification. Patients with cavernous sinus invasion were excluded.All patients received a perioperative computed tomography scan with our iCT scanner. Thirty patients are reported, including 14 large and 16 giant pituitary adenomas, including 14 nonfunctional and 16 growth hormone–secreting tumors. The overall gross total resection (GTR), near-total resection, and subtotal resection rates were 83.3%, 16.7%, and 3.3%, respectively. iCT scanning detected residual in 13 of 30 patients, including 4 with 14 large (29%) and 9 with 16 (56.3%) giant adenomas promoting further surgery. iCT use improved GTR from 43.8% to 81.3% in giant adenomas and from 71% to 86% in large adenomas. Of the 13 patients in whom iCT detected residual disease, none required >2 iCT scans. No intraoperative complications were observed.iCT can improve extent of resection in large and giant pituitary adenomas and facilitate maximum safe resection such as GTR or near-total resection in patients where such should be attempted. iCT use may reduce iatrogenic complications and has select financial benefits in our patients' socioeconomic demographics. However, further prospective controlled studies are required to affirm our conclusions.

Initial Intraoperative Experience with Robotic-Assisted Pedicle Screw Placement with Cirq® Robotic Alignment: An Evaluation of the First 70 Screws.

Background: Robot-guided spine surgery is based on a preoperatively planned trajectory that is reproduced in the operating room by the robotic device. This study presents our initial experience with thoracolumbar pedicle screw placement using Brainlab’s Cirq® surgeon-controlled robotic arm (BrainLab, Munich, Germany). Methods: All patients who underwent robotic-assisted implantation of pedicle screws in the thoracolumbar spine were included in the study. Our workflow, consisting of preoperative imagining, screw planning, intraoperative imaging with automatic registration, fusion of the preoperative and intraoperative imaging with a review of the preplanned screw trajectories, robotic-assisted insertion of K-wires, followed by a fluoroscopy-assisted insertion of pedicle screws and control iCT scan, is described. Results: A total of 12 patients (5 male and 7 females, mean age 67.4 years) underwent 13 surgeries using the Cirq® Robotic Alignment Module for thoracolumbar pedicle screw implantation. Spondylodiscitis, metastases, osteoporotic fracture, and spinal canal stenosis were detected. A total of 70 screws were implanted. The mean time per screw was 08:27 ± 06:54 min. The mean time per screw for the first 7 surgeries (first 36 screws) was 16:03 ± 09:32 min and for the latter 6 surgeries (34 screws) the mean time per screw was 04:35 ± 02:11 min (p < 0.05). Mean entry point deviation was 1.9 ± 1.23 mm, mean deviation from the tip of the screw was 2.61 ± 1.6 mm and mean angular deviation was 3.5° ± 2°. For screw-placement accuracy we used the CT-based Gertzbein and Robbins System (GRS). Of the total screws, 65 screws were GRS A screws (92.85%), one screw was a GRS B screw, and two further screws were grade C. Two screws were D screws (2.85%) and underwent intraoperative revision. There were no perioperative deficits. Conclusion: Brainlab’s Cirq® Robotic Alignment surgeon-controlled robotic arm is a safe and beneficial method for accurate thoracolumbar pedicle screw placement with high accuracy.

Usefulness of Intraoperative Computed Tomography on Extent of Resection of Large and Giant Pituitary Adenomas. Experience from a Developing Country

The literature on the use of intraoperative computed tomography (iCT) is sparse. We provide our experience of the usefulness of iCT in extent of resection in large and giant pituitary adenomas. A retrospective review was performed of cases using the endonasal endoscopic technique in which iCT was used. Demographic factors, number of scans, and impact on the extent of resection are reported, with visual acuity and field changes. Tumors were graded according to the Hardy classification. Patients with cavernous sinus invasion were excluded. All patients received a perioperative computed tomography scan with our iCT scanner. Thirty patients are reported, including 14 large and 16 giant pituitary adenomas, including 14 nonfunctional and 16 growth hormone-secreting tumors. The overall gross total resection (GTR), near-total resection, and subtotal resection rates were 83.3%, 16.7%, and 3.3%, respectively. iCT scanning detected residual in 13 of 30 patients, including 4 with 14 large (29%) and 9 with 16 (56.3%) giant adenomas promoting further surgery. iCT use improved GTR from 43.8% to 81.3% in giant adenomas and from 71% to 86% in large adenomas. Of the 13 patients in whom iCT detected residual disease, none required >2 iCT scans. No intraoperative complications were observed. iCT can improve extent of resection in large and giant pituitary adenomas and facilitate maximum safe resection such as GTR or near-total resection in patients where such should be attempted. iCT use may reduce iatrogenic complications and has select financial benefits in our patients' socioeconomic demographics. However, further prospective controlled studies are required to affirm our conclusions.

Intraoperative Computed Tomography-Based Navigation with Augmented Reality for Lateral Approaches to the Spine.

Background. Lateral approaches to the spine have gained increased popularity due to enabling minimally invasive access to the spine, less blood loss, decreased operative time, and less postoperative pain. The objective of the study was to analyze the use of intraoperative computed tomography with navigation and the implementation of augmented reality in facilitating a lateral approach to the spine. Methods. We prospectively analyzed all patients who underwent surgery with a lateral approach to the spine from September 2016 to January 2021 using intraoperative CT applying a 32-slice movable CT scanner, which was used for automatic navigation registration. Sixteen patients, with a median age of 64.3 years, were operated on using a lateral approach to the thoracic and lumbar spine and using intraoperative CT with navigation. Indications included a herniated disc (six patients), tumors (seven), instability following the fracture of the thoracic or lumbar vertebra (two), and spondylodiscitis (one). Results. Automatic registration, applying intraoperative CT, resulted in high accuracy (target registration error: 0.84 ± 0.10 mm). The effective radiation dose of the registration CT scans was 6.16 ± 3.91 mSv. In seven patients, a control iCT scan was performed for resection and implant control, with an ED of 4.51 ± 2.48 mSv. Augmented reality (AR) was used to support surgery in 11 cases, by visualizing the tumor outline, pedicle screws, herniated discs, and surrounding structures. Of the 16 patients, corpectomy was performed in six patients with the implantation of an expandable cage, and one patient underwent discectomy using the XLIF technique. One patient experienced perioperative complications. One patient died in the early postoperative course due to severe cardiorespiratory failure. Ten patients had improved and five had unchanged neurological status at the 3-month follow up. Conclusions. Intraoperative computed tomography with navigation facilitates the application of lateral approaches to the spine for a variety of indications, including fusion procedures, tumor resection, and herniated disc surgery.

Assessment of planning reproducibility in three-dimensional field-in-field radiotherapy technique for breast cancer: impact of surgery-simulation interval

The three-dimensional field-in-field (3-D FIF) technique for radiotherapy is an advanced, state-of-the-art method that uses multileaf collimators to generate a homogeneous and conformal dose distribution via segmental subfields. The purpose of this study is to evaluate the dosimetric reproducibility of 3-D FIF plans using the original simulation computed tomography (iCT) scans and re-simulation CT (rCT) scans for whole breast irradiation (WBI) schedule. This study enrolled a total of 34 patients. The study population underwent iCT scans for standard WBI and took rCT scans after 45 Gy of WBI for cone down boost plans. The dosimetric parameters (V105%, V103%, V100%, V98%, V95%, V90%, V50%), plan quality indices (conformity index, homogeneity index) and clinical parameters (isocenter-breast axis, isocenter-lung axis, soft tissue volumes within radiation field, lung volumes within radiation field) were assessed. The median time interval from surgery to iCT was 33 days and from iCT to rCT was 35 days. All dosimetric parameters exhibited statistically significant differences between iCT and rCT among cohorts with a surgery-iCT interval of < 60 days. Homogeneity index showed a statistically significant increase from iCT to rCT among all cohorts. Soft tissue volumes (p = 0.001) and isocenter-breast axis (p = 0.032) exhibited statistically significant differences among cohorts with surgery-iCT interval < 60 days. Regarding the reproducibility of the 3-D FIF WBI plans, significant changes were observed in dosimetric and clinical factors, particularly in study cohorts with a surgery-simulation interval < 60 days. The main contributing factor of these transitions seemed to be the changes in volume of the soft tissue within the WBI field. Further confirmative studies are necessary to determine the most suitable timing and technique for WBI.

Rule of Four: A Value-Based Approach to Aortic Stent Graft Inventory Creation for the Treatment of Blunt Thoracic Aortic Injuries Using Real Patient Aortic Measurements

As blunt thoracic aortic injury (BTAI) treatment has shifted from open to thoracic endovascular aortic repair, logistical challenges exist in creating and maintaining inventories of appropriately sized stent grafts, including storage demands, shelf-life management and cost. We hypothesized that most injured aortas can be successfully repaired with a narrow range of stent graft sizes and present a value-based anatomic approach to optimizing inventory. Computed tomography scans of all patients with BTAI admitted to our level I trauma center from April 2010 to December 2018 were reviewed. Patients with anatomy incompatible with thoracic endovascular aortic repair were excluded. For each patient, after aortic sizing a set of two stent grafts most likely to be utilized was selected from a list of twenty commercially available stent graft sizes by the manufacturer with the longest history of US Food and Drug Administration approval for BTAI. Stent graft sizes were then ranked based on the number of cases they would be suiTable for. Twenty-eight patients with BTAI were identified and three were excluded based on anatomic considerations. Most patients were male (68%), mean age 42.3 ± 20.2 years, mean Injury Severity Score 37.0 ± 9.8. Overall mortality was 25%. The Table summarizes the percentages of patients successfully treated by each combination of stent graft sizes. Of the 20 available stent graft options, a select combination of four stent grafts would successfully treat 96% of the patients in this study. Based on actual computed tomography scan aortic measurements, we demonstrated that an inventory of four sent-graft sizes was sufficient to successfully treat 96% of patients with BTAI. These data can be utilized as a value-based approach to aortic stent graft institutional inventory creation and maintenance.Table ICT scan measurements for graft ranking (left), percentage of patients with BTAI successfully treated with each stent-graft size and combination (right).VesselDiameter (mm ± SD)Aorta, at L carotid a. ostium23.4 ± 3.4Aorta, at L subclavian a. ostium22.2 ± 3.9Aorta, proximal to injury20.6 ± 4.3Aorta, distal to injury20.3 ± 4.5Common iliac a.9.1 ± 1.9External iliac a.7.4 ± 1.6Graft size combinations% Cases26, 26-21, 28, 31 mm9626, 26-21, 28 mm8426, 28, 31 mm8426, 28 mm7226 mm only5228 mm only4426 - 21 mm only3631 mm only28 Open table in a new tab

Intraoperative Computed Tomography and Finite Element Modelling for Multimodal Image Fusion in Brain Surgery.

intraoperative computer tomography (iCT) and advanced image fusion algorithms could improve the management of brainshift and the navigation accuracy. To evaluate the performance of an iCT-based fusion algorithm using clinical data. Ten patients with brain tumors were enrolled; preoperative MRI was acquired. The iCT was applied at the end of microsurgical resection. Elastic image fusion of the preoperative MRI to iCT data was performed by deformable fusion employing a biomechanical simulation based on a finite element model. Fusion accuracy was evaluated: the target registration error (TRE, mm) was measured for rigid and elastic fusion (Rf and Ef) and anatomical landmark pairs were divided into test and control structures according to distinct involvement by the brainshift. Intraoperative points describing the stereotactic position of the brain were also acquired and a qualitative evaluation of the adaptive morphing of the preoperative MRI was performed by 5 observers. The mean TRE for control and test structures with Rf was 1.81±1.52 and 5.53±2.46 mm, respectively. No significant change was observed applying Ef to control structures; the test structures showed reduced TRE values of 3.34±2.10 mm after Ef (P<.001). A 32% average gain (range 9%-54%) in accuracy of image registration was recorded. The morphed MRI showed robust matching with iCT scans and intraoperative stereotactic points. The evaluated method increased the registration accuracy of preoperative MRI and iCT data. The iCT-based non-linear morphing of the preoperative MRI can potentially enhance the consistency of neuronavigation intraoperatively.

Comparison of Intraoperative Computed Tomography Scan with Postoperative Magnetic Resonance Imaging for Determining Deep Brain Stimulation Electrode Coordinates

Deep brain stimulation (DBS) is an effective therapy for a variety of refractory movement disorders. Accurate lead placement in the target nucleus is critical to ensure therapeutic effects and to minimize side effects, and intraoperative computed tomography (iCT) scan has been used to target and confirm lead position. The objective of this study is to compare the accuracy of determining the x, y, and z coordinates of final lead placement using iCT scan relative to postoperative magnetic resonance imaging (MRI). We conducted a retrospective study on 83patients who underwent insertion of 145 DBS leads from 2015 to 2017 at a single institution. iCT scan was merged with the preoperative MRI to determine lead coordinates on both magnetic resonance and computed tomography images independently, and the absolute differences between the x, y, and z coordinates between the 2 scans along with the Euclidean vectors were calculated. The mean absolute differences ± standard error of the mean between iCT scan and postoperative MRI coordinates were as follows: x= 0.01 ± 0.09 mm (P=0.89), y= 1.67 ± 0.14 mm (P < 0.001), and z= 2.75 ±0.15 mm (P < 0.001). The average Euclidean vector difference was 3.21 ± 0.15 mm (P < 0.001). Significant differences exist between iCT scan and postoperative MRI DBS y and z lead coordinates, but not with x coordinates. Based on this series, iCT scan is more accurate when confirming x coordinates, and less accurate for confirming y and z coordinates during DBS operations.

Reliable navigation registration in cranial and spine surgery based on intraoperative computed tomography.

Low registration errors are an important prerequisite for reliable navigation, independent of its use in cranial or spinal surgery. Regardless of whether navigation is used for trajectory alignment in biopsy or implant procedures, or for sophisticated augmented reality applications, all depend on a correct registration of patient space and image space. In contrast to fiducial, landmark, or surface matching-based registration, the application of intraoperative imaging allows user-independent automatic patient registration, which is less error prone. The authors' aim in this paper was to give an overview of their experience using intraoperative CT (iCT) scanning for automatic registration with a focus on registration accuracy and radiation exposure. A total of 645 patients underwent iCT scanning with a 32-slice movable CT scanner in combination with navigation for trajectory alignment in biopsy and implantation procedures (n = 222) and for augmented reality (n = 437) in cranial and spine procedures (347 craniotomies and 42 transsphenoidal, 56 frameless stereotactic, 59 frame-based stereotactic, and 141 spinal procedures). The target registration error was measured using skin fiducials that were not part of the registration procedure. The effective dose was calculated by multiplying the dose length product with conversion factors. Among all 1281 iCT scans obtained, 1172 were used for automatic patient registration (645 initial registration scans and 527 repeat iCT scans). The overall mean target registration error was 0.86 ± 0.38 mm (± SD) (craniotomy, 0.88 ± 0.39 mm; transsphenoidal, 0.92 ± 0.39 mm; frameless, 0.74 ± 0.39 mm; frame-based, 0.84 ± 0.34 mm; and spinal, 0.80 ± 0.28 mm). Compared with standard diagnostic scans, a distinct reduction of the effective dose could be achieved using low-dose protocols for the initial registration scan with mean effective doses of 0.06 ± 0.04 mSv for cranial, 0.50 ± 0.09 mSv for cervical, 4.12 ± 2.13 mSv for thoracic, and 3.37 ± 0.93 mSv for lumbar scans without impeding registration accuracy. Reliable automatic patient registration can be achieved using iCT scanning. Low-dose protocols ensured a low radiation exposure for the patient. Low-dose scanning had no negative effect on navigation accuracy.

Neuroendoscopic Surgery with a Combination of Image Detectable Sheath, Intraoperative Computed Tomography Scan, and Navigation System Improves Accuracy and Safety in Minimally Invasive Evacuation of Intracerebral Hematoma: Technical Note

Recent studies have confirmed the effectiveness of minimally invasive endoscopic surgery for intracerebral hematoma (ICH). However, improvements are needed because incomplete hematoma removal may offset the surgical benefits of the technique. We describe a technique of neuroendoscopic surgery using an image detectable sheath, intraoperative computed tomography (iCT) scan, and a navigation system. This is a retrospective study of 15 consecutive patients with spontaneous ICH who received neuroendoscopic surgery. During the surgery, a transparent sheath was fastened tightly to the scalp with 3.0 nylon. The patient's head was covered with a sterilized vinyl sheet and subsequent iCT scan visualized the orientation of the endoscopic sheath and the extent of residual hematoma, allowing the surgeon to decide to continue to remove the hematoma or to finish the treatment. The median hematoma evacuation rate was 93% (interquartile range, 82.2%-95.9%). The Glasgow Coma Scale score of all patients significantly improved at 1 week after the operation (P < 0.05). No complications associated with the procedure were observed. The combination of our techniques improves accuracy and safety of minimally invasive surgical evacuation of hematoma. Performing surgery with iCT scan also improves the spatial recognition of surgeons and therefore may be of educational value.

An initial experience with intraoperative O-Arm for deep brain stimulation surgery: can it replace post-operative MRI?

Deep brain stimulation (DBS) is used to treat movement disorders, severe psychiatric disorders, and neuropathic pain, among other diseases. Advanced neuroimaging techniques allow direct or indirect localization of the target site, which is verified in many centers by the intraoperative recording of unitary neuronal activity. Intraoperative image acquisition technology (e.g., O-Arm) is increasingly used for accurate electrode positioning throughout the surgery. The aim of our study is to analyze the initial experience of our team in the utilization of O-Arm for planning DBS and monitoring its precision and accuracy throughout the procedure. The study included 13 patients with movement disorders. All underwent DBS with the intraoperative O-arm image acquisition system (iCT) and Medtronic StealthStation S7 cranial planning system, placing a total of 25 electrodes. For each patient, we calculated the difference between real and theoretic x, y, z coordinates, using the paired Student's t test to evaluate absolute and directional differences and the one-sample Student's t test to analyze differences in Euclidean distances. No statistically significant differences were found in absolute, directional, or Euclidean distances between intended and actual x, y, and z coordinates, based on iCT scan. Our experience confirms that utilization of the O-Arm system in DBS provides accurate and precise verification of electrode placements throughout the procedure. Recent studies found no significant differences between iCT and postoperative MRI, the current gold standard. Further prospective studies are warranted to test the elimination of postoperative MRI when this system is used.

Image-Guided Spinal Surgery and Robotics in MIS: Where Are We Now?

Use of pedicle screws is widespread in spinal surgery for degenerative, traumatic, and oncological diseases. The conventional technique is based on the recognition of anatomic landmarks, preparation and palpation of cortices of the pedicle under control of an intraoperative C-arm (iC-arm) fluoroscopy. With these conventional methods, the median pedicle screw accuracy ranges from 86.7% to 93.8%, even if perforation rates range from 21.1% to 39.8%.The development of novel intraoperative navigational techniques, commonly referred to as image-guided surgery (IGS), provide simultaneous and multiplanar views of spinal anatomy. IGS technology can increase the accuracy of spinal instrumentation procedures and improve patient safety. These systems, such as fluoroscopy-based image guidance ("virtual fluoroscopy") and computed tomography (CT)-based computer-guidance systems, have sensibly minimized risk of pedicle screw misplacement, with overall perforation rates ranging from between 14.3% and 9.3%, respectively."Virtual fluoroscopy" allows simultaneous two-dimensional (2D) guidance in multiple planes, but does not provide any axial images; quality of images is directly dependent on the resolution of the acquired fluoroscopic projections. Furthermore, computer-assisted surgical navigation systems decrease the reliance on intraoperative imaging, thus reducing the use of intraprocedure ionizing radiation. The major limitation of this technique is related to the variation of the position of the patient from the preoperative CT scan, usually obtained before surgery in a supine position, and the operative position (prone). The next technological evolution is the use of an intraoperative CT (iCT) scan, which would allow us to solve the position-dependent changes, granting a higher accuracy in the navigation system.

Ultrasound-guided intrapleural positioning of pleural catheters: influence on immediate lung expansion and pleurodesis in patients with recurrent malignant pleural effusion.

ABSTRACT Objective:To evaluate the role of intrapleural positioning of a pleural catheter in early lung expansion and pleurodesis success in patients with recurrent malignant pleural effusion (RMPE). Methods:This was a retrospective study nested into a larger prospective cohort study including patients with RMPE recruited from a tertiary university teaching hospital between June of 2009 and September of 2014. The patients underwent pleural catheter insertion followed by bedside pleurodesis. Chest CT scans were performed twice: immediately before pleurodesis (iCT) and 30 days after pleurodesis (CT30). Catheter positioning was categorized based on iCT scans as posterolateral, anterior, fissural, and subpulmonary. We used the pleural volume on iCT scans to estimate early lung expansion and the difference between the pleural volumes on CT30 and iCT scans to evaluate radiological success of pleurodesis. Clinical pleurodesis success was defined as no need for any other pleural procedure. Results:Of the 131 eligible patients from the original study, 85 were included in this nested study (64 women; mean age: 60.74 years). Catheter tip positioning was subpulmonary in 35 patients (41%), anterior in 23 (27%), posterolateral in 17 (20%), and fissural in 10 (12%). No significant differences were found among the groups regarding early lung expansion (median residual pleural cavity = 377 mL; interquartile range: 171-722 mL; p = 0.645), radiological success of pleurodesis (median volume = 33 mL; interquartile range: −225 to 257 mL; p = 0.923), and clinical success of pleurodesis (85.8%; p = 0.676). Conclusions:Our results suggest that the position of the tip of the pleural catheter influences neither early lung expansion nor bedside pleurodesis success in patients with RMPE.

Orbit-associated tumors: navigation and control of resection using intraoperative computed tomography.

OBJECT Treatment of skull base lesions is complex and usually requires a multidisciplinary approach. In meningioma, which is the most common tumor entity in this region, resection is considered to be the most important therapeutic step to avoid tumor recurrence. However, resection of skull base lesions with orbital or optic nerve involvement poses a challenge due to their anatomical structure and their proximity to eloquent areas. Therefore the main goal of surgery should be to achieve the maximum extent of resection while preserving neurological function. In the postoperative course, medical and radiotherapeutic strategies may then be successfully used to treat possible tumor residues. Methods to safely improve the extent of resection in skull base lesions therefore are desirable. The current study reports the authors' experience with the use of intraoperative CT (iCT) combined with neuronavigation with regard to feasibility and possible benefits of the method. METHODS Those patients with tumorous lesions in relationship to the orbit, sphenoid wing, or cavernous sinus who were surgically treated between October 2008 and December 2013 using iCT-based neuronavigation and in whom an intraoperative scan was obtained for control of resection were included. In all cases a second iCT scan was performed under sterile conditions after completion of navigation-guided microsurgical tumor resection. The surgical strategy was adapted accordingly; if necessary, resection was continued. RESULTS Twenty-three patients (19 with WHO Grade I meningioma and 4 with other lesions) were included. The most common clinical symptoms were loss of visual acuity and exophthalmus. Intraoperative control of resection by iCT was successfully obtained in all cases. Intraoperative imaging changed the surgical approach in more than half (52.2%) of these patients, either because iCT demonstrated unexpected residual tumor masses or because the second scan revealed additional tumor tissue that was not detected in the first scan due to overlay by osseous tumor parts; in these cases resection was continued. In the remaining cases resection was concluded as planned because iCT verified the surgeon's microscopic estimation of tumor resection status. Postoperative visual outcome was favorable in more than 80% of patients. CONCLUSIONS Intraoperative CT allows control of resection in case of uncertainty and can help to improve the extent of maximal safe resection, especially in case of osseous tumor parts and masses within the orbit.

Intraoperative Computed Tomography Navigation for Transpedicular Screw Fixation to Treat Unstable Thoracic and Lumbar Spine Fractures

Transpedicular screw (TPS) fixation in unstable thoracic and lumbar (TL) spine fractures remains technically difficult because of destroyed anatomical landmarks, unstable gross segments, and discrepancies in anatomic orientation using conventional anatomic landmarks, fluoroscopic guidance, or computed tomography (CT)-based navigation. In this study, we evaluated the safety and accuracy of TPS placement under intraoperative computed tomography (iCT) navigation in managing unstable TL spine fractures.From 2010 to 2013, we retrospectively reviewed the Spine Operation Registry records of patients who underwent posterior instrumented fusion to treat unstable TL spine fractures via the iCT navigation system. An unstable spine fracture was identified as AO/Magerl classification type B or type C.In all, 316 screws in 37 patients with unstable TL spine fractures were evaluated and involved 7 thoracic, 23 thoracolumbar junctional, and 7 lumbar fractures. The accuracy of TPS positioning in the pedicle without breach was 98% (310/316). The average number of iCT scans per patient was 2.1 (range 2–3). The average total radiation dose to patients was 15.8 mSv; the dose per single level exposure was 2.7 mSv. The TPS intraoperative revision rate was 0.6% (2/316) and no neurovascular sequela was observed. TPS fixation using the iCT navigation system obtained a 98% accuracy in stabilizing unstable TL spine fractures. A malplaced TPS could be revised during real-time confirmation of the TPS position, and no secondary operation was required to revise malplaced screws.The iCT navigation system provides accurate and safe management of unstable TL spine fractures. In addition, operating room personnel, including surgeons and nurses, did not need to wear heavy lead aprons as they were not exposed to radiation.

Accuracy and workflow of navigated spinal instrumentation with the mobile AIRO(®) CT scanner.

Current solutions for navigated spine surgery remain hampered by restrictions in surgical workflow as well as a limited versatility and applicability. Against this background, we report the first experience of navigated spinal instrumentation with the mobile AIRO(®) intraoperative computed tomography (iCT) scanner. AIRO(®) iCT was used for navigated posterior spinal instrumentation of 170 screws in 23 consecutive patients operated on in our Department between the first use of the system in May 2014 and August 2014. The indications for AIRO(®) were based on the surgical region, anatomical complexity and the need for >3 segment instrumentation. Following navigated screw insertion, screw positions were confirmed intraoperatively by a second iCT scan. CT data on screw placement accuracy were retrospectively reviewed and analyzed by an independent observer. AIRO(®)-based spinal navigation was easy to implement and successfully accomplished in all patients, adding around 18-34 min to the net surgery time. A systematic description of the authors' approach, setup in the OR and workflow integration of the AIRO(®) is presented. Analysis of screw placement accuracy revealed 9 (5.3%) screws with minor pedicle breaches (<2 mm). A total of 7 screws (4.1%) were misplaced >2 mm, resulting in an accuracy rate of 95.9%. The AIRO(®) system is an easy-to-use and versatile iCT for navigated spinal instrumentation and provides high pedicle screw accuracy rates. Although the authors' experience suggests that the learning curve associated with AIRO(®)-based spinal navigation is steep, a systematic user-based approach to the technology is required.

The Use of Neuronavigation and Intraoperative Imaging in Spinal Stabilization Surgery.

Misplacement of pedicle screw is the serious complication of spinal surgeries. Intraoperative imaging techniques and navigation systems are currently in use for the prevention of this complication. The aim of this study was to document the results of our experience with the navigation and intraoperative imaging technique and to share our experience with our colleagues. Between 2011 and 2014, one hundred and two patients underwent instrumented spinal surgery while using intraoperative computed tomography (iCT) and a navigation system. All patients had a CT scan performed no more than three days postoperatively to confirm adequate placement of the screws. The accuracy of pedicle screw placement was assessed by postoperative CT scan. Pedicle violations were graded according to an established classification system. In the 36-month period, a total of 610 screws in 102 patients were evaluated. Stabilization surgery was performed in the lumbosacral region in 51 (50%) patients, lumbar region in 35 (34.31%) patients, cervical region in 5 (4.9%) patients, thoracolumbar region in 7 (6.86%) patients and thoracic region in 4 (3.92%) patients. Of the 610 screws, 396 (64.91%) were placed in lumbar, 66 (10.81%) in thoracic, 106 (17.37%) in sacral and 42 (6.8%) in cervical vertebrae. Of the 610 screws, 599 screws (98.18%) were placed without a breach. Grade 1 breaches occurred in 8 screws (1.31%), Grade 2 breaches occurred in 2 screws (0.32%), and Grade 3 breaches in 1 screw (0.16%). No dural defect or neurological deficit occurred after the surgeries. The use of an iCT scan associated with a navigation system increases the accuracy of pedicle screw placement. This system protects the surgical team from fluoroscopic radiation exposure and the patient from the complications of screw misplacement and repeated surgeries.

Feasibility of Intraoperative Computed Tomography Navigation System for Pedicle Screw Insertion of the Thoracolumbar Spine

STUDY DESIGN:: A retrospective analysis of feasibility of intraoperative computed tomography (iCT) navigation for pedicle screw insertion of the thoraco-lumbar spine OBJECTIVES:: This study assessed the feasibility of an iCT navigation system by evaluating the screw insertion time, screw revision time, and learning curve of the iCT surgical team in patients who underwent thoraco-lumbar pedicle screw surgery using this navigation system. SUMMARY OF BACKGROUND DATA:: The iCT navigation system has been reported to improve the accuracy and safety of pedicle screw insertion. However, the assessment of the feasibility of spinal instrumentation guided by iCT navigation system is limited. METHODS:: From the time iCT navigation system was set-up to a period covering 16 months, consecutive patients who underwent thoracic or lumbar spinal pedicle screw surgery were enrolled. The screw insertion and screw revision times were estimated using the system's automatic time recording between the intra-operative CT scans. The insertion time per screw of the first 50 patients not requiring screw revision was also analyzed to evaluate the learning curve of the iCT surgical team. RESULTS:: There were 178 patients with a total of 932 pedicle screws. The cortical breach rate was 3.2% and the screw revision rate was 1.4%. The insertion time per screw was 10.2±6.3▒min and the screw revision time was 13.8±9.9▒min. The learning curve of the iCT surgical team for pedicle screw insertion guided by this navigation system was not steep and experience from less than 10 patients was adequate to provide familiarity with this system. CONCLUSION:: The iCT navigation system is clinically feasible for thoraco-lumbar pedicle screw surgery. It provides high-level safety and accuracy, as well as ease of screw revision when required.

Intraoperative computed tomography with integrated navigation system for individualized decompression of congenital craniovertebral junction malformation

Objective To assess the feasibility and potential utility of intraoperative computed tomography( iCT)with integrated neuronavigation system (NNS) in individualized decompressive procedure of complex craniovertebral junction malformation ( CVJM ).Methods We reported our first 19 complex CVJM cases including 11male and 8 female patients ( mean age,33.9 y; age range.13 to 58 y).A sliding gantry 40 - slice CT scanner was installed in a preexisting operating room. Image data was transferred directly from the scanner into the NNS using an automated registration system.We applied this technology to transoral odontoidectomy in 17 patients. Moreover,with the extra help of iCT integrated with NNS,odontoidectomy through posterior midline approach,and transoral atlantal lateral mass resection were,for the first time,performed for treatment of complex CVJM.Results Of the 19 cases,assessment of iCT scans obtained in 4 indicated further bone removal was required.The results revealed that the goal of osseous resection had been met.Neuronavigation was found to correlate well with the intra - operative findings and the recalibration was uneventful in all cases and had an accuracy of 1.6mm (1.2 ～ 2.0mm).All patients were clinically evaluated by Nurick grade criteria,and neurological deficits were monitored after 3 months of surgery.Fifteen patients were improved by at least 1Nurick grade,whereas the grade did not change in 4 patients.Conclusions iCT with integrated NNS was found both feasible and beneficial in the surgical management of complex CVJM.In this unusual patient population,the technique appeared to be valuable in negotiating complex anatomy and achieving a safe and predictable decompression. Key words: Intraoperative computed tomography; Neuronavigation system; Craniovertebral junction malformation; Odontoidectomy