- 3rd Year Medical Student, University of Glasgow, Wolfson School of Medicine, Glasgow, Scotland, United Kingdom,
- Visiting Medical Student, Allama Iqbal Medical College, Department of Neurosurgery, Jinnah Hospital, Lahore, Pakistan,
- Department of Neurosurgery, Allama Iqbal Medical College, Jinnah Hospital, Lahore, Pakistan.
Department of Neurosurgery, Allama Iqbal Medical College, Jinnah Hospital, Lahore, Pakistan.
DOI:10.25259/SNI_303_2020Copyright: © 2020 Surgical Neurology International This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.
How to cite this article: Mohammad Ashraf1,2, Nabeel Choudhary3, Syed Shahzad Hussain3, Usman Ahmad Kamboh3, Naveed Ashraf3. Role of intraoperative computed tomography scanner in modern neurosurgery – An early experience. 15-Aug-2020;11:247
How to cite this URL: Mohammad Ashraf1,2, Nabeel Choudhary3, Syed Shahzad Hussain3, Usman Ahmad Kamboh3, Naveed Ashraf3. Role of intraoperative computed tomography scanner in modern neurosurgery – An early experience. 15-Aug-2020;11:247. Available from: https://surgicalneurologyint.com/surgicalint-articles/10210/
Background: Intraoperative imaging addresses the limitations of frameless neuronavigation systems by providing real-time image updates. With the advent of new multidetector intraoperative computed tomography (CT), soft tissue can be visualized far better than before. We report the early departmental experience of our intraoperative CT scanner’s use in a wide range of technically challenging neurosurgical cases.
Methods: We retrospectively analyzed the data of all patients in whom intraoperative CT scanner was utilized. Out of 31 patients, 24 (77.4%) were cranial and 8 (22.6%) spinal cases. There were 13 male (41.9%) and 18 (58.1%) female patients, age ranged from 1 to 83 years with a mean age of 34.29 years ±17.54 years. Seven patients underwent spinal surgery, 2 cases were of orbital tumors, and 16 intra-axial brain tumors, including 5 low- grade gliomas, 10 high-grade gliomas, and 1 colloid cyst. There were four sellar lesions and two multiloculated hydrocephalus.
Results: The intraoperative CT scan guided us to correct screw placement and was crucial in managing four complex spinal instabilities. In intracranial lesions, 59% of cases were benefitted due to intraoperative CT scan. It helped in the precise placement of ventricular catheter in multiloculated hydrocephalus and external ventricular drain for a third ventricular colloid cyst.
Conclusion: Intraoperative CT scan is safe and logistically and financially advantageous. It provides versatile benefits allowing for safe and maximal surgery, requiring minimum changes to an existing neurosurgical setup. Intraoperative CT scan provides clinical benefit in technically difficult cases and has a smooth workflow.
Keywords: Intraoperative computed tomography scan, Image-guided neurosurgery, Glioma surgery, Spine surgery, Multiloculated hydrocephalus, Third ventricular colloid cyst
Intraoperative imaging modalities are important tools in the armamentarium of modern neurosurgeons as these greatly have helped overcome the challenges faced by traditional neuronavigation systems. Conventionally, image-guided neuronavigation systems have helped localize complex lesions in the brain. This complexity can be attributed to the complicated anatomy of the brain that has fascinated neurosurgeons and anatomists alike. The navigation system in surgery produces the tip of a pointer on an image. The system calibrates preoperative images to the intraoperative coordinate system of the patient using a transformation matrix creating a link between preoperative imaging and anatomical structures giving surgeons a 3-D orientation of the position of the region of interest.[
The significant limitation of navigation, however, is the presumption that the brain and skull are rigid structures,[
The main modalities include intraoperative ultrasound (iUS), intraoperative magnetic resonance imaging (iMRI), and intraoperative computed tomography (iCT) scanner. The iUS is more widely available and less costly. Recent advances have yielded promising results with 3-D ultrasound that uses shear waves as opposed to longitudinal waves, linear regression analysis shows that it correlates better with preoperative MRIs.[
MRI is considered to be the gold standard imaging modality for soft-tissue lesions. One prospective randomized controlled trial utilized iMRI to increase the extent of resection,[
Intraoperative CT scan has been available as a portable device since the early 2000s and has been used with great success in spinal surgeries. With the development of multidetector CT (MDCT), soft-tissue image resolution is improving and its use in neurosurgical suites is increasing. It can be easily incorporated into a preexisting setup and requires very little changes; some of these include lead shielding and radiolucent table top with a radiolucent Mayfield/Doro head holder. We recently procured Airo Brainlab 32-slice MDCT and incorporated it into our existing operating theaters. No special surgical or anesthetic instrument/equipment changes were required. We have used this for both spine and cranial surgeries since October 2019 and present our early experience of its uses and benefits.
This is a descriptive case series. We retrospectively analyzed data of our patients who underwent spinal and cranial surgery where the intraoperative CT scanner was utilized. The Department of Neurosurgery, Allama Iqbal Medical College, Jinnah Hospital, Lahore is the first neurosurgery department in Pakistan to have an intra operative CT scanner and use it in our regular clinical practice. This included a total of 31 patients since October 2019–March 2020; of which 24 (77.4%) were cranial and 7 (22.6%) were spinal cases. There were 13 male (41.9%) and 18 (58.1%) female patients. The ages of our patients ranged from 1 to 83 years with a mean age of 34.29 years ±17.54. Patient information was entered and analyzed in SPSS version 25.
For most cranial cases, preoperative MRI was acquired according to our institutional imaging protocol. This included T1, T2 and T1 with contrast for contrast enhancing lesions.
Patients were positioned after general anesthesia with a dedicated radiolucent Doro skull clamp and radiolucent pins. All neurosurgical positions were appropriate except the sitting position. [
Despite using radiolucent head clamp and pins, artifacts were still encountered due to the high density of head clamp. To minimize this, the pins or clamp were placed caudal to the epicenter of lesion to avoid artifact. According to the manufacturer’s settings, the standard volumetric image acquisition protocol was used giving 1 mm axial slices with a 512 × 512 picture resolution. Our iCT has an aperture of 107 cm and the maximum field of view is 51.2 cm. The standard 25 cm field of view was used to cover the entire skull; however, increased field of view was utilized in areas where required. For cranial cases, we scanned from the vertex to the tip of the nose or 3 cm caudal to the lesion and for the surface registration of the neuronavigation. The scanner automatically calculated the dose of radiation based on the weight and height of the patient. There are three modes to scan in, “standard” and “normal” for bone and “sharp” for soft tissue. The acquisition of the images can be done by the surgeons/theater staff and little technical assistance is required minimizing the need for dedicated staff.
Before start of surgery, a single preoperative CT scan was acquired as a reference to compare with intraoperative CT images. The preoperative CT scan images were transferred through USB as DICOM files to the Medtronic Stealth S7 navigation and registration system and merged with preoperative imaging. Surgery was proceeded as standard with navigation assistance and when the surgeon thought, the procedure had been completed or wanted to assess the extent of resection/shunt placement another intraoperative CT scan was performed and merged with the preoperative CT scan for comparison to decide if further action was required. The average number of scans was two, one preoperative and one intraoperative.
Out of our 21 cranial cases, there were two cases of orbital tumors and both benefited from intervention with the iCT to increase the extent of resection. There were four sellar lesions, in one case, we intervened further as iCT notified us of residual tumor. In another case, the iCT revealed an intraoperative complication which influenced our decision to not proceed with further resection of residual disease. Out of our 15 intra-axial brain tumors, 9 had further resection done as shown by the iCT and out of 7 spinal fixations, 4 cases benefitted from screw redirection. In two cases of multiloculated hydrocephalus, the iCT was beneficial in redirecting the ventricular end of ventriculoperitoneal shunt and in one case of third ventricular colloid cyst, the use of iCT resulted in safe surgery.
Clinical localization of lesions within the central nervous system became possible as scientists explored the functional regions of the brain and nervous system. This localization was dramatically improved when imaging studies such as angiography, air ventriculography, and later cross-sectional imaging modalities such as CT and MRI came in to clinical practice. The history of image-guided surgery saw a major technological advance with the Leksell stereotactic frame invented in 1949[
There are currently sparse data regarding the uses of intraoperative CT scan, its use in spinal surgery has been established;[
Out of our seven spinal patients, two patients required fixation at the craniovertebral (CV) junction. One of them, a 59-year-old male required both anterior and posterior approach as the anterior pathology (fractured and cranially displaced odontoid) was done trans-orally. The iCT was crucial to allow us to orientate our self, correctly direct the screw placement and resect the odontoid peg. [
Two patients required fixation of the cervical-thoracic junction. In spinal surgery, junctional area such as cervical- thoracic region and CV junction is poorly visualized on standard C-arm X-ray and is of anatomical complexity. In these cases, the iCT turned out to be extremely helpful. [
For the first CV junction case, where both anterior and posterior approaches were used, we required three intraoperative scans; however, the subsequent patients of both CV junction and cervical-thoracic junction required two intraoperative scan each. The other 3 (42.8%) cases did not require correction of screw placement and a single intraoperative CT scan confirmed this. The iCT saved 4 (57.1%) patients from further surgery. In one study done by Tormenti et al., it was shown that using iCT scan yielded an overall accuracy of 98.9% (n = 12) in simple thoracic and lumbar fixations while the accuracy was 94.8% (n = 14) in the fluoroscopy group in assessing if screws are correctly placed.[
iCT was used to quantify residual disease in three sellar tumors and one fungal growth in the sella. One tumor required further resection due to residual disease, this was a case of a 23-year-old male with a growth hormone secreting pituitary adenoma (acromegaly). Out of the three tumors, where no further action was taken the iCT quantified the extent of resection and showed us in two cases that further resection was not required. These included an 18-year-old female with a sellar fungal growth and a 40-year-old female with a pituitary adenoma. However, in one case, we could not proceed further despite the iCT showing residual disease. This was a transcranial approach for a large macroadenoma in a 44-year-old female. Surgery could not be proceeded as the ipsilateral A1 branch of the anterior cerebral artery was injured and there was poor visualization of the contralateral A1, both of which were engulfed within the tumor. The iCT was performed to find out the details of the operative and perioperative area. Since there was only a localized hematoma in the suprasellar region, it was decided not to proceed as it may further jeopardize the patient.
Of the two orbital tumors operated, both benefitted from the iCT. One was a case of fungal granuloma in a 39-year- old female and an intraoperative scan allowed us to detect residual disease and hematoma at the apex of the orbit. The residual disease in the small cavity of the orbit would have led to great morbidity for this patient. The other case, a 23-year-old female, was of an osteoma of sphenoid in which the iCT helped to monitor the extent of bony resection. The ability to detect hematoma is a testament to the improving iCT technology that can better visualize soft tissue as a previous study reported that such a complication (hematoma) could not be picked up on their iCT.[
Multiloculated hydrocephalus is a very difficult entity to manage.[
There can be limitations to cranial and cervical spine surgery due to smaller bore of intraoperative CT scanners as reported by Barbagallo et al.,[
The limited number of RCTs utilizing iMRI highlights an important point, that is, institutions equipped with iMRI accept the surrogate outcome which is the extent of resection, to improve progression free and overall survival. The disadvantage with iMRI is the extremely high cost not only of the machine itself but also of the associated requirements such as a dedicated operation theater and MRI compatible operating tools and increased operative time. Furthermore, the logistics make it difficult to incorporate it into a preexisting setup. Recent studies suggested that there is no reasonable justification for a low field iMRI in a standard neurosurgical setup, at least not in its current state.[
Not surprisingly a surgeon’s preferred choice, the iMRI available in a single operation theater, requiring major financial investment to develop a setup of dedicated rooms, staff and equipment would be economically unfeasible. This may also increase the overall operation time such that there would be less cases done per day.[
Our experience has demonstrated that newer iCT scanners can provide versatile benefits in a wide variety of neurosurgical procedures both in adult and pediatric patients, are cheaper and logistically easier to integrate, and require little input of additional staff [
At present, from our experience, the iCT is not only a gold standard imaging modality for spinal surgery but a standard of care for difficult spinal and cranial surgical procedures. Further studies are required to establish its use as a beneficial intraoperative real-time imaging modality that should be utilized in specific patients where it is likely to provide benefit and improve outcome for individual patients. It may be added that more multicenter controlled trials are required to affirm our conclusions.
Our experience has demonstrated that iCT provides versatile benefits in a wide variety of neurosurgical procedures in both adult and pediatric cases, is cheaper and logistically easier to integrate, and requires little input of additional staff. The iCT provided clinical benefit in our technically difficult cases and has a smooth workflow.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. For this type of study ethical board approval is not required by our institution.
The authors certify that they have obtained all appropriate patient consent.
Publication of this article was made possible by the James I. and Carolyn R. Ausman Educational Foundation.
There are no conflicts of interest.
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