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THE INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY Int J Med Robotics Comput Assist Surg 2006; 2: 161–167. Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/rcs.89

ORIGINAL ARTICLE

Image-guided microneurosurgical management of vascular lesions using navigated computed tomography angiography. An advanced IGS technology application†

S Chibbaro* L Tacconi University Hospital, Trieste, Italy *Correspondence to: S Chibbaro, Via del Muraglione 2, 34100 Trieste, Italy. E-mail: [email protected] † No

conflict of interest was declared.

Abstract Background Image-guided neurosurgery has become a standard practice in the last few years, with more than 2000 surgical navigation stations installed worldwide. In the same time several reports have also demonstrated the efficacy and accuracy of computed tomography angiography (CTA) in assessing cerebral vascular pathologies. Therefore, the CTA data have recently been implemented into the different navigation systems available on the market, making this new technique widely applied. The objective of this paper is to discuss and evaluate the clinical usefulness of navigated CTA in planning and performing surgery of neurovascular lesions. Methods Raw images acquired from an helical CTA are automatically postprocessed on an independent workstation by using a three-dimensional (3D) volume-rendering images engine and/or using thresholding and drawing tools. Results The data obtained provide useful information in the preoperative stage by reconstructing the vascular tree with regard to lesion volume, aneurysm neck, dome projection, perforating vessels and their relationship with the lesion and the surrounding anatomy. Furthermore, it can help in the identification of an arteriovenous malformation (AVM) nidus and recognition of its feeding and draining vessels. Conclusion This fascinating technique can give some invaluable advantages on the management of cerebral vascular lesions and provides excellent information not always available on traditional digital subtraction angiography investigation. It has also proved to be very accurate, particularly regarding the correlation between the 3D volume-rendered CT angiography and the intraoperative findings. Copyright  2006 John Wiley & Sons, Ltd. Keywords aneurysms; cerebrovascular malformation; advanced neuronavigation; computed tomography angiography; 3D images; volume rendering

Introduction

Accepted: 26 March 2006

Copyright  2006 John Wiley & Sons, Ltd.

When performing aneurysm and small AVM surgery, is essential to conduct a preoperative evaluation of their morphological features. Shape, projection, volume, relationship with surrounding structures, perforating vessels, blood supply, drainage and complexity of vascular architecture are important

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features in planning the best surgical strategy, hence avoiding major complications (1,4,8,23). Conventional digital subtraction angiography (DSA), 3D computed tomography angiography (3D-CTA) and magnetic resonance angiography (MRA) (2) cannot always fully provide a complete and clearly understandable evaluation of all vascular structure in three dimensions. Recent reports in the literature (1,3,5,9,10,13,15–17,19,27) seem to indicate helical CTA as a very accurate and sensitive method for detecting cerebral aneurysms and characterization of features. It is also a much less invasive diagnostic tool. In recent years diagnostic imaging and software technology has remarkably advanced and it is now possible to postprocess raw images from the volumetric helical scan on an independent station, using a 3D volume-rendering processor (6,7,11,12,14,25,28). The objective of this technique is the optimum craniotomy location and intraoperative 3D guidance to the lesion.

Methods CTA and neuronavigation For the image-guided procedure, CTA is performed by a multislice CT system with a slice thickness of

S. Chibbaro and L. Tacconi

1 mm without gaps and/or overlap, and a reconstruction interval of 0.5 mm. Prior to the start of data acquisition, superficial fiducials are placed on the patient’s skin, mostly around the planned craniotomy site. Data acquisition starts generally with a 20 s delay of contrast agent injection, although recently we have started data acquisition at the time of peak enhancement, which is determined individually for each patient when the threshold of 80 Hounsfield units is reached at the internal carotid artery. The amount of contrast medium injected varies, depending on adult or paediatric patients, from 2.2 to 3 ml/s, using a power injector. The scan covers the whole head and fiducials, beginning at the foramen magnum, with a caudo-cranial table movement. The scanner gantry is set to zero in order to facilitate neuronavigation (1,5,13,18). The datasets obtained are transferred to an IGS station through an electronic network or magnetic disk to build up 3D models of vessels, using thresholding and drawing tools (Figure 6) and more recently by automatic postprocessing using new 3D volume-rendering software, implemented on StealthStation by Medtronic (Figs 1,2) and on Vectorvision by BrainLAB (Figure 6). In order to plan surgery, the 3D model is accurately and thoroughly analysed, also using rotational projections to obtain complete information and a 3D appreciation of the

Figure 1. Automated 3D volume-rendered angio-CT (by Medtronic Stealth-Station), showing an anterior communicating artery aneurysm Copyright  2006 John Wiley & Sons, Ltd.

Int J Med Robotics Comput Assist Surg 2006; 2: 161–167. DOI: 10.1002/rcs

Image-guided Microsurgery of Vascular Lesions Using Navigated CTA

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Figure 2. Automated 3D volume-rendered angio-CT (by Medtronic Stealth-Station) of an anterior communicating artery aneurysm and its relationship with the surrounding vessels

Figure 3. Automated 3-D volume rendered Angio-CT (by Medtronic Stealth-Station). Magnified particular of figure 3, which shows a middle cerebral artery bifurcation aneurysm and its relation to close bony structures during operative navigation with the pointer indicating the vascular lesion Copyright  2006 John Wiley & Sons, Ltd.


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Figure 4. Automated 3D volume-rendered angio-CT (by Medtronic Stealth-Station) of a middle cerebral artery bifurcation aneurysm, its exact position in relation to the surrounding structures and the possibility of reaching it through a small and centred craniotomy

Figure 5. Automated 3D volume-rendered angio-CT (by Medtronic Stealth-Station), showing a middle cerebral artery bifurcation aneurysm and its relationship to close bony structures Copyright  2006 John Wiley & Sons, Ltd.



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Figure 6. Manual reconstruction, using thresholding and drawing tools from angio-MRI (by BrainLAB Vector-Vision), of a carotid aneurysm

lesion, its neck position and its relationship with the surrounding structures (Figs 1–4, and 6. During surgery the 3D vessel model is displayed on the IGS screen (Figs 3–6); in this way it can be compared with the intraoperative view in order to give to the surgeon as much information as possible. This technique may also help to locate the exact location of distal aneurysms. When the pathology is at the skull base, the bony structure, automatically displayed together with all the vessels, can be removed utilizing a cut mode uncovering the anatomy and giving to the surgeon more knowledge and confidence in approaching this part of the head (Fig. 4). This is not a technique which can replace anatomical dissection training, but it can help to navigate some parts of the brain that are not often seen by those who are not specialized and dedicated vascular neurosurgeons.

Results It is our opinion that this technique can give the following advantages: 1. Post-processing images can be achieved automatically and rapidly (in few seconds), thanks to the new volume-rendering software. Copyright  2006 John Wiley & Sons, Ltd.

2. This technique gives additional information not available on traditional DSA, making surgery more accurate, easier, faster and safer. In particular it gives to the surgeon the ability to understand the real position of the aneurysm with respect to the surgical position of the patient, by being able to rotate the images through 360◦ . 3. Navigated CTA is helpful in identifying the optimal skin incision site and in tailoring the craniotomy to the minimum, allowing also, in case of small AVMs, the optimal route to the lesion and its safe removal, sparing eloquent brain areas. In fact it is also possible to import and/or fuse into these images those of functional MRI. In the management of MCA aneurysm and small AVMs, navigated CTA has also a major impact, resulting in a better centred craniotomy over the Silvian fissure and avoiding extensive detachment of temporal muscle and its subsequent atrophy, with all the related problems for the patient. 4. Accuracy of navigation in localizing lesions may be 1 mm or less. 5. Navigated angio-CTA is less invasive than DSA as it uses less radiation, is faster and requires fewer resources. 6. Raw image data can be acquired and transferred to the IGS station by technicians and/or general radiologists; the investigation and its post-processing can be done Int J Med Robotics Comput Assist Surg 2006; 2: 161–167. DOI: 10.1002/rcs

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in few minutes, making this technique a very good option in any emergency surgery. 7. CTA, particularly with the automatic processing software, has a better definition than MRA, as MRA has worse spatial localization and accuracy and is more prone to create artefacts from fast-moving blood contents or in the presence of acute or subacute intracerebral blood. 8. The IGS system equipped with the head-up display (HUD) function, which superimposes a transparent computer-generated image of a previously segmented structure on the microscope field of view tracked by the navigation system, enables the surgeon to choose the optimal dissection pathway, as he is able to see the focused region as well as the superimposed virtual image. This tool might also be useful in cases of premature aneurysm bleeding, when the surgeon is not able to see the neck, as it could allow placement of a real clip on the virtual aneurysm neck. 9. The manual technique using thresholding and drawing tools produces the best quality images. However, this is a time-consuming technique (it can take up to 80 min) and can be highly operator-dependent. Therefore, we do not think it is routinely applicable and should be limited to selected lesions close to the skull base, as it gives a very good definition of bony and vascular structures at the same time.


to support a statistical appraisal. Other important aspects are the smaller amount of radiation with CTA compared to DSA, its less invasive nature and smaller requirements of resources in terms of staff, equipment and costs. As a last but very important point, it can be performed easily in many emergency situations.

Conclusion The 3D data integration provides operative views of the vascular lesion (4–7,12,25,26), avoiding major problems such as premature bleeding and/or ischaemic complications which often occur due to insufficient anatomical understanding of complex vascular lesions (20,21). It should be considered that, although the learning curve for manipulating datasets is quite rapid, it still takes some time to fully and precisely elaborate the images. It is a cost-effective technique, allowing a smaller and tailored craniotomy with a major impact on surgery of MCA aneurysms and small AVMs. The ‘near’ future with the more precise navigation system might be to allow ‘blind’ clipping/exclusion of a lesion by mean of placing a real clip on a virtual aneurysm neck or blood vessel (22,24).

References Discussion In dealing with intracranial aneurysms and small AVMs, cerebral four-vessel angiography still remains the basic gold standard investigation, although it cannot always provide a complete evaluation of morphological features of the vascular lesion with its surrounding anatomy. Furthermore, for some types of lesions, it is important to have some specific information: better definition of the bone and soft tissue surrounding the lesion and/or exact understanding of the surrounding vascular tree. All these aspects are brilliantly provided by volume-rendered CTA coupled with an IGS system (6,7,11,12,14,25,28). This technique can give the neurosurgeon a better understanding of the real position of the anatomical structures he will encounter during surgery, giving a sort of a preoperative planning. This possibility may be particularly important in the presence of a ruptured aneurysm with a surrounding intracerebral haematoma, in fact the neurosurgeon could decrease the risk of reaching the aneurysm’s dome during blood clot removal. The optical definition and anatomical projection of the vascular lesion with this technique is also superior to that of DSA alone. Furthermore, the correlation of the 3D volume-rendering CT angiography with the intraoperative findings is excellent, as has already been discussed by one of the authors in a recently published paper (28) as well as by others (4–7,11,12,15,17,25). With respect to the system’s accuracy, it seems to be similar to that of the IGS system, although we do not yet have sufficient data Copyright  2006 John Wiley & Sons, Ltd.

1. Carvi y Nievas MN, Haas E, Hollerhage HG, Drathen C. Complementary use of computed tomographic angiography in treatment planning for posterior fossa subarachnoid hemorrhage. Neurosurgery 2002; 50: 1283–1289. 2. Harrison MJ, Johnson BA, Gardner GM. Preliminary results on the management of unruptured intracranial aneurysms with magnetic resonance angiography and computed tomographic angiography. Neurosurgery 1997; 40: 947–957. 3. Kato Y, Sano H, Katada K. Application of three-dimensional CT angiography (3D-CT angiography) to cerebral aneurysms. Surg Neurol 1999; 52: 113–122. 4. Villablanca JP, Hooshi P, Martin N. Three-dimensional helical computerized tomography angiography in the diagnosis, characterization and management of middle cerebral artery aneurysms: comparison with conventional angiography and intraoperative findings. J Neurosurg 2002; 97: 1322–1332. 5. Villablanca JP, Martin N, Jahan R. Volume-rendered helical computerized tomography angiography in the detection and characterization of intracranial aneurysms. J Neurosurg 2000; 93: 254–264. 6. Coenen VA, Dammert S, Reinges MH. Image-guided microneurosurgical management of small cerebral arteriovenous malformations: the value of navigated computed tomographic angiography. Neuroradiology 2005; 47(1): 66–72. 7. Schmid-Elsaesser R, Muacevic A, Holtmannspotter M. Neuronavigation based on CT angiography for surgery of intracranial aneurysms: primary experience with unruptured aneurysms. Minim Invasive Neurosurg 2003; 46(5): 69–77. 8. Zipfel GJ, Bradshaw P, Bova FJ. Do the morphological characteristics of arteriovenous malformations affect the results of radiosurgery? J Neurosurg 2004; 101(3): 393–401. 9. Tanaka H, Numaguchi Y, Konno S, et al. Initial experience with helical CT and 3D reconstruction in therapeutic planning of cerebral AVMs: comparison with 3D time-of-flight MRA and digital subtraction angiography. J Comput Assist Tomogr 1997; 21(5): 811–817. 10. Matsumoto M, Endo Y, Sato M. Acute aneurysm surgery using three-dimensional CT angiography without conventional catheter angiography. Fukushima J Med Sci 2002; 48(2): 63–73. Int J Med Robotics Comput Assist Surg 2006; 2: 161–167. DOI: 10.1002/rcs


11. Matsumoto M, Sato M, Nakano M. Three-dimensional computerized tomography angiography-guided surgery of acutely ruptured cerebral aneurysms. J Neurosurg 2001; 94(5): 718–727. 12. Albert FK, Wirtz CR, Forsting M. Image-guided excision of a ruptured feeding artery ‘pedicle aneurysm’ associated with an arteriovenous malformation in a child: case report. Comput Aided Surg 1997; 2(1): 5–10. 13. Calhoun PS, Kuszyk BS, Heath DG. Three-dimensional volume rendering of spiral CT data: theory and method. Radiographics 1999; 19(3): 745–764. 14. Hernes TA, Ommedal S, Lie T. Stereoscopic navigationcontrolled display of preoperative MRI and intraoperative 3D ultrasound in planning and guidance of neurosurgery: new technology for minimally invasive image-guided surgery approaches. Minim Invasive Neurosurg 2003; 46(3): 129–137. 15. Hoh BL, Cheung AC, Rabinov JD. Results of a prospective protocol of computed tomographic angiography in place of catheter angiography as the only diagnostic and pretreatment planning study for cerebral aneurysms by a combined neurovascular team. Neurosurgery 2004; 54(6): 1329–1340. 16. Kato Y, Katada K, Hayakawa M. Can 3D CTA surpass DSA in diagnosis of cerebral aneurysm? Acta Neurochir 2001; 143: 245–250. 17. Korogi Y, Takahashi M, Katada K. Intracranial aneurysms: detection with three-dimensional CT angiography with volumerendering – comparison with conventional angiographic and surgical findings. Radiology 1999; 211: 497–506. 18. Kallmes DF, Evans AJ, Woodcock RJ. Optimization of parameters for the detection of cerebral aneurysm: CT angiography of a model. Radiology 1996; 200: 403–405. 19. Hashimoto H, Iida J, Hironaka Y. Use of spiral computerized tomography angiography in patients with subarachnoid

Copyright  2006 John Wiley & Sons, Ltd.

20.

21.

22.

23.

24.

25.

26.

27.

28.

167

hemorrhage in whom subtraction angiography did not reveal cerebral aneurysms. J Neurosurg 2000; 92: 278–283. Batjer H, Samson D. Intraoperative aneurismal rupture: incidence, outcome, and suggestions for surgical management. Neurosurgery 1986; 18: 701–707. Houkin K, Kuroda S, Takahashi A. Intra-operative premature rupture of the cerebral aneurysms. Analysis of the causes and management. Acta Neurochir 1999; 141: 1255–1263. Koyama T, Okudera H, Kobayashi S. Computer-assisted geometric design of cerebral aneurysms for surgical simulation. Neurosurgery 1995; 36: 541–546. Boor S, Resch KM, Perneczky A. Virtual endoscopy of the basal cisterns: its value in planning the neurosurgical approach. Minim Invasive Neurosurg 1998; 41: 177–182. Koyama T, Hongo K, Tanaka Y. Simulation of the surgical manipulation involved in clipping a basilar artery aneurysm: concepts of virtual clipping. J Neurosurg 2000; 93: 355–360. Russel SM, Woo HH, Joseffer SS. Role of frameless stereotaxy in the surgical treatment of cerebral arteriovenous malformations. Technique and outcomes in a controlled study of 44 consecutive patients. Neurosurgery 2002; 51: 1108–1118. Tirakotai W, Sure U, Benes L. Image-guided transsylvian, transinsular approach for insular cavernous angiomas. Neurosurgery 2003; 53: 1299–1305. Kongasniemi M, Machela T, Koskinen S. Detection of intracranial aneurysms with two-dimensional and threedimensional multislice helical computed tomography angiography. Neurosurgery 2004; 54: 336–341. Benvenuti L, Chibbaro S, Carnesecchi S. Automated threedimensional volume rendering of helical computer tomography angiography for aneurysms: An advanced application of neuronavigation technology. Neurosurgery 2005; 57: 69–77.
