‘‘Contrast-Less’’ Stent-Assisted Coiling of an A1 Aneurysm Stephan A. Munich, MD,* Heike Theessen, RT,† Andrew K. Johnson, MD,* and Demetrius K. Lopes, MD*
Background: Iodine-based contrast medium used in diagnostic and therapeutic cerebrovascular imaging may cause renal toxicity, especially in patients with underlying renal impairment. Contrast dilution may impede efforts of the neurointerventionalist to treat intracranial vascular pathology. Methods: A 36-year-old man with renal impairment presented with an unruptured A1 segment anterior cerebral artery aneurysm. Previously obtained magnetic resonance angiography was fused with intraoperative noncontrast computed tomography and live 2-dimensional fluoroscopic images. The aneurysm was successfully treated with stent-assisted coil embolization without the use of contrast. Results: Neurointervention without contrast was feasible, and although the presented case is one example, the imaging fusion techniques used in this case can substantially decrease the exposure to contrast and subsequent risk of renal injury during intracranial procedures. Conclusions: Further development of and experience with this technique is needed to improve its safety and efficacy. Key Words: Aneurysm—cerebral aneurysm— endovascular—image fusion—stent-assisted coiling. Ó 2014 by National Stroke Association
Introduction The International Subarachnoid Hemorrhage Trial and the International Study of Unruptured Intracranial Aneurysms have suggested that endovascular techniques may provide safe and effective treatment for cerebral aneurysms.1,2 Three-dimensional (3D) reconstructions have allowed for improved assessment of intracerebral blood vessel anatomy and its relationship to surrounding osseous structures. More recently, real-time integration of fluoroscopic images with 3D reconstructions has
From the *Department of Neurosurgery, Rush University Medical Center, Chicago, Illinois; and †Siemens Medical Solution USA, Inc., Hoffman Estates, Illinois. Received January 9, 2014; revision received March 21, 2014; accepted April 4, 2014. Funding: None declared. Disclosures: S.A.M. has no financial relationships, and D.K.L. has financial and research relationships with Covidien, Stryker, and Penumbra. Address correspondence to Stephan A. Munich, MD, Department of Neurosurgery, Rush University Medical Center, 1725 W. Harrison St, Suite 855, Chicago, IL 60612. E-mail: [email protected]. 1052-3057/$ - see front matter Ó 2014 by National Stroke Association http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2014.04.013
permitted more detailed assessments of aneurysm morphology and potential treatment options. Diagnostic and therapeutic cerebrovascular imaging is traditionally obtained using iodine-based contrast material. However, iodinated contrast is often associated with renal toxicity, particularly in patients with underlying renal disease.3 Previous efforts to address this issue have included decreases in the amount of contrast used and the use of diluted contrast medium. In these cases, the patient still remains exposed to potentially harmful contrast material. Recently, Kocer et al4 have described the use of fused magnetic resonance angiography (MRA) and 2D fluoroscopic images during stenting of a left internal carotid artery (ICA) cavernous aneurysm. In this case, however, minimal contrast was used at 3 points during the procedure—for placement of the guiding catheter into the carotid artery, verification of aneurysm location, and after stent deployment. Their report demonstrates that accurate stent placement for the treatment of proximal intracranial aneurysms is possible with minimal contrast administration. This report describes a technique for stent-assisted coiling of a left A1 aneurysm using fused MRA and 2D fluoroscopic imaging. Only 4 mL of contrast medium were used to verify the degree of aneurysm occlusion after stent and coil placement. To the authors’ knowledge, this is the first report
Journal of Stroke and Cerebrovascular Diseases, Vol. 23, No. 9 (October), 2014: pp 2283-2286
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of intracranial stent-assisted coiling, a technically complex procedure, using MRA fluoroscopic fusion imaging.
Clinical Presentation The patient is a 36-year-old man with polycystic kidney disease who underwent MRA at the recommendation of his nephrologist after complaining of headaches. He was found to have a 3-mm left A1 aneurysm (Fig 1). After explanation of the risks associated with observation and intervention, including microsurgical clipping and endovascular therapy, including the risks associated with postoperative antiplatelet therapy, the patient elected to undergo endovascular treatment of this aneurysm. Given the patient’s chronic renal disease (baseline creatinine 2.5 mg/dL), coregistered MRA fluoroscopy imaging was used during his treatment to minimize contrast exposure. The patient was informed of the novelty of the technique and its lack of proven efficacy in rigorous trials. He wished to proceed using this technique given its potential of avoiding nephrotoxicity associated with iodinated contrast. After administration of general anesthesia, a noncontrast 5s DynaCT (Siemens Healthcare, Forchheim, Germany) was acquired in the angiography suite. The patient was then prepared for the intervention, and femoral access was obtained in a standard fashion. A neuron 6-French guide and catheter (Penumbra, Alameda, CA) was navigated into the left ICA. No contrast was required for this maneuver. In the meantime, a 3D time-of-flight (TOF) magnetic resonance (MR) data set was imported to the X-workplace (Siemens Healthcare) and loaded in syngo InSpace. In addition, the reconstructed images of the 5s DynaCT were loaded, and 3D/3D Fusion software was activated. Both data sets, MR and DynaCT, were shown, whereas the MR multiplanar reconstructions were visualized in an inverted rendering mode to better visualize the bony structures. Both data sets were manually aligned, so that bony landmarks roughly matched and an automatic registration mode was activated. After checking the registration based on axial, sagittal, and coronal multiplanar reconstruction images, the registration matrix was stored.
With this fusion step, the preoperative MR image was registered to the patient’s current position in the angiography suite. Then, only the 3D TOF MR reconstruction was loaded in syngo InSpace, and a suitable volume rendering technique preset was chosen, before syngo iPilot Dynamic was selected. This step allowed visual overlay of the 3D TOF MR images to live fluoroscopic images (Fig 2). This MR-based 3D roadmap was used to navigate through the left ICA and into the left A1, where a 14-mm Enterprise stent (Cordis Neurovascular, Miami, FL) was deployed. Manual realignment of the 3D roadmap was performed based on the course of the guidewire. An Excelsior SL-10 microcather (Boston Scientific, Fremont, CA) selectively catheterized the aneurysm for placement of 12 cm of Target detachable coils (Stryker Neurovascular, Fremont, CA). The coregistered roadmap required catheter navigation using single-plane digital subtraction angiography (DSA). On the coregistered fused image, the aneurysm appeared to be well occluded. To assess aneurysm occlusion, a conventional biplane DSA was performed using 4 mL of contrast medium. This confirmed complete occlusion of the aneurysm (Fig 3). The total fluoroscopy time was 32 minutes. The patient’s postoperative creatinine remained stable (2.3 mg/dL).
Discussion Patients with polycystic kidney disease harboring intracranial aneurysms present a particular challenge to the neuroendovascular surgeon. Prone to the development of intracranial aneurysms, they may need to undergo multiple, separate treatments as new aneurysms develop. Whether to intervene in the setting, asymptomatic aneurysms further complicates the management of these patients. An increased risk of aneurysm rupture and the observation that rupture tends to cluster in families has been reported.5,6 Neumann et al7 recently confirmed this increased risk, reporting a 63% rupture rate in patients with polycystic kidney disease, including 6 of 22 patients with aneurysms less than 3 mm and 9 patients with aneurysms less than 7 mm. After investigation into the patient’s family history and a detailed discussion
Figure 1. Anteroposterior (A) and lateral (B) views of 3D time-of-flight magnetic resonance angiography demonstrating a superiorly projecting left A1 aneurysm.
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Figure 2. Lateral fluoroscopic image demonstrating successful navigation of the catheter within the left internal carotid artery and anterior cerebral artery (ACA) (A). Lateral coregistered 3dimensional magnetic resonance angiography roadmap-fluoroscopic image demonstrating the presence of the catheter across the aneurysm neck in the ACA (B).
with these patients regarding the risks and benefits of aneurysm treatment, it may be prudent to intervene even in the setting of small aneurysms. Which treatment modality to employ is particularly important in these patients. On one hand, the potential of multiple treatments for multiple/new aneurysms favors endovascular therapy because repeated craniotomies and vessel dissection may be associated with increased morbidity. On the other hand, the need for repeated administration of iodinated contrast to patients whose renal function is already compromised may place the patient at increased risk for further renal impairment. In these patients, detailed discussions regarding the risks and benefits of each treatment, and the patient’s involvement in the decision-making process, are imperative. Endovascular therapy provides a minimally invasive and potentially less morbid alternative to microsurgical clipping. Endovascular therapy offers a significant advantage in patients with underlying medical comorbidities that render them high risk for open surgery. However, one limitation to endovascular treatment is the requirement for administration of iodine-based contrast medium, which is nephrotoxic. This is a particular concern in pa-
Figure 3. Anteroposterior (A) and lateral (B) digital subtraction angiographic images demonstrating successful stent-assisted coiling of the left A1 aneurysm.
tients with underlying renal disease as the risk of contrast-induced nephropathy may be as high as 27% in patients with pre-existing renal insufficiency.3 Advances in imaging techniques have allowed for safer and more diverse applications of endovascular therapy. With the introduction of real-time 3D imaging in the angiography suite and the development of image fusion techniques, it is now possible to take full advantage of preoperative imaging for guidance during complex procedures. Lin et al report the fusion of a previously acquired computed tomography angiogram (CTA) with fluoroscopic images, allowing for 3D roadmapping of the arteries from the aortic arch to the proximal intracranial arteries.8 They propose that this technique may decrease the amount of contrast material required during DSA. However, this method still requires the administration of contrast medium to obtain the CTA. More recently, Kocer et al4 have described the use of fused MRA and fluoroscopic images for neuronavigation during placement of a flow-diverting stent for treatment of a left ICA cavernous aneurysm. They successfully navigated the proximal intracranial vasculature and accurately deployed the stent using minimal contrast
S.A. MUNICH ET AL.
2286
medium. Additionally, their use of MRA instead of CTA eliminated the need for contrast administration during planning images. However, the aneurysm they treated was located proximally within the intracranial circulation and, although reduced, contrast medium was still administered at multiple points during the procedure. Here, we describe the use of MRA fluoroscopy fusion images for stent-assisted coiling of an A1 aneurysm. We used the coregistered MRA fluoroscopic roadmap images only, without additional contrast administration or image acquisition, for introduction of the catheter to the site of pathology. The aneurysm was located in the A1 segment of the left anterior cerebral artery, requiring navigation not only through the curves of the intracranial ICA but also past the ICA bifurcation and into the anterior cerebral artery. Furthermore, after deployment of a stent, we used the coregistered images to selectively catheterize the aneurysm with a microcatheter and to deploy detachable coils within it. Only 4 mL of contrast medium were used in this case, which was administered after successful treatment of the aneurysm. The intervention itself was performed in a contrast-less fashion. Although the treatment was successful in this case, there are several limitations with the contrast-less technique described here. First, as demonstrated in Figure 2, there can be misregistration of the guidewire and the 3D overlay. Although we realigned the image according to the position of the guidewire, real-time automated correction of the coregistered roadmap with the guidewire, the patient’s position, and the complex 3D vessel anatomy would improve the safety of this technique. Another problem that cannot be addressed with our technique is deformation of the vessels that occurs during and after intervention. Catheterization and wire placement can decrease the exactness of fused imaging, particularly with small lesions. Gao et al9 recently described angular remodeling of cerebral vessels after stent deployment. These subtle changes in the vasculature are not accounted for in the preoperative imaging and may affect accuracy of stent and/or coil deployment. A third pitfall of this technique in aneurysm treatment is the reliance on noninvasive imaging in situations where DSA remains the gold standard. Specifically, evaluation of the aneurysm before treatment is superior with DSA. Similarly, intraoperative assessment of aneurysm occlusion could not be performed even in the presented case without contrast. The treatment was successful before the assessment because of its ability to estimate the coil requirement of the aneurysm. Although this report reveals complete treatment of an aneurysm without the use of contrast, the aforementioned limitations of the technique demonstrate its infancy and its need for further development. Traditional techniques
could have been performed in this case, specifically, contrast dilution and preoperative and postoperative renal protective strategies (intravenous fluids and acetylcysteine administration). However, we believe that further improvement of our technique to address the above-mentioned limitations will permit a safe and effective alternative to these traditional strategies.
Conclusions Fusion of 3D MRA and overlay of MRA images to live fluoroscopy provides an accurate means of intracranial endovascular navigation. Using this technique, a cerebral aneurysm underwent stent-assisted embolization without the use of contrast before completion of treatment. Highquality imaging feedback is critical for safe and accurate aneurysm treatment, and although this case highlights an example of contrast minimization, the risks and benefits of contrast at each stage of treatment should be appropriately weighed. Further development of this technique is needed to improve its safety and efficacy.
References 1. Molyneux A, Kerr R, International Subarachnoid Aneurysm Trial (ISAT) Collaborative Group, et al. International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomized trial. J Stroke Cerebrovasc Dis 2002;11:304-314. 2. Wiebers DO, Whisnant JP, Huston J III, et al. Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment. Lancet 2003;362:103-110. 3. Barrett BJ. Contrast nephrotoxicity. J Am Soc Nephrol 1994;5:125-137. 4. Kocer N, Kizilkilic O, Babic D, et al. Fused magnetic resonance angiography and 2D fluoroscopic visualization for endovascular intracranial neuronavigation. J Neurosurg 2013;118:1000-1002. 5. Ring T, Spiegelhalter D. Risk of intracranial aneurysm bleeding in autosomal-dominant polycystic kidney disease. Kidney Int 2007;72:1400-1402. 6. Gieteling EW, Rinkel GJ. Characteristics of intracranial aneurysms and subarachnoid haemorrhage in patients with polycystic kidney disease. J Neurol 2003;250:418-423. 7. Neumann HP, Malinoc A, Bacher J, et al. Characteristics of intracranial aneurysms in the else kroner-fresenius registry of autosomal dominant polycystic kidney disease. Cerebrovasc Dis Extra 2012;2:71-79. 8. Lin CJ, Blanc R, Clarencon F, et al. Overlying fluoroscopy and preacquired CT angiography for road-mapping in cerebral angiography. AJNR Am J Neuroradiol 2010; 31:494-495. 9. Gao B, Baharoglu MI, Malek AM. Angular remodeling in single stent-assisted coiling displaces and attenuates the flow impingement zone at the neck of intracranial bifurcation aneurysms. Neurosurgery 2013;72:739-748. discussion 748.
Background: Iodine-based contrast medium used in diagnostic and therapeutic cerebrovascular imaging may cause renal toxicity, especially in patients with underlying renal impairment. Contrast dilution may impede efforts of the neurointerventionalist to treat intracranial vascular pathology. Methods: A 36-year-old man with renal impairment presented with an unruptured A1 segment anterior cerebral artery aneurysm. Previously obtained magnetic resonance angiography was fused with intraoperative noncontrast computed tomography and live 2-dimensional fluoroscopic images. The aneurysm was successfully treated with stent-assisted coil embolization without the use of contrast. Results: Neurointervention without contrast was feasible, and although the presented case is one example, the imaging fusion techniques used in this case can substantially decrease the exposure to contrast and subsequent risk of renal injury during intracranial procedures. Conclusions: Further development of and experience with this technique is needed to improve its safety and efficacy. Key Words: Aneurysm—cerebral aneurysm— endovascular—image fusion—stent-assisted coiling. Ó 2014 by National Stroke Association
Introduction The International Subarachnoid Hemorrhage Trial and the International Study of Unruptured Intracranial Aneurysms have suggested that endovascular techniques may provide safe and effective treatment for cerebral aneurysms.1,2 Three-dimensional (3D) reconstructions have allowed for improved assessment of intracerebral blood vessel anatomy and its relationship to surrounding osseous structures. More recently, real-time integration of fluoroscopic images with 3D reconstructions has
From the *Department of Neurosurgery, Rush University Medical Center, Chicago, Illinois; and †Siemens Medical Solution USA, Inc., Hoffman Estates, Illinois. Received January 9, 2014; revision received March 21, 2014; accepted April 4, 2014. Funding: None declared. Disclosures: S.A.M. has no financial relationships, and D.K.L. has financial and research relationships with Covidien, Stryker, and Penumbra. Address correspondence to Stephan A. Munich, MD, Department of Neurosurgery, Rush University Medical Center, 1725 W. Harrison St, Suite 855, Chicago, IL 60612. E-mail: [email protected]. 1052-3057/$ - see front matter Ó 2014 by National Stroke Association http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2014.04.013
permitted more detailed assessments of aneurysm morphology and potential treatment options. Diagnostic and therapeutic cerebrovascular imaging is traditionally obtained using iodine-based contrast material. However, iodinated contrast is often associated with renal toxicity, particularly in patients with underlying renal disease.3 Previous efforts to address this issue have included decreases in the amount of contrast used and the use of diluted contrast medium. In these cases, the patient still remains exposed to potentially harmful contrast material. Recently, Kocer et al4 have described the use of fused magnetic resonance angiography (MRA) and 2D fluoroscopic images during stenting of a left internal carotid artery (ICA) cavernous aneurysm. In this case, however, minimal contrast was used at 3 points during the procedure—for placement of the guiding catheter into the carotid artery, verification of aneurysm location, and after stent deployment. Their report demonstrates that accurate stent placement for the treatment of proximal intracranial aneurysms is possible with minimal contrast administration. This report describes a technique for stent-assisted coiling of a left A1 aneurysm using fused MRA and 2D fluoroscopic imaging. Only 4 mL of contrast medium were used to verify the degree of aneurysm occlusion after stent and coil placement. To the authors’ knowledge, this is the first report
Journal of Stroke and Cerebrovascular Diseases, Vol. 23, No. 9 (October), 2014: pp 2283-2286
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S.A. MUNICH ET AL.
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of intracranial stent-assisted coiling, a technically complex procedure, using MRA fluoroscopic fusion imaging.
Clinical Presentation The patient is a 36-year-old man with polycystic kidney disease who underwent MRA at the recommendation of his nephrologist after complaining of headaches. He was found to have a 3-mm left A1 aneurysm (Fig 1). After explanation of the risks associated with observation and intervention, including microsurgical clipping and endovascular therapy, including the risks associated with postoperative antiplatelet therapy, the patient elected to undergo endovascular treatment of this aneurysm. Given the patient’s chronic renal disease (baseline creatinine 2.5 mg/dL), coregistered MRA fluoroscopy imaging was used during his treatment to minimize contrast exposure. The patient was informed of the novelty of the technique and its lack of proven efficacy in rigorous trials. He wished to proceed using this technique given its potential of avoiding nephrotoxicity associated with iodinated contrast. After administration of general anesthesia, a noncontrast 5s DynaCT (Siemens Healthcare, Forchheim, Germany) was acquired in the angiography suite. The patient was then prepared for the intervention, and femoral access was obtained in a standard fashion. A neuron 6-French guide and catheter (Penumbra, Alameda, CA) was navigated into the left ICA. No contrast was required for this maneuver. In the meantime, a 3D time-of-flight (TOF) magnetic resonance (MR) data set was imported to the X-workplace (Siemens Healthcare) and loaded in syngo InSpace. In addition, the reconstructed images of the 5s DynaCT were loaded, and 3D/3D Fusion software was activated. Both data sets, MR and DynaCT, were shown, whereas the MR multiplanar reconstructions were visualized in an inverted rendering mode to better visualize the bony structures. Both data sets were manually aligned, so that bony landmarks roughly matched and an automatic registration mode was activated. After checking the registration based on axial, sagittal, and coronal multiplanar reconstruction images, the registration matrix was stored.
With this fusion step, the preoperative MR image was registered to the patient’s current position in the angiography suite. Then, only the 3D TOF MR reconstruction was loaded in syngo InSpace, and a suitable volume rendering technique preset was chosen, before syngo iPilot Dynamic was selected. This step allowed visual overlay of the 3D TOF MR images to live fluoroscopic images (Fig 2). This MR-based 3D roadmap was used to navigate through the left ICA and into the left A1, where a 14-mm Enterprise stent (Cordis Neurovascular, Miami, FL) was deployed. Manual realignment of the 3D roadmap was performed based on the course of the guidewire. An Excelsior SL-10 microcather (Boston Scientific, Fremont, CA) selectively catheterized the aneurysm for placement of 12 cm of Target detachable coils (Stryker Neurovascular, Fremont, CA). The coregistered roadmap required catheter navigation using single-plane digital subtraction angiography (DSA). On the coregistered fused image, the aneurysm appeared to be well occluded. To assess aneurysm occlusion, a conventional biplane DSA was performed using 4 mL of contrast medium. This confirmed complete occlusion of the aneurysm (Fig 3). The total fluoroscopy time was 32 minutes. The patient’s postoperative creatinine remained stable (2.3 mg/dL).
Discussion Patients with polycystic kidney disease harboring intracranial aneurysms present a particular challenge to the neuroendovascular surgeon. Prone to the development of intracranial aneurysms, they may need to undergo multiple, separate treatments as new aneurysms develop. Whether to intervene in the setting, asymptomatic aneurysms further complicates the management of these patients. An increased risk of aneurysm rupture and the observation that rupture tends to cluster in families has been reported.5,6 Neumann et al7 recently confirmed this increased risk, reporting a 63% rupture rate in patients with polycystic kidney disease, including 6 of 22 patients with aneurysms less than 3 mm and 9 patients with aneurysms less than 7 mm. After investigation into the patient’s family history and a detailed discussion
Figure 1. Anteroposterior (A) and lateral (B) views of 3D time-of-flight magnetic resonance angiography demonstrating a superiorly projecting left A1 aneurysm.
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Figure 2. Lateral fluoroscopic image demonstrating successful navigation of the catheter within the left internal carotid artery and anterior cerebral artery (ACA) (A). Lateral coregistered 3dimensional magnetic resonance angiography roadmap-fluoroscopic image demonstrating the presence of the catheter across the aneurysm neck in the ACA (B).
with these patients regarding the risks and benefits of aneurysm treatment, it may be prudent to intervene even in the setting of small aneurysms. Which treatment modality to employ is particularly important in these patients. On one hand, the potential of multiple treatments for multiple/new aneurysms favors endovascular therapy because repeated craniotomies and vessel dissection may be associated with increased morbidity. On the other hand, the need for repeated administration of iodinated contrast to patients whose renal function is already compromised may place the patient at increased risk for further renal impairment. In these patients, detailed discussions regarding the risks and benefits of each treatment, and the patient’s involvement in the decision-making process, are imperative. Endovascular therapy provides a minimally invasive and potentially less morbid alternative to microsurgical clipping. Endovascular therapy offers a significant advantage in patients with underlying medical comorbidities that render them high risk for open surgery. However, one limitation to endovascular treatment is the requirement for administration of iodine-based contrast medium, which is nephrotoxic. This is a particular concern in pa-
Figure 3. Anteroposterior (A) and lateral (B) digital subtraction angiographic images demonstrating successful stent-assisted coiling of the left A1 aneurysm.
tients with underlying renal disease as the risk of contrast-induced nephropathy may be as high as 27% in patients with pre-existing renal insufficiency.3 Advances in imaging techniques have allowed for safer and more diverse applications of endovascular therapy. With the introduction of real-time 3D imaging in the angiography suite and the development of image fusion techniques, it is now possible to take full advantage of preoperative imaging for guidance during complex procedures. Lin et al report the fusion of a previously acquired computed tomography angiogram (CTA) with fluoroscopic images, allowing for 3D roadmapping of the arteries from the aortic arch to the proximal intracranial arteries.8 They propose that this technique may decrease the amount of contrast material required during DSA. However, this method still requires the administration of contrast medium to obtain the CTA. More recently, Kocer et al4 have described the use of fused MRA and fluoroscopic images for neuronavigation during placement of a flow-diverting stent for treatment of a left ICA cavernous aneurysm. They successfully navigated the proximal intracranial vasculature and accurately deployed the stent using minimal contrast
S.A. MUNICH ET AL.
2286
medium. Additionally, their use of MRA instead of CTA eliminated the need for contrast administration during planning images. However, the aneurysm they treated was located proximally within the intracranial circulation and, although reduced, contrast medium was still administered at multiple points during the procedure. Here, we describe the use of MRA fluoroscopy fusion images for stent-assisted coiling of an A1 aneurysm. We used the coregistered MRA fluoroscopic roadmap images only, without additional contrast administration or image acquisition, for introduction of the catheter to the site of pathology. The aneurysm was located in the A1 segment of the left anterior cerebral artery, requiring navigation not only through the curves of the intracranial ICA but also past the ICA bifurcation and into the anterior cerebral artery. Furthermore, after deployment of a stent, we used the coregistered images to selectively catheterize the aneurysm with a microcatheter and to deploy detachable coils within it. Only 4 mL of contrast medium were used in this case, which was administered after successful treatment of the aneurysm. The intervention itself was performed in a contrast-less fashion. Although the treatment was successful in this case, there are several limitations with the contrast-less technique described here. First, as demonstrated in Figure 2, there can be misregistration of the guidewire and the 3D overlay. Although we realigned the image according to the position of the guidewire, real-time automated correction of the coregistered roadmap with the guidewire, the patient’s position, and the complex 3D vessel anatomy would improve the safety of this technique. Another problem that cannot be addressed with our technique is deformation of the vessels that occurs during and after intervention. Catheterization and wire placement can decrease the exactness of fused imaging, particularly with small lesions. Gao et al9 recently described angular remodeling of cerebral vessels after stent deployment. These subtle changes in the vasculature are not accounted for in the preoperative imaging and may affect accuracy of stent and/or coil deployment. A third pitfall of this technique in aneurysm treatment is the reliance on noninvasive imaging in situations where DSA remains the gold standard. Specifically, evaluation of the aneurysm before treatment is superior with DSA. Similarly, intraoperative assessment of aneurysm occlusion could not be performed even in the presented case without contrast. The treatment was successful before the assessment because of its ability to estimate the coil requirement of the aneurysm. Although this report reveals complete treatment of an aneurysm without the use of contrast, the aforementioned limitations of the technique demonstrate its infancy and its need for further development. Traditional techniques
could have been performed in this case, specifically, contrast dilution and preoperative and postoperative renal protective strategies (intravenous fluids and acetylcysteine administration). However, we believe that further improvement of our technique to address the above-mentioned limitations will permit a safe and effective alternative to these traditional strategies.
Conclusions Fusion of 3D MRA and overlay of MRA images to live fluoroscopy provides an accurate means of intracranial endovascular navigation. Using this technique, a cerebral aneurysm underwent stent-assisted embolization without the use of contrast before completion of treatment. Highquality imaging feedback is critical for safe and accurate aneurysm treatment, and although this case highlights an example of contrast minimization, the risks and benefits of contrast at each stage of treatment should be appropriately weighed. Further development of this technique is needed to improve its safety and efficacy.
References 1. Molyneux A, Kerr R, International Subarachnoid Aneurysm Trial (ISAT) Collaborative Group, et al. International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomized trial. J Stroke Cerebrovasc Dis 2002;11:304-314. 2. Wiebers DO, Whisnant JP, Huston J III, et al. Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment. Lancet 2003;362:103-110. 3. Barrett BJ. Contrast nephrotoxicity. J Am Soc Nephrol 1994;5:125-137. 4. Kocer N, Kizilkilic O, Babic D, et al. Fused magnetic resonance angiography and 2D fluoroscopic visualization for endovascular intracranial neuronavigation. J Neurosurg 2013;118:1000-1002. 5. Ring T, Spiegelhalter D. Risk of intracranial aneurysm bleeding in autosomal-dominant polycystic kidney disease. Kidney Int 2007;72:1400-1402. 6. Gieteling EW, Rinkel GJ. Characteristics of intracranial aneurysms and subarachnoid haemorrhage in patients with polycystic kidney disease. J Neurol 2003;250:418-423. 7. Neumann HP, Malinoc A, Bacher J, et al. Characteristics of intracranial aneurysms in the else kroner-fresenius registry of autosomal dominant polycystic kidney disease. Cerebrovasc Dis Extra 2012;2:71-79. 8. Lin CJ, Blanc R, Clarencon F, et al. Overlying fluoroscopy and preacquired CT angiography for road-mapping in cerebral angiography. AJNR Am J Neuroradiol 2010; 31:494-495. 9. Gao B, Baharoglu MI, Malek AM. Angular remodeling in single stent-assisted coiling displaces and attenuates the flow impingement zone at the neck of intracranial bifurcation aneurysms. Neurosurgery 2013;72:739-748. discussion 748.
