- To know the visualization of various intracranial stents by silent MRA and 3D TOF-MRA

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1 Visualization of Various Intracranial Stents by Non-Contrast Enhanced MRA Using Ultrashort Echo Time with Arterial Spin Labeling (Silent MRA) and 3D TOF-MRA Poster No.: C-0834 Congress: ECR 2017 Type: Educational Exhibit Authors: N. Takano, M. Suzuki, R. Irie, M. Yamamoto, H. Hoshito, K. Kumamaru, M. Hori, H. Oishi, S. Aoki; Tokyo/JP Keywords: Artifacts, Aneurysms, Catheters, Angioplasty, MR-Angiography, Vascular, Interventional vascular, Arteries / Aorta DOI: /ecr2017/C-0834 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 39

2 Learning objectives - To know the feature of silent MRA (Fig.1 : Silent MRA image) - To know the visualization of various intracranial stents by silent MRA and 3D TOF-MRA - How to select appropriate MRA technique at the various situations - To know the usefulness of silent MRA for intracranial arterial desease treated with intracranial stents Images for this section: Page 2 of 39

3 Fig. 1: Silent MRA of intracranial artery * Non-contrast enhanced technique * Wide FOV (180 mm) * High blood flow signal * Non background tissue - Tokyo/JP Page 3 of 39

4 Background Silent MRA is non-contrast enhanced MRA that uses ultrashort echo time (UTE) with [1,2] arterial spin labeling. Ultrashort TE of silent MRA minimizes phase dispersion of the labeled blood flow signal and decrease magnetic susceptibility by metallic stents. On the other hand, 3D TOF-MRA is complicated by imaging artifacts produced by these devices, because it is affected by susceptibility artifact and RF shielding. The visualization at two types of MRA is different by deployed stent structure, material and diameter etc. : Silent MRA (non-contrast enhanced MRA using Ultrashort echo time with arterial spin labeling) MR angiography obtained with Silent Scan(Fig.2). Silent means that this sequence(70db, background noise level) is quiet compare with conventional scan(110db) [3]. Fig. 2: Pulse sequence of silent scan (GE Healthcare) Page 4 of 39

5 References: - Tokyo/JP Silent MRA has two important features; Data acquisition is based on 3D radial sampling using ultrashort TE. (silent scan) ASL technique is used as a preparation pulse for visualization of the blood flow. Ultrashort TE (TE=0.016msec) Minimizing phase dispersion and decreasing magnetic susceptibility. Decreasing the effect of disturbed flow. Arterial spin labeling Subtraction of images before and after labeling. Easy to interpret as they only consit of the blood flow signal. Intensive for saturation effects and it helps to visualize a vessel, regardless of its direction (3D TOF-MRA is used in-flow effect for visualization of blood flow. Therefore, it is affected by flow direction.) : Scan detail of silent MRA (Fig.2-4) Silent MRA based on ASL and 3D radial sampling of UTE. (Fig.2,3) Subtraction images are provided from control and labeled images. In the results, we obtain the MIP images. (Fig.4) Page 5 of 39

6 Fig. 3: Scan detail of silent MRA (ASL : Preparation plus for visualization of the blood flow) References: - Tokyo/JP Page 6 of 39

7 Fig. 4: Source images of silent MRA References: - Tokyo/JP : Endvascular treatment of intracranial aneurysms Coil emboliazation Three-dimensional TOF-MRA is widely used as a noninvasive substitute for DSA for the follow-up of coiled aneurysms [4-8]. Stent-assisted coil embolization Although there have been reports of 3D TOF-MRA being used after stent-assisted coil [5,6,8] embolization, it remains difficult to visualize flow in an intracranial stent using this method owing to magnetic susceptibility and radiofrequency (RF) shielding. However, the visualization of MRA is different by deployed stent structure, material and diameter etc. Page 7 of 39

8 Images for this section: Fig. 2: Pulse sequence of silent scan (GE Healthcare) - Tokyo/JP Fig. 3: Scan detail of silent MRA (ASL : Preparation plus for visualization of the blood flow) Page 8 of 39

9 - Tokyo/JP Fig. 4: Source images of silent MRA - Tokyo/JP Page 9 of 39

10 Findings and procedure details : Visualization of various intracranial stents by silent MRA and 3D TOF-MRA «Intracranial stents» Enterprise stent (Codman & Shurtleff, Inc., Raynham, Mass, USA) Neuroform stent (Stryker, Fremont, California, USA) Wingspan stent (Boston Scientific, Natick, MA, USA) Low-profile Visualized Intraluminal Support (LVIS Jr. stent; MicroVentionTerumo, Tustin, California, USA) Low-profile Visualized Intraluminal Support (LVIS stent; MicroVentionTerumo, Tustin, California, USA) «Coronary stents (other resource)» Resolute Integrity stent (Medtronic, Santa Rosa, California, USA) Multi-Link VISION stent (Abbott Vascular, USA) Driver stent (Medtronic, USA) [Enterprise stent] Fig.5a The Enterprise stent is self-expandble, nitinol and closed-cell design. The marker [5,9] [10] comprises tantalum. The thickness of the stent strut is 76µm. This stent has thicker stent strut. Therefore, strong susceptibility artifact and RF shielding are assumed. #CASE 1. (Fig.9) 74 y.o, Female, Lt IC Aneurysm, stent-assisted coil embolization Enterprise stent (4.5*22mm), closed-cell, nitinol The quality of visualization of the reconstructed artery of silent MRA was superior than that of 3D TOF-MRA. Moreover, silent MRA could depict the neck remnant (red arrow). Three-dimensional TOF-MRA shows strong signal loss of stented segment. Threedimensional TOF-MRA could not depict the neck remnant. Page 10 of 39

11 Fig. 9: Enterprise stent (4.5*22mm), closed-cell, nitinol References: - Tokyo/JP #CASE 2. (Fig.10) 65 y.o, Female, Rt IC Aneurysm, stent-assisted coil embolization Enterprise stent (4.5*22mm), closed-cell, nitinol The quality of visualization of the reconstructed artery of silent MRA was superior than that of 3D TOF-MRA. Silent MRA could depict the neck remnant (yellow arrow). Three- Page 11 of 39

12 dimensional TOF-MRA shows complete signal loss of stented segment, and could not depict the neck remnant. Fig. 10: Enterprise stent (4.5*22mm), closed-cell, nitinol References: Irie R et al. (2015) Assessing Blood Flow in an Intracranial Stent: A Feasibility Study of MR Angiography Using a Silent Scan after Stent-Assisted Page 12 of 39

13 Coil Embolization for Anterior Circulation Aneurysms. AJNR Am J Neuroradiol. May;36: [Neuroform stent] Fig.5b The Neuroform stent is self-expandble, nitinol and open-cell design. The marker comprises stainless steel and platinum [8,11]. The thickness of the stent strut is 65µm [10]. This stent has thinner stent strut. Compare with Enterprise stent, weak susceptibility artifact and RF shielding are assumed. #CASE 3. (Fig.11) 67 y.o, Female, Lt IC-PC Aneurysm, stent-assisted coil embolization Neuroform stent (4.5*20mm), open-cell, nitinol The quality of visualization of the reconstructed artery of silent MRA was nearly equal than that of 3D TOF-MRA. Because Neuroform stent has thinner stent strut and open-cell design. In the result, magnetic susceptibility and RF shielding are weak than Enterprise stent. Page 13 of 39

14 Fig. 11: Neuroform stent (4.5*20mm), open-cell, nitinol References: - Tokyo/JP #CASE 4. (Fig.12) 77 y.o, Female, ACA Aneurysm, stent-assisted coil embolization Neuroform stent (2.5*20mm), open-cell, nitinol Page 14 of 39

15 The quality of visualization of the reconstructed artery of silent MRA was superior than that of 3D TOF-MRA. Three-dimensional TOF-MRA shows strong signal loss of stented segment (yellow arrow). Moreover, Distal stent edge is strong signal loss (red arrow). [11] This is "marker band effect". Agid et al reported a "marker band effect" that appeared in small arteries with a diameter of 2 mm or less and of different alloy than the rest of the stent (usually made of platinum), which creates a stronger local susceptibility artifact [11]. This case is relatively small diameter. The Neuroform stents are made of platinum, which creates a strong magnetic susceptibility artifact [11]. Page 15 of 39

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17 Fig. 12: Neuroform stent (2.5*20mm), open-cell, nitinol References: - Tokyo/JP [Wingspan stent] Fig.6 The Wingspan stent is self-expandble, nitinol and open-cell design. The structure of this stent is similar to Neuroform stent. The deployment of this stent, we need pre-ballonning. Depending on the situation, this stent needs post-ballonning. #CASE 5. (Fig.13) 60 y.o, male, Lt ICA stenosis, PTA (POBA + Stent) Wingspan stent (4.5*15mm), open-cell, nitinol The quality of visualization of the reconstructed artery of silent MRA was nearly equal than that of 3D TOF-MRA. Wingspan stent is open-cell design stent. Therefore, visualization of the reconstructed artery is similar to Neuroform stent. However, both MRA is depicted thinner at stented segment in comparison with DSA image. Page 17 of 39

18 Fig. 13: Wingspan stent (4.5*15mm), open-cell, nitinol References: - Tokyo/JP Page 18 of 39

19 [LVIS Jr. stent] Fig.7 The LVIS Jr. stent is self-expandble, nitinol and single wire bladed stent. This stent is relatively small diameter, three radiopaque tantalum markers on the proximal and distal tines with three tantalum helical strands within the stent body [12]. #CASE 6. (Fig.14) 65 y.o, Female, AcomA Aneurysm, X-configuration stent-assisted coil embolization LVIS Jr. stents (2.5*23, 2.5*17mm), single wire bladed stent, closed-cell, nitinol Three-dimensional TOF-MRA shows almost complete signal loss of stented segment. On the other hand, silent MRA is good visualization of stented segment in spite of Xconfiguration stent-assisted coil embolization case. Moreover, silent MRA could depict the neck remnant (yelllow arrow). This case used diameter of 2.5mm stents. It is assumed that strong magnetic susceptibility and RF shielding. However, silent MRA could decreased their issues. Because silent MRA uses ultrashort TE. Page 19 of 39

20 Fig. 14: LVIS Jr. stents (2.5*23, 2.5*17mm), single wire bladed stent, closed-cell, nitinol References: - Tokyo/JP [LVIS stent] Fig.8 The LVIS stent is self-expandble, nitinol and single wire bladed stent. The diameter of LVIS stent is larger than that of LVIS Jr. stent. This stent demonstrates four distal Page 20 of 39

21 radiopaque markers and four proximal paired markers. 1 mm circular cell size of the stent [12]. #CASE 7. (Fig.15) 68 y.o, male, Lt IC Aneurysm, stent-assisted coil embolization LVIS stent (4.5*23mm), single wire bladed stent, closed-cell, nitinol Three-dimensional TOF-MRA shows medium signal loss of stented segment and not depicted the neck remnant. Silent MRA shows minimum signal loss of stented segment. Moreover, silent MRA could depict the neck remnant (yelllow arrow). This case used diameter of 4.5mm stent. This stent is assumed weak magnetic susceptibility and RF shielding than LVIS Jr. stent. Therefore, 3D TOF-MRA could visualize in stent flow. However, 3D TOF-MRA could not depict the neck remnant. It is caused that TOF-MRA uses in-flow effect. In-flow effect is affected by blood flow velocity and direction. The flow of neck remnant is slow and turbulent flow. Therefore, signal loss happened and was not able to depict neck remnant in 3D TOF-MRA. Page 21 of 39

22 Fig. 15: LVIS stent (4.5*23mm), single wire bladed stent, closed-cell, nitinol References: - Tokyo/JP #Coronary stent 1. (Fig.16) 59 y.o, Male, Lt ICA stenosis, PTA (POBA + Stent) Integlity stent (4.0*18, 4.0*15 mm), Bare Metal Stent for coronary artery, Cobalt alloy Fig. 16: Integlity stent (4.0*18, 4.0*15 mm), Bare Metal Stent for coronary artery, Cobalt alloy References: - Tokyo/JP #Coronary stent 2. (Fig.17) Page 22 of 39

23 72 y.o, male, Lt ICA stenosis, PTA (POBA + Stent) Multi-Link VISION stent, Bare Metal Stent for coronary artery, Cobalt alloy Fig. 17: Multi-Link VISION stent, Bare Metal Stent for coronary artery, Cobalt alloy References: - Tokyo/JP Page 23 of 39

24 #Coronary stent 3. (Fig.18) 77 y.o, male, Lt ICA stenosis, PTA (POBA + Stent) Driver stent, Bare Metal Stent for coronary artery, Cobalt alloy Fig. 18: Driver stent, Bare Metal Stent for coronary artery, Cobalt alloy References: - Tokyo/JP : Characteristic of two types of MRA «Silent MRA (Bold is advantage)» Page 24 of 39

25 Ultrashort TE (decrease susceptibility artifact and RF shielding) ASL (visualize blood flow, not affected by flow direction) Large FOV (18cm) Large voxel size (1.0 or 1.2mm isotropic) Long scan time (7~12minutes) # Motion artifact Unique sequence (GEHC product, 3Tesla and Head-Neck-coil only) «3D TOF-MRA (Bold is advantage)» Relatively long TE (2~3msec) In-flow effect (visualize blood flow, affected by flow direction) Short scan area (7~8cm) Small voxel size (0.3~0.5mm) Short scan time (5min) An obstacle by artifact of T1 shortning materials (hemorrhage etc) Saturation effect (decrease blood flow signal) : How to select appropriate MRA technique at the various situations * Open-cell design stent Silent MRA # 3D TOF-MRA (large diameter case) Silent MRA > 3D TOF-MRA (small diameter case : mm) * Closed-cell design stent Silent MRA > 3D TOF-MRA * Bladed stent Silent MRA > 3D TOF-MRA * Depiction of neck or aneurysm remnant Silent MRA > 3D TOF-MRA * Wide scan coverage Silent MRA > 3D TOF-MRA * Decreasing of the susceptibility artifacts Silent MRA > 3D TOF-MRA * High resolution MRA Page 25 of 39

26 3D TOF-MRA > Silent MRA * Short scan time 3D TOF-MRA > Silent MRA * Providing of many patients 3D TOF-MRA > Silent MRA * Coronary stent (coballt alloy) Silent MRA > 3D TOF-MRA, Silent MRA # 3D TOF-MRA : Usefulness of silent MRA for intracranial aneurysm treated with intracranial stents The quality of visualization of the reconstructed artery of silent MRA was superior than that of 3D TOF-MRA in many cases. Furthermore, dipiction of neck remnant is visualized in silent MRA. On the other hand, 3D TOF-MRA is complicated by metalic device for visualization of stented artery, depiction of remnant. (Fig.9,10,14 and 15) Silent MRA has few disadvantages than 3D TOF-MRA, however, silent MRA has more advantages for patients treated with intracranial stents. [10,11] Contrast-enhanced MRA, CTA and X-ray DSA were necessary so far. However, as for the silent MRA, an evaluation after the stent-assisted coil embolization is possible by non contrast-enhanced. For after treated with intracranial stents, aneurysm residua, in-stent stenosis due to intimal hyperplasia, recanalization and stent occlusion from thrombus should be evaluated by several follow-up imaging techniques [13,14]. Therefore, silent MRA might be useful for intracranial aneurysm treated with intracranial stents. Images for this section: Page 26 of 39

27 Fig. 5: a. Enterprise stent (Codman & Shurtleff, Inc., Raynham, Mass, USA) b. Neuroform stent (Stryker, Fremont, California, USA) Padalino DJ et al. (2013) Enterprise stent for waffle-cone stent-assisted coil embolization of large wide-necked arterial bifurcation aneurysms Surg Neurol Int. 4:9. Fig. 6: Wingspan stent (Boston Scientific, Natick, MA, USA) Page 27 of 39

28 Bose A et al. (2007) A novel, self-expanding, nitinol stent in medically refractory intracranial atherosclerotic stenoses: the Wingspan study. Stroke. May;38(5): Fig. 7: Low-profile Visualized Intraluminal Support (LVIS Jr. stent; MicroVentionTerumo, Tustin, California, USA) Poncyljusz W et al. (2015) The LVIS/LVIS Jr. stents in the treatment of wide-neck intracranial aneurysms: multicentre registry. J Neurointerv Surg. Jul;7(7): Page 28 of 39

29 Fig. 8: Low-profile Visualized Intraluminal Support (LVIS stent; MicroVention-Terumo, Tustin, California, USA) Poncyljusz W et al. (2015) The LVIS/LVIS Jr. stents in the treatment of wide-neck intracranial aneurysms: multicentre registry. J Neurointerv Surg. Jul;7(7): Page 29 of 39

30 Fig. 9: Enterprise stent (4.5*22mm), closed-cell, nitinol - Tokyo/JP Page 30 of 39

31 Fig. 10: Enterprise stent (4.5*22mm), closed-cell, nitinol Irie R et al. (2015) Assessing Blood Flow in an Intracranial Stent: A Feasibility Study of MR Angiography Using a Silent Scan after Stent-Assisted Coil Embolization for Anterior Circulation Aneurysms. AJNR Am J Neuroradiol. May;36: Page 31 of 39

32 Fig. 11: Neuroform stent (4.5*20mm), open-cell, nitinol - Tokyo/JP Page 32 of 39

33 Page 33 of 39

34 Fig. 12: Neuroform stent (2.5*20mm), open-cell, nitinol - Tokyo/JP Fig. 13: Wingspan stent (4.5*15mm), open-cell, nitinol Page 34 of 39

35 - Tokyo/JP Fig. 14: LVIS Jr. stents (2.5*23, 2.5*17mm), single wire bladed stent, closed-cell, nitinol - Tokyo/JP Page 35 of 39

36 Fig. 15: LVIS stent (4.5*23mm), single wire bladed stent, closed-cell, nitinol - Tokyo/JP Page 36 of 39

37 Conclusion Silent MRA might be useful for intracranial arterial desease treated with intracranial stents. Visualization of in-stent flow is different by various intracranial stents in MR imaging. Three-dimensional TOF-MRA has some advantages. However, silent MRA has more advantage than that of 3D TOF-MRA. We should select the appropriate MRA sequence according to the situation. Personal information Corresponding author: Nao Takano RT (Radiological Technologist), MMSc (Master of Medical Science) Department of Radiology, Graduate School of Medicine, Juntendo University, Hongo, Bunkyo-ku, Tokyo , Japan Phone: (5263,5247) Fax: References 1. Irie R, Suzuki M, Yamamoto M, et al. Assessing Blood Flow in an Intracranial Stent:A Feasibility Study of MR Angiography Using a Silent Scan after Stent-Assisted Coil Embolization for Anterior Circulation Aneurysms. AJNR Am J Neuroradiol 2015 May;36: Takano N, Suzuki M, Irie R, et al. Usefulness of Non-Contrast-Enhanced Magnetic Resonance Angiography Using a Silent Scan for Follow-Up after Y-Configuration StentAssisted Coil Embolization for Basilar Tip Aneurysms. AJNR Am J Neuroradiol 2017 [Epub ahead of print] Page 37 of 39

38 3. Alibek S, Vogel M, Sun W, et al. Acoustic noise reduction in MRI using Silent Scan: an initial experience. Diagn Interv Radiol 2014 Jul-Aug;20: Lavoie P, Gariépy JL, Milot G, et al. Residual flow after cerebral aneurysm coil occlusion: diagnostic accuracy of MR angiography. Stroke 2012 Mar;43: Cho WS, Kim SS, Lee SJ, et al. The effectiveness of 3T time-of-flight magnetic resonance angiography for follow-up evaluations after the stent-assisted coil embolization of cerebral aneurysms. Acta Radiol 2014 Jun;55: Cho YD, Kim KM, Lee WJ, et al. Time-of-flight magnetic resonance angiography for follow-up of coil embolization with enterprise stent for intracranial aneurysm: usefulness of source images. Korean J Radiol 2014 Jan-Feb;15: Shaafsma JD, Velthuis BK, Majoie CB, et al. Intracranial aneurysms treated with coil placement: test characteristics of follow-up MR angiography - multicenter study 1. Radiology : Choi JW, Roh HG, Moon WJ, et al. Optimization of MR Parameters of 3D TOF-MRA for Various Intracranial Stents at 3.0T MRI. Neurointervention 2011 Aug;6: Takayama K, Taoka T, Nakagawa H, et al. Usefulness of contrast-enhanced magnetic resonance angiography for follow-up of coil embolizatoin with the enterprise stent for cerebral aneurysms. J Comput Assist Tomogr 2011 Sep-Oct;35: Choi JW, Roh HG, Moon WJ, et al. Time-resolved 3D contrast-enhanced MRA on 3.0T : a non-invasive follow-up technique after stent-assisted coil embolization of the intracranial aneurysm. Korean J Radiol 2011 Nov-Dec;12: Agid R, Schaaf M, Farb R. CE-MRA for follow-up of aneurysms post stent-assisted coiling. Interv Neuroradiol 2012 Sep;18: Poncyljusz W, Bili#ski P, Safranow K, et al. The LVIS/LVIS Jr. stents in the treatment of wide neck intracranial aneurysms: multicentre registry. J NeuroIntervent Surg 2015;7: Fiorella D, Albuquerque FC, Deshmukh VR, et al. Usefulness of the Page 38 of 39

39 Neuroform stent for the treatment of cerebral aneurysms: results at initial (3-6-mo) follow-up. Neurosurgery 2005;56: , discussion Siddiqui MA, Bhattacharya J, Lindsay KW, et al. Horizontal stentassisted coil embolisation of wide-necked intracranial aneurysms with the Enterprise stent: a case series with early angiographic followup. Neuroradiology 2009;51: Page 39 of 39