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Kato H, Ootani N, Abiru K, Okahara M. Investigating Signal Loss due to a Carotid Artery Stent in 3D-TOF-MRA. Magn Reson Med Sci 2021; 20:303-311. [PMID: 32963183 PMCID: PMC8424025 DOI: 10.2463/mrms.mp.2019-0083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Purpose: In this study, we investigated the factors of signal loss out because of the presence of a stent and optimized imaging parameters for improvement in depiction ability. Methods: We investigated the relationship between the stent type and magnetic susceptibility effect by measuring the signal value between the inside and outside of the stent with different Bw and TE for two different kinds of stents respectively. Similarly, flip angles were changed for two different kinds of stents respectively to the signal intensity between the inside and the outside of the stent was measured, in which examine the relationship between the stent type and the Ernst angles in RF-shielding effect. The conventional imaging parameters and the optimum imaging parameters for each stent obtained from the result of the phantom experiment were examined. Optimized 3D time-of-flight MR angiography (3D-TOF-MRA) was performed and compared with conventional 3D-TOF-MRA and computed tomography angiography (CTA). Results: The influence of the magnetic susceptibility effect is small in the central part of Carotid Wallstent and in PRECISE, and large in the Carotid Wallstent at the both ends. The influence of RF-shielding effect was large at PRECISE, where the Ernst angle was greatly shifted while the effect is no longer influenced at Carotid Wallstent. Both Carotid Wallstent and PRECISE made imaging capability improved by optimizing the imaging parameters. Conclusion: During clinical imaging of patients post-carotid artery stenting (CAS) using our protocol, the ability to visualize blood vessels was improved. Thus, we demonstrated that the ability of 3D-TOF-MRA post-CAS was improved via optimizing imaging parameters.
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Affiliation(s)
- Hiroshi Kato
- Radiology Department, Federation of National Public Service Personnel Mutual Aid Associations Shinbeppu Hospital
| | - Norio Ootani
- Radiology Department, Federation of National Public Service Personnel Mutual Aid Associations Shinbeppu Hospital
| | - Kentaro Abiru
- Radiology Department, Federation of National Public Service Personnel Mutual Aid Associations Shinbeppu Hospital
| | - Mika Okahara
- Radiology Department, Federation of National Public Service Personnel Mutual Aid Associations Shinbeppu Hospital
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Heo YJ, Jeong HW, Baek JW, Kim ST, Jeong YG, Lee JY, Jin SC. Pointwise Encoding Time Reduction with Radial Acquisition with Subtraction-Based MRA during the Follow-Up of Stent-Assisted Coil Embolization of Anterior Circulation Aneurysms. AJNR Am J Neuroradiol 2019; 40:815-819. [PMID: 30975655 DOI: 10.3174/ajnr.a6035] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 03/11/2019] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Time-of-flight MR angiography, though widely used after coil embolization, is associated with limitations owing to magnetic susceptibility and radiofrequency shielding following stent-assisted coil embolization. We evaluated the pointwise encoding time reduction with radial acquisition (PETRA) sequence in subtraction-based MRA (qMRA) using an ultrashort TE relative to TOF-MRA during the follow-up of stent-assisted coil embolization for anterior circulation aneurysms. MATERIALS AND METHODS Twenty-five patients (3 men and 22 women; mean age, 59.1 ± 14.0 years) underwent stent-assisted coil embolization for anterior circulation aneurysms and were retrospectively evaluated using TOF-MRA and PETRA qMRA data from the same follow-up session. Two neuroradiologists independently reviewed both MRA findings and subjectively graded flow within the stents (relative to the latest DSA findings) and occlusion status (complete occlusion or neck/aneurysm remnant). Interobserver and intermodality agreement for TOF-MRA and PETRA qMRA were evaluated. RESULTS The mean score for flow visualization within the stents was significantly higher in PETRA qMRA than in TOF-MRA (P < .001 for both observers), and good interobserver agreement was reported (κ = 0.63). The aneurysm occlusion status of PETRA qMRA (observer 1, 92.0%; observer 2, 88.0%) was more consistent with DSA than with TOF-MRA (observer 1, 76.0%; observer 2, 80.0%), and there was a better intermodality agreement between DSA and PETRA qMRA than between DSA and TOF-MRA. CONCLUSIONS These findings indicate that PETRA qMRA is a useful follow-up technique for patients who have undergone stent-assisted coil embolization for anterior circulation aneurysms.
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Affiliation(s)
- Y J Heo
- From the Departments of Radiology (Y.J.H., H.W.J., J.W.B.)
| | - H W Jeong
- From the Departments of Radiology (Y.J.H., H.W.J., J.W.B.)
| | - J W Baek
- From the Departments of Radiology (Y.J.H., H.W.J., J.W.B.)
| | - S T Kim
- Neurosurgery (S.T.K., Y.G.J.)
| | | | - J Y Lee
- Internal Medicine (J.Y.L.), Inje University Busan Paik Hospital, Busan, Korea
| | - S-C Jin
- Department of Neurosurgery (S.-C.J.), Inje University Haeundae Paik Hospital, Busan, Korea
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Follow-up of intracranial aneurysms treated with stent-assisted coiling: Comparison of contrast-enhanced MRA, time-of-flight MRA, and digital subtraction angiography. J Neuroradiol 2017; 44:44-51. [DOI: 10.1016/j.neurad.2016.10.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 10/04/2016] [Accepted: 10/10/2016] [Indexed: 11/24/2022]
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Timsit C, Soize S, Benaissa A, Portefaix C, Gauvrit JY, Pierot L. Contrast-Enhanced and Time-of-Flight MRA at 3T Compared with DSA for the Follow-Up of Intracranial Aneurysms Treated with the WEB Device. AJNR Am J Neuroradiol 2016; 37:1684-9. [PMID: 27102311 DOI: 10.3174/ajnr.a4791] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 02/28/2016] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Imaging follow-up at 3T of intracranial aneurysms treated with the WEB Device has not been evaluated yet. Our aim was to assess the diagnostic accuracy of 3D-time-of-flight MRA and contrast-enhanced MRA at 3T against DSA, as the criterion standard, for the follow-up of aneurysms treated with the Woven EndoBridge (WEB) system. MATERIALS AND METHODS From June 2011 to December 2014, patients treated with the WEB in our institution, then followed for ≥6 months after treatment by MRA at 3T (3D-TOF-MRA and contrast-enhanced MRA) and DSA within 48 hours were included. Aneurysm occlusion was assessed with a simplified 2-grade scale (adequate occlusion [total occlusion + neck remnant] versus aneurysm remnant). Interobserver and intermodality agreement was evaluated by calculating the linear weighted κ. MRA test characteristics and predictive values were calculated from a 2 × 2 contingency table, by using DSA data as the standard of reference. RESULTS Twenty-six patients with 26 WEB-treated aneurysms were included. The interobserver reproducibility was good with DSA (κ = 0.71) and contrast-enhanced-MRA (κ = 0.65) compared with moderate with 3D-TOF-MRA (κ = 0.47). Intermodality agreement with DSA was fair with both contrast-enhanced MRA (κ = 0.36) and 3D-TOF-MRA (κ = 0.36) for the evaluation of total occlusion. For aneurysm remnant detection, the prevalence was low (15%), on the basis of DSA, and both MRA techniques showed low sensitivity (25%), high specificity (100%), very good positive predictive value (100%), and very good negative predictive value (88%). CONCLUSIONS Despite acceptable interobserver reproducibility and predictive values, the low sensitivity of contrast-enhanced MRA and 3D-TOF-MRA for aneurysm remnant detection suggests that MRA is a useful screening procedure for WEB-treated aneurysms, but similar to stents and flow diverters, DSA remains the criterion standard for follow-up.
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Affiliation(s)
- C Timsit
- From the Department of Neuroradiology (C.T., S.S., A.B., L.P.), Hôpital Maison Blanche, Université de Champagne-Ardenne, Reims, France
| | - S Soize
- From the Department of Neuroradiology (C.T., S.S., A.B., L.P.), Hôpital Maison Blanche, Université de Champagne-Ardenne, Reims, France
| | - A Benaissa
- From the Department of Neuroradiology (C.T., S.S., A.B., L.P.), Hôpital Maison Blanche, Université de Champagne-Ardenne, Reims, France
| | - C Portefaix
- CReSTIC SIC EA3804 (C.P.), Université de Champagne-Ardenne, Reims, France
| | - J-Y Gauvrit
- Department of Neuroradiology (J.-Y.G.), Hôpital Pontchaillou, Rennes, France Unité VISAGES U746 INSERM-INRIA (J.-Y.G.), IRISA UMR CNRS 6074, University of Rennes, Rennes, France
| | - L Pierot
- From the Department of Neuroradiology (C.T., S.S., A.B., L.P.), Hôpital Maison Blanche, Université de Champagne-Ardenne, Reims, France
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Lettau M, Bendszus M, Hähnel S. Angiographic CT: in vitro comparison of different carotid artery stents-does stent orientation matter? Neuroradiology 2013; 55:675-82. [PMID: 23411716 DOI: 10.1007/s00234-013-1152-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 01/29/2013] [Indexed: 11/25/2022]
Abstract
INTRODUCTION Our aim was to evaluate the in vitro visualization of different carotid artery stents on angiographic CT (ACT). Of particular interest was the influence of stent orientation to the angiography system by measurement of artificial lumen narrowing (ALN) caused by the stent material within the stented vessel segment to determine whether ACT can be used to detect restenosis within the stent. METHODS ACT appearances of 17 carotid artery stents of different designs and sizes (4.0 to 11.0 mm) were investigated in vitro. Stents were placed in different orientations to the angiography system. Standard algorithm image reconstruction and stent-optimized algorithm image reconstruction was performed. For each stent, ALN was calculated. RESULTS With standard algorithm image reconstruction, ALN ranged from 19.0 to 43.6 %. With stent-optimized algorithm image reconstruction, ALN was significantly lower and ranged from 8.2 to 18.7 %. Stent struts could be visualized in all stents. Differences in ALN between the different stent orientations to the angiography system were not significant. CONCLUSION ACT evaluation of vessel patency after stent placement is possible but is impaired by ALN. Stent orientation of the stents to the angiography system did not significantly influence ALN. Stent-optimized algorithm image reconstruction decreases ALN but further research is required to define the visibility of in-stent stenosis depending on image reconstruction.
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Affiliation(s)
- Michael Lettau
- Division of Neuroradiology, Department of Neurosurgery, University of Freiburg Medical Center, Breisacher Str. 64, 79106 Freiburg, Germany.
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Seok JH, Choi HS, Jung SL, Ahn KJ, Kim MJ, Shin YS, Kim BS. Artificial luminal narrowing on contrast-enhanced magnetic resonance angiograms on an occasion of stent-assisted coiling of intracranial aneurysm: in vitro comparison using two different stents with variable imaging parameters. Korean J Radiol 2012; 13:550-6. [PMID: 22977321 PMCID: PMC3435851 DOI: 10.3348/kjr.2012.13.5.550] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Accepted: 03/15/2012] [Indexed: 11/15/2022] Open
Abstract
Objective Intracranial stenting for stent-assisted coiling of aneurysms requires adequate follow-up imaging. The aim of this in vitro study was to compare in-stent artificial luminal narrowing on contrast-enhanced MR angiograms (CE-MRA) when applying Neuroform® and Enterprise® stents for stent-assisted coiling. Materials and Methods Two intracranial nitinol stents (Enterprise® and Neuroform®) were placed in silicon tubes and then imaged at 3 T and 1.5 T by the use of a T1-weighted three-dimensional spoiled gradient-echo sequence with minimal TR and TE. CE-MRAs were obtained by using different imaging planes, voxel sizes, and bandwidths, and with or without parallel imaging. Artificial lumen narrowing (ALN) was calculated and the results were compared. Results Lower magnetic field strength, axial plane perpendicular to axis of stent, and wider bandwidth resulted in a lower ALN on CE-MRA for both stents. Larger voxel size resulted in lower ALN for Neuroform® stent. The parallel imaging acceleration factor did not affect ALN. The mean ALN was lower for Neuroform®, but it was not significant by a paired t test. Conclusion CE-MRA of the stented lumen of vascular phantom was partially impaired with ALN. Consequently, image plane orientation, magnetic field strength, bandwidth, and voxel size should be adjusted appropriately to reduce ALN.
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Affiliation(s)
- Jee Hyun Seok
- Department of Radiology, Seoul St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul 137-701, Korea
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MR Angiography of Peripheral Arterial Stents: In Vitro Evaluation of 22 Different Stent Types. Radiol Res Pract 2010; 2011:478175. [PMID: 22091380 PMCID: PMC3197262 DOI: 10.1155/2011/478175] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Accepted: 06/27/2010] [Indexed: 11/17/2022] Open
Abstract
Purpose. To evaluate stent lumen visibility of a large sample of different peripheral arterial (iliac, renal, carotid) stents using magnetic resonance angiography in vitro. Materials and Methods. 21 different stents and one stentgraft (10 nitinol, 7 316L, 2 tantalum, 1 cobalt superalloy, 1 PET + cobalt superalloy, and 1 platinum alloy) were examined in a vessel phantom (vessel diameters ranging from 5 to 13 mm) filled with a solution of Gd-DTPA. Stents were imaged at 1.5 Tesla using a T1-weighted 3D spoiled gradient-echo sequence. Image analysis was performed measuring three categories: Signal intensity in the stent lumen, lumen visibility of the stented lumen, and homogeneity of the stented lumen. The results were classified using a 3-point scale (good, intermediate, and poor results). Results. 7 stents showed good MR lumen visibility (4x nitinol, 2x tantalum, and 1x cobalt superalloy). 9 stents showed intermediate results (5x nitinol, 2x 316L, 1x PET + cobalt superalloy, and 1x platinum alloy) and 6 stents showed poor results (1x nitinol, and 5x 316L). Conclusion. Stent lumen visibility varies depending on the stent material and type. Some products show good lumen visibility which may allow the detection of stenoses inside the lumen, while other products cause artifacts which prevent reliable evaluation of the stent lumen with this technique.
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Lettau M, Sauer A, Heiland S, Rohde S, Reinhardt J, Bendszus M, Hähnel S. In vitro comparison of different carotid artery stents: a pixel-by-pixel analysis using CT angiography and contrast-enhanced MR angiography at 1.5 and 3 T. Neuroradiology 2009; 52:823-30. [PMID: 19924409 DOI: 10.1007/s00234-009-0625-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Accepted: 10/29/2009] [Indexed: 10/20/2022]
Abstract
INTRODUCTION CT angiography (CTA) and MR angiography (MRA) are increasingly used methods for evaluation of stented vessel segments. The purpose of this study was to compare CTA, contrast-enhanced MRA (CEMRA) at 1.5 T, and CEMRA at 3 T for the visualization of carotid artery stents and to define the best noninvasive imaging technique for each stent. METHODS CTA and CEMRA appearances of 18 carotid artery stents of different designs and sizes (4.0 to 10.0 mm) were investigated in vitro. The profile of the contrast-to-noise ratio (CNR) of the lumen of each stent was calculated semiautomatically by a pixel-by-pixel analysis using the medical imaging software OSIRIS. For each stent, artificial lumen narrowing (ALN) was calculated. RESULTS In all but one stents, ALN was lower on CEMRA at 3 T than at 1.5 T. With CEMRA at 3 T and at 1.5 T, ALN in most nitinol stents was lower than in the groups of stainless steel and cobalt alloy stents. In most nitinol stents, ALN on CEMRA at 3 T was lower than on CTA. In all stainless steel stents and cobalt alloy stents, ALN was lower on CTA than on CEMRA. With CTA and CEMRA, in most stents ALN decreased with increasing stent diameter. CONCLUSION CTA and CEMRA evaluation of vessel patency after stent placement is possible, but considerably impaired by ALN. Investigators should be informed about the method of choice for every stent.
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Affiliation(s)
- Michael Lettau
- Division of Neuroradiology, Department of Neurology, University of Heidelberg, Medical Center, Im Neuenheimer Feld 400, Heidelberg, Germany.
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Lettau M, Sauer A, Heiland S, Rohde S, Bendszus M, Hähnel S. Carotid artery stents: in vitro comparison of different stent designs and sizes using CT angiography and contrast-enhanced MR angiography at 1.5T and 3T. AJNR Am J Neuroradiol 2009; 30:1993-7. [PMID: 19749216 DOI: 10.3174/ajnr.a1743] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE CT angiography (CTA) and MR angiography (MRA) are increasingly used methods for evaluation of stented vessel segments. Our aim was to compare CTA, contrast-enhanced MRA (CE-MRA) at 1.5T, and CE-MRA at 3T for the visualization of carotid artery stents and to define the best noninvasive imaging technique as an alternative to conventional angiography for each stent. MATERIALS AND METHODS CTA and CE-MRA appearances of 18 carotid artery stents of different designs and sizes (4.0 to 10.0 mm) were investigated in vitro. For each stent, artificial lumen narrowing (ALN) was calculated. RESULTS With CE-MRA at 3T and at 1.5T, ALN in most nitinol stents was lower than that in the groups of stainless steel and cobalt alloy stents. In most nitinol stents and in both cobalt alloy stents, ALN was lower on CE-MRA at 3T than at 1.5T. In all stainless steel stents, ALN was lower on CTA than on CE-MRA. With CTA and CE-MRA, in most stents ALN decreased with increasing stent diameter. CONCLUSIONS CTA and CE-MRA evaluation of vessel patency after stent placement is possible but is considerably impaired by ALN. Investigators should be informed about the method of choice for every stent. Stent manufacturers should be aware of potential artifacts caused by their stents during noninvasive diagnostic methods such as CTA and CE-MRA.
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Affiliation(s)
- M Lettau
- Department of Neurology, University of Heidelberg Medical Center, Heidelberg, Germany.
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Hähnel S, Nguyen-Trong TH, Rohde S, Hartmann M, Braun C, Sartor K, Heiland S. 3.0 Tesla contrast-enhanced MR angiography of carotid artery stents: in vitro measurements as compared with 1.5 Tesla. J Neuroradiol 2006; 33:75-80. [PMID: 16733419 DOI: 10.1016/s0150-9861(06)77234-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND AND PURPOSE To assess the appearance of carotid artery stents at 3.0 Tesla contrast enhanced magnetic resonance angiography (CE-MRA) as compared with 1.5 Tesla. METHODS 19 stents (GUIDANT Acculink, GUIDANT Dynalink, BOSTON SCIENTIFIC SMART Neuroform, GUIDANT Omnilink, EV3 Protege, BOSTON SCIENTIFIC Carotid Wallstent, ABBOTT Xact) of different materials (nitinol, stainless steal, cobalt alloy) and different sizes (4.0 mm-10.0 mm) were investigated regarding their appearance on CE-MRA at 3.0 Tesla and at 1.5 Tesla. For each stent artificial lumen narrowing (ALN) was calculated based on a pixel-by-pixel profile of the contrast-to-noise-ratio giving an objective indicator for the size of the evaluable stent diameter. RESULTS Only in two stents (Omnilink 7.0 mm, Omnilink 10.0 mm) was ALN higher at 3.0 Tesla relative to 1.5 Tesla. In all other stents ALN at 3.0 Tesla was the same or even lower as compared with 1.5 Tesla. In contrast to the ferromagnetic stents where ALN was typically higher than 85%, in most of the nitinol stents (Acculink, Dynalink, Neuroform, Protege) ALN was below 35%. In the Xact stents ALN was generally 100% at 1.5 Tesla and ranged between 31.8% and 100% at 3.0 Tesla. CONCLUSION CE-MRA after carotid artery stenting is considerably impaired by ALN both at 1.5 Tesla and at 3.0 Tesla. Nevertheless, CE-MRA is well suited for the examination of carotid artery stents made of nitinol at both field strengths. Stent manufacturers should be aware of potential artifacts caused by their stents during noninvasive diagnostic methods such as CE-MRA.
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Affiliation(s)
- S Hähnel
- Division of Neuroradiology, Department of Neurology, University of Heidelberg Medical Center, Im Neuenheimer Feld 400, D 69120 Heidelberg, Germany.
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Wall A, Kugel H, Bachman R, Matuszewski L, Krämer S, Heindel W, Maintz D. 3.0 T vs. 1.5 T MR angiography: In vitro comparison of intravascular stent artifacts. J Magn Reson Imaging 2005; 22:772-9. [PMID: 16270296 DOI: 10.1002/jmri.20445] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To evaluate the signal characteristics of different iliac artery stents in MR angiography (MRA) at 3 T in comparison with 1.5 T. MATERIALS AND METHODS Sixteen iliac artery stents were implanted in plastic tubes filled with a solution of Gd-DTPA and imaged at 3 T and 1.5 T using a T1-weighted 3D spoiled gradient-echo sequence. Image analysis included a subjective assessment of artifact characteristics, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurements in stented and unstented vessel parts, and quantitative measurements of total artifact size. RESULTS The pattern of stent artifacts inside the stents evidently did not differ at 3 T and 1.5 T. The average total size of the artifact areas surrounding the stents was significantly larger at 3 T (P < 0.03). However, within the stented part of the vessel phantom, the signal of the lumen and its contrast to modeled surrounding tissue was significantly higher at the higher field. The mean SNR of the lumen increased from 95.5 at 1.5 T to 127.3 at 3 T, and the CNR of the vessel increased from 70.3 to 93. CONCLUSION Assessment of the stent lumen in iliac artery stents in a phantom model is not compromised by imaging at 3 T compared to 1.5 T. The signal gain inside the stented part of the vessel lumen at higher field compensates for the higher degree of stent artifacts seen in stents made of steel or cobalt.
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Affiliation(s)
- Alexander Wall
- Department of Clinical Radiology, University of Münster, Münster, Germany.
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Spuentrup E, Ruebben A, Mahnken A, Stuber M, Kölker C, Nguyen TH, Günther RW, Buecker A. Artifact-free coronary magnetic resonance angiography and coronary vessel wall imaging in the presence of a new, metallic, coronary magnetic resonance imaging stent. Circulation 2005; 111:1019-26. [PMID: 15723984 DOI: 10.1161/01.cir.0000156462.97532.8f] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Coronary in-stent restenosis cannot be directly assessed by magnetic resonance angiography (MRA) because of the local signal void of currently used stainless steel stents. The aim of this study was to investigate the potential of a new, dedicated, coronary MR imaging (MRI) stent for artifact-free, coronary MRA and in-stent lumen and vessel wall visualization. METHODS AND RESULTS Fifteen prototype stents were deployed in coronary arteries of 15 healthy swine and investigated with a double-oblique, navigator-gated, free-breathing, T2-prepared, 3D cartesian gradient-echo sequence; a T2-prepared, 3D spiral gradient-echo sequence; and a T2-prepared, 3D steady-state, free-precession coronary MRA sequence. Furthermore, black-blood vessel wall imaging by a dual-inversion-recovery, turbo spin-echo sequence was performed. Artifacts of the stented vessel segment and signal intensities of the coronary vessel lumen inside and outside the stent were assessed. With all investigated sequences, the vessel lumen and wall could be visualized without artifacts, including the stented vessel segment. No signal intensity alterations inside the stent when compared with the vessel lumen outside the stent were found. CONCLUSIONS The new, coronary MRI stent allows for completely artifact-free coronary MRA and vessel wall imaging.
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Affiliation(s)
- Elmar Spuentrup
- Department of Diagnostic Radiology, Technical University of Aachen, Aachen, Germany
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Busch M, Vollmann W, Bertsch T, Wetzler R, Bornstedt A, Schnackenburg B, Schnorr J, Kivelitz D, Taupitz M, Grönemeyer D. On the heating of inductively coupled resonators (stents) during MRI examinations. Magn Reson Med 2005; 54:775-82. [PMID: 16149073 DOI: 10.1002/mrm.20618] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Stents that have been implanted to preserve the results of vascular dilatation are frequently affected by in-stent restenosis, which ideally should be followed up by a noninvasive diagnostic modality. Active MRI stents can enable this kind of follow-up, while normal metallic stents can not. The prototype stents investigated in this study were designed as electric resonating circuits without a direct connection to the MR imager, and function as inductively coupled transmit coils. The model of a long solenoid coil is used to describe the additional power loss caused by such resonators. The theoretically estimated temperature increase is verified by measurements for different resonators and discussed for worst-case conditions. The RF power absorption of an active resonator is negligible compared to the total power absorbed during MRI. The local temperature increase observed for prototypes embedded in phantoms is in a range that excludes direct tissue damage. However, ruptures in the conducting structure of a resonator can cause hot spots, which may establish a high local temperature. This hazard can be reduced by designing resonators with a low quality (Q) factor or by setting the circuit slightly off resonance; however, this would lower the nominal amplification for which the resonator was designed.
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Affiliation(s)
- Martin Busch
- Grönemeyer Institut für Mikrotherapie, Universität Witten/Herdecke, Bochum, Germany.
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Buecker A, Spuentrup E, Ruebben A, Mahnken A, Nguyen TH, Kinzel S, Günther RW. New metallic MR stents for artifact-free coronary MR angiography: feasibility study in a swine model. Invest Radiol 2004; 39:250-3. [PMID: 15087718 DOI: 10.1097/01.rli.0000116894.48384.c2] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
RATIONALE AND OBJECTIVES The objective of this study was to investigate the potential for artifact-free coronary magnetic resonance angiography (cMRA) in the presence of dedicated metallic MR stents in vitro and in a swine model. METHODS All investigations were performed at 1.5 T, applying a standard cMRA gradient echo sequence with a T2 preparation pulse. Two prototypes of each hand-woven, mechanically woven, and lasered Aachen Resonance Coronary MR Stents made out of an MR-compatible metallic alloy and dilated to 2.5 mm and 4 mm were examined in a water bath. RESULTS Artifact behavior was judged independently by 2 radiologists as showing "no artifacts" for all tested stent types. Signal-to-noise ratios inside and outside of the stents were measured yielding a Pearson correlation coefficient of 0.98 (y = 1.22 + 0.92x). Nineteen stents (8 hand woven, 3 mechanically woven, 8 lasered) were deployed in coronary arteries of 19 domestic pigs and were examined by cMRA. Artifact behavior of the stents was analyzed by measuring the signal-to-noise ratio at the stent positions and compared with signal-to-noise ratio measurements outside of the stents, yielding a Pearson correlation coefficient of 0.90 (y = -0.75 + 1.06x). CONCLUSIONS All 3 prototypes of coronary MR stents allowed complete visualization of the stent lumen and consequently determination of stent patency by cMRA.
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Affiliation(s)
- Arno Buecker
- Clinic of Diagnostic Radiology, University of Technology, Pauwelsstrasse 30, D-52057 Aachen, Germany.
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Létourneau-Guillon L, Soulez G, Beaudoin G, Oliva VL, Giroux MF, Qin Z, Boussion N, Therasse E, De Guise J, Cloutier G. CT and MR Imaging of Nitinol Stents with Radiopaque Distal Markers. J Vasc Interv Radiol 2004; 15:615-24. [PMID: 15178723 DOI: 10.1097/01.rvi.00000127898.23424.01] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE To evaluate imaging characteristics and artifacts of a nitinol stent with distal tantalum markers with computed tomography (CT) angiography and magnetic resonance (MR) angiography. MATERIALS AND METHODS A vascular phantom was built to simulate in-stent restenosis. A nitinol stent with tantalum markers (Luminexx stent) was evaluated with CT angiography in different orientations relative to the z-axis and with MR angiography in different positions relative to both B0 and the readout gradient. Stenosis measurements were compared with conventional digital subtraction angiography for both modalities. In-stent signal intensity obtained with different flip angles was assessed in two nitinol stents with distal markers (Luminexx stent and SMART stent) and one without markers (Memotherm-FLEXX stent). RESULTS Stenosis detection was not possible with CT angiography when the stent was perpendicular to the z-axis because of streak-like artifacts induced by tantalum markers. Stenosis evaluation with multiplanar reformation was accurate when the stent was in parallel and oblique orientations relative to the table axis. With MR angiography, metallic artifacts were mostly related to the stent orientation with B0, whereas orientation of the readout gradient had little influence. The mean error (overestimation) for stenosis measurements varied between 0.1% and 7.4% for CT imaging in parallel and oblique positions and 3.6% and 9.5% for MR imaging. Higher flip angles did not improve signal intensity inside the three stents tested. CONCLUSION CT and MR angiography can be used for evaluating the patency of stents with distal markers that are parallel or oblique relative to the table axis (iliac, carotid, or femoral stents). MR angiography is preferred if the stent is perpendicular to the table axis (renal stent).
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Affiliation(s)
- Laurent Létourneau-Guillon
- Department of Radiology, CHUM-Notre-Dame Hospital, 1560 Sherbrooke East, Montreal, Quebec, Canada, H2L 4M1.
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Trost DW, Zhang HL, Prince MR, Winchester PA, Wang Y, Watts R, Sos TA. Three-dimensional MR angiography in imaging platinum alloy stents. J Magn Reson Imaging 2004; 20:975-80. [PMID: 15558574 DOI: 10.1002/jmri.20209] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To evaluate visualization inside platinum stents with three-dimensional contrast-enhanced magnetic resonance angiography (CE-MRA). MATERIALS AND METHODS Breath-hold three-dimensional gadolinium (Gd) MRA was performed on 18 patients with 22 platinum stents in the renal (n = 18), celiac (n = 1), superior mesenteric (n = 1), and iliac (n = 2) arteries. Electronic calibers were used to measure the lumen diameter within the stent and just distal to the stent to calculate percent stenosis. MRA accuracy was determined from the difference between percent stenosis measured on MRA and digital subtracted angiography (DSA). The patients were imaged at flip angles of 45 degrees , 60 degrees , 75 degrees , 90 degrees , and 150 degrees . RESULTS MRA demonstrated the stent lumen in all of the patients, with a mean difference between MRA and DSA of 21%. For stents oriented parallel to B0 (iliac arteries) the difference was only 10%, as compared to 22% for stents perpendicular to B0. The flip angle with the best agreement between MRA and DSA was 75 degrees (16%). CONCLUSION The lumen of a platinum stent can be imaged with three-dimensional CE-MRA, although grading of restenosis has limited accuracy. The best results were obtained with a flip angle of 75 degrees and for stents in the iliac arteries parallel to B0.
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Affiliation(s)
- David W Trost
- Department of Radiology, Weill Cornell Medical College, New York, New York 10022, USA
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van Holten J, Wielopolski P, Brück E, Pattynama PMT, van Dijk LC. High flip angle imaging of metallic stents: Implications for MR angiography and intraluminal signal interpretation. Magn Reson Med 2003; 50:879-83. [PMID: 14523976 DOI: 10.1002/mrm.10600] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Intraluminal stent signal characterization by MRI is generally hampered by signal loss from the metallic stent material. This signal loss is related to magnetic susceptibility and RF shielding. Even when stent materials with low magnetic susceptibility are used, RF shielding can still be problematic. In this article we have shown that high flip angle imaging enables morphology assessment and tissue characterization in stents made of stainless steel 316L, NiTinol, and ABI-alloy.
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Spuentrup E, Ruebben A, Stuber M, Günther RW, Buecker A. Metallic renal artery MR imaging stent: artifact-free lumen visualization with projection and standard renal MR angiography. Radiology 2003; 227:897-902. [PMID: 12773688 DOI: 10.1148/radiol.2273020354] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A cardiac-triggered free-breathing three-dimensional (3D) balanced fast field-echo projection renal magnetic resonance (MR) angiographic sequence was investigated for in-stent lumen visualization of a dedicated metallic renal artery stent. Fourteen prototype stents were deployed in the renal arteries of six pigs (in two pigs, three stents were deployed). Projection renal MR angiography was compared with standard contrast material-enhanced 3D breath-hold MR angiography. Artifact-free in-stent lumen visualization was achieved with both projection MR angiography and contrast-enhanced MR angiography. These promising results warrant further studies for visualization of in-stent restenosis.
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Affiliation(s)
- Elmar Spuentrup
- Department of Diagnostic Radiology, Technical University of Aachen, Pauwelsstrasse 30, 52057 Aachen, Germany.
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Wang Y, Truong TN, Yen C, Bilecen D, Watts R, Trost DW, Prince MR. Quantitative evaluation of susceptibility and shielding effects of nitinol, platinum, cobalt-alloy, and stainless steel stents. Magn Reson Med 2003; 49:972-6. [PMID: 12704782 DOI: 10.1002/mrm.10450] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The purpose of this study is to quantitatively estimate the shielding and susceptibility effects of commonly used metallic stents on MR signal. Two experiments were performed using a 3D gradient echo sequence with short TE to image a stent phantom: 1) short TR and high flip angle (contrast enhanced MRA parameters), and 2) long TR (TR >> T(1)) and low flip angle. The factor characterizing susceptibility effects was estimated from the signal phase of the first experiment, and then the factor characterizing the shielding effects was derived from the second experiment. Susceptibility induced signal loss was negligible (<1%) for nonstainless-steel (nitinol, platinum, and cobalt-alloy) stents and totally destructive (100%) for the stainless steel stent. Signal loss due to RF shielding was 31-62% for nitinol stents, 14-50% for platinum stents, 50-77% for the cobalt-alloy stents (undetermined for the stainless steel stent), varied with stent orientation, diameter, and wall geometry. In summary, stents made of nitinol, platinum, and cobalt-alloy have negligible susceptibility effects but stents made of stainless steel may have complete dephasing. All stents have substantial shielding effects, which vary with composition, geometry, and orientation. Large platinum stents may have the smallest artifacts and are the best suited for postinterventional MR imaging.
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Affiliation(s)
- Yi Wang
- Department of Radiology, Weill Medical College of Cornell University, New York, New York, USA.
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Kivelitz D, Wagner S, Schnorr J, Wetzler R, Busch M, Melzer A, Taupitz M, Hamm B. A vascular stent as an active component for locally enhanced magnetic resonance imaging: initial in vivo imaging results after catheter-guided placement in rabbits. Invest Radiol 2003; 38:147-52. [PMID: 12595794 DOI: 10.1097/01.rli.0000052981.82153.a1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
RATIONALE AND OBJECTIVE A vascular stent constructed as a high frequency resonator improves the local signal-to-noise ratio at magnetic resonance (MR) imaging. After catheter placement and intravascular expansion, the stent can be used as an inductively coupled coil for MRI. The imaging properties of this balloon-expandable active MRI stent (AMRIS) were evaluated after x-ray fluoroscopy guided placement in the abdominal aorta of five rabbits using MR angiography (MRA) and flow measurements. METHODS The AMRIS was implanted in the abdominal aorta of five rabbits using a balloon catheter inserted through the common carotid artery. The rabbits were examined by MRA (3D fast low-angle shot) at 1.5 tesla before and after intravenous injection of an iron-oxide-based blood pool contrast medium (dose 50 micro mol Fe/kg) and flow measurements (ECG-triggered phase contrast cine gradient-echo sequence). Signal-to-noise ratios (SNR) were calculated and flow volume curves were generated. The in-stent increase in temperature was measured in vitro using a fiberoptic thermometry system. RESULTS The SNR was 5.0 +/- 0.6 outside the stent and 23.2 +/- 14.1 within the stent ( < 0.0 5) in plain MRA, 19.5 +/- 5.0 outside and 30.7 +/- 8.2 within the stent ( < 0.05) in contrast enhanced MRA, and 5.8 +/- 1.6 and 13.9 +/- 5.9, respectively ( < 0.05) in the magnitude images of the flow measurements. Flow volume curves within and distal to the stent were comparable. CONCLUSIONS The expandable active MRI stent produces local signal enhancement in MRA and MR flow measurements after catheter placement and thus may improve assessment of the stented vessel segment by MR imaging.
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Affiliation(s)
- Dietmar Kivelitz
- Institut für Radiologie, Charité, Medizinische Fakultät, Humboldt-Universität zu Berlin, Berlin, Germany.
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Buecker A, Spuentrup E, Ruebben A, Günther RW. Artifact-free in-stent lumen visualization by standard magnetic resonance angiography using a new metallic magnetic resonance imaging stent. Circulation 2002; 105:1772-5. [PMID: 11956117 DOI: 10.1161/01.cir.0000015852.60212.db] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Metallic stents cause susceptibility and radiofrequency artifacts on MR images, which, up to now, have not allowed for complete visualization of the stent lumen by MR angiography. The aim of this study was to investigate the potential of a new dedicated renal MRI stent for artifact-free in-stent lumen visualization in vitro and in a swine model. METHODS AND RESULTS In vitro investigations were performed with prototypes of balloon-expandable Aachen Resonance Renal MRI Stents dilated to diameters of 3 to 6 mm and placed in an aqueous gadolinium solution (1:25). Phase-contrast and contrast-enhanced T1-weighted gradient echo images were acquired. Renal MRI stents (n=12) were deployed in the renal arteries of 6 pigs. Renal arteries were examined with phase-contrast angiography and with flow measurements before and after stent placement in the stented area, respectively. Additionally, a contrast-enhanced, T1-weighted, spoiled-gradient echo sequence after administration of 0.2 mmol gadolinium-DTPA/kg body weight was performed after stent placement. The visibility of artifacts was analyzed on in vitro and in vivo images by two investigators who knew the stent positions. Stent positions were determined visually (in vitro) or by x-ray angiography (animal experiments). No artifacts were detected independent of the applied imaging sequence and the stent orientation to the main magnetic field. CONCLUSION The examined prototypes of fully MR-compatible MRI stents allow artifact-free visualization of the stent lumen with phase-contrast and contrast-enhanced T1-weighted angiography, as well as phase-contrast flow measurements in the stented area.
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Affiliation(s)
- Arno Buecker
- Clinic of Diagnostic Radiology, University of Technology Aachen, Germany.
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