1
|
van Helvert M, Engelhard S, Voorneveld J, van der Vee M, Bosch JG, Versluis M, Groot Jebbink E, Reijnen MMPJ. High-frame-rate contrast-enhanced ultrasound particle image velocimetry in patients with a stented superficial femoral artery: a feasibility study. Eur Radiol Exp 2022; 6:32. [PMID: 35790584 PMCID: PMC9256892 DOI: 10.1186/s41747-022-00278-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 04/14/2022] [Indexed: 11/20/2022] Open
Abstract
Background Local blood flow affects vascular disease and outcomes of endovascular treatment, but quantifying it is challenging, especially inside stents. We assessed the feasibility of blood flow quantification in native and stented femoral arteries, using high-frame-rate (HFR) contrast-enhanced ultrasound (CEUS) particle image velocimetry (PIV), also known as echoPIV. Methods Twenty-one patients with peripheral arterial disease, recently treated with a stent in the femoral artery, were included. HFR CEUS measurements were performed in the native femoral artery and at the inflow and outflow of the stent. Two-dimensional blood flow was quantified through PIV analysis. EchoPIV recordings were visually assessed by five observers and categorised as optimal, partial, or unfeasible. To evaluate image quality and tracking performance, contrast-to-tissue ratio (CTR) and vector correlation were calculated, respectively. Results Fifty-eight locations were measured and blood flow quantification was established in 49 of them (84%). Results were optimal for 17/58 recordings (29%) and partial for 32 recordings (55%) due to loss of correlation (5/32; 16%), short vessel segment (8/32; 25%), loss of contrast (14/32; 44%), and/or shadows (18/32; 56%). In the remaining 9/58 measurements (16%) no meaningful flow information was visualised. Overall, CTR and vector correlation were lower during diastole. CTR and vector correlation were not different between stented and native vessel segments, except for a higher native CTR at the inflow during systole (p = 0.037). Conclusions Blood flow quantification is feasible in untreated and stented femoral arteries using echoPIV. Limitations remain, however, none of them related to the presence of the stent. Trial registration ClinicalTrials.gov, NCT04934501 (retrospectively registered). Supplementary Information The online version contains supplementary material available at 10.1186/s41747-022-00278-w.
Collapse
Affiliation(s)
- Majorie van Helvert
- Multi-Modality Medical Imaging Group, TechMed Centre, University of Twente, Enschede, The Netherlands. .,Department of Vascular Surgery, Rijnstate Hospital, Arnhem, The Netherlands. .,Physics of Fluids Group, TechMed Centre, University of Twente, Enschede, The Netherlands.
| | - Stefan Engelhard
- Multi-Modality Medical Imaging Group, TechMed Centre, University of Twente, Enschede, The Netherlands.,Department of Vascular Surgery, Rijnstate Hospital, Arnhem, The Netherlands.,Physics of Fluids Group, TechMed Centre, University of Twente, Enschede, The Netherlands
| | - Jason Voorneveld
- Department of Biomedical Engineering, Thorax Center, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Marije van der Vee
- Department of Vascular Surgery, Rijnstate Hospital, Arnhem, The Netherlands.,Physics of Fluids Group, TechMed Centre, University of Twente, Enschede, The Netherlands
| | - Johan G Bosch
- Department of Biomedical Engineering, Thorax Center, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Michel Versluis
- Physics of Fluids Group, TechMed Centre, University of Twente, Enschede, The Netherlands
| | - Erik Groot Jebbink
- Multi-Modality Medical Imaging Group, TechMed Centre, University of Twente, Enschede, The Netherlands.,Department of Vascular Surgery, Rijnstate Hospital, Arnhem, The Netherlands
| | - Michel M P J Reijnen
- Multi-Modality Medical Imaging Group, TechMed Centre, University of Twente, Enschede, The Netherlands.,Department of Vascular Surgery, Rijnstate Hospital, Arnhem, The Netherlands
| |
Collapse
|
2
|
Nakai R, Goto K, Shima K, Kodama T, Iwata H. Dual-phase Au-Pt alloys free from magnetic susceptibility artifacts in magnetic resonance imaging. Magn Reson Imaging 2021; 85:19-27. [PMID: 34653577 DOI: 10.1016/j.mri.2021.10.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 09/27/2021] [Accepted: 10/10/2021] [Indexed: 11/29/2022]
Abstract
PURPOSE Magnetic resonance imaging (MRI) devices are frequently used in image-based diagnosis. In the case of large artifacts, which are generated in magnetic resonance (MR) images when magnetic materials, such as metals, are present in the body, these devices are less useful. This study aimed to develop a dual-phase Au-Pt alloy that does not generate artifacts in MR images and has high workability to prepare medical devices. MATERIALS AND METHODS A processing method to produce a dual-phase Au-Pt alloy was established, and the magnetic susceptibility and artifacts of different alloy compositions were determined using a SQUID (superconducting quantum interference device) flux meter and a 1.5 T-MRI system. The crystallographic phases of the prepared alloy samples were identified using X-ray diffraction. Sample cross-sections were observed using a metallurgical microscope. Furthermore, a thinning test was conducted to examine alloy workability. RESULTS Dual-phase Au-Pt alloys Au70Pt30 and Au67Pt33-the former heat-treated at 800 and 850 °C and the latter heat-treated at 900 °C-generated minimal artifacts when imaged in a 1.5 T-MRI system. Their volume magnetic susceptibility increased as the heat-treatment temperature decreased. The alloy surfaces were observed to be uniform. Moreover, the workability of the dual-phase alloy was considerably better than that of the single-phase alloy. CONCLUSION Volume magnetic susceptibility could be controlled by changing the composition and processing temperature of the Au-Pt alloys. Dual-phase Au-Pt alloys those do not generate magnetic susceptibility artifacts in MRI images and have good workability could be prepared. The alloys are expected to be used in the preparation of various implantable medical devices.
Collapse
Affiliation(s)
| | - Kenji Goto
- Isehara Technical Center, Tanaka Kikinzoku Kogyo K.K., Japan
| | - Kunihiro Shima
- Material Development Department, Tanaka Kikinzoku Kogyo K.K., Japan
| | - Tomonobu Kodama
- Department of Neurosurgery, Jikei University School of Medicine, Japan
| | - Hiroo Iwata
- Graduate School of Medicine, Kyoto University, Japan
| |
Collapse
|
3
|
Halitcan B, Bige S, Sinan B, Ilkay A, Ergun D, Fatih A, Anil A. The implications of magnetic resonance angiography artifacts caused by different types of intracranial flow diverters. J Cardiovasc Magn Reson 2021; 23:69. [PMID: 34092251 PMCID: PMC8182930 DOI: 10.1186/s12968-021-00753-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 04/06/2021] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Serial cerebral angiographic imaging is necessary to ensure cerebral aneurysm occlusion after flow diverter placement. Time-of-flight (TOF)-magnetic resonance angiography (MRA) is used for this purpose due to its lack of radiation, contrast media and complications. The comparative diagnostic yield of TOF-MRA for different flow diverters has not been previously analyzed. PURPOSE To evaluate the diagnostic accuracy of TOF-MRA in cerebral aneurysms treated w divertersith different flow diverters. MATERIALS AND METHODS Flow-diverted patients whose cerebral follow-up MRA and digital subtraction angiograms (DSA) were obtained within 6 weeks were retrospectively identified. The DSA (as gold standard) and MRA images of these patients were compared by two readers (blinded to both patient data and endovascular procedure data) for residual aneurysms and the status of the parent artery for each type of flow diverter. In a second group of patients, magnetic susceptibility artifacts were manually measured and compared for different FDs. RESULTS Seventy-six patients (85 aneurysms) were included in group one, and 86 patients (95 aneurysms) were included in group 2. TOF-MRA and DSA showed almost perfect agreement for residual aneurysms (κ = 0.88, p < 0.001) (positive predictive value (PPV) = 1.00, specificity = 1.00, negative predictive value (NPV) = 0.89, sensitivity = 0.89). Intermodality agreement (κ = 0.97 vs. κ = 0.74, p < 0.005) and sensitivity (0.97 vs. 0.77, NPV: 0.96 vs. 0.77) were highest with nitinol stents. MRA and DSA showed no agreement for occluded or stenotic parent vessels (κ = 0.13, p = 0.015, specificity = 0.44, NPV = 1.00, sensitivity = 1.00). Specificity was lower in chromium-cobalt based FDs than in nitinol devices (specificity = 0.08 vs. 0.60). Chromium-cobalt stents generated the largest artifacts (p < 0.005). The size of the device-related artifact, in millimeters, increased in respective order, for the Silk, Derivo, Pipeline and Surpass devices. CONCLUSION Unlike DSA, TOF-MRA is susceptible to dissimilarities between flow diverters. MRA is not well-suited for research studies comparing different flow diverters. Nitinol FDs appear to be advantageous for TOF-MRA follow-up so as not to miss small aneurysm remnants or clinically relevant parent artery stenosis.
Collapse
Affiliation(s)
- Batur Halitcan
- Department of Radiology, Ministry of Health Ankara City Hospital, Ankara, Turkey
| | - Sayin Bige
- Department of Radiology, Ministry of Health Ankara City Hospital, Ankara, Turkey
| | - Balci Sinan
- Department of Radiology, Hacettepe University Hospitals, Ankara, Turkey
| | - Akmangit Ilkay
- Department of Radiology, Ministry of Health Ankara City Hospital, Ankara, Turkey
| | - Daglioglu Ergun
- Department of Neurosurgery, Ministry of Health Ankara City Hospital, Ankara, Turkey
| | - Alagoz Fatih
- Department of Neurosurgery, Ministry of Health Ankara City Hospital, Ankara, Turkey
| | - Arat Anil
- Department of Radiology, Hacettepe University Hospitals, Ankara, Turkey.
| |
Collapse
|
4
|
Michalska M, Kazimierczak W, Leszczyński W, Nadolska K, Bryl Ł. Contemporary follow-up imaging after endovascular repair of lower extremity atherosclerotic lesions. Pol J Radiol 2018; 83:e634-e642. [PMID: 30800203 PMCID: PMC6384408 DOI: 10.5114/pjr.2018.80348] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 11/22/2018] [Indexed: 12/22/2022] Open
Abstract
Atherosclerotic disease is currently one of the most important problems of modern medicine because it is a leading cause of increased morbidity, morbidity and mortality, and disability in the Western World. Atherosclerosis of the lower limbs (peripheral arterial disease - PAD) significantly affects the quality of life and in a considerable proportion of patients is a cause of disability. Radical treatment of PAD, both surgical and endovascular, aims at revascularisation of ischaemic tissues distal to obstructed arteries. Surveillance imaging is an important part of patient management after endovascular repair of PAD. Apart from availability and contraindications, challenges of imaging include calcifications, flow dynamics, and stent-related artefacts. The aim of this paper was to review the current literature on imaging methods for follow-up after endovascular repair of atherosclerotic lesions, with special attention paid to novel techniques. As a non-invasive modality, ultrasound is still the first-line examination, but computed tomography angiography remains a current state-of-the art technique for follow-up. However, since current imaging recommendations seem not to adhere to contemporary imaging possibilities, more attention should be paid to recent improvements in magnetic resonance angiography technology.
Collapse
|
5
|
Bouillot P, Brina O, Delattre BMA, Ouared R, Pellaton A, Yilmaz H, Machi P, Lovblad KO, Farhat M, Pereira VM, Vargas MI. Neurovascular stent artifacts in 3D-TOF and 3D-PCMRI: Influence of stent design on flow measurement. Magn Reson Med 2018; 81:560-572. [DOI: 10.1002/mrm.27352] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 03/22/2018] [Accepted: 04/19/2018] [Indexed: 11/10/2022]
Affiliation(s)
- Pierre Bouillot
- Departement of Neuroradiology; Geneva University Hospitals; Geneva Switzerland
- Laboratory for Hydraulic Machines (LMH); École Polytechnique Fédérale de Lausanne (EPFL); Lausanne Switzerland
| | - Olivier Brina
- Departement of Neuroradiology; Geneva University Hospitals; Geneva Switzerland
- Division of Neuroradiology, Department of Medical Imaging; Toronto Western Hospital, University Health Network; Toronto Ontario Canada
| | | | - Rafik Ouared
- Departement of Neuroradiology; Geneva University Hospitals; Geneva Switzerland
| | - Alain Pellaton
- Departement of Neuroradiology; Geneva University Hospitals; Geneva Switzerland
| | - Hasan Yilmaz
- Departement of Neuroradiology; Geneva University Hospitals; Geneva Switzerland
| | - Paolo Machi
- Departement of Neuroradiology; Geneva University Hospitals; Geneva Switzerland
| | - Karl-Olof Lovblad
- Departement of Neuroradiology; Geneva University Hospitals; Geneva Switzerland
| | - Mohamed Farhat
- Laboratory for Hydraulic Machines (LMH); École Polytechnique Fédérale de Lausanne (EPFL); Lausanne Switzerland
| | - Vitor Mendes Pereira
- Departement of Neuroradiology; Geneva University Hospitals; Geneva Switzerland
- Division of Neuroradiology, Department of Medical Imaging; Toronto Western Hospital, University Health Network; Toronto Ontario Canada
- Division of Neurosurgery, Department of Surgery; Toronto Western Hospital, University Health Network; Toronto Ontario Canada
| | - Maria Isabel Vargas
- Departement of Neuroradiology; Geneva University Hospitals; Geneva Switzerland
| |
Collapse
|
6
|
Barbati ME, Gombert A, Toonder I, van Vuuren TMAJ, Schleimer K, Grommes J, Wittens CHA, Jalaie H. Detecting stent geometry changes after venous recanalization using duplex ultrasound. Phlebology 2018; 34:8-16. [DOI: 10.1177/0268355518757240] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Background Patients with post-thrombotic syndrome due to chronic venous obstruction and resistant to conservative management can benefit from endovenous revascularization. The current study investigated the usefulness of duplex ultrasound in monitoring the stent changes over the time. Method All duplex ultrasound images of treated patients were reviewed retrospectively. The stent diameter and area during the follow-up visits have been analyzed. Result A total of 210 stents were placed in 137 limbs. Duplex ultrasound findings showed a decrease in area of stent in all patients (mean: 0.69 cm2). Reduction of stent area over the time was a predictor of stent patency (odds ratio: 0.910; confidence interval: 0.832–0.997). Conclusion Duplex ultrasound has sufficient accuracy in detection of stent changes and its patency. There is a discrepancy between diameter of the stent lumen in vitro and after deployment in all patients. Stent occlusion is related to reduction of stent lumen over the time rather than the percent of the stenosis.
Collapse
Affiliation(s)
- Mohammad E Barbati
- Department of Vascular Surgery, University Hospital Aachen, Aachen, Germany
| | - Alexander Gombert
- Department of Vascular Surgery, University Hospital Aachen, Aachen, Germany
| | - Irwin Toonder
- Department of Vascular Surgery, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Timme MAJ van Vuuren
- Department of Vascular Surgery, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Karina Schleimer
- Department of Vascular Surgery, University Hospital Aachen, Aachen, Germany
| | - Jochen Grommes
- Department of Vascular Surgery, University Hospital Aachen, Aachen, Germany
| | - Cees HA Wittens
- Department of Vascular Surgery, University Hospital Aachen, Aachen, Germany
- Department of Vascular Surgery, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Houman Jalaie
- Department of Vascular Surgery, University Hospital Aachen, Aachen, Germany
- Department of Vascular Surgery, Maastricht University Medical Centre, Maastricht, The Netherlands
| |
Collapse
|
7
|
Preparation of an Au-Pt alloy free from artifacts in magnetic resonance imaging. Magn Reson Imaging 2017; 44:38-45. [DOI: 10.1016/j.mri.2017.07.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 07/06/2017] [Indexed: 11/20/2022]
|
8
|
Gitsioudis G, Fortner P, Stuber M, Missiou A, Andre F, Müller OJ, Katus HA, Korosoglou G. Off-resonance magnetic resonance angiography improves visualization of in-stent lumen in peripheral nitinol stents compared to conventional T1-weighted acquisitions: an in vitro comparison study. Int J Cardiovasc Imaging 2016; 32:1645-1655. [PMID: 27535040 DOI: 10.1007/s10554-016-0955-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 08/02/2016] [Indexed: 10/21/2022]
Abstract
To compare the value of inversion recovery with on-resonant water suppression (IRON) to conventional T1-weighted (T1w) MRA and computed tomography angiography (CTA) for visualization of peripheral nitinol stents. We visualized 14 different peripheral nitinol stents in vitro both using Gadolinium (Gd) and ultrasmall superparamagnetic iron nanoparticles (USPIOs) for conventional T1w and IRON-MRA using clinical grade 1.5T MR scanner and iodinated contrast material for CTA using a 256-slice CT scanner. Parameter assessment included signal- and contrast-to-noise ratio (S/CNR), relative in-stent signal and artificial lumen narrowing. X-ray angiography served as gold standard for diameter assessment. Gd-enhanced IRON-MRA exhibited highest in-stent SNR and CNR values compared to conventional T1w MRA (IRON (Gd/USPIO): SNR = 30 ± 3/21 ± 2, CNR = 23 ± 2/14 ± 1; T1w: SNR = 16 ± 1/14 ± 2, CNR = 12 ± 1/10 ± 1, all p < 0.05). Furthermore, IRON-MRA achieved highest relative in-stent signal both using Gd and USPIO (IRON (Gd/USPIO): 121 ± 8 %/103 ± 6 %; T1w: 73 ± 2 %/66 ± 4 %; CTA: 84 ± 6 %, all p < 0.05). However, artificial lumen narrowing appeared similar in all imaging protocols (IRON (Gd/USPIO): 21 ± 3 %/21 ± 2 %; T1w: 16 ± 4 %/17 ± 3 %; CTA: 19 ± 2 %, all p = NS). Finally, IRON-MRA provided improvement of the in-stent lumen visualization with an 'open-close-open' design, which revealed a complete in-stent signal loss in T1w MRA. IRON-MRA improves in-stent visualization in vitro compared to conventional T1w MRA and CTA. In light of the in vitro results with Gd-enhanced IRON-MRA, the clinical implementation of such an approach appears promising.
Collapse
Affiliation(s)
- Gitsios Gitsioudis
- Clinic of Internal Medicine, Department of Cardiology, University of Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany.
| | - Philipp Fortner
- Clinic of Internal Medicine, Department of Cardiology, University of Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
| | - Matthias Stuber
- Russell H. Morgan Department of Radiology and Radiological Sciences, Division of MR Research, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,Center for Biomedical Imaging (CIBM), University Hospital Lausanne, Lausanne, Switzerland
| | - Anna Missiou
- Clinic of Internal Medicine, Department of Cardiology, University of Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
| | - Florian Andre
- Clinic of Internal Medicine, Department of Cardiology, University of Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
| | - Oliver J Müller
- Clinic of Internal Medicine, Department of Cardiology, University of Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
| | - Hugo A Katus
- Clinic of Internal Medicine, Department of Cardiology, University of Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
| | - Grigorios Korosoglou
- Clinic of Internal Medicine, Department of Cardiology, University of Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
| |
Collapse
|
9
|
Non-invasive imaging of bioresorbable coronary scaffolds using CT and MRI: First in vitro experience. Int J Cardiol 2016; 206:101-6. [DOI: 10.1016/j.ijcard.2016.01.028] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2015] [Revised: 12/10/2015] [Accepted: 01/01/2016] [Indexed: 11/17/2022]
|
10
|
Kono K, Shintani A, Terada T. Non-enhanced magnetic resonance angiography can evaluate restenosis after carotid artery stenting with the Carotid Wallstent. Acta Neurochir (Wien) 2014; 156:1713-9. [PMID: 24890936 DOI: 10.1007/s00701-014-2142-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Accepted: 05/21/2014] [Indexed: 11/30/2022]
Abstract
BACKGROUND Carotid artery stenting (CAS) requires follow-up imaging to assess in-stent restenosis (ISR). This study aimed to determine whether non-enhanced magnetic resonance angiography (NE-MRA) is useful for evaluating ISR. METHOD Between 2009 and 2013, we performed 118 consecutive CAS procedures using the Precise stent (n = 78) and the Carotid Wallstent (n = 40). We reviewed 1.5 T NE-MRA and examined visualization of the stent lumen and the degree of ISR if present. Other imaging modalities were used as references. RESULTS NE-MRA performed just after CAS was not able to visualize the stent lumen in all patients because of metal artifacts. In the Carotid Wallstent group, follow-up NE-MRA was available in 22 patients. The stent lumen was visible more than three months after CAS in all patients. Among them, >40 % ISR was observed by other modalities in eight lesions. The degree of restenosis measured by NE-MRA (y%) had a linear relationship with that measured by conventional angiography (x%) (y = 0.97x-0.4, r = 0.79, P = 0.021). In one case among 17 without ISR (6 %), NE-MRA showed false ISR. In the Precise stent group, NE-MRA did not visualize the stent lumen in the follow-up period. CONCLUSIONS NE-MRA can visualize the stent lumen in the Carotid Wallstent more than three months after CAS, but not in the Precise stent at follow-up. This delayed visualization might depend on endothelialization of the stent lumen. The degree of ISR measured by NE-MRA is comparable to that by conventional angiography. NE-MRA can evaluate ISR after CAS with the Carotid Wallstent (100 % sensitivity and 94 % specificity).
Collapse
Affiliation(s)
- Kenichi Kono
- Department of Neurosurgery, Wakayama Rosai Hospital, 93-1 Kinomoto, Wakayama, 640-8505, Japan,
| | | | | |
Collapse
|
11
|
Magnetic resonance imaging of iatrogeny: understanding imaging artifacts related to medical devices. ACTA ACUST UNITED AC 2014; 39:411-23. [DOI: 10.1007/s00261-013-0065-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
12
|
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.
Collapse
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
| | | | | | | | | | | | | |
Collapse
|
13
|
In vitro stent lumen visualisation of various common and newly developed femoral artery stents using MR angiography at 1.5 and 3 tesla. Eur Radiol 2012; 23:588-95. [PMID: 22898936 DOI: 10.1007/s00330-012-2625-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Revised: 07/18/2012] [Accepted: 07/18/2012] [Indexed: 10/28/2022]
|
14
|
Bunck AC, Jüttner A, Kröger JR, Burg MC, Kugel H, Niederstadt T, Tiemann K, Schnackenburg B, Crelier GR, Heindel W, Maintz D. 4D phase contrast flow imaging for in-stent flow visualization and assessment of stent patency in peripheral vascular stents--a phantom study. Eur J Radiol 2012; 81:e929-37. [PMID: 22770579 DOI: 10.1016/j.ejrad.2012.05.032] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Revised: 04/26/2012] [Accepted: 05/04/2012] [Indexed: 10/28/2022]
Abstract
PURPOSE 4D phase contrast flow imaging is increasingly used to study the hemodynamics in various vascular territories and pathologies. The aim of this study was to assess the feasibility and validity of MRI based 4D phase contrast flow imaging for the evaluation of in-stent blood flow in 17 commonly used peripheral stents. MATERIALS AND METHODS 17 different peripheral stents were implanted into a MR compatible flow phantom. In-stent visibility, maximal velocity and flow visualization were assessed and estimates of in-stent patency obtained from 4D phase contrast flow data sets were compared to a conventional 3D contrast-enhanced magnetic resonance angiography (CE-MRA) as well as 2D PC flow measurements. RESULTS In all but 3 of the tested stents time-resolved 3D particle traces could be visualized inside the stent lumen. Quality of 4D flow visualization and CE-MRA images depended on stent type and stent orientation relative to the magnetic field. Compared to the visible lumen area determined by 3D CE-MRA, estimates of lumen patency derived from 4D flow measurements were significantly higher and less dependent on stent type. A higher number of stents could be assessed for in-stent patency by 4D phase contrast flow imaging (n=14) than by 2D phase contrast flow imaging (n=10). CONCLUSIONS 4D phase contrast flow imaging in peripheral vascular stents is feasible and appears advantageous over conventional 3D contrast-enhanced MR angiography and 2D phase contrast flow imaging. It allows for in-stent flow visualization and flow quantification with varying quality depending on stent type.
Collapse
Affiliation(s)
- Alexander C Bunck
- Department of Clinical Radiology, University Hospital Münster, Albert-Schweitzer-Campus 1, Building A1, 48149 Muenster, Germany.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Prabhakaran S, Wells KR, Jhaveri MD, Lopes DK. Hemodynamic changes following wingspan stent placement--a quantitative magnetic resonance angiography study. J Neuroimaging 2011; 21:e109-13. [PMID: 19732297 DOI: 10.1111/j.1552-6569.2009.00425.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Quantitative magnetic resonance angiography (QMRA) is a noninvasive imaging modality that provides anatomic and physiologic measurements of arteries. We used QMRA to assess hemodynamic changes following Wingspan stent placement for intracranial stenosis. METHODS We reviewed patients treated with Wingspan stents for intracranial stenosis who had baseline and follow-up QMRA data. We compared volumetric flow rates (VFRs) (mL/minute) pre- and poststenting using paired t-tests. P<.05 was considered significant. RESULTS Among 9 patients (mean age 65.8 years, mean 71% degree of stenosis), lesions were located in the supraclinoid internal carotid arteries in 3, middle cerebral arteries in 3, and intracranial vertebrobasilar arteries in 3. VFR and degree of stenosis were moderately correlated (r=-.670, P=.002). The mean VFR in the stenotic artery increased from 81.2 mL/minute to 133.3 mL/minute (P=.020) or by 64.2% after stenting. Total cerebral blood flow, flow in nonstented vessels, and collateral flow in circle of Willis vessels did not significantly change. CONCLUSION We found that QMRA is a promising noninvasive method for the measurement of cerebral hemodynamics following intracranial Wingspan stent placement. Larger prospective studies are needed to confirm our findings.
Collapse
Affiliation(s)
- Shyam Prabhakaran
- Department of Neurological Sciences, Radiology and Neurosurgery, Rush University Medical Center, Chicago, IL 60612, USA.
| | | | | | | |
Collapse
|
16
|
Dual-Source CT Angiography of Peripheral Arterial Stents: In Vitro Evaluation of 22 Different Stent Types. Radiol Res Pract 2011; 2011:103873. [PMID: 22091369 PMCID: PMC3195368 DOI: 10.1155/2011/103873] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 05/06/2011] [Accepted: 05/06/2011] [Indexed: 11/17/2022] Open
Abstract
Purpose. To test different peripheral arterial stents using four image reconstruction approaches with respect to lumen visualization, lumen attenuation and image noise in dual-source multidetector row CT (DSCT) in vitro. Methods and Materials. 22 stents (nitinol, steel, cobalt-alloy, tantalum, platinum alloy) were examined in a vessel phantom. All stents were imaged in axial orientation with standard parameters. Image reconstructions were obtained with four different convolution kernels. To evaluate visualization characteristics of the stent, the lumen diameter, intraluminal density and noise were measured. Results. The mean percentage of the visible stent lumen diameter from the nominal stent diameter was 74.5% ± 5.7 for the medium-sharp kernel, 72.8% ± 6.4 for the medium, 70.8% ± 6.4 for the medium-smooth and 67.6% ± 6.6 for the smooth kernel. Mean values of lumen attenuation were 299.7HU ± 127 (medium-sharp), 273.9HU ± 68 (medium), 270.7HU ± 53 (medium-smooth) and 265.8HU ± 43. Mean image noise was: 54.6 ± 6.3, 20.5 ± 1.7, 16.3 ± 1.7, 14.0 ± 2 respectively. Conclusion. Visible stent lumen diameter varies depending on stent type and scan parameters. Lumen diameter visibility increases with the sharpness of the reconstruction kernel. Smoother kernels provide more realistic density measurements inside the stent lumen and less image noise.
Collapse
|
17
|
Plank CM, Wolf F, Langenberger H, Weber M, Beitzke D, Stadler A, Schillinger M, Lammer J, Loewe C. Improved detection of in-stent restenosis by blood pool agent-enhanced, high-resolution, steady-state magnetic resonance angiography. Eur Radiol 2011; 21:2158-65. [PMID: 21556908 DOI: 10.1007/s00330-011-2145-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Revised: 03/10/2011] [Accepted: 03/18/2011] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The aim of this study was to assess whether visualisation of in-stent changes can be improved with high-resolution, steady-state, blood pool contrast-enhanced MR angiography compared with first-pass MR angiography. Intra-arterial digital subtraction angiography (DSA) served as the reference standard. METHODS Twenty patients after stent placement in the superficial femoral artery (SFA) underwent MRA prior to reintervention. MRA of the SFA includes first-pass MRA as well as 3D high-resolution MRA in the steady state (SS-MRA) after injection of Gadofosveset trisodium. Sensitivity and specificity values for the detection of significant in-stent lesions by means of SS-MRA were calculated at the proximal, middle and distal stent segments in comparison to DSA. Kappa statistics were used to determine agreement between the two techniques. RESULTS Sensitivity and specificity values for the detection of significant stenosis with SS-MRA reached 95% in the proximal, 100% in the middle and 100% in the distal stent segment. Kappa coefficients between SS-MRA and DSA were 0.789, 0.797 and 0.859 for the proximal, middle and distal segments, whereas the Kappa coefficients for FP-MRA were 0,211, 0,200 and 0,594 in these segments, respectively. CONCLUSION Detection of in stent stenosis is significantly improved using SS MRA, in comparison to state-of-the-art FP-MRA.
Collapse
Affiliation(s)
- Christina M Plank
- Department of Radiology, Division of Cardiovascular and Interventional Radiology, Medical University of Vienna, Vienna, Austria
| | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Perisinakis K, Manousaki E, Zourari K, Tsetis D, Tzedakis A, Papadakis A, Karantanas A, Damilakis J. Accuracy of multislice CT angiography for the assessment of in-stent restenoses in the iliac arteries at reduced dose: a phantom study. Br J Radiol 2011; 84:244-50. [PMID: 21325364 PMCID: PMC3473874 DOI: 10.1259/bjr/63029326] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Revised: 01/22/2010] [Accepted: 03/10/2010] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE We investigated the potential of low-dose CT angiography for accurate assessment of in-stent restenoses (ISRs) of the iliac artery. METHOD A Rando anthropomorphic phantom (Alderson Research Labs, Stanford, CA), custom-made wax simulating hyperplastic tissue and a nitinol stent were used to simulate a patient with clinically relevant iliac artery ISRs. The cylindrical lumen was filled with a solution of iodine contrast medium diluted in saline, representing a patient's blood during CT angiography. The phantom was subjected to standard- and low-dose angiographic exposures using a modern multidetector (MD) CT scanner. The percentage of ISR was determined using the profile along a line normal to the lumen axis on reconstructed images of 2 and 5 mm slice thickness. Percentage ISRs derived using the standard- and low-dose protocols were compared. In a preliminary study, seven patients with stents were subjected to standard- and low-dose MDCT angiography during follow-up. The resulting images were assessed and compared by two experienced radiologists. RESULTS The accuracy in measuring the percentage ISR was found to be better than 12% for all simulated stenoses. The differences between percentage ISRs measured on images obtained at 120 kVp/160 mAs and 80 kVp/80 mAs were below 6%. Patient image sets acquired using low-exposure factors were judged to be of satisfactory diagnostic quality. The assessment of ISR did not differ significantly between image sets acquired using the standard factors and those acquired using the low-exposure factors, although the mean reduction in patient effective dose was 48%. CONCLUSION A reduction in exposure factors during MDCT angiography of the iliac artery is possible without affecting the accuracy in the determination of ISRs.
Collapse
Affiliation(s)
- K Perisinakis
- Department of Medical Physics, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece.
| | | | | | | | | | | | | | | |
Collapse
|
19
|
Ganguly A, Simons J, Schneider A, Keck B, Bennett NR, Fahrig R. In-vitro Imaging of Femoral Artery Nitinol Stents for Deformation Analysis. J Vasc Interv Radiol 2011; 22:236-43. [DOI: 10.1016/j.jvir.2010.10.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Revised: 08/14/2010] [Accepted: 10/20/2010] [Indexed: 11/28/2022] Open
|
20
|
Ganguly A, Simons J, Schneider A, Keck B, Bennett NR, Herfkens RJ, Coogan SM, Fahrig R. In-vivo Imaging of Femoral Artery Nitinol Stents for Deformation Analysis. J Vasc Interv Radiol 2011; 22:244-9. [DOI: 10.1016/j.jvir.2010.10.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Revised: 10/20/2010] [Accepted: 10/20/2010] [Indexed: 10/18/2022] Open
|
21
|
MRI may be sufficient for noninvasive assessment of great vessel stents: an in vitro comparison of MRI, CT, and conventional angiography. AJR Am J Roentgenol 2010; 195:865-71. [PMID: 20858811 DOI: 10.2214/ajr.09.4166] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
OBJECTIVE The purpose of this study was to compare the diagnostic performance of MRI and CT assessment of great vessel stents in an in vitro model. MATERIALS AND METHODS Three contemporary great vessel stent materials (nitinol, platinum-iridium, and stainless steel) were assessed with three luminal conditions: no stenosis, internal stenosis, and external stenosis. Stents of the same material were implanted into an aorta model that was attached to an animal bypass pump with pulsatile flow. Each stent was imaged with conventional angiography as reference standard, 10 different MRI sequences, and CT. The sensitivity and specificity for the identification of stent stenosis was determined and stent lumen measurements compared. RESULTS Of the investigated MRI sequences, three had the highest overall sensitivity and specificity for the identification of stent stenosis in all studied materials: through-plane gradientrecalled echo (GRE) with 75° flip angle (100% and 95%, respectively), in- and through-plane steady-state free precession (SSFP) (99% and 90%) and MR angiography (MRA) with 75° flip angle (93% and 85%). Comparable sensitivity and specificity were achieved with CT (98% and 93%). GRE, SSFP, and MRA sequences tended to underestimate stent lumen diameter in externally nonstenosed stents and overestimate diameter in internally stenosed stents (p < 0.05). CT slightly underestimated external stenoses in all stent types (p < 0.05). CONCLUSION Defined MRI sequences are feasible to assess nitinol, platinum-iridium, and stainless steel great vessel stents with diagnostic performance comparable with CT.
Collapse
|
22
|
Comparing different MR angiography strategies of carotid stents in a vascular flow model: toward stent-specific recommendations in MR follow-up. Neuroradiology 2010; 53:359-65. [PMID: 20721544 PMCID: PMC3077747 DOI: 10.1007/s00234-010-0753-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2010] [Accepted: 07/27/2010] [Indexed: 11/27/2022]
Abstract
INTRODUCTION Carotid artery stenting (CAS) requires adequate follow-up imaging to assess complications such as in-stent stenosis or occlusion. Options include digital subtraction angiography, CT angiography, ultrasound, and MR angiography (MRA), which may offer a non-invasive option for CAS follow-up imaging. The aim of this study was to assess contrast-enhanced MRA (CE-MRA) and three-dimensional time-of-flight MRA (3D-TOF) for visualization of the in-stent lumen in different carotid stents. METHODS In this study, we compared CE-MRA and 3D-TOF of five different carotid stents (Guidant Acculink®, Cordis Precise®, Boston Wallstent®, Abbot Vascular Xact®, Cook Zilver®) in three diameters (4, 6, and 8 mm) using a vascular flow model at 3.0 T with the help of a recently developed carotid surface coil. Stent-related artifacts were objectively assessed by calculating artificial lumen narrowing (ALN) and relative in-stent signal (RIS). RESULTS RIS and ALN depended heavily on stent type, stent diameter, and the employed MR sequence. ALN and RIS were relatively favorable for Acculink®, Precise®, and Zilver® stents with both CE-MRA and 3D-TOF. CE-MRA provided better results for the Wallstent, while the Xact stent was difficult to visualize with both MRA protocols. CONCLUSION Both CE-MRA and 3D-TOF are viable options for depicting the in-stent lumen in carotid stents. For specific stents, 3D-TOF provided image quality comparable to CE-MRA and may thus be suitable for in vivo assessment. Development of stent-specific pathways for follow-up imaging seems advisable to address stent-related differences in image quality.
Collapse
|
23
|
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.
Collapse
|
24
|
Perceptibility and Quantification of in-Stent Stenosis With Six Peripheral Arterial Stent Types in Vitro: Comparison of 16-MDCT Angiography, 64-MDCT Angiography, and MR Angiography. AJR Am J Roentgenol 2010; 194:1346-51. [PMID: 20410424 DOI: 10.2214/ajr.09.3062] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
25
|
Shedden L, Oldroyd K, Connolly P. Current issues in coronary stent technology. Proc Inst Mech Eng H 2009; 223:515-24. [PMID: 19623905 DOI: 10.1243/09544119jeim541] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Coronary artery stents have become the medical device of choice for the treatment of coronary artery disease. Since their introduction in 1987, significant advances in stent technology have taken place. A major objective of these developments was the reduction of in-stent restenosis, the formation of neointimal tissue inside the stent triggered by vessel injury and the inflammatory response, which results in renarrowing of the coronary artery. Improvements in strut configuration, thickness, and materials have enhanced deliverability and reduced vessel damage. Currently available drug-eluting stents release drugs that reduce neointimal formation through the arrest of cell proliferation. Drug-eluting stents have significantly reduced rates of in-stent restenosis. However, concerns have been raised with respect to their long-term safety, particularly in relation to the occurrence of late thrombosis. The post-procedural monitoring of stent-related complications is also of interest, including the relative suitability of invasive techniques such as angiography and intravascular ultrasound, and non-invasive techniques such as computed tomography and magnetic resonance imaging scanning. This paper reviews the current issues in stent technology.
Collapse
Affiliation(s)
- L Shedden
- Department of Bioengineering, University of Strathclyde, Glasgow, UK
| | | | | |
Collapse
|
26
|
Magnetic resonance angiography: current status in the planning and follow-up of endovascular treatment in lower-limb arterial disease. Cardiovasc Intervent Radiol 2009; 32:397-405. [PMID: 19130124 DOI: 10.1007/s00270-008-9467-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2008] [Revised: 10/13/2008] [Accepted: 10/16/2008] [Indexed: 10/21/2022]
Abstract
Magnetic resonance angiography (MRA) has become an established imaging modality in the management of lower-limb arterial disease, with emerging roles in treatment planning and follow-up. Contrast-enhanced MRA is now the most widely used technique with clinically acceptable results in the majority of patients. Difficulties in imaging and image interpretation are recognised in certain subgroups, including patients with critical limb ischaemia as well as patients with stents. Although newer contrast agents and refined imaging protocols may offer some solutions to these problems, this optimism is balanced by concerns about the toxicity of certain gadolinium chelates. Further development of interventional MRA remains one of the most significant challenges in the development of magnetic resonance imaging-guided peripheral vascular intervention. The status of MRA in managing patients with lower-limb arterial disease in current clinical practice is reviewed.
Collapse
|
27
|
Lehmpfuhl M, Hao C, Martirosian P, Schick F. Flussuntersuchungen an Strömungsphantomen im Vor- und Nachlauf stenoseförmiger Verengungen mittels geschwindigkeitskodierter MRT und numerischer Simulation der Fluiddynamik / Fluid studies on flow behaviour in narrowing vessels with PC-velocimetry and numerical simulations. BIOMED ENG-BIOMED TE 2009; 54:38-47. [DOI: 10.1515/bmt.2009.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
|
28
|
Quality improvement guidelines for endovascular treatment of iliac artery occlusive disease. Cardiovasc Intervent Radiol 2008; 31:238-45. [PMID: 18034277 DOI: 10.1007/s00270-007-9095-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Endovascular therapy is the treatment of choice for type A and the preferred treatment for type B lesions. In selective patients, this type of treatment can be applied in type C and even type D lesions. Ipsilateral femoral, contralateral femoral, and brachial approach and both the intraluminal and subintimal space can be used for successful recanalization. The application of stents has improved the immediate hemodynamic and probably long-term clinical results of iliac percutaneous transluminal angioplasty. However, the superiority of primary or direct stenting over selective stenting has not been proven yet. The choice of stent type depends on lesion morphology and location but otherwise there is insufficient evidence to support the use of a particular stent design. There is insufficient evidence to justify routine use of covered stents. All patients should receive antiaggregant therapy following endovascular recanalization of iliac arteries. There is no consensus regarding prophylaxis with antibiotics in iliac recanalization procedures.
Collapse
|
29
|
Quantification and Detectability of In-Stent Stenosis with CT Angiography and MR Angiography in Arterial Stents In Vitro. AJR Am J Roentgenol 2007; 189:1238-42. [PMID: 17954666 DOI: 10.2214/ajr.07.2501] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
30
|
Low G, Mizzi A, Ong K, Lau PF, McKinstery J. Technical inadequacies of peripheral contrast-enhanced magnetic resonance angiography: incidence, causes and management strategies. Clin Radiol 2006; 61:937-45. [PMID: 17018306 DOI: 10.1016/j.crad.2006.06.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2006] [Revised: 06/13/2006] [Accepted: 06/25/2006] [Indexed: 11/23/2022]
Abstract
AIM To assess the incidence, causes and effects of technical inadequacies in peripheral contrast-enhanced magnetic resonance angiography (CE-MRA) and to discuss relevant management strategies. MATERIALS AND METHODS A retrospective analysis of 249 peripheral CE-MRA examinations was performed using the radiology department's RIS/PACS (radiology information system/picture archiving and communication system) database. All failed or technically inadequate MRAs were reviewed. In cases that underwent further imaging by conventional angiography (CA), we assessed if relevant arterial disease had been masked on the MRA. RESULTS Of the 249 examinations, 215 (86.3%) were technically satisfactory while 34 (13.7%) were a combination of technical inadequacies [29 cases (11.6%)] and examination failures [five cases (2%)]. The causes of technical inadequacies were: (1) venous contamination (13 cases; 5.2%), (2) motion-induced subtraction artefact (eight cases; 3.2%), (3) stent-induced artefact (four cases; 1.6%), (4) inadequate scan coverage (two cases; 0.8%), and (5) contrast timing error (two cases; 0.8%). The causes of failed examinations were: (1) inability to tolerate lying in the scanner (three cases; 1.2%) and (2) inability to fit into the scanner (two cases; 0.8%). Fifteen (44.1%) of the 34 cases underwent further imaging by CA, and in eight of these there was significant arterial disease that was missed on the MRA. CONCLUSION Technical inadequacies occur in a small but significant proportion of peripheral CE-MRAs and can mask significant arterial disease. Knowledge of the potential causes of technical problems and the relevant management options is important for quality assurance and for limiting the need for an alternative investigation.
Collapse
Affiliation(s)
- G Low
- Department of Radiology, Hairmyres Hospital, East Kilbride, UK
| | | | | | | | | |
Collapse
|
31
|
Hamer OW, Borisch I, Paetzel C, Nitz WR, Seitz J, Feuerbach S, Zorger N. In vitroevaluation of stent patency and in-stent stenoses in 10 metallic stents using MR angiography. Br J Radiol 2006; 79:636-43. [PMID: 16641417 DOI: 10.1259/bjr/57301879] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
In vitro study to investigate the suitability of contrast enhanced magnetic resonance angiography (CEMRA) for determination of stent patency and grading of in-stent stenoses in 10 metallic stents. The Acculink carotid, DynaLink, Easy Wallstent, JostentSelfX XF, Luminexx, Omnilink, sinus-SuperFlex, SMART, Symphony and ZA stent were separately placed in a vascular phantom. Dedicated stenoses inside the stents generated a concentric lumen narrowing of 50%. CEMRA was performed for each stent. Signal loss inside the stents and artificial lumen narrowing were assessed objectively using the evaluation software of the MR imager. Moreover, three blinded observers determined visibility of stent patency and in-stent stenoses subjectively on a 3-point scale and graded in-stent stenoses. Loss of signal intensity within the stent lumen ranged between 90% (Wallstent) and 5% (ZA), artificial lumen narrowing between 56% (Symphony) and 22% (ZA). For the Symphony and Wallstent, visibility of patency and in-stent stenoses was impaired and the observers' grading exaggerated the degree of stenoses (by 23% and 33%, respectively). For the remainder of stents, patency and stenoses were visible and stenoses were graded accurately (less than 10% discrepancy from reference standard). In this in vitro study, eight of 10 stents presented with MRI characteristics which enabled determination of stent patency and accurate grading of clinically relevant in-stent stenoses.
Collapse
Affiliation(s)
- O W Hamer
- Department of Radiology, University Hospital of Regensburg, Franz-Josef-Strauss-Allee 11, 93042 Regensburg, Germany
| | | | | | | | | | | | | |
Collapse
|
32
|
Heuschmid M, Wiesinger B, Tepe G, Luz O, Kopp AF, Claussen CD, Duda SH. Evaluation of various image reconstruction parameters in lower extremity stents using multidetector-row CT angiography: initial findings. Eur Radiol 2006; 17:265-71. [PMID: 16733677 DOI: 10.1007/s00330-006-0315-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2005] [Revised: 02/26/2006] [Accepted: 04/25/2006] [Indexed: 11/25/2022]
Abstract
Image quality, visible lumen and patency of lower limb stents was assessed by multidetector-row computed tomography (MDCT) angiography using various reconstruction parameters and the results compared with conventional angiography. Fourteen patients (25 stents) were evaluated. From MDCT datasets, axial and coronal oblique reformations were reconstructed using differing reconstruction parameters (slice thickness, kernel, views). Artifacts and image quality were assessed using a five-degree scale (1=excellent, 5=poor). Visible stent diameter was measured. Stenosis severity was compared with calibrated catheter angiography. The image quality of medium and sharp image kernels were good/fair (1.9-2.4), while smooth kernel provided only acceptable/poor image quality (3.9-4.4). Coronal oblique images were rated superior to assess in-stent lumen rather than axial. Using medium and sharp kernels, the visible stent lumen was significantly greater than using smooth kernel (P<0.001). thirteen out of fourteen patients (24/25 stents) were correctly classified as patent. In one patient, in-stent stenosis (> or =50%) was falsely diagnosed using CT angiography (CTA) with smooth kernel and was, therefore, rated as false positive. Coronal oblique views, as well as medium and sharp kernels, have shown the best results regarding image quality to assess stent patency in the lower limb. Therefore, MDCT could be a valuable non-invasive modality for stent imaging in the peripheral vasculature.
Collapse
Affiliation(s)
- Martin Heuschmid
- Department of Diagnostic Radiology, University Hospital Tuebingen, Eberhard-Karls-University, Hoppe-Seyler-Strasse 3, 72076 Tuebingen, Germany.
| | | | | | | | | | | | | |
Collapse
|
33
|
Busch MHJ, Vollmann W, Grönemeyer DHW. Finite volume analysis of temperature effects induced by active MRI implants: 2. Defects on active MRI implants causing hot spots. Biomed Eng Online 2006; 5:35. [PMID: 16729878 PMCID: PMC1513583 DOI: 10.1186/1475-925x-5-35] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2006] [Accepted: 05/26/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Active magnetic resonance imaging implants, for example stents, stent grafts or vena cava filters, are constructed as wireless inductively coupled transmit and receive coils. They are built as a resonator tuned to the Larmor frequency of a magnetic resonance system. The resonator can be added to or incorporated within the implant. This technology can counteract the shielding caused by eddy currents inside the metallic implant structure. This may allow getting diagnostic information of the implant lumen (in stent stenosis or thrombosis for example). The electro magnetic rf-pulses during magnetic resonance imaging induce a current in the circuit path of the resonator. A by material fatigue provoked partial rupture of the circuit path or a broken wire with touching surfaces can set up a relatively high resistance on a very short distance, which may behave as a point-like power source, a hot spot, inside the body part the resonator is implanted to. This local power loss inside a small volume can reach (1/4) of the total power loss of the intact resonating circuit, which itself is proportional to the product of the resonator volume and the quality factor and depends as well from the orientation of the resonator with respect to the main magnetic field and the imaging sequence the resonator is exposed to. METHODS First an analytical solution of a hot spot for thermal equilibrium is described. This analytical solution with a definite hot spot power loss represents the worst case scenario for thermal equilibrium inside a homogeneous medium without cooling effects. Starting with this worst case assumptions additional conditions are considered in a numerical simulation, which are more realistic and may make the results less critical. The analytical solution as well as the numerical simulations use the experimental experience of the maximum hot spot power loss of implanted resonators with a definite volume during magnetic resonance imaging investigations. The finite volume analysis calculates the time developing temperature maps for the model of a broken linear metallic wire embedded in tissue. Half of the total hot spot power loss is assumed to diffuse into both wire parts at the location of a defect. The energy is distributed from there by heat conduction. Additionally the effect of blood perfusion and blood flow is respected in some simulations because the simultaneous appearance of all worst case conditions, especially the absence of blood perfusion and blood flow near the hot spot, is very unlikely for vessel implants. RESULTS The analytical solution as worst case scenario as well as the finite volume analysis for near worst case situations show not negligible volumes with critical temperature increases for part of the modeled hot spot situations. MR investigations with a high rf-pulse density lasting below a minute can establish volumes of several cubic millimeters with temperature increases high enough to start cell destruction. Longer exposure times can involve volumes larger than 100 mm3. Even temperature increases in the range of thermal ablation are reached for substantial volumes. MR sequence exposure time and hot spot power loss are the primary factors influencing the volume with critical temperature increases. Wire radius, wire material as well as the physiological parameters blood perfusion and blood flow inside larger vessels reduce the volume with critical temperature increases, but do not exclude a volume with critical tissue heating for resonators with a large product of resonator volume and quality factor. CONCLUSION The worst case scenario assumes thermal equilibrium for a hot spot embedded in homogeneous tissue without any cooling due to blood perfusion or flow. The finite volume analysis can calculate the results for near and not close to worst case conditions. For both cases a substantial volume can reach a critical temperature increase in a short time. The analytical solution, as absolute worst case, points out that resonators with a small product of inductance volume and quality factor (Q V(ind) < 2 cm3) are definitely save. Stents for coronary vessels or resonators used as tracking devices for interventional procedures therefore have no risk of high temperature increases. The finite volume analysis shows for sure that also conditions not close to the worst case reach physiologically critical temperature increases for implants with a large product of inductance volume and quality factor (Q V(ind) > 10 cm3). Such resonators exclude patients from exactly the MRI investigation these devices are made for.
Collapse
Affiliation(s)
- Martin HJ Busch
- Grönemeyer Institute for Microtherapy, University of Witten/Herdecke, Universitätsstr. 142, D-44799 Bochum, Germany
| | - Wolfgang Vollmann
- Department of mathematics, physics and chemistry, TFH University of Applied Sciences, Luxemburger Straße 10, D-13353 Berlin, Germany
| | - Dietrich HW Grönemeyer
- Grönemeyer Institute for Microtherapy, University of Witten/Herdecke, Universitätsstr. 142, D-44799 Bochum, Germany
| |
Collapse
|
34
|
Peloschek P, Sailer J, Loewe C, Schillinger M, Lammer J. The role of multi-slice spiral CT angiography in patient management after endovascular therapy. Cardiovasc Intervent Radiol 2006; 29:756-61. [PMID: 16528628 DOI: 10.1007/s00270-004-0066-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVES To bring out the role of multi-slice spiral CT angiography (MS-CTA) in patient management after endovascular therapy of subclavian artery stenosis. METHODS Twenty-one consecutive patients with clinically suspected restenosis after endovascular treatment of subclavian artery stenosis or occlusion were included in the study. Eleven patients had been treated with percutaneous transluminal angioplasty (PTA) alone and 10 with PTA and stenting. The mean follow-up period after PTA or stenting was 57 (+/-27 SD) months. CTA was performed using a bolus-triggered high-resolution protocol with biphasic intravenous contrast medium injection. Axial images and curved planar reformations (CPRs) were rated by three readers with regard to patency of supra-aortic vessels. Imaging findings were correlated with a standardized clinical assessment. RESULTS All examinations were of diagnostic quality. Of 21 referred patients, 7 had significant reobstruction of the treated subclavian artery. Six of the 7 patients with significant restenosis on CTA were treated conservatively (antiplatelet agents), despite 2 of them being symptomatic on the standardized clinical assessment, which showed a sensitivity and specificity of 86% in predicting stenosis. One patient was treated with PTA and stent deployment because of strong subjective suffering. CONCLUSION MS-CTA is useful for exclusion or quantification of clinically suspected restenosis in carefully selected patients after endovascular therapy where ultrasound is inconclusive and/or contrast-enhanced magnetic resonance angiography is contraindicated.
Collapse
Affiliation(s)
- P Peloschek
- Department of Radiology, Medical University of Vienna -- AKH, Währinger Gürtel 18-20, Vienna 1090, Austria.
| | | | | | | | | |
Collapse
|
35
|
Breuckmann F, Nassenstein K, Boese D, Opherk D, Quick HH, Barkhausen J, Erbel R. Successful nitinol stent implantation in a large coronary aneurysm: post-interventional patency assessment by magnetic resonance imaging. Int J Cardiovasc Imaging 2006; 22:501-5. [PMID: 16518666 DOI: 10.1007/s10554-005-9058-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2005] [Accepted: 11/17/2005] [Indexed: 10/25/2022]
Abstract
Nitinol stents are thought to exhibit reduced occurrence of artifacts and may be suitable for magnetic resonance imaging (MRI) evaluation of stent localization and in-stent patency even in coronary-sized stent grafts. A 54-year-old male patient presented with a large coronary post-stenotic aneurysm of the right coronary artery (RCA) beside significant stenoses of the left circumflex coronary artery (LCX) and the left anterior descending coronary artery (LAD) with aneurysm formation. After implantation of stent grafts to the LAD and LCX, two polymermembrane-covered nitinol stent grafts were placed into the RCA. A control MR examination 7 days following the RCA intervention showed successful occlusion of the former aneurysm, no post-interventional endoleak, and bright signal within the stent indicating stent patency. Thus, coronary MRI after nitinol stent implantation in coronary aneurysms is feasible for post-interventional early imaging control at least as far as the exclusion of possible endoleaks is concerned.
Collapse
Affiliation(s)
- Frank Breuckmann
- Department of Cardiology, West German Heart Center Essen, University of Duisburg-Essen, Essen, Germany.
| | | | | | | | | | | | | |
Collapse
|
36
|
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.
Collapse
Affiliation(s)
- Alexander Wall
- Department of Clinical Radiology, University of Münster, Münster, Germany.
| | | | | | | | | | | | | |
Collapse
|
37
|
Hamer OW, Finkenzeller T, Borisch I, Paetzel C, Zorger N, Feuerbach S, Nitz W. In Vivo Evaluation of Patency and In-Stent Stenoses After Implantation of Nitinol Stents in Iliac Arteries Using MR Angiography. AJR Am J Roentgenol 2005; 185:1282-8. [PMID: 16247150 DOI: 10.2214/ajr.04.1389] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE Our study was a prospective in vivo study to evaluate whether MR angiography is suitable for assessing stent patency and grading in-stent stenoses and to examine whether the accuracy of MR angiography changes with time after stent implantation. SUBJECTS AND METHODS In a prospective study, 34 iliac stenoses in 27 patients were treated by implantation of 35 nitinol stents. MR angiography was performed immediately after stent placement for 32 stents, and both digital subtraction angiography (DSA) and MR angiography were repeated at the 6-month follow-up for 23 stents. Three blinded observers assessed stent patency and the degree of in-stent stenoses on MR angiography and DSA (the standard of reference) images. The difference between the observers' grading of stenoses on DSA and on MR angiography was determined. Statistical analysis was performed using the Student's t test for paired samples. RESULTS Stent patency was assessed correctly for all stents and both sets of MR angiography images. Evaluation of DSA 1 images (obtained at end of implantation procedure) revealed that 96.9% of in-stent stenoses were less than 50%. On DSA 2 images (obtained at follow-up), 95.7% of in-stent stenoses were graded as less than 50%. The difference between grading of stenoses on DSA and MR angiography images was 15.0% +/- 16.0% (minimum, 0.0%; maximum, 63.3%) for DSA 1 versus MR angiography 1 (statistically significant, p = 0.037) and 9.8% +/- 13.5% (minimum, 0.0%; maximum, 63.3%) for MR angiography 2 versus DSA 2 (not statistically significant, p = 0.355). CONCLUSION Patency was correctly assessed for all stents on MR angiography. The quality of MR angiography regarding characterization of in-stent stenoses improved with time after stent placement. However, discrepancies of more than 60% between grading of lumen narrowing on DSA and MR angiography images occurred even at the 6-month follow-up. Thus, MR angiography is not yet a reliable technique for characterization of in-stent stenoses.
Collapse
Affiliation(s)
- Okka W Hamer
- Department of Diagnostic Radiology, University Hospital of Regensburg, Franz-Josef-Strauss-Allee 11, 93042 Regensburg, Germany.
| | | | | | | | | | | | | |
Collapse
|
38
|
Borisch I, Hamer OW, Zorger N, Feuerbach S, Link J. In Vivo Evaluation of the Carotid Wallstent on Three-dimensional Contrast Material–enhanced MR Angiography: Influence of Artifacts on the Visibility of Stent Lumina. J Vasc Interv Radiol 2005; 16:669-77. [PMID: 15872322 DOI: 10.1097/01.rvi.0000156187.35215.22] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE Contrast material-enhanced magnetic resonance (MR) angiography is increasingly used in postinterventional imaging after implantation of endovascular stents. The main limitations are stent-related artifacts compromising the visibility of the stent lumen. The aim of this in vivo study is the evaluation of contrast-enhanced MR angiography imaging characteristics of the carotid Wallstent. MATERIALS AND METHODS The carotid arteries of 29 patients were examined with contrast-enhanced MR angiography 3-6 days and/or 7-23 months after implantation of a carotid Wallstent into the internal carotid artery. Images were evaluated with regard to the diameter and signal intensity (SI) of the visible stent lumen. Digital subtraction angiography (DSA) was used as the standard of reference. RESULTS Stent-related artifacts on contrast-enhanced MR angiography caused an artificial lumen narrowing and a reduction of the SI within the stent. Artifacts were pronounced on imaging 3-6 days after stent implantation, but 68% of stents imaged 7-23 months after stent implantation presented with a significantly decreased artificial signal reduction and an improved visibility of the stent lumen. CONCLUSIONS The results of this study indicate that a reliable evaluation of the stent lumen is limited as a result of an artificial decrease of the SI inside the stent. However, in follow-up examinations 7-23 months after stent implantation, visibility of the stent lumen was improved and diagnostic reliability of contrast-enhanced MR angiography was markedly increased. A probable explanation for this phenomenon might be the formation of a neointimal layer covering the stent struts and thereby reducing stent-related artifacts.
Collapse
Affiliation(s)
- Ingitha Borisch
- Department of Diagnostic Radiology, University Hospital Regensburg, Germany.
| | | | | | | | | |
Collapse
|
39
|
Busch MHJ, Vollmann W, Schnorr J, Grönemeyer DHW. Finite volume analysis of temperature effects induced by active MRI implants with cylindrical symmetry: 1. Properly working devices. Biomed Eng Online 2005; 4:25. [PMID: 15819973 PMCID: PMC1087857 DOI: 10.1186/1475-925x-4-25] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2004] [Accepted: 04/08/2005] [Indexed: 11/10/2022] Open
Abstract
Background Active Magnetic Resonance Imaging implants are constructed as resonators tuned to the Larmor frequency of a magnetic resonance system with a specific field strength. The resonating circuit may be embedded into or added to the normal metallic implant structure. The resonators build inductively coupled wireless transmit and receive coils and can amplify the signal, normally decreased by eddy currents, inside metallic structures without affecting the rest of the spin ensemble. During magnetic resonance imaging the resonators generate heat, which is additional to the usual one described by the specific absorption rate. This induces temperature increases of the tissue around the circuit paths and inside the lumen of an active implant and may negatively influence patient safety. Methods This investigation provides an overview of the supplementary power absorbed by active implants with a cylindrical geometry, corresponding to vessel implants such as stents, stent grafts or vena cava filters. The knowledge of the overall absorbed power is used in a finite volume analysis to estimate temperature maps around different implant structures inside homogeneous tissue under worst-case assumptions. The "worst-case scenario" assumes thermal heat conduction without blood perfusion inside the tissue around the implant and mostly without any cooling due to blood flow inside vessels. Results The additional power loss of a resonator is proportional to the volume and the quality factor, as well as the field strength of the MRI system and the specific absorption rate of the applied sequence. For properly working devices the finite volume analysis showed only tolerable heating during MRI investigations in most cases. Only resonators transforming a few hundred mW into heat may reach temperature increases over 5 K. This requires resonators with volumes of several ten cubic centimeters, short inductor circuit paths with only a few 10 cm and a quality factor above ten. Using MR sequences, for which the MRI system manufacturer declares the highest specific absorption rate of 4 W/kg, vascular implants with a realistic construction, size and quality factor do not show temperature increases over a critical value of 5 K. Conclusion The results show dangerous heating for the assumed "worst-case scenario" only for constructions not acceptable for vascular implants. Realistic devices are safe with respect to temperature increases. However, this investigation discusses only properly working devices. Ruptures or partial ruptures of the wires carrying the electric current of the resonance circuits or other defects can set up a power source inside an extremely small volume. The temperature maps around such possible "hot spots" should be analyzed in an additional investigation.
Collapse
Affiliation(s)
- Martin HJ Busch
- Research and Development Center for Microtherapy (EFMT), D-44799 Bochum, Germany
- Grönemeyer Institute for Microtherapy, University of Witten/Herdecke, D-44799 Bochum, Germany
| | | | - Jörg Schnorr
- Institut für Radiologie, Charité, Medizinische Fakultät, Humboldt-Universität zu Berlin, D-10117 Berlin, Germany
| | - Dietrich HW Grönemeyer
- Grönemeyer Institute for Microtherapy, University of Witten/Herdecke, D-44799 Bochum, Germany
| |
Collapse
|
40
|
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.
Collapse
Affiliation(s)
- Elmar Spuentrup
- Department of Diagnostic Radiology, Technical University of Aachen, Aachen, Germany
| | | | | | | | | | | | | | | |
Collapse
|
41
|
Hagspiel KD, Leung DA, Nandalur KR, Angle JF, Dulai HS, Spinosa DJ, Matsumoto AH, Christopher JM, Ahmed H, Berr SS. Contrast-Enhanced MR Angiography at 1.5 T After Implantation of Platinum Stents: In Vitro and In Vivo Comparison with Conventional Stent Designs. AJR Am J Roentgenol 2005; 184:288-94. [PMID: 15615990 DOI: 10.2214/ajr.184.1.01840288] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE The objective of our study was to evaluate the in vitro and in vivo 3D contrast-enhanced MR angiography characteristics of a new platinum-based balloon-expandable stent system and compare this system with a variety of competing metallic stents. MATERIALS AND METHODS All experiments were performed on 1.5-T scanners. In vitro experiments were performed using 10 stents implanted into a custom-built phantom. Different orientations of the stents along the magnetic field and multiple flip angles were examined. In addition, 19 patients underwent contrast-enhanced MR angiography after the implantation of 36 stents, including four patients with six platinum stents. Angiographic correlation was available for all 19 patients, and luminal patency and stent-induced artifacts were assessed quantitatively. RESULTS Of the tested balloon-expandable stents, only the platinum-based stents created artifact causing luminal narrowing of 30% or less. All other balloon-expandable stents induced larger artifacts that resulted in higher degrees of narrowing. Thus, if patent, the platinum-based stents allow significant in-stent stenosis to be ruled out reliably. Selected nitinol- or tantalum-based self-expandable stents also are suitable in this regard. CONCLUSION Of the tested devices, platinum-based stents are the only type of currently available balloon-expandable stent that creates 30% or less artifact-induced apparent stenosis and thus are suitable for MR angiography.
Collapse
Affiliation(s)
- Klaus D Hagspiel
- Department of Radiology, Division of Interventional Radiology, University of Virginia Health System, Box 800170, Charlottesville, VA 22908, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
42
|
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.
Collapse
Affiliation(s)
- Martin Busch
- Grönemeyer Institut für Mikrotherapie, Universität Witten/Herdecke, Bochum, Germany.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
43
|
Gawenda M, Gossmann A, Krüger K, Zaehringer M, Hahn M, Wassmer G, Brunkwall J. Comparison of Magnetic Resonance Imaging and Computed Tomography of 8 Aortic Stent-Graft Models. J Endovasc Ther 2004; 11:627-34. [PMID: 15615553 DOI: 10.1583/03-1130mr.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
PURPOSE To report the systematic comparison of magnetic resonance imaging (MRI) with contrast-enhanced computed tomography (CT) for evaluating 8 different aortic stent-graft models. METHODS MR angiography (MRA) was performed using a 1.5-T whole body system within 2 days of a CT examination (4 detector row scanner) on 8 patients with one of these stent-graft models: AneuRx, Endofit, PowerLink, Excluder, LifePath, Talent, Vanguard, or Zenith. Using a 4-point scale (maximum score 112 points), 4 independent readers (1 vascular surgeon and 3 radiologists) rated the impact of stent-related artifacts on the diagnostic quality of each imaging method for 28 parameters: length, diameter, collateral aortic side branches, stent-graft prostheses, and contrast. Each examiner also scored his personal diagnostic confidence with each stent-graft model. RESULTS The scores for diagnostic confidence in the CT imaging were 4 points for each stent-graft, with the exception of the LifePath (3 points). The diagnostic confidence in the MR images was mainly poor, with a median score of only 1; however, 3 stent-grafts (AneuRx, Excluder, and Vanguard) received > or =3 points. The total scores for comparative assessment were significantly different (p<0.05) between CT imaging (111.5) and MR (58.5). CT studies of all stent-grafts received >101 points, while only 3 devices acquired >80 points (AneuRx, Excluder, and Vanguard). Bland-Altman analysis showed that the reliability of the 4 readers was higher using the CT method. The total assessment scores of the stent-graft systems were related only on the different imaging methods (p<0.0001) and not to the different readers (p=0.983). CONCLUSIONS CT and MRI are fast, reliable means of providing all relevant information for stent-graft surveillance. Of 8 different stent-graft models, only 3 could be adequately assessed by MRA. Therefore, the potential advantages of the MR technique (e.g., use of minimally nephrotoxic contrast media, lack of ionizing radiation) are available only to a small proportion of patients.
Collapse
Affiliation(s)
- Michael Gawenda
- Division of Vascular Surgery, University of Cologne, Germany.
| | | | | | | | | | | | | |
Collapse
|
44
|
Abstract
From an initially simple concept, vascular stents have evolved into highly specialized instruments, and are poised to develop into sophisticated drug-delivery systems. Although primary research has mostly targeted the coronary circulation, newer generation stents, deliverable almost anywhere, retarding neointimal hyperplasia and thrombosis, and promoting endothelial overgrowth, will offer the next approximation of true vascular healing. This, in turn,promises to promote less invasive, safer, and finally durable endovascular solutions to current surgical problems.
Collapse
Affiliation(s)
- Nicolas Nelken
- Department of Surgery, University of California, San Francisco, CA 94143, USA.
| | | |
Collapse
|
45
|
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).
Collapse
Affiliation(s)
- Laurent Létourneau-Guillon
- Department of Radiology, CHUM-Notre-Dame Hospital, 1560 Sherbrooke East, Montreal, Quebec, Canada, H2L 4M1.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
46
|
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.
Collapse
Affiliation(s)
- David W Trost
- Department of Radiology, Weill Cornell Medical College, New York, New York 10022, USA
| | | | | | | | | | | | | |
Collapse
|
47
|
Hofmann LV, Liddell RP, Arepally A, Montague B, Yang X, Bluemke DA. In Vivo Intravascular MR Imaging: Transvenous Technique for Arterial Wall Imaging. J Vasc Interv Radiol 2003; 14:1317-27. [PMID: 14551280 DOI: 10.1097/01.rvi.0000092904.31640.be] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE To determine, in vivo, the potential for transvenous magnetic resonance (MR) imaging of the arterial wall and to assess appropriate MR pulse sequences for this method. MATERIALS AND METHODS MR imaging was performed on 19 vessels (right renal artery, N = 9; left renal artery N = 2; external iliac artery, N = 4; abdominal aorta, N = 4) in nine swine. The animals were either low-density lipoprotein receptor knockout (N = 5) or Yucatan mini-pigs fed an atherogenic diet for 6 to 11 weeks (N = 4). The intravascular MR coil/guide wire (IVMRG) (Surgi-Vision, Gaithersburg, MD) was introduced via the external iliac vein into the inferior vena cava (IVC). The following electrocardiograph-gated MR pulse sequences were obtained: T1-weighted precontrast with and without fat saturation and T1-weighted postcontrast with fat saturation. Two observers scored wall signal and conspicuity and classified the vessel as normal, abnormal, or stented. Images were compared with histopathologic findings. RESULTS The T1-weighted precontrast without fat saturation, T1-weighted precontrast with fat saturation, and T1-weighted postcontrast images correlated with histopathologic findings in 12 of 15 vessels, eight of 10 vessels, and 14 of 16 vessels, respectively. Abnormal histopathologic findings included: arterial wall thickening (N = 3), arterial dissection (N = 2), focal fibrous plaque (N = 2), adherent thrombus (N = 1). The T1-weighted postcontrast images were not compromised by artifacts and had the highest score for vessel wall signal and conspicuity. T1-weighted precontrast images were compromised by chemical shift artifact and poor blood suppression. Negligible artifacts were created by the platinum stent. CONCLUSION The T1-weighted fat saturated postcontrast pulse sequence was superior to other sequences for transvenous MR imaging of the arterial wall.
Collapse
Affiliation(s)
- Lawrence V Hofmann
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins Medical Institutions, Blalock 545, 600 North Wolfe Street, Baltimore, Maryland 21287, USA.
| | | | | | | | | | | |
Collapse
|
48
|
Weigel S, Tombach B, Maintz D, Klotz S, Vestring T, Heindel W, Fischbach R. Thoracic aortic stent graft: comparison of contrast-enhanced MR angiography and CT angiography in the follow-up: initial results. Eur Radiol 2003; 13:1628-34. [PMID: 12835978 DOI: 10.1007/s00330-003-1832-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2002] [Revised: 11/26/2002] [Accepted: 01/02/2003] [Indexed: 11/25/2022]
Abstract
The objective of this study was to compare contrast-enhanced magnetic resonance angiography (CE MRA) and multislice computed tomographic angiography (MS CTA) in the follow-up of thoracic stent-graft placement. The CE MRA and MS CTA were performed following nitinol stent-graft treatment due to thoracic aneurysm ( n=4), intramural bleeding ( n=2) and type-B aortic dissection ( n=5). Corresponding evaluation of arterial-phase imaging characteristics focused on the stent-graft morphology and leakage assessment. Stent-graft and aneurysm extensions were comparable between both techniques. Complete exclusion (aneurysm, n=4; dissection, n=2) was assessed with high confidence with CE MRA and MS CTA. Incomplete exclusion (intramural bleeding, n=2; dissection, n=3) was assigned to lower confidence scores on CE MRA compared with MS CTA. On CE MRA the stent-graft lumen demonstrated an inhomogeneous signal, the stent struts could not be assessed. The CE MRA can be used as alternative non-invasive imaging for follow-up of nitinol stent grafts. Arterial-phase leak assessment can be less evident in CE MRA compared with MS CTA studies; therefore, the use of late-phase imaging seems to be necessary. The diagnostic gap of stent-graft fracture evaluation using MRA may be filled with plain radiographs.
Collapse
Affiliation(s)
- Stefanie Weigel
- Department of Clinical Radiology, University of Muenster, Albert-Schweitzer-Strasse 33, 48149 Muenster, Germany.
| | | | | | | | | | | | | |
Collapse
|
49
|
Honda M, Obuchi M, Sugimoto H. Artifacts of vena cava filters ex vivo on MR angiography. Magn Reson Med Sci 2003; 2:71-7. [PMID: 16210823 DOI: 10.2463/mrms.2.71] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
We evaluated magnetic susceptibility artifacts of nine types of vena cava filters in MR angiography (MRA) at 1.0T ex vivo in order to assess the filters' compatibility with MRA. Each filter (tulip filter, tulip MReye filter, stainless Greenfield filter, titanium Greenfield filter, TrapEase filter, Simon filter, LGM Vena-Tech filter, Antheor temporary filter, and Bird's nest filter) was inserted into an acrylic tube (20 or 25 mm in diameter, 15 or 30 cm in length). Gd-DTPA was poured into each tube at a concentration of 1/500 and each was placed in a water-filled container for imaging. We evaluated artifacts of the filters according to the following criteria: signal void beyond the tube, 3+; signal void within the tube but at more than one-half the diameter of the tube, 2+; and signal void within the tube but at less than one-half the diameter of the tube, 1+. We evaluated artifacts originating at the tip, intermediate portion, and distal end of the filters. We judged the artifacts as follows: tulip (3+, 3+, 3+); tulip MReye (2+, 1+, 1+); stainless Greenfield (2+, 1+, 2+); titanium Greenfield (1+, 1+, 1+); TrapEase (1+, 2+, 1+); Simon (2+, 2+, 1+); LGM (2+, 2+, 1+); Antheor (2+, 2+, 2+); and Bird's nest (3+, 3+, 3+). The numbers in parentheses refer to the degree of signal void at the tip, intermediate portion, and distal end of the filter, respectively. The tulip filter and Bird's nest filter made of 304 stainless steel caused extensive signal voids beyond the areas defined by the filters. The signal voids in the remaining seven filters were limited to within the tube. We concluded that seven of the nine filters were compatible with MRA ex vivo.
Collapse
Affiliation(s)
- Minoru Honda
- Department of Radiology, Showa University Fujigaoka Hospital, Yokohama, Japan.
| | | | | |
Collapse
|
50
|
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.
Collapse
Affiliation(s)
- Elmar Spuentrup
- Department of Diagnostic Radiology, Technical University of Aachen, Pauwelsstrasse 30, 52057 Aachen, Germany.
| | | | | | | | | |
Collapse
|