Acta Neurochir DOI 10.1007/s00701-014-2142-5
CLINICAL ARTICLE - VASCULAR
Non-enhanced magnetic resonance angiography can evaluate restenosis after carotid artery stenting with the Carotid Wallstent Kenichi Kono & Aki Shintani & Tomoaki Terada
Received: 1 March 2014 / Accepted: 21 May 2014 # Springer-Verlag Wien 2014
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 NEMRAwas 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).
Keywords Carotid artery stenting . Carotid Wallstent . Follow-up examination . Non-enhanced magnetic resonance angiography . Restenosis
K. Kono (*) : A. Shintani : T. Terada Department of Neurosurgery, Wakayama Rosai Hospital, 93-1 Kinomoto, Wakayama 640-8505, Japan e-mail: [email protected]
This was a retrospective study. We incidentally found an interesting observation that NE-MRA visualized lumen at the stented lesion after CAS in some cases and reviewed NE-MRA after CAS. Although we reviewed consecutive
Introduction Follow-up examinations of carotid artery stenting (CAS) are essential because in-stent restenosis (ISR) significantly increases the rate of stroke [21]. Conventional angiography is the standard diagnostic modality and provides excellent imaging of the stent lumen. However, to avoid procedure-related complications of angiography, alternative imaging modalities have also been used. Ultrasonography is less invasive but has disadvantages, such as operator dependency, and nonvisualization underneath calcification or stenotic lesions at a high position in the neck. Computed tomographic angiography (CTA) has disadvantages of metal artifacts inside stents [13], and use of contrast material, which has the risk of worsening renal function. Visualization of the stent lumen by contrast-enhanced magnetic resonance angiography (CEMRA) has been examined in vivo and in vitro [5, 8–10, 13, 15, 19]. However, gadolinium-based contrast agents for MRA should not be used for renal-insufficient patients because of the risk of nephrogenic systemic fibrosis [1]. Non-enhanced MRA (NE-MRA) is non-invasive and operator-independent. We assessed whether NE-MRA is useful for visualizing the stent lumen and evaluating ISR after CAS.
Materials and methods
Acta Neurochir
cases of CAS, NE-MRA at the neck was performed only in the part of the cases. For example, NE-MRA was performed for patients with contralateral cervical carotid artery stenosis or carotid artery stenosis at the petrous portion. Therefore, institutional review board approval or patient consent was unnecessary for this retrospective study. Patient and imaging Between July 2008 and January 2013, we performed 118 consecutive CAS procedures. Stent placement was completed in all patients. We used the Precise stent (Cordis Neurovascular, Miami Lakes, FL) in 78 patients and the Carotid Wallstent (Boston Scientific, Natick, MA) in 40 patients. Operators selected stent types by their preference based on clinical characteristics of each patient. Diffusion-weighted imaging was routinely performed on the next day. At the same time, NE-MRA at the neck was performed in 67 cases using a 1.5 T Achieva scanner (Philips Healthcare, Best, the Netherlands). At various intervals after CAS, NE-MRA at the neck was also performed in 77 patients. NE-MRA at the neck consisted of three-dimensional time-of-flight gradientecho sequences. The parameters were as follows: 16-channel phased array head coil; repetition time, 19 ms; echo time, 6.9 ms; flip angle, 17°; matrix size, 512×256; field of view, 180 mm × 180 mm; slice thickness, 1 mm; the number of slices, 150; and acquisition time, 3 min. For follow-up examinations of CAS, we performed conventional angiography, ultrasonography, or CTA every 3–6 months. In this study, we defined >40 % stenosis as ISR, and examined ISR by conventional angiography, ultrasonography, or CTA. In NE-MRA, we examined whether the stent lumen was visible. We categorized this visibility into two groups; invisible and visible. When visible, we further examined the degree of stenosis if it was present. Examination of NE-MRA was performed independently by two experienced neurosurgeons (K.K. and A.S.). The average degree of stenosis was used. The degree of stenosis in any imaging modality was measured based on the criteria of the North American Symptomatic Carotid Endarterectomy Trial (NASCET). Statistical analysis We performed statistical analysis using SPSS version 20 (IBM Corp., Armonk, NY). Baseline characteristics between the Precise and Carotid Wallstent groups were examined by the Student’s t-test, chi-squared test, or Fisher’s exact test. To compare degrees of stenosis measured by NE-MRA and other imaging modalities, linear regression analysis and Spearman’s correlation analysis were performed. For all statistical tests, P
CLINICAL ARTICLE - VASCULAR
Non-enhanced magnetic resonance angiography can evaluate restenosis after carotid artery stenting with the Carotid Wallstent Kenichi Kono & Aki Shintani & Tomoaki Terada
Received: 1 March 2014 / Accepted: 21 May 2014 # Springer-Verlag Wien 2014
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 NEMRAwas 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).
Keywords Carotid artery stenting . Carotid Wallstent . Follow-up examination . Non-enhanced magnetic resonance angiography . Restenosis
K. Kono (*) : A. Shintani : T. Terada Department of Neurosurgery, Wakayama Rosai Hospital, 93-1 Kinomoto, Wakayama 640-8505, Japan e-mail: [email protected]
This was a retrospective study. We incidentally found an interesting observation that NE-MRA visualized lumen at the stented lesion after CAS in some cases and reviewed NE-MRA after CAS. Although we reviewed consecutive
Introduction Follow-up examinations of carotid artery stenting (CAS) are essential because in-stent restenosis (ISR) significantly increases the rate of stroke [21]. Conventional angiography is the standard diagnostic modality and provides excellent imaging of the stent lumen. However, to avoid procedure-related complications of angiography, alternative imaging modalities have also been used. Ultrasonography is less invasive but has disadvantages, such as operator dependency, and nonvisualization underneath calcification or stenotic lesions at a high position in the neck. Computed tomographic angiography (CTA) has disadvantages of metal artifacts inside stents [13], and use of contrast material, which has the risk of worsening renal function. Visualization of the stent lumen by contrast-enhanced magnetic resonance angiography (CEMRA) has been examined in vivo and in vitro [5, 8–10, 13, 15, 19]. However, gadolinium-based contrast agents for MRA should not be used for renal-insufficient patients because of the risk of nephrogenic systemic fibrosis [1]. Non-enhanced MRA (NE-MRA) is non-invasive and operator-independent. We assessed whether NE-MRA is useful for visualizing the stent lumen and evaluating ISR after CAS.
Materials and methods
Acta Neurochir
cases of CAS, NE-MRA at the neck was performed only in the part of the cases. For example, NE-MRA was performed for patients with contralateral cervical carotid artery stenosis or carotid artery stenosis at the petrous portion. Therefore, institutional review board approval or patient consent was unnecessary for this retrospective study. Patient and imaging Between July 2008 and January 2013, we performed 118 consecutive CAS procedures. Stent placement was completed in all patients. We used the Precise stent (Cordis Neurovascular, Miami Lakes, FL) in 78 patients and the Carotid Wallstent (Boston Scientific, Natick, MA) in 40 patients. Operators selected stent types by their preference based on clinical characteristics of each patient. Diffusion-weighted imaging was routinely performed on the next day. At the same time, NE-MRA at the neck was performed in 67 cases using a 1.5 T Achieva scanner (Philips Healthcare, Best, the Netherlands). At various intervals after CAS, NE-MRA at the neck was also performed in 77 patients. NE-MRA at the neck consisted of three-dimensional time-of-flight gradientecho sequences. The parameters were as follows: 16-channel phased array head coil; repetition time, 19 ms; echo time, 6.9 ms; flip angle, 17°; matrix size, 512×256; field of view, 180 mm × 180 mm; slice thickness, 1 mm; the number of slices, 150; and acquisition time, 3 min. For follow-up examinations of CAS, we performed conventional angiography, ultrasonography, or CTA every 3–6 months. In this study, we defined >40 % stenosis as ISR, and examined ISR by conventional angiography, ultrasonography, or CTA. In NE-MRA, we examined whether the stent lumen was visible. We categorized this visibility into two groups; invisible and visible. When visible, we further examined the degree of stenosis if it was present. Examination of NE-MRA was performed independently by two experienced neurosurgeons (K.K. and A.S.). The average degree of stenosis was used. The degree of stenosis in any imaging modality was measured based on the criteria of the North American Symptomatic Carotid Endarterectomy Trial (NASCET). Statistical analysis We performed statistical analysis using SPSS version 20 (IBM Corp., Armonk, NY). Baseline characteristics between the Precise and Carotid Wallstent groups were examined by the Student’s t-test, chi-squared test, or Fisher’s exact test. To compare degrees of stenosis measured by NE-MRA and other imaging modalities, linear regression analysis and Spearman’s correlation analysis were performed. For all statistical tests, P
