Characterisation of carotid plaques with ultrasound elastography: feasibility and correlation with high-resolution magnetic resonance imaging

Objectives

To evaluate the ability of ultrasound non-invasive vascular elastography (NIVE) strain analysis to characterise carotid plaque composition and vulnerability as determined by high-resolution magnetic resonance imaging (MRI).

Methods

Thirty-one subjects with 50 % or greater carotid stenosis underwent NIVE and high-resolution MRI of internal carotid arteries. Time-varying strain images (elastograms) of segmented plaques were generated from ultrasonic raw radiofrequency sequences. On MRI, corresponding plaques and components were segmented and quantified. Associations between strain parameters, plaque composition and symptomatology were estimated with curve-fitting regressions and Mann–Whitney tests.

Results

Mean stenosis and age were 72.7 % and 69.3 years, respectively. Of 31 plaques, 9 were symptomatic, 17 contained lipid and 7 were vulnerable on MRI. Strains were significantly lower in plaques containing a lipid core compared with those without lipid, with 77–100 % sensitivity and 57–79 % specificity (P?<?0.032). A statistically significant quadratic fit was found between strain and lipid content (P?<?0.03). Strains did not discriminate symptomatic patients or vulnerable plaques.

Conclusions

Ultrasound NIVE is feasible in patients with significant carotid stenosis and can detect the presence of a lipid core with high sensitivity and moderate specificity. Studies of plaque progression with NIVE are required to identify vulnerable plaques.

Key points

? Non-invasive vascular elastography (NIVE) provides additional information in vascular ultrasound ? Ultrasound NIVE is feasible in patients with significant carotid stenosis ? Ultrasound NIVE detects a lipid core with high sensitivity and moderate specificity ? Studies on plaque progression with NIVE are required to identify vulnerable plaques     

Semi-automatic quantitative measurements of intracranial internal carotid artery stenosis and calcification using CT angiography

Introduction

Intracranial carotid artery atherosclerotic disease is an independent predictor for recurrent stroke. However, its quantitative assessment is not routinely performed in clinical practice. In this diagnostic study, we present and evaluate a novel semi-automatic application to quantitatively measure intracranial internal carotid artery (ICA) degree of stenosis and calcium volume in CT angiography (CTA) images.

Methods

In this retrospective study involving CTA images of 88 consecutive patients, intracranial ICA stenosis was quantitatively measured by two independent observers. Stenoses were categorized with cutoff values of 30% and 50%. The calcification in the intracranial ICA was qualitatively categorized as absent, mild, moderate, or severe and quantitatively measured using the semi-automatic application. Linear weighted kappa values were calculated to assess the interobserver agreement of the stenosis and calcium categorization. The average and the standard deviation of the quantitative calcium volume were calculated for the calcium categories.

Results

For the stenosis measurements, the CTA images of 162 arteries yielded an interobserver correlation of 0.78 (P?Conclusions Quantitative degree of stenosis measurement of the intracranial ICA on CTA is feasible with a good interobserver agreement ICA. Qualitative calcium categorization agrees well with quantitative measurements.     

Association between proximal internal carotid artery steno-occlusive disease and diffuse wall thickening in its petrous segment: a magnetic resonance vessel wall imaging study

Purpose

Significant stenosis or occlusion in carotid arteries may lead to diffuse wall thickening (DWT) in the arterial wall of downstream. This study aimed to investigate the correlation between proximal internal carotid artery (ICA) steno-occlusive disease and DWT in ipsilateral petrous ICA.

Methods

Symptomatic patients with atherosclerotic stenosis (>0%) in proximal ICA were recruited and underwent carotid MR vessel wall imaging. The 3D motion sensitized-driven equilibrium prepared rapid gradient-echo (3D-MERGE) was acquired for characterizing the wall thickness and longitudinal extent of the lesions in petrous ICA and the distance from proximal lesion to the petrous ICA. The stenosis degree in proximal ICA was measured on the time-of-flight (TOF) images.

Results

In total, 166 carotid arteries from 125 patients (mean age 61.0 ± 10.5 years, 99 males) were eligible for final analysis and 64 showed DWT in petrous ICAs. The prevalence of severe DWT in petrous ICA was 1.4%, 5.3%, 5.9%, and 80.4% in ipsilateral proximal ICAs with stenosis category of 1%–49%, 50%–69%, 70%–99%, and total occlusion, respectively. Proximal ICA stenosis was significantly correlated with the wall thickness in petrous ICA (r = 0.767, P < 0.001). Logistic regression analysis showed that proximal ICA stenosis was independently associated with DWT in ipsilateral petrous ICA (odds ratio (OR) = 2.459, 95% confidence interval (CI) 1.896–3.189, P < 0.001].

Conclusion

Proximal ICA steno-occlusive disease is independently associated with DWT in ipsilateral petrous ICA.

     

Intracranial carotid artery disease in patients with recent neurological symptoms: high prevalence on CTA

Introduction

Novel postprocessing techniques have enabled accurate quantification of intracranial carotid atherosclerotic disease on CT Angiography (CTA). Our purpose was to estimate the prevalence of intracranial carotid artery disease, i.e., stenosis and calcium, on CTA in patients with recent neurological symptoms.

Methods

The degree of stenosis and calcium volume of 162 extracranial and intracranial internal carotid arteries (ICAs) was quantitatively measured on CTA images of 88 consecutive patients with recent neurological symptoms and extracranial ICA stenosis as screened by ultrasound. The prevalence of intracranial ICA stenosis and presence of calcium was estimated and correlated with extracranial ICA stenosis.

Results

Intracranial ICA stenosis was observed in 83 % (95 %CI: 77–89 %) and 39 % (95 %CI: 31–47 %) for a stenosis of ≥30 % and ≥50 %, respectively. Only on the symptomatic side, a statistical significant correlation between intracranial and extracranial stenoses was observed (Pearson's r 0.32, P?=?0.006). In the 37 arteries with an extracranial ICA stenosis of ≥70 %, 89 % (95 %CI: 79–99 %) and 46 % (95 %CI: 30–62 %) of the intracranial ICA showed a stenosis of ≥30 % and ≥50 %, respectively.

Conclusion

In our population of patients with recent neurological symptoms and extracranial stenosis as screened by ultrasound, CTA imaging resulted in a substantially higher prevalence of intracranial ICA disease than previously reported. This remarkably high prevalence of intracranial ICA disease on CTA may have important future implications for acute and preventive treatment strategies.     

Wall morphology,blood flow and wall shear stress: MR findings in patients with peripheral artery disease

Objectives

To investigate the influence of atherosclerotic plaques on femoral haemodynamics assessed by two-dimensional (2D) phase-contrast (PC) magnetic resonance imaging (MRI) with three-directional velocity encoding.

Methods

During 1 year, patients with peripheral artery disease and an ankle brachial index <1.00 were enrolled. After institutional review board approval and written informed consent, 44 patients (age, 70?±?12 years) underwent common femoral artery MRI. Patients with contra-indications for MRI were excluded. Sequences included 2D time-of-flight, proton-density, T1-weighted and T2-weighted MRI. Electrocardiogram (ECG)-gated 2D PC-MRI with 3D velocity encoding was acquired. A radiologist classified images in five categories. Blood flow, velocity and wall shear stress (WSS) along the vessel circumference were quantified from the PC-MRI data.

Results

The acquired images were of good quality for interpretation. There were no image quality problems related to poor ECG-gating or slice positioning. Velocities, oscillatory shear stress and total flow were similar between patients with normal arteries and wall thickening/plaque. Patients with plaques demonstrated regionally increased peak systolic WSS and enhanced WSS eccentricity.

Conclusions

Combined multi-contrast morphological imaging of the peripheral arterial wall with PC-MRI with three-directional velocity encoding is a feasible technique. Further study is needed to determine whether flow is an appropriate marker for altered endothelial cell function, vascular remodelling and plaque progression.

Key Points

? Femoral plaques are associated with altered dynamics of peripheral blood flow. ? Multi-contrast MRI can investigate the presence and type of atherosclerotic plaques. ? Three-dimensional velocity-encoding phase-contrast MRI can investigate flow and wall shear stress. ? Atherosclerotic peripheral arteries demonstrate increased systolic velocities and wall shear stress.     

Intracranial artery velocity measurement using 4D PC MRI at 3 T: comparison with transcranial ultrasound techniques and 2D PC MRI

Introduction

4D phase contrast MR imaging (4D PC MRI) has been introduced for spatiotemporal evaluation of intracranial hemodynamics in various cerebrovascular diseases. However, it still lacks validation with standards of reference. Our goal was to compare blood flow quantification derived from 4D PC MRI with transcranial ultrasound and 2D PC MRI.

Methods

Velocity measurements within large intracranial arteries [internal carotid artery (ICA), basilar artery (BA), and middle cerebral artery (MCA)] were obtained in 20 young healthy volunteers with 4D and 2D PC MRI, transcranial Doppler sonography (TCD), and transcranial color-coded duplex sonography (TCCD). Maximum velocities at peak systole (PSV) and end diastole (EDV) were compared using regression analysis and Bland–Altman plots.

Results

Correlation of 4D PC MRI measured velocities was higher in comparison with TCD (r?=?0.49–0.66) than with TCCD (0.35–0.44) and 2D PC MRI (0.52–0.60). In mid-BA and ICA C7 segment, a significant correlation was found with TCD (0.68–0.81 and 0.65–0.71, respectively). No significant correlation was found in carotid siphon. On average over all volunteers, PSVs and EDVs in MCA were minimally underestimated compared with TCD/TCCD. Minimal overestimation of velocities was found compared to TCD in mid-BA and ICA C7 segment.

Conclusion

4D PC MRI appears as valid alternative for intracranial velocity measurement consistent with previous reference standards, foremost with TCD. Spatiotemporal averaging effects might contribute to vessel size-dependent mild underestimation of velocities in smaller (MCA), and overestimation in larger-sized (BA and ICA) arteries, respectively. Complete spatiotemporal flow analysis may be advantageous in anatomically complex regions (e.g. carotid siphon) relative to restrictions of ultrasound techniques.     

In vivo hemodynamic analysis of intracranial aneurysms obtained by magnetic resonance fluid dynamics (MRFD) based on time-resolved three-dimensional phase-contrast MRI

Introduction

Hemodynamics is thought to play a very important role in the initiation, growth, and rupture of intracranial aneurysms. The purpose of our study was to perform in vivo hemodynamic analysis of unruptured intracranial aneurysms of magnetic resonance fluid dynamics using time-resolved three-dimensional phase-contrast MRI (4D-Flow) at 1.5 T and to analyze relationships between hemodynamics and wall shear stress (WSS) and oscillatory shear index (OSI).

Methods

This study included nine subjects with 14 unruptured aneurysms. 4D-Flow was performed by a 1.5-T magnetic resonance scanner with a head coil. We calculated in vivo streamlines, WSS, and OSI of intracranial aneurysms based on 4D-Flow with our software. We evaluated the number of spiral flows in the aneurysms and compared the differences in WSS or OSI between the vessel and aneurysm and between whole aneurysm and the apex of the spiral flow.

Results

3D streamlines, WSS, and OSI distribution maps in arbitrary direction during the cardiac phase were obtained for all intracranial aneurysms. Twelve aneurysms had one spiral flow each, and two aneurysms had two spiral flows each. The WSS was lower and the OSI was higher in the aneurysm compared to the vessel. The apex of the spiral flow had a lower WSS and higher OSI relative to the whole aneurysm.

Conclusion

Each intracranial aneurysm in this study had at least one spiral flow. The WSS was lower and OSI was higher at the apex of the spiral flow than the whole aneurysmal wall.     

Haemodynamic alterations in cerebral blood vessels after carotid artery revascularisation: quantitative analysis using 2D phase-contrast MRI

Objectives

This study was conducted to evaluate the effect of revascularisation, whether revascularisation improves total cerebral blood flow volume (_FVTCBF), and how cerebral veins would respond to altered _FVTCBF.

Methods

The 39 carotid artery stenoses in 37 patients who underwent revascularisation including 32 stentings and 7 endarterectomies were included in this prospective study. From the two-dimensional phase-contrast (2D-PC) MRI acquired before and after revascularisation, the flow volumes (FVs) of the arteries and veins were compared using paired t-test. The relationships between these parameters were correlated using Pearson’s correlation coefficient.

Results

The mean FV in the treated carotid artery (proportion of treated artery among total FV) increased from 162.06 ml/min (25.80 %) to 267.71 ml/min (37.21 %; P?<?0.001). Revascularisation increased the _FVTCBF of patients from 638.66 ml/min to 716.72 ml/min (P?<?0.001). The FV of the internal jugular veins, superior sagittal and straight sinuses (_FVSS + SSS), and transverse sinuses increased after revascularisation (P?<?0.05). Positive relationships were shown between the _FVTCBF and the _FVSS + SSS (r?=?0.584–0.741, P?<?0.001).

Conclusions

Revascularisation improves the _FVTCBF by increasing the FV in the treated carotid artery. The venous drainages are closely linked to _FVTCBF. 2D-PC-MRI is a feasible method for evaluating comprehensively the haemodynamic improvement after revascularisation.

Key Points

? Revascularisation may be beneficial in ischaemic strokes due to carotid artery stenosis. ? Revascularisation of the affected artery increases total cerebral blood flow volume ( _FV TCBF). ? Cerebral venous drainage, closely linked to _FV TCBF, is also improved. ? Two-dimensional phase-contrast MRI can comprehensively assess these haemodynamic improvements after carotid revascularisation.     

Evaluation of distal turbulence intensity for the detection of both plaque ulceration and stenosis grade in the carotid bifurcation using clinical Doppler ultrasound

Objectives

To determine the interrelationship of stenosis grade and ulceration with distal turbulence intensity (TI) in the carotid bifurcation measured using conventional clinical Doppler ultrasound (DUS) in vitro, in order to establish the feasibility of TI as a diagnostic parameter for plaque ulceration.

Methods

DUS TI was evaluated in a matched set of ulcerated and smooth-walled carotid bifurcation phantoms with various stenosis severities (30, 50, 60 and 70 %), where the ulcerated models incorporated a type 3 ulceration.

Results

Post-stenotic TI was significantly elevated owing to ulceration in the mild and moderate stenoses (P?<?0.001). TI increased with stenosis severity in both the ulcerated and non-ulcerated series, with a statistically significant effect of increasing stenosis severity (P?<?0.001). Whereas TI in the mild and non-ulcerated moderate stenoses was less than 20.4?±?1.3 cm s^?1, TI in the ulcerated moderate and severe models was higher than 25.6 ±1.3 cm s^?1, indicating a potential diagnostic threshold.

Conclusion

We report a two-curve relationship of stenosis grade and ulceration to distal TI measured using clinical DUS in vitro. Clinical DUS measurement of distal TI may be a diagnostic approach to detecting ulceration in the mild and moderately stenosed carotid artery.

Key Points

? Patients with carotid artery plaque ulcerations are at higher risk of stroke. ? Clinical Doppler ultrasound is routinely used to detect carotid artery stenosis. ? Doppler ultrasound turbulence intensity can detect ulceration in realistic flow models. ? Turbulence intensity also increases with stenosis severity independent of ulceration. ? Doppler ultrasound should help in assessing both stenosis severity and ulceration.     

Initial experience of carotid artery stenting using the Carotid WALLSTENT and FilterWire EZ in Japan

Purpose

The Carotid WALLSTENT (CWS) and Filter-Wire EZ (FWEZ) embolic protection devices for use in carotid arterial stenting (CAS) were newly approved for national health insurance coverage in Japan in April 2010. This article describes our initial experience of CAS using the CWS and FWEZ.

Material and methods

A group of 14 patients (12 men, 2 women; mean age 70.1 years, range 59?C83 years) with 15 carotid artery stenoses at high risk for carotid endarterectomy were treated by CAS using the CWS and FWEZ. Of these stenoses, 5 were symptomatic with ??50% stenosis of the common or internal carotid artery (ICA), and 10 were asymptomatic with ??80% stenosis. The rates of technical success, ICA flow impairment during filter protection, periprocedural ischemic stroke, 30-day major adverse events (MAEs) (stroke, death, myocardial infarction), and development of new ischemic lesions on diffusion-weighted imaging (DWI) were assessed.

Results

CAS was successful in all cases. There was no ICA flow impairment, periprocedural ischemic stroke, or MAEs. DWI showed new ipsilateral ischemic lesions in only one patient (6.7%).

Conclusion

Our initial clinical experience using the CWS and FEWZ for CAS was generally excellent, and the incidence of postprocedural ischemic lesions was low.     

Non-ECG-gated unenhanced MRA of the carotids: Optimization and clinical feasibility

Objectives

To optimise and assess the clinical feasibility of a carotid non-ECG-gated unenhanced MRA sequence.

Methods

Sixteen healthy volunteers and 11 patients presenting with internal carotid artery (ICA) disease underwent large field-of-view balanced steady-state free precession (bSSFP) unenhanced MRA at 3T. Sampling schemes acquiring the k-space centre either early (kCE) or late (kCL) in the acquisition window were evaluated. Signal and image quality was scored in comparison to ECG-gated kCE unenhanced MRA and TOF. For patients, computed tomography angiography was used as the reference.

Results

In volunteers, kCE sampling yielded higher image quality than kCL and TOF, with fewer flow artefacts and improved signal homogeneity. kCE unenhanced MRA image quality was higher without ECG-gating. Arterial signal and artery/vein contrast were higher with both bSSFP sampling schemes than with TOF. The kCE sequence allowed correct quantification of ten significant stenoses, and it facilitated the identification of an infrapetrous dysplasia, which was outside of the TOF imaging coverage.

Conclusions

Non-ECG-gated bSSFP carotid imaging offers high-quality images and is a promising sequence for carotid disease diagnosis in a short acquisition time with high spatial resolution and a large field of view.

Key Points

? Non-ECG-gated unenhanced bSSFP MRA offers high-quality imaging of the carotid arteries. ? Sequences using early acquisition of the k-space centre achieve higher image quality. ? Non-ECG-gated unenhanced bSSFP MRA allows quantification of significant carotid stenosis. ? Short MR acquisition times and ungated sequences are helpful in clinical practice. ? High 3D spatial resolution and a large field of view improve diagnostic performance.     

Calcium at the carotid siphon as an indicator of internal carotid artery stenosis

Objectives

Carotid siphon calcification is often visible on unenhanced head CT (UCT), but the relation to proximal carotid artery stenosis (CAS) is unclear. We investigated the association of carotid siphon calcification with the presence of CAS.

Methods

This IRB-waived retrospective study included 160 consecutive patients suspected of stroke (age 64?±?14 years, 63 female) who underwent head UCT and CTA of the head and neck. CAS was rated on CTA as not present or present with non-significant (<50 %), moderate (50–69 %) or significant (≥70 %) stenosis. Presence, shape (on UCT) and volume (on CTA) of carotid siphon calcifications were related to CAS.

Results

Carotid siphon calcification was absent in 41 % of patients and bilateral in 94 % of those with calcifications. Presence, shape and volume of calcification resulted in odds ratios for having significant CAS of 10.1, 3.9 and 8.4, with 95 % CIs of 1.3–79.6, 1.1–14.1 and 2.6–26.8, respectively. Corresponding NPVs were 0.98, 0.98 and 0.96, while PPVs were 0.14, 0.07 and 0.29, respectively.

Conclusion

Absence of calcification in the carotid artery siphon on UCT has high negative predictive value for carotid artery stenosis in patients with suspected stroke. However, siphon calcification is not a reliable indicator of significant carotid artery stenosis.

Key Points

? Many stroke patients do not have calcification in the carotid artery siphon. ? Carotid stenosis ≥50?% is unlikely in stroke patients without siphon calcification. ? Carotid siphon calcium is a poor indicator of significant carotid artery stenosis.     

Quantitative assessment of changes in carotid plaques during cilostazol administration using three-dimensional ultrasonography and non-gated magnetic resonance plaque imaging

Introduction

Cilostazol, an antiplatelet agent, is reported to induce the regression of atherosclerotic changes. However, its effects on carotid plaques are unknown. Hence, we quantitatively investigated the changes that occur within carotid plaques during cilostazol administration using three-dimensional (3D) ultrasonography (US) and non-gated magnetic resonance (MR) plaque imaging.

Methods

We prospectively examined 16 consecutive patients with carotid stenosis. 3D-US and T1-weighted MR plaque imaging were performed at baseline and 6?months after initiating cilostazol therapy (200?mg/day). We measured the volume and grayscale median (GSM) of the plaques from 3D-US data. We also calculated the contrast ratio (CR) of the carotid plaque against the adjacent muscle and areas of the intraplaque components: fibrous tissue, lipid, and hemorrhage components.

Results

The plaque volume on US decreased significantly (median at baseline and 6?months, 0.23 and 0.21?cm³, respectively; p?=?0.03). In the group exhibiting a plaque volume reduction of more than 10%, GSM on US increased significantly (24.8 and 71.5, respectively; p?=?0.04) and CR on MRI decreased significantly (1.13 and 1.04, respectively; p?=?0.02). In this group, in addition, the percent area of the fibrous component on MRI increased significantly (68.6% and 79.4%, respectively; p?=?0.02), while those of the lipid and hemorrhagic components decreased (24.9% and 20.5%, respectively; p?=?0.12) (1.0% and 0.0%, respectively; p?=?0.04). There were no substantial changes in intraplaque characteristics in either US or MRI in the other group.

Conclusions

3D-US and MR plaque imaging can quantitatively detect changes in the size and composition of carotid plaques during cilostazol therapy.     

Karotisstents – eine Standortbestimmung

Clinical/methodical issue

Therapy of carotid stenosis should be based on an accurate assessment of the stenosis and a differentiation between symptomatic and asymptomatic patients.

Standard radiological methods

According to current guidelines carotid artery stenting (CAS) can be considered as an established therapeutic alternative to carotid endarterectomy (CEA).

Methodical innovations

For the therapy of carotid stenosis CAS has become established as a minimally invasive alternative to CEA because the complication rate has been reduced due to growing experience, technical innovations and external quality assessment.

Performance

The CAS procedure should be performed in centers with documented complication rates of <?3?% for asymptomatic and <?6?% for symptomatic stenoses.

Achievements

Overall there are no significant differences between CAS and CEA in the treatment of carotid stenosis concerning the secondary prophylactic effect.

Practical recommendations

Ideally an interdisciplinary approach should be chosen for the therapy regime. Revascularization of asymptomatic stenoses should be considered critically as these patients might profit from optimized conservative medicinal therapy.     

Novel 3D-CT evaluation of carotid stent volume: greater chronological expansion of stents in patients with vulnerable plaques

Introduction

Although self-expanding carotid stents may dilate gradually, the degrees of residual stenosis have been quantified by the NASCET criteria, which is too simple to reflect the configuration of the stented artery. We measured the volumes of the stent lumens chronologically by 3D-CT in patients after carotid artery stenting (CAS), and analyzed the correlations between the volume change and medical factors.

Methods

Fourteen patients with carotid artery stenosis were treated using self-expanding, open-cell stents. All patients underwent preoperative plaque MRI (magnetization-prepared rapid acquisition gradient-echo, MPRAGE) and chronological 3D-CT examinations of their stents immediately after their placement and 1 day, 1 week, and 1 month after the procedure. The volume of the stent lumen was measured using a 3D workstation. The correlations between stent volume and various factors including the presence of underlying diseases, plaque characteristics, and the results of the CAS procedure were analyzed.

Results

Stent volume gradually increased in each case and had increased by 1.04–1.55 (mean, 1.25)-fold at 1 postoperative month. The presence of underlying medical diseases, plaque length, the degree of residual stenosis immediately after CAS, and plaque calcification did not have an impact on the change in stent volume. On the other hand, the stent volume increase was significantly larger in the patients with vulnerable plaques that demonstrated high MPRAGE signal intensity (P?<?0.05).

Conclusions

A 3D-CT examination is useful for precisely measuring stent volume. Self-expanding stents in carotid arteries containing vulnerable plaques expand significantly more than those without such plaques in a follow-up period.     

The normal internal carotid artery: a computed tomography angiographic study

Introduction

Systematic computed tomography angiographic (CTA) studies investigating variation in internal carotid artery (ICA) luminal diameters (LDs) are scarce. Knowledge of the normal intra-individual LD variability would provide a cut-off value for detection of more subtle collapses. In addition, low intra-individual variability would allow using contralateral LD as a reference for estimation of stenosis degree in cases where ipsilateral measurement is hampered. Therefore, our aim was to investigate intra-individual LD variation of normal ICA.

Methods

We retrospectively collected multidetector high-speed CTAs of 104 patients younger than 40 years who were considered not to have carotid pathology. We carried out independent measurements of the common carotid artery (CCA) and ICA LDs bilaterally from axial source images by two observers, analysing side-to-side LD differences from averaged double measurements with a paired t test.

Results

We discovered no significant side-to-side LD differences. In the female group, the mean differences (mm) with 95 % confidence intervals were 0.08 (0.00, 0.17) for CCA and 0.03 (?0.04, 0.11) for ICA, with ICA LD standard deviation of 0.4 mm. In the male group, these were: 0.06 (?0.04, 0.17), 0.02 (-0.07, 0.11) and 0.4 mm, respectively. We detected no ICA agenesis.

Conclusion

The intrinsic intra-individual variation of the LD of normal ICA is minimal. This uniformity may serve as the basis for detection of subtle grades of side-to-side variation caused by pathology.     

Effect of carotid artery stenting on cerebral blood flow: evaluation of hemodynamic changes using arterial spin labeling

Introduction

The purpose of this work was to quantitatively evaluate the hemodynamic changes after carotid artery stenting (CAS) by measuring cerebral blood flow (CBF) using arterial spin labeling (ASL).

Methods

Twenty sets of pre- and postprocedural CBF maps were acquired using ASL in patients who underwent CAS. Vascular territory- and anatomical structure-based regions of interest were applied to the CBF maps. Relative CBF (rCBF) was calculated by adjusting ipsilateral CBF with contralateral CBF. To assess the changes in rCBF after CAS (ΔrCBF), we calculated the following difference: $ \Delta\mathrm{rCBF}=\mathrm{rCB}{{\mathrm{F}}_{\mathrm{postprocedural}}}-\mathrm{rCB}{{\mathrm{F}}_{\mathrm{preprocedural}}} $ .

Results

Postprocedural CBFs were significantly higher than preprocedural CBFs for internal carotid artery and middle cerebral artery territories (P?<?0.05 in both). Postprocedural rCBFs were also significantly higher than preprocedural rCBFs for internal carotid artery and middle cerebral artery territories (P?<?0.05 in both). Significant correlations were observed between preprocedural rCBF and ΔrCBF for the internal carotid artery and middle cerebral artery territories (r?=??0.7211, P?=?0.0003 and r?=??0.6427, P?=?0.0022, respectively). Areas in which the ΔrCBF values were >5.00 ml?100 g^?1 min^?1 were the precentral, postcentral, middle frontal, middle temporal (caudal), superior parietal, and angular gyri.

Conclusions

ASL has potential as a noninvasive imaging tool for the quantitative evaluation of hemodynamic changes after CAS. CAS improves cerebral perfusion in patients with carotid artery stenosis, and patients with greater perfusion deficits prior to CAS have greater improvement in perfusion after CAS. In addition, eloquent areas show the greatest improvement in perfusion.     

Assessment of baseline hemodynamic parameters within infarct progression areas in acute stroke patients using perfusion-weighted MRI

Introduction

The value of perfusion MRI for identifying the tissue at risk has been questioned. Our objective was to assess baseline perfusion-weighted imaging parameters within infarct progression areas.

Methods

Patients with anterior circulation stroke without early reperfusion were included from a prospective MRI database. Sequential MRI examinations were performed on admission, 2?C3?h (H2), 2?C3?days (D2), and between 15 and 30?days after the initial MRI. Maps of baseline time-to-peak (TTP), mean transit time (MTT), cerebral blood volume (CBV), and cerebral blood flow (CBF) were calculated. Lesion extension areas were defined as pixels showing de novo lesions between each MRI and were generated by subtracting successive lesion masks: V₀, baseline diffusion-weighted imaging (DWI) lesion; V₁, lesion extension between baseline and H2 DWI; V₂, lesion extension from H2 to D2 DWI; and V₃, lesion extension from D2 DWI to final FLAIR. Repeated measures analysis was used to compare hemodynamic parameters within the baseline diffusion lesion and subsequent lesion extension areas.

Results

Thirty-two patients were included. Baseline perfusion parameters were significantly more impaired within the acute DWI lesion compared to lesion extension areas (TTP, p?p?p?p?p?=?0.01) and TTP (p?=?0.01) was found within successive lesion growth areas.

Conclusion

A decreasing gradient of severity for TTP and MTT was observed within successive infarct growth areas.     

Factors affecting long-term restenosis after carotid stenting for carotid atherosclerotic disease

Introduction

The most significant factors leading to restenosis are yet to be described in the literature. The purpose of our study was to identify the incidence of restenosis in our patients with carotid artery stenting (CAS) for carotid atherosclerotic disease and to identify risk factors that are significantly responsible or related to the restenosis.

Methods

In this retrospective analysis of patients who underwent CAS for atherosclerotic disease between years 2002 and 2006, we studied various demographic, clinical, and medical factors, plaque characteristics, and technical aspects of CAS. All patients were followed up with carotid Doppler ultrasound at baseline (after 2 to 4?weeks of CAS) and then with Doppler ultrasound and clinically for various intervals of time. The restenosis was classified based on carotid Doppler ultrasound results. Clinically, restenosis was classified as symptomatic or asymptomatic. Pearson correlation coefficient was used to assess the statistical correlation of the different factors with the incidence of restenosis.

Results

We had a total of 105 patients, with a total of 204.6 patient-year follow-up (mean, 1.95?years; range, 0?C7.3?years). The overall incidence of restenosis was 26.7?% (n?=?28): mild, 7.6?% (n?=?8); moderate, 10.5?% (asymptomatic, 11; symptomatic, 0); and severe, 8.6?% (asymptomatic, 5; symptomatic, 4). Overall, 14.3?% (n?=?4) patients with restenosis were symptomatic and 7.1?% (n?=?2) underwent retreatment. Post-stenting residual stenosis greater than either 30?% (p?=?0.016) or 50?% (p?=?0.05) were significant for long-term restenosis. Plaques longer than 20?mm were significantly related to restenosis (p?<?0.001).

Conclusion

The most important factor to explain restenosis was the immediate post-CAS residual stenosis and length of the plaque.     

Optimisation of vascular input and output functions in CT-perfusion imaging using 256(or more)-slice multidetector CT

Objectives

To evaluate the accuracy and reproducibility of CT-perfusion (CTP) by finding the optimal artery for the arterial input function (AIF) and re-evaluating the necessity of the venous output function (VOF).

Methods

Forty-four acute ischaemic stroke patients who underwent non-enhanced CT, CTP and CT-angiography using 256-slice multidetector computed tomography (MDCT) were evaluated. The anterior cerebral artery (ACA), middle cerebral artery (MCA), internal carotid artery (ICA) and basilar artery were selected as the AIF. Subsequently the resulting area under the time–enhancement curve of the AIF (AUC_AIF) and quantitative perfusion measurements were analysed by repeated measures ANOVA and subsequently the paired t test. To evaluate reproducibility we examined if the VOF could be deleted by comparing the perfusion measurements using versus not using the VOF (paired t test).

Results

The AUC_AIF and perfusion measurements resulting from the different AIFs showed significant group differences (all P?<?0.0001). The ICA had the largest AUC_AIF and resulted in the highest mean transient time (MTT) and lowest cerebral blood flow (CBF), whereas the basilar artery showed the lowest cerebral blood volume (CBV). Not using the VOF showed significantly higher CBV and CBF in 66 % of patients on the ipsilateral (P?<?0.0001 and P?=?0.007, respectively) and contralateral hemisphere (P?<?0.0001 and P?=?0.019, respectively).

Conclusion

Selecting the ICA as the AIF and continuing the use of the VOF would improve the accuracy of CTP.

Key Points

? Perfusion imaging is an increasingly important aspect of multidetector computed tomography (MDCT). ? Vascular input functions were evaluated for CT-perfusion using 256-slice MDCT. ? Selecting different arterial input functions (AIFs) leads to variation in quantitative values. ? Using the internal carotid artery for AIF provides optimal perfusion values. ? Deleting the venous output function would be detrimental for validity.