Quantitative assessment of the flow distribution in the branches of the external carotid by non-injected flow MRI.

Owing to the lack of databases of blood flow distributions in the external carotid branches, surgeons currently rely on per-operative imaging and on their experience to choose the recipient vessels for microsurgical facial reconstructions. But, thanks to three-dimensional phase contrast angiography (PCA) and kinematic CINE phase contrast (PC) sequences, MRI technologies have the potential to provide quantitative anatomical and hemodynamic information without injection of contrast agent. Having developed and optimized PC-MRI sequences for the small facial vessels, our objective was to investigate the haemodynamic and blood flow distribution in the external carotid branches. We included 31 healthy volunteers in an MRI prospective study. Two-dimensional CINE PC-MRI sequences (average duration time of 2 min 40 s ± 24 s) were performed in the external carotid collaterals (n = 290). A statistical analysis of the flow measurements showed that, despite large interpersonal variabilities, a general flow distribution pattern was obtained by dividing the vessel flow rates by the external carotid artery one (providing local percentages of the incoming flow). The vessels could then be classified in three haemodynamic groups (p < 0.05 Student's test): "low flow" group (lingual artery-12.5 ± 5% of incoming flow), "intermediate flow" group (superior thyroid artery-16.5 ± 10%, internal maxillary artery-20.5 ± 11%, superficial temporal artery-18.4 ± 6%), "high flow" group (facial artery -26.6 ± 10%). Thanks to this general flow distribution mapping, it is now possible to estimate the flow rates in the distal branches of any individual from a single blood flow measurement in the external carotid artery.

Dynamic Cerebral Autoregulation Assessment Using Extracranial Internal Carotid Artery Doppler Ultrasonography.

Transcranial Doppler ultrasonography of the middle cerebral artery (MCA) is frequently used to assess dynamic cerebral autoregulation (dCA); however, this is difficult in patients with poor temporal bone windows. In the study described here, we investigated the agreement and sensitivity of dCA indices determined from the extracranial internal carotid artery (ICA) and those determined from the MCA. Measurements for 32 stroke patients and 59 controls were analyzed. Measurement of the mean flow correlation index (Mx) and transfer function analysis based on spontaneous blood pressure fluctuation were simultaneously performed for the extracranial ICA and MCA. The mean values of Mx and phase shift did not significantly differ between the ICA and MCA (mean difference: Mx = 0.01; phase shift of very low frequency [VLF] = 0.7°, low frequency [LF] = 3.3° and high frequency = 4.5°), but the gains in VLF and LF in the ICA were significantly lower than those in the MCA (mean difference: gain of VLF = -0.13, gain of LF = -0.10). The intra-class correlation coefficient between the dCA indices of the ICA and MCA was favorable in Mx (0.76) and the phase shift of VLF (0.72). The area under the receiver operating characteristic curve for stroke diagnosis did not differ among the dCA indices. We conclude that dCA assessed from the ICA is as effective as that from the MCA, but the results are not interchangeable.

Dural carotid cavernous fistulas: endovascular treatment and assessment of the correlation between clinical symptoms and the Cognard classification system.

OBJECTIVE: To present our experience with endovascular treatment of dural carotid cavernous fistulas (DCCFs) and determine if there is a correlation between clinical symptoms and the Cognard classification system. METHODS: We searched our institutional neurovascular database to identify patients treated for DCCFs from January 1995 to May 2015. DCCFs were defined as a vascular shunt between meningeal branches of the internal carotid artery (ICA), external carotid artery (ECA), or both, draining into the cavernous sinus. Clinical symptoms were recorded based on clinical examination. Lesions were classified on angiography using the Cognard and Barrow classification systems. Treatment goal was defined as symptomatic cure based on clinical examination, cure of ophthalmic venous drainage, and cortical venous reflux on angiography. RESULTS: The search revealed 37 patients with DCCFs; 32 DCCFs underwent endovascular treatment. The primary treatment goal was met in 30/32 (94%) lesions, with one neurologic complication (1/34; 3%). We identified 31 Cognard IIa fistulas, 4 Cognard IIa+b, 2 Cognard IIb, 7 Barrow B, 7 Barrow C, and 23 Barrow D fistulas. Eye redness, proptosis, and ocular pain were significantly lower in the Cognard IIb group than in the Cognard IIa and IIa+b groups (p=0.0015). Intracranial hemorrhage was more likely in the Cognard IIb group than in the Cognard IIa and IIa+b groups, with marginal significance (p=0.054). No correlation was seen between symptomatology and the Barrow classification. CONCLUSIONS: Endovascular treatment of DCCFs has a high degree of clinical success and a low complication rate. The Cognard system is suitable for grading DCCFs as it correlates with presenting symptomatology and venous drainage patterns. The Barrow classification adds no value in grading DCCFs.

Assessment of shear stress related parameters in the carotid bifurcation using mouse-specific FSI simulations.

The ApoE(-)(/)(-) mouse is a common small animal model to study atherosclerosis, an inflammatory disease of the large and medium sized arteries such as the carotid artery. It is generally accepted that the wall shear stress, induced by the blood flow, plays a key role in the onset of this disease. Wall shear stress, however, is difficult to derive from direct in vivo measurements, particularly in mice. In this study, we integrated in vivo imaging (micro-Computed Tomography-µCT and ultrasound) and fluid-structure interaction (FSI) modeling for the mouse-specific assessment of carotid hemodynamics and wall shear stress. Results were provided for 8 carotid bifurcations of 4 ApoE(-)(/)(-) mice. We demonstrated that accounting for the carotid elasticity leads to more realistic flow waveforms over the complete domain of the model due to volume buffering capacity in systole. The 8 simulated cases showed fairly consistent spatial distribution maps of time-averaged wall shear stress (TAWSS) and relative residence time (RRT). Zones with reduced TAWSS and elevated RRT, potential indicators of atherosclerosis-prone regions, were located mainly at the outer sinus of the external carotid artery. In contrast to human carotid hemodynamics, no flow recirculation could be observed in the carotid bifurcation region.

Quantitative Assessment of Neovascularization after Indirect Bypass Surgery: Color-Coded Digital Subtraction Angiography in Pediatric Moyamoya Disease.

BACKGROUND AND PURPOSE: For the postoperative follow-up in pediatric patients with Moyamoya disease, it is essential to evaluate the degree of neovascularization status. Our aim was to quantitatively assess the neovascularization status after bypass surgery in pediatric Moyamoya disease by using color-coded digital subtraction angiography. MATERIALS AND METHODS: Time-attenuation intensity curves were generated at ROIs corresponding to surgical flap sites from color-coded DSA images of the common carotid artery, internal carotid artery, and external carotid artery angiograms obtained pre- and postoperatively in 32 children with Moyamoya disease. Time-to-peak and area under the curve values were obtained. Postoperative changes in adjusted time-to-peak (ΔTTP) and ratios of adjusted area under the curve changes (ΔAUC ratio) of common carotid artery, ICA, and external carotid artery angiograms were compared across clinical and angiographic outcome groups. To analyze diagnostic performance, we categorized clinical outcomes into favorable and unfavorable groups. RESULTS: The ΔTTP at the common carotid artery increased among clinical and angiographic outcomes, in that order, with significant differences (P = .003 and .005, respectively). The ΔAUC ratio at the common carotid artery and external carotid artery also increased, in that order, among clinical and angiographic outcomes with a significant difference (all, P = .000). The ΔAUC ratio of ICA showed no significant difference among clinical and angiographic outcomes (P = .418 and .424, respectively). The ΔTTP for the common carotid artery of >1.27 seconds and the ΔAUC ratio of >33.5% for the common carotid artery and 504% for the external carotid artery are revealed as optimal cutoff values between favorable and unfavorable groups. CONCLUSIONS: Postoperative changes in quantitative values obtained with color-coded DSA software showed a significant correlation with outcome scores and can be used as objective parameters for predicting the outcome in pediatric Moyamoya disease, with an additional cutoff value calculated through the receiver operating characteristic curve.

Presence of external carotid artery plaque independently predicts mortality in patients without internal carotid artery atherosclerosis.

BACKGROUND: The presence of plaque in the external carotid artery (ECA) detected on carotid duplex ultrasound (CDU) is of unknown clinical significance and may not be reported in routine clinical practice. We hypothesize that ECA plaque in the absence of plaque in the other cervical vessels is a risk factor for increased all-cause mortality. OBJECTIVES: To determine the significance of ECA plaque on all-cause mortality in the absence of internal carotid artery (ICA) or common carotid artery (CCA) plaque. METHODS: We queried the Non-Invasive Vascular Laboratory database for all CDUs performed between 1 January 2005 and 31 December 2005. All images were reviewed for the presence of plaque. Studies were included if plaque was absent in both the CCA and the ICA. Chart review was performed to obtain demographic and clinical information. All-cause mortality was determined using the Social Security Death Index. RESULTS: A total of 500 patient studies met the inclusion criteria; 64 patients (12.8%) had plaque in one or both ECAs. There was no significant difference in age (mean 58.1 ± 14.8 years), race (82.5% white), or sex (64.4% male) between those with and without ECA plaque. There was a significant difference in all-cause mortality between patients with and without isolated ECA plaque after adjustment for age, sex, low-density lipoprotein cholesterol, smoking, hypertension, body mass index, and surgery within 30 days of CDU (adjusted hazard ratio 2.60, 95% CI 1.46-4.66, p<0.001). CONCLUSIONS: The presence of plaque isolated to the ECA is an independent predictor of all-cause mortality and may impart important prognostic information for patients referred for CDU.

The influence of obesity on the assessment of carotid intima-media thickness.

BACKGROUND: The assessment of carotid intima-media thickness (CIMT) may improve cardiovascular risk prediction. The optimal protocol for CIMT measurement is unclear. CIMT may be measured in the common carotid artery (CCA), carotid bifurcation (CB), and internal carotid artery (ICA), but measurements from CB and ICA are more difficult to obtain. We studied the influence of body mass index (BMI) and atheroma plaques on the capacity to obtain CIMT measurements at different carotid sites. METHODS: Using an automatic system, CIMT was measured in 700 subjects aged 45-75, in the near and far walls of CCA, CB, and ICA bilaterally. The presence of atheroma plaques, BMI and vascular risk factors were recorded. RESULTS: CIMT measurements in CCA were possible in all except one subject. It was not possible to obtain CIMT measurements at CB or ICA in 24.1% of normal weight and 58.8% of obese subjects. The likelihood of obtaining CIMT measurement at all carotid sites decreased as the BMI increased. Atheroma plaques in a carotid segment did not preclude CIMT measurement at this site. CONCLUSIONS: CIMT measurements in distal carotid segments are more challenging in obese subjects. Measuring CIMT at CCA remains feasible in obese subjects and should be the primary endpoint in these subjects. Nevertheless, CB and ICA measurements, when feasible, would improve risk classification.

Assessment of vascular supply of hypervascular extra-axial brain tumors with 3T MR regional perfusion imaging.

BACKGROUND AND PURPOSE: The vascular supply of extra-axial brain tumors provided by the external carotid artery has not been studied with RPI. The purpose of this work was to determine whether RPI assessment is feasible and provides information on the vascular supply of hypervascular extra-axial brain tumors. MATERIALS AND METHODS: Conventional ASL and RPI studies were performed at 3T in 8 consecutive patients with meningioma. On the basis of MRA results, we performed RPI by placing a selective labeling slab over the external carotid artery. Five patients underwent DSA before surgery. Two neuroradiologists independently evaluated the overall image quality, the degree of tumor perfusion, and the extent of the tumor vascular territory on conventional ASL and RPI. RESULTS: In overall quality of conventional ASL and RPI, no images interfered with interpretation. In comparisons of the vascular tumor territory identified by the conventional ASL and RPI techniques, the territories coincided in 3 cases, were partially different in 4, and completely different in 1. The interobserver agreement was very good (kappa = 0.82). In 5 patients who underwent DSA, the 4 patients in whom the dominant supply was the external carotid artery were scored as coincided or partially different. The 1 patient in whom the vascular supply was from the internal carotid artery was scored as completely different. CONCLUSIONS: RPI with selective labeling of the external carotid artery is feasible and may provide information about the vascular supply of hypervascular extra-axial brain tumors.

Assessment of CE-MRA for the rapid detection of supra-aortic vascular disease.

BACKGROUND: Contrast-enhanced MR angiography (CE-MRA) using a combined head and neck coil permits non-invasive imaging of the vasculature from the aortic arch through to the Circle of Willis in less than 2 minutes. OBJECTIVE: To determine the accuracy of CE-MRA for the detection of vascular pathology, in particular vascular stenoses, using digital subtraction angiography (DSA) as the gold standard. METHODS: In a prospective study of 81 patients referred for DSA, CE-MRA and DSA studies were performed within 72 hours of each other. CE-MRA was performed on a 1.5 Tesla clinical MRI scanner using a five-channel neurovascular array (head and neck coil), with dynamic tracking of the IV gadolinium bolus. CE-MRAs and DSA films were read by two interventional neuroradiologists blinded to the clinical presentation of the patient. RESULTS: On DSA, there were 77 vascular stenoses > or =50% identified, 51 extracranial and 26 intracranial. The overall sensitivity of CE-MRA using the neurovascular array for the detection of vascular stenoses > or =50% was 57% (95% CI: 46 to 68%) with a specificity of 98% (97 to 99%). The sensitivity for the detection of extracranial vascular stenoses > or =50% was 82% (72 to 93%) with a specificity of 97% (96 to 98%). However, the sensitivity for the detection of intracranial vascular stenoses > or =50% was only 8% (0 to 18%), with a specificity of 99% (98 to 100%). CONCLUSIONS: At this stage Contrast-enhanced MR angiography using a neurovascular coil shows promise as a rapid, specific, and noninvasive screening method for extracranial vascular disease, but not for intracranial vascular disease.

A new angle-independent Doppler ultrasonic device for assessment of blood flow volume in the extracranial internal carotid artery.

OBJECTIVE: To evaluate a new angle-independent ultrasonic device for assessment of blood flow volume in the internal carotid artery. METHODS: In vitro, a pulsatile pump was set to provide an outflow of physiological fluid at 500 mL/min through an 8-mm-diameter tube. Flow volume rates were measured 10 times by 10 different operators and compared with time-collected flow volume rates. In vivo, internal and common carotid artery blood flow volumes were measured in 28 volunteers by 2 operators using a FlowGuard device (Biosonix Ltd). Internal and common carotid artery diameters and blood flow volumes were also assessed by Duplex sonography and compared with FlowGuard measurements. In 10 volunteers, internal carotid artery blood flow volume changes in response to monitored breath manipulations were recorded. RESULTS: In vitro, intraoperator variability was 4.04% (range, 2%-5.7%). The mean error rate +/- SD was 3.54% +/- 0.8% (range, 2.7%-5.2%). In vivo, the mean common carotid artery blood flow volume was 456 +/- 39 mL/min (range, 417-583 mL/min) with a mean diameter of 6.7 +/- 0.7 mm (range, 5.8-8.7 mm). The mean internal carotid artery blood flow volume was 277 +/- 25 mL/min (range, 239-338 mL/min) with a mean diameter of 5 +/- 0.5 mm (range, 4.1-6.1 mm). No significant difference was found between operators. Internal carotid artery diameter and blood flow volume measured by the FlowGuard were closely correlated with the results of Duplex sonography. Repeated shifts of end-tidal CO2 induced reproducible changes in internal carotid artery flow volume: 187.5 +/- 18.1 mL/min at 26.8 +/- 1.9 mm Hg and 382.1 +/- 18.2 mL/min at 47 +/- 2.2 mm Hg. CONCLUSIONS: The FlowGuard showed that volume flow studies in the internal carotid artery could be easily performed, with results compatible with those of previous clinical reports. Duplex comparative results and breath-induced changes in internal carotid artery flow volume justify further evaluation of the system.

Power Doppler imaging: initial evaluation as a screening examination for carotid artery stenosis.

PURPOSE: To evaluate power Doppler imaging as a possible screening examination for carotid artery stenosis. MATERIALS AND METHODS: In the principal pilot study, a prospective, blinded comparison of power Doppler imaging with duplex Doppler imaging, the reference-standard method, was conducted in 100 consecutive patients routinely referred for carotid artery imaging at a large, private multispecialty clinic. In the validation pilot study, a prospective, blinded comparison of power Doppler imaging with digital subtraction angiography, the reference-standard method, was conducted in 20 consecutive patients routinely referred at a teaching hospital. Using conservative assumptions, the authors performed cost-effectiveness analysis. RESULTS: Power Doppler imaging produced diagnostic-quality images in 89% of patients. When the images of the patients with nondiagnostic examinations were regarded as positive, power Doppler imaging had an area under the receiver operating characteristic curve, A(z), of 0.87, sensitivity of 70%, and specificity of 91%. The validation study results were very similar. The cost-effectiveness of screening and, as indicated, duplex Doppler imaging as the definitive diagnostic examination and endarterectomy was $47,000 per quality-adjusted life-year. CONCLUSION: The A(z) value for power Doppler imaging compares well with that for mammography, a generally accepted screening examination, and with most other imaging examinations. Power Doppler imaging is likely to be a reasonably accurate and cost-effective screening examination for carotid artery stenosis in asymptomatic populations.

Preoperative assessment of the carotid bifurcation. Can magnetic resonance angiography and duplex ultrasonography replace contrast arteriography?

BACKGROUND AND PURPOSE: Noninvasive studies are used with increasing frequency to assess the carotid bifurcation before endarterectomy. Therefore, assessment of their diagnostic accuracies is essential for appropriate patient management. We prospectively evaluate two noninvasive tests, magnetic resonance angiography (MRA) and duplex ultrasonography (DU), as potential replacements for contrast arteriography (CA). METHODS: A blinded comparison of three-dimensional time-of-flight (TOF) MRA, two-dimensional TOF MRA, and DU in 176 arteries was performed. CA was used as the standard of comparison. RESULTS: Three-dimensional TOF MRA had a sensitivity of 94%, a specificity of 85%, and an accuracy of 88% for the identification of 70% to 99% stenosis; two-dimensional TOF MRA had a sensitivity and specificity that were approximately 10% lower than those of three-dimensional TOF MRA. DU resulted in a sensitivity of 94%, a specificity of 83%, and an accuracy of 86%. Combining data from three-dimensional TOF MRA and DU, allowing for CA only for disparate results, yielded a sensitivity of 100%, a specificity of 91%, and an accuracy of 94% among concordant noninvasive tests, with CA required in 16% of arteries. MRA accurately differentiated 17 carotid occlusions from 16 high-grade (90% to 99%) stenoses, whereas with DU two patent arteries were identified as occluded and one occluded artery was identified as patent. CONCLUSIONS: Three-dimensional TOF MRA is the most accurate noninvasive test. Combined use of MRA and DU results in a marked increase in accuracy to a level that obviates the need for CA in a majority of patients.

Carotid bifurcation stenosis: a comparative study between MR angiography and duplex scanning with respect to digital subtraction angiography.

PURPOSE: This study compared sensitivity, specificity and diagnostic accuracy of Echoduplex and Magnetic Resonance Angiography (MRA) in the evaluation of carotid bifurcation stenosis. MATERIAL AND METHODS: Twenty-five patients with clinical signs suggestive for cerebrovascular insufficiency (CVI) were studied with Duplex scan, MRA and Digital Subtraction angiography (DSA). Gold standard was the angiographic examination. RESULTS: on equal value of sensitivity (80.5%), MRA showed 96% specificity versus 81% of Duplex scan, 89.4% diagnostic accuracy versus 80.9% for Duplex scan. As for stenosis over 31%, the value of sensitivity did not change i.e., 80.5%; MRA showed 100% specificity versus 97.1% for Duplex, 91.2% diagnostic accuracy versus 89.1% respectively. These values compared by the test for categorial analysis and correspondence analysis (p < 0.05) did not indicate any statistically significant difference. DISCUSSION: on the basis of our experience and as shown by current literature [2, 12] we can state that both MR-angiography and Duplex scan fail in quantifying correctly carotid stenosis with consequent over- and underestimation [3, 4]. However, they can be considered effective diagnostic procedures in a screening program [12, 16]; they are accurate, safe and accepted by the population. CONCLUSIONS: on the basis of the cost in planning the screening of a population at risk for CVI, Duplex scanning is still to be considered the elective procedure.

Assessment of autopsic samples of carotid atherosclerosis in the aged by intravascular ultrasound.

To assess the value of intravascular ultrasound in detecting carotid atherosclerosis, we compared the ultrasound images of 48 carotid artery segments from autopsies with their histological findings. The results showed that by intravascular ultrasonography one could distinguish between elastic and muscular tissues of arteries, determine the lesions of fibroelastosis and calcified plaques on arterial wall, and precisely measure the wall thickness, inner and outer diameter, luminal area and cross-sectional area of arteries with a high correlation between the data measured from ultrasonography and histological study (r values were 0.98, 0.97, 0.97, 0.96 and 0.96, respectively). This study suggests that intravascular ultrasound might be effectively used for morphological study and detection of atherosclerotic lesions in vivo.

[Importance of morphologic evaluation of carotid lesions in their correlation with cerebral ischemic pathology]. / Importancia de la valoración morfológica de las lesiones carotídeas en su correlación con patología isquémica cerebral.

Authors present a review of 182 atheromatous plaques into the extracranial carotid trunks. Diagnosis of such pathologies were made by Eco-Doppler on 615 patients. Objective was to determinate the emboligen potential of the plaques following structural and functional criteria. Almost all the symptomatic plaques with functional disturbances showed some structural injury with emboligen potential. Two third parts of all the symptomatic diseases hemodynamically no-significant were associated with plaques with emboligen power. On stenosis higher than 70%, functional criterium was more important for study than structural criterium.

Non-invasive assessment of carotid arteries: a comparison of techniques used in two laboratories.

Fifty-one patients were examined non-invasively in two different laboratories and underwent angiography for carotid artery disease. Results of the two examinations and angiography were compared. In one laboratory continuous wave Doppler ultrasonography of the accessible extracranial arteries was used; in the other laboratory spectral analysis of the Doppler signals and angioscan imaging of the bifurcation was carried out. Accuracy of the two examinations (when compared with angiography) were similar for stenoses of more than 50%; spectral analysis and angioscan were better than continuous wave Doppler in detection of less than 50% stenoses.

Accuracy and indications of diagnostic studies for extracranial carotid disease.

We reviewed extracranial carotid studies in two groups of patients. The first group consisted of 200 patients who had been evaluated by both duplex scanning (DS) and direct arch-selective carotid arteriography (SCA). The second group consisted of 100 patients who had been evaluated by both intravenous digital subtraction angiography (IDSA) and conventional SCA. In 200 patients DS disclosed a 92% accuracy in delineating stenotic internal carotid disease and was accurate in recognizing ulcerative disease in 76% of patients. A review of the 100 patients studied by both IDSA and SCA showed that in 40% IDSA gave excellent correlation with SCA; in 35%, good correlation; and in 25%, poor correlation. In 10% DS was more accurate in delineating ulcerative disease than was IDSA, and on occasion DS was even more diagnostic than SCA. The relative accuracy, cost, risk, and clinical usefulness of each carotid diagnostic modality are discussed.