Effect of Image Normalization on Carotid Plaque Classification and the Risk of Ipsilateral Hemispheric Ischemic Events: Results from the Asymptomatic Carotid Stenosis and Risk of Stroke Study

Nicolaides, Andrew; Kakkos, Stavros K.; Griffin, Maura; Sabetai, Michael M.; Dhanjil, Surinder; Thomas, D. J.; Geroulakos, George; Georgiou, Niki; Francis, Susan T.; Isabel, Elena; Doré, Caroline J

doi:10.2310/6670.2005.50082

Cited by 33 publications

(57 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…We have also excluded from our segmentation experiments images with extensive echolucency and calcification. This problem is inherent to ultrasound and could be only resolved by using other techniques, like MRI [25]. Backscattered ultrasound is also angle dependent.…”

Section: Discussionmentioning

confidence: 97%

“…The normalization method used in this study was documented to be helpful in the manual contour extraction [21] as well as the snakes segmentation of the IMT [19]. Moreover, this method increased the classification accuracy of different plaque types as assessed by the experts [25].…”

Section: Discussionmentioning

confidence: 99%

“…This improved the IMC visualization. Moreover, the new spatial compound imaging technique might optimize further carotid plaque imaging [21,25,35]. Furthermore, the estimation and positioning of the initial snake contour may sometimes result to segmentation errors.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Snakes based segmentation of the common carotid artery intima media

et al. 2007

View full text Add to dashboard Cite

Ultrasound measurements of the human carotid artery walls are conventionally obtained by manually tracing interfaces between tissue layers. In this study we present a snakes segmentation technique for detecting the intima-media layer of the far wall of the common carotid artery (CCA) in longitudinal ultrasound images, by applying snakes, after normalization, speckle reduction, and normalization and speckle reduction. The proposed technique utilizes an improved snake initialization method, and an improved validation of the segmentation method. We have tested and clinically validated the segmentation technique on 100 longitudinal ultrasound images of the carotid artery based on manual measurements by two vascular experts, and a set of different evaluation criteria based on statistical measures and univariate statistical analysis. The results showed that there was no significant difference between all the snakes segmentation measurements and the manual measurements. For the normalized despeckled images, better snakes segmentation results with an intra-observer error of 0.08, a coefficient of variation of 12.5%, best Bland-Altman plot with smaller differences between experts (0.01, 0.09 for Expert1 and Expert 2, respectively), and a Hausdorff distance of 5.2, were obtained. Therefore, the pre-processing of ultrasound images of the carotid artery with normalization and speckle reduction, followed by the snakes segmentation algorithm can be used successfully in the measurement of IMT complementing the manual measurements. The present results are an expansion of data published earlier as an extended abstract in IFMBE Proceedings (Loizou et al. IEEE Int X Mediterr Conf Medicon Med Biol Eng POS-03 499:1-4, 2004).

show abstract

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Snakes based segmentation of the common carotid artery intima media

et al. 2007

View full text Add to dashboard Cite

show abstract

“…Though various sonographically determined plaque features have been proposed to aid in the identification of high-risk plaque such as plaque ulceration [57] or stenosis progression [58], perhaps the most well-studied [59,60,61,62,63,64,65,66,67] risk marker for which there is level 2a evidence [68] is the presence of predominantly echolucent plaque. Histopathologic investigations [69,70] suggest that predominantly echolucent plaque may contain a relatively high proportion of lipid-rich necrotic core or intraplaque hemorrhage, which are the known constituents of more advanced, complicated atherosclerotic plaque [37,38].…”

Section: Plaque Vulnerability For Stroke Risk Assessmentmentioning

confidence: 99%

“…Similarly, there is significant variability in the sonographic criteria used to define plaque echolucency, and therefore techniques that rely upon a quantitative imaging parameter, such as a normalized gray-scale median, may improve standardization of image assessment [63]. In addition, though to-date CT has to date performed relatively poorly in discriminating between specific tissue types in carotid plaque [53,91,92], recent work [93,94,95,96,97] suggests that plaque with greater volumes of ‘soft' or low-attenuation plaque relative to calcified plaque may represent a relatively simple scheme for identifying those carotid plaques most likely to cause ischemic symptoms.…”

Section: Future Directions In Stroke Risk Assessment Studiesmentioning

confidence: 99%

Moving Beyond Luminal Stenosis: Imaging Strategies for Stroke Prevention in Asymptomatic Carotid Stenosis

Gupta¹,

Marshall

2015

Cerebrovasc Dis

View full text Add to dashboard Cite

Background: With progressive improvements in medical therapy and resultant reductions in stroke risk, luminal stenosis criteria are no longer adequate to inform decisions to pursue surgical revascularization in patients with asymptomatic carotid artery stenosis. Summary: In this evidence-based review, we discuss the imaging-based risk stratification strategies that take into account factors beyond luminal stenosis measurements, including cerebral hemodynamics and plaque composition. The existing literature lends support to the use of certain imaging tests in patients with asymptomatic carotid stenosis including cerebrovascular reserve testing, MRI of plaque composition, ultrasound of plaque echolucency, and transcranial Doppler evaluation for microemboli. The highest quality evidence thus far in the literature includes only systematic reviews and meta-analyses of cohort studies with no randomized trials having yet been performed to show how these newer imaging biomarkers could be used to inform treatment decisions in asymptomatic carotid stenosis. Beyond the need for randomized trials, there are additional important steps needed to improve the relevance of evidence supporting risk assessment strategies. Imaging studies evaluating the risk of stroke in carotid disease should clearly define asymptomatic versus symptomatic disease, use uniform definitions of clearly defined outcome measures such as ipsilateral stroke, ensure that imaging interpretations are performed in a manner blinded to treatments and other risk factors, and include cohorts which are on modern intensive medical therapy. Such studies of risk stratification for asymptomatic carotid stenosis will be most valuable if they can integrate multiple high-risk features (including clinical risk factors) into a multi-factorial risk assessment strategy in a manner that is relatively simple to implement and generalizable across a wide range of practice settings. Key Messages: Together, modern imaging strategies allow for a more mechanistic assessment of stroke risk in carotid disease compared to luminal stenosis measurements alone, which, with further validation in randomized controlled trials, may improve current efforts at stroke prevention in asymptomatic carotid stenosis.

show abstract