title: Three-dimensional carotid ultrasound segmentation variability dependence on signal difference and boundary orientation.
abstract: Quantitative measurements of the progression (or regression) of carotid plaque burden are important in monitoring patients and evaluating new treatment options. We previously developed a quantitative metric to analyze changes in carotid plaque morphology from 3-D ultrasound (US) on a point-by-point basis. This method requires multiple segmentations of the arterial wall and lumen boundaries to obtain the local standard deviation (SD) of vessel-wall-plus-plaque thickness (VWT) so that t-tests could be used to determine whether a change in VWT is statistically significant. However, the requirement for multiple segmentations makes clinical trials laborious and time-consuming. Therefore, this study was designed to establish the relationship between local segmentation SD and local signal difference on the arterial wall and lumen boundaries. We propose metrics to quantify segmentation SD and signal difference on a point-by-point basis, and studied whether the signal difference at arterial wall or lumen boundaries could be used to predict local segmentation SD. The ability to predict the local segmentation SD could eliminate the need of repeated segmentations of a 2-D transverse image to obtain the local segmentation standard deviation, thereby making clinical trials less laborious and saving time. Six subjects involved in this study were associated with different degrees of atherosclerosis: three carotid stenosis subjects with mean plaque area >3 cm(2) and >60% carotid stenosis were involved in a clinical study evaluating the effect of atorvastatin, a cholesterol-lowering and plaque-stabilizing drug; and three subjects with carotid plaque area >0.5 cm(2) were subjects with moderate atherosclerosis. Our results suggest that when local signal difference is higher than 8 greyscale value (GSV), the local segmentation SD stabilizes at 0.05 mm and is thus predictable. This information provides a target value of local signal difference on the arterial boundaries that should be achieved to obtain an accurate prediction of local segmentation SD. (E-mail: bcychiu@alumni.uwo.ca).
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada. bcychiu@alumni.uwo.ca
authors.forename: Bernard
authors.initials: B
authors.lastname: Chiu
authors.forename: Adam
authors.initials: A
authors.lastname: Krasinski
authors.forename: J David
authors.initials: JD
authors.lastname: Spence
authors.forename: Grace
authors.initials: G
authors.lastname: Parraga
authors.forename: Aaron
authors.initials: A
authors.lastname: Fenster
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000924:Anticholesteremic Agents / Q000627:therapeutic use; D050197:Atherosclerosis / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000473:pathology; D000069059:Atorvastatin; D001699:Biometry / Q000379:methods*; D002339:Carotid Arteries / Q000000981:diagnostic imaging* / Q000473:pathology; D016893:Carotid Stenosis / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000473:pathology; D005260:Female; D006538:Heptanoic Acids / Q000627:therapeutic use; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010363:Pattern Recognition, Automated / Q000379:methods*; D011758:Pyrroles / Q000627:therapeutic use; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013499:Surface Properties; D014463:Ultrasonography
chemical_list: D000924:Anticholesteremic Agents; D006538:Heptanoic Acids; D011758:Pyrroles; D000069059:Atorvastatin