Semi-Automated Segmentation of Three-dimensional Ultrasound Carotid Artery Plaque Volume

Imaging Research Laboratories, Robarts Research Institute,Department of Medical Biophysics, Biomedical Engineering Graduate Program,

The University of Western Ontario, London, CANADA

April 4, 2012

T. Lindenmaier D. Buchanan, S. McKay, I. Gyacskov, A. Fenster and G. Parraga

Overview

• Atherosclerosis and the carotid artery• Image acquisition using ultrasound• Imaging phenotypes of carotid atherosclerosis• Limitations of current methods• Development of semi-automated measurement• Application and Reproducibility

Libby, Peter. Inflammation in Atherosclerosis. Nature. December 2002.

Motivation: Carotid Atherosclerosis

ICA ECA

CCA

BF

Cerebrovascular disease accounts for 10% of all deaths worldwide1

1WHO, 2004

Motivation: Atherosclerosis in Carotid Artery

Ultrasound of Carotid Atherosclerosis

Intima-Media Thickness

Courtesy of Christiane Mallet

Manual Planimetry Measurements

lumen-intima

media-adventitia

Axial ViewLongitudinal View

Vessel Wall VolumeEgger et al. J Ultrasound Med. (2008)

Carotid Atherosclerosis: US Measurements

Total Plaque VolumeAl-Shali et al. Atherosclerosis. (2005)

Egger et al. Ultrasound Med Biol. (2007)

Intima-Media ThicknessBuchanan et al. Accepted to Ultrasound Med Biol. (2012)

Total Plaque AreaRiccio et al. Cardiovascular Ultrasound. (2006)

Manual Segmentation of 3DUS TPV

• User sets axis of segmentation • Measurements made in an axial view at 1mm inter-slice distance• Inter-slice distance multiplied by segmentation area to calculate volume

100 500400300200 600V (mm3)

CV

(%)

5

1015

20

0

Total Plaque VolumeAdapted from Landry et al. Stroke. (2004)

0

Limitations of Current MeasurementsIntima-Media Thickness (IMT)• Narrow dynamic range (0.5mm to 1.0mm)• 1-dimensional measurement• No plaque

Total Plaque Area (TPA)• High inter-observer variability• 2-dimensional measurement• Not adequate to estimate 3D change with 2D measurement

Total Plaque Volume (TPV)• Long measurement time (slice-by-slice)• Laborious

Semi-automated TPV Measurement

Longitudinal ViewAxial View

Semi-Automated TPV Measurement

Contour 1(longitudinal view) Contour 2

(axial view)Contour 3

(axial view)

Contour 4(axial view)

Mea

sure

men

t Vie

wS

chem

atic

of

Long

itudi

nal V

iew

Min Z Max ZC1 C2 C3 C4

C1

C2 C3 C4

Semi-Automated TPV Measurement

)(2AP 61 = A P

31 = V j

1-m

0 jFjj

1-m

0 j Fj

c

ba

P

1Van Gelder. Graphic Gems 5. (1995)

V = volume

PFj = representative vertex

Aj = area of triangle

Min Z Max Z

x

z

y

Methodology

Selection of 23

echogenic plaques from 17 subjects

2x5 rounds of semi - automated segmentation

Images measured 5x with 5 Minutes

between measurements

Images measured 5x with 20 hours

between measurements

1 round manual segmentation

Manual vs. SA Measurements

Results

Landry et al. Stroke. (2004)

Conclusion• Intra-observer variability similar to manual measurement

variability reported by Landry et al. (2004)

• High correlation between manual and SA for both time durations between measurements

• The manual TPV measurement can be replaced by the novel segmentation method.

• If adopted for clinical use, measurements could be generated right away (faster diagnosis).

Acknowledgements

Research TeamSandra Halko CRCC RPT Shayna McKay BSc Andrew Wheatley BSc Miranda Kirby BScStephen Costella MEScAmir Owrangi MScTrevor Szekeres MRTSarah SvenningsenLauren Villemaire

Supervisory CommitteeGrace Parraga PhDDaniel Buchanan BSc

CollaboratorsAaron Fenster PhD FCCPMIgor Gyacskov

Thank you