1. T. Lindenmaier D. Buchanan, S. McKay, I. Gyacskov,
Semi-Automated Segmentation of Three-dimensional Ultrasound Carotid Artery Plaque Volume
T. Lindenmaier D. Buchanan, S. McKay, I. Gyacskov,
A. Fenster and G. Parraga
Imaging Research Laboratories, Robarts Research Institute, Department of Medical Biophysics, Biomedical Engineering Graduate Program, The University of Western Ontario, London, CANADA
April 4, 2012

2. 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

3. Motivation: Carotid Atherosclerosis
Libby, Peter. Inflammation in Atherosclerosis. Nature. December 2002.

4. ICA
ECA
CCA BF

5. Motivation: Atherosclerosis in Carotid Artery
Cerebrovascular disease accounts for 10% of all deaths worldwide1
1WHO, 2004

6. Ultrasound of Carotid Atherosclerosis
Intima-Media Thickness
Courtesy of Christiane Mallet

7. Manual Planimetry Measurements
lumen-intima
media-adventitia
Longitudinal View
Axial View

8. Intima-Media Thickness
Carotid Atherosclerosis: US Measurements
Vessel Wall Volume
Egger et al. J Ultrasound Med. (2008)
Intima-Media Thickness
Buchanan et al. Accepted to Ultrasound Med Biol. (2012)
Total Plaque Volume
Al-Shali et al. Atherosclerosis. (2005)
Egger et al. Ultrasound Med Biol. (2007)
Total Plaque Area
Riccio et al. Cardiovascular Ultrasound. (2006)

9. 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
500
400
300
200
600
V (mm3)
CV (%) 5 10 15 20
Total Plaque Volume
Adapted from Landry et al. Stroke. (2004)

10. Limitations of Current Measurements
Intima-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

11. Semi-automated TPV Measurement
Longitudinal View
Axial View

12. Schematic of Longitudinal View
Semi-Automated TPV
Measurement
Contour 1
(longitudinal view)
Contour 2
(axial view)
Contour 3
(axial view)
Contour 4
(axial view)
Measurement View
Schematic of Longitudinal View C1 C2 C3 C4
Min Z
Max Z

13. Semi-Automated TPV MeasurementC1
Min Z
C2 C3 C4
Max Z x z y c b a P
V = volume
PFj = representative vertex
Aj = area of triangle
1Van Gelder. Graphic Gems 5. (1995)

14. Methodology echogenic plaques from 17 subjects Selection of 23
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

15. Manual vs. SA Measurements

16. Results
Landry et al. Stroke. (2004)

19. 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).

20. Acknowledgements Research Team Sandra Halko CRCC RPT Shayna McKay BSc
Andrew Wheatley BSc
Miranda Kirby BSc
Stephen Costella MESc
Amir Owrangi MSc
Trevor Szekeres MRT
Sarah Svenningsen
Lauren Villemaire
Supervisory Committee
Grace Parraga PhD
Daniel Buchanan BSc
Collaborators
Aaron Fenster PhD FCCPM
Igor Gyacskov 20

21. Thank you