What are bifurcations really like anatomically?...• Knowledge of bifurcation anatomy is essential,...

What are bifurcations

really like anatomically?

Insights from a CT atlas

Pau Medrano-Gracia and John Ormiston

Mark Webster, Susann Beier, Alistair Young and Brett Cowan

Background

• Knowledge of bifurcation anatomy is essential,

yet available data are limited

• The aim of this project is to create the world’s

first detailed statistical atlas of the anatomy of

the coronary arteries in normal and diseased

patients

A major reason for the project was to generate

anatomically correct bifurcation phantoms/models.

Perhaps patient specific bifurcation stents will be

3D printed.

2

Susann Beier (2015)

Data and methods

• Approved by local Ethics Committee

• Written consent

– Patients with zero calcium score and no stenoses (N=300)

Access to clinical data and CT angiography images

• Demographics: 55 ± 9 years, 64% females

• Automatic fully three-dimensional measurements

3

CTA extraction of

centrelines and surfaces

4

Medrano-Gracia, Pau, et al. "Construction of a Coronary Artery Atlas from CT

Angiography." Medical Image Computing and Computer-Assisted Intervention–MICCAI

2014. Springer International Publishing, 2014. 513-520.

Examples

5

What is a computational atlas?

• Set of probability distributions:

– Centrelines Tree statistics

• Angles, lengths, curvature, tortuosity,

average tree

– Luminal surfaces Shape statistics

• Diameter, tapering, cross-sectional profiles,

geometric laws

– Patient data

• Clinical risk factors, demographics

leads to a comprehensive 3-dimensional description

of the coronary tree, i.e. an atlas

6Medrano-Gracia, Pau, et al. "Construction of a Coronary Artery Atlas from CT Angiography." Medical Image Computing and Computer-Assisted Intervention–

MICCAI 2014. Springer International Publishing, 2014. 513-520.

CTACoronary

modelsAtlas

AtlasCADPrinting

Statistical pipeline

Engineering pipelinePatient Population

2 4 6 8 10 12 14 16-20

0

20

40

60

80

100

120

Angle

(deg)

Depth (mm)

Bifurcation (per depth)

Incoming (per depth)

0 20 40 60 80 100 1200

2

4

6

8

10

12

14

16

18

20

Angle (deg)

No.

of

patients

Bifurcation (per patient)

Incoming (per patient)

-1.5 -1 -0.5 0 0.5 1 1.5

-1

-0.5

0

0.5

1

1.5Mode 2 (16.4 %, N=100)

-2

+2

-20

0

20

40

60 -40

-20

0

20

-60

-40

-20

0

lad

d1

omb

lcx

om1

d1b

lmb

Framework

Advanced modeling

8Medrano-Gracia et al. (2015). A Statistical Model of the Left Main Bifurcation. MICCAI-STENT. October 2015.

~3,000 points

per bifurcation

1. Segmentation

2. LM selection

3. Co-registration

4. Principal

component

analysis

Left main (N=199)

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Mean SD

Left main diam., mm 3.7 0.7

LAD diam., mm 3.3 0.7

LCX diam., mm 3.2 0.7

Conf. Dmax, mm 5.2 2.3

Conf. Dmin, mm 3.8 0.8

Eccentricity 1.4 0.6

Angle A, degrees 127.7 20.1

Angle B, degrees 67.3 23.8

Angle C, degrees 148.1 16.2

Inflow angle, degrees 14.4 21.1

Left main length, mm 8.5 5.5

Finet’s ratio 0.58 0.06

Lumen eccentricity was calculated as Dmax / Dmin.

Intermediate (N=65)

10

Mean SD

Left-main diam., mm 3.7 0.7

LAD diam., mm 3.3 0.7

LCX diam., mm 3.1 0.7

Int. diam., mm 2.9 0.7





Angle B1, degrees 57.3 20.3

Angle B2, degrees 43.6 14.1



Angle D, degrees 138.3 24.1


Left main length, mm 9.4 4.6


Diagonal (N=213)

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Mean SD

LAD-PMV diam., mm 3.5 0.6

LAD-DMV, diam., mm 3.1 0.7

Diagonal diam., mm 2.5 0.6










Obt. Marginal (N=151)

12

Mean SD

LCX-PMV diam., mm 3.4 0.6

LCX-DMV diam., mm 2.9 0.7

OM diam., mm 2.7 0.7










RCA crux (N=174)

13

Mean SD

RCA diam., mm 3.6 0.6

PDA diam., mm 2.6 0.6

PLB diam., mm 2.5 0.6






Angles C, degrees 146.8 16.2


Length from ostium, mm 108.0 26.1



Literature comparison

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Reference Method Bifurc. Age N Female Disease? B (deg) Inflow B’ (deg)

Dzavik 2006 Angio/crush (mixed) 63±12 133 24% PCI 63±12

Pflederer 2006 16-CT LM NR 100 NR Suspected 80±27

Kawasaki 2009 64-CT LM 66±12 209 34% Suspected 72±22

Girasis 2010 2D/3D QCA LM 65±10 266 26% Diseased 106±22 (+8 ES)

Godino 2010 Angio/crush LM NR 75 NR PCI 78±28

Rubinshtein 2012 2D/3D QCA LM 66±11 203 31% Suspected 74±25

Zhang 2015 2D/3D QCA (mixed) 58±10 1,200 23% Lesion Median: 52, IQR: 29

Our study 64-CT 3D LAD-LCX 55±9 300 64% Free 68±24 14±21

NR = Not Reported; QCA = Quantitative Coronary Angiography

Geometric relationships

15

Table 1. Diameter geometric models (19) fitted to our data. RMS = Root Mean Square; PMV = proximal 1

main vessel; DMV = distal main vessel; SB = sub-branch. 2

Model Geometric relation RMS error

Murray 𝐷𝑃𝑀𝑉3 = 𝐷𝐷𝑀𝑉

3 + 𝐷𝑆𝐵3 2.60

Area-preservation 𝐷𝑃𝑀𝑉2 = 𝐷𝐷𝑀𝑉

2 + 𝐷𝑆𝐵2 1.35

Huo-Kassab (HK) 𝐷𝑃𝑀𝑉7/3

= 𝐷𝐷𝑀𝑉7/3

+ 𝐷𝑆𝐵7/3

1.61

Best fit to our data* 𝐷𝑃𝑀𝑉0.4 = 𝐷𝐷𝑀𝑉

0.4 + 𝐷𝑆𝐵0.4 0.98

Finet 𝐷𝑃𝑀𝑉 = 0.678 (𝐷𝐷𝑀𝑉 + 𝐷𝑆𝐵) 0.16

*Domain search was constrained to 𝛼 = [−0.5,4] for 𝐷𝑃𝑀𝑉𝑎 = 𝐷𝐷𝑀𝑉

𝑎 + 𝐷𝑆𝐵𝑎 3

𝐷𝑃𝑀𝑉𝑎 = 𝐷𝐷𝑀𝑉

𝑎 + 𝐷𝑆𝐵𝑎

𝐷𝑃𝑀𝑉 𝐷𝐷𝑀𝑉 + 𝐷𝑆𝐵 =0.655 ± 0.171

Future Work

• Are there any significant shape differences:

– Between bifurcations

– With a diseased sample

– By demographics

• Modeling of the ostium and aortic root

• Further investigate shape of SB origin and DMV

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Summary

• We have created an atlas of the normal coronary anatomy with a focus on

Bifurcation measurements

• We can 3D print anatomically true bifurcation phantoms based on

population models

• These models can also be used for accurate and representative

hemodynamic simulations and realistic bench-testing

17

Thank you

• Co-investigators

Brett Cowan, John Ormiston, Mark Webster,

Susann Beier and Alistair Young

• Do you have an application for our true shape models? Get in touch:

[email protected]

[email protected]

• Funding & Support

18

mailto:[email protected]

mailto:[email protected]

What are bifurcations really like anatomically?...• Knowledge of bifurcation anatomy is essential,...

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