Motion Correction on Dual ECG and Respiratory Gated 3D Cardiac PET/CT Data

Mohammad Dawood1,3,4, T Kösters2, M Fieseler1,3, F Büther1,4, X Jiang3, KP Schäfers1,4

1European Institute of Molecular Imaging, University of Münster2Institute for Computational and Applied Mathematics, University of Münster

3Institute of Computer Science, University of Münster4University Hospital Münster

M. Dawood EIMI, Münster

Problem: Motion during data acquisition

PET, Minutes

CT, Seconds

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Problem: 1. Attenuation correction

Inspiration Expiration

PET: Respiratory phases

CT: Static

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Problem: 2. Image blur

Extent of motion

Superimposed image

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Motion artifacts lead to errors:

• wrong „staging“ of the tumors (Osman et al 2003, Erdi et al 2004)

• „Uptake Values“ are incorrect (Nakamoto et al 2004)

• small tumors may remain undetected (Papathanassiou et al 2005)

Solution?

Gating + Motion Correction

Clinical relevance

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Method: Amplitude- vs. Time-based gating

P1 Amplitude basedP1 Time based

P2 Amplitude basedP2 Time based

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Solution: Part 2 - Optical flow

Brightness consistency constraint

I(x,y,z,t) = I(x+∂x,y+∂y,z+∂z,t+∂t)

I.V = -It

I = Grey valueV = Flowx,y,z,t = Position

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Solution: Part 2 - Optical flow

Lucas/Kanade: Optical flow is locally consistent

Ix1Vx+Iy1Vy+Iz1Vz = -It1

. . . .

. . . .

. . . .IxnVx+IynVy+IznVz = -Itn

Local consistency

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Horn/Schunck: Optical flow is globally smooth

∫((I.V+It)+(|u|2+|v|2+|w|2))dxdydz

Solution: Part 2 - Optical flow

Brightness consistency Global smoothness

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Lucas/Kanade + Horn/Schunck + Discontinuity Preservation

Solution: Part 2 - Optical flow

Dawood et al, IEEE Trans Med Imaging, August 2008

Local consistency Global smoothness

∫ (ψ1(I.V+It)+αψ2(w,|u|2+|v|2+|w|2)) dxdydz

Discontinuity preservation

Ψ2 (w,s)

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Results: Visual

PET-Data before correction-8 gates

PET-Data after correction-8 gates

Remaining Motion ~ 0.3 mm << 1 Voxel

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+

Dual ecg and respiratory gating and motion correction

Cardiac contraction, 6 gates

Respiratory motion, 6 gates

Combined motion, 36 gates

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After motion correction, 36 gates

Combined motion, 36 gates

Results: Visual

Combined motion, 36 gates, motion corrected

M. Dawood EIMI, Münster

Data-based motion correction and reconstruction

Data-based approach outperfoms the image-based motion correction

Lamare et al, Phys Med Bio, 2007

Line of Response

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Attenuation correction: PET-derived dynamic CT-based mu-map

Dynamic CT-based mu-maps derived from a static mu-map and motion information from the PET

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Dual ecg and respiratory gating and motion correction

Target Gate Ungated Motion Corrected

M. Dawood EIMI, Münster

One gate 12,5 mm

Before motion correction 17,2 mm

After motion correction 12,5 mm

Results: Myocardial thickness

M. Dawood EIMI, Münster

Results: Myocardial thickness

Thank you!