Multi-modal fluorescence imaging of contracting intact hearts

Transcription

1 Multi-modal fluorescence imaging of contracting intact hearts ESR4: Vineesh Kappadan Project Supervisor: Prof.Ulrich Parlitz & Dr.Jan Christoph Biomedical Physics Group Max Planck Institute for Dynamics and Self Organization, Göttingen, Germany Second Be-Optical Workshop Montpellier-La Grande Motte, France, March 18-19,2018 Max Planck Institute for Dynamics and Self-Organization

2 Introduction: Imaging a beating heart Electrical impulses are responsible for mechanical contraction Sinus Rhythm Contraction of a cardiomyocyte [Virtualheart.org F. Fenton] Excitation Contraction Coupling Ventricular Fibrillation Membrane Voltage Calcium Contraction [Numerical simulation by P. Bittihn, Biomedical Physics Group, MPIDS 2012]

3 Research goal: Study of electromechanical interactions Electro-mechanical interactions are bi-directionally coupled Excitation Contraction Coupling (ECC) Electrical activity Mechanical activity Mechano Electric Feedback (MEF) [Stretch activated channels] Study of electro-mechanical interactions of the heart simultaneous imaging of voltage and calcium from a beating heart

4 State-of-the-art: Fluorescent imaging of heart Action potential waves from a beating rabbit heart Signal distortion due to motion Motion artifacts : Challenge Inhomogeneous illumination also causes motion artifact by drifting the baseline Usage of pharmacological agents (Electromechanical uncouplers) to suppress mechanical motion (example: Blebbistatin) Adverse effects on the electrophysiology of heart [Stender et al.] Loss of correspondence between the camera pixel and heart tissue

5 Fluorescent imaging of voltage and calcium Heart loaded with voltage sensitive fluorescent dye Voltage dependent fluorescent emission Heart loaded with calcium sensitive fluorescent dye Calcium dependent fluorescent emission

6 Multiparametric Optical Mapping by Fluorescent Imaging Langendorff-perfused Rabbit heart loaded with voltage and calcium sensitive dyes 10mm Excitation 550nm camera 500fps 250fps 250fps 10mm Voltagesensitive Calciumsensitive Dye 1 Dye 2 Excitation 650nm dual-bandpass filter Lee et al, 2011 [1] 10mm [2] 2 x 250fps 2ms t 2 channels: illumination + exposure scheme LED switching box 1. P. Lee, P. Kohl; Heart Rhythm, I. Uzelac, J. Christoph, S. Luther, F. Fenton 2014

7 Solution to motion artifact: marker free motion tracking A six parameter affine model is used Assumption of brightness constancy Affine Transform Test image f(x,y) Reference image g(x,y) Difference image Goal is to minimize the quadratic error function E=σ R [ f x m 5, y m 6 g m 1 x + m 2 y + m 5, m 3 x + m 4 y + m 6 ] 2 Affine matrix A= m 1 m 2 m 3 m 4 m 5 and m 6 are displacement vectors [Periaswami et al. Differential affine motion estimation for medical image registration,international Symposium on Optical science and Technology, San Diego, 2000]

8 Contrast enhancement: To preserve brightness constancy Enhancement of image contrast by local normalization I CE (x,y)= I(x,y) min(s) max S min(s) S: sub region of the image surrounding the pixel (x,y) Contrast enhancement before motion tracking [ J. Christoph, J. Schröder-Schetelig, S. Luther. Electromechanical optical mapping, Prog. Biophys. Mol. Bio., 2017]

9 Motion tracking on experimental data during sinus rhythm Action potential Calcium concentration Without motion tracking With motion tracking+compensation

10 Motion tracking of heart with Action Potential (AP) Sinus rhythm Ventricular Fibrillation AP without motion tracking AP from a motion tracked+compensated heart Motion compensation by motion tracking

11 Time series during sinus rhythm Voltage signal without motion tracking Voltage signal from a motion compensated heart

12 Variation of time delay between voltage and calcium signals during Ventricular Fibrillation

13 Thank you for your attention!