Dynamic holographic imaging of the beating heart. How far to go ? Patrick Hunziker, MD ICU / Cardiology / Physics in Medicine Research Group Basel University Hospital, Switzerland Massachusetts General Hospital, Boston USA Massachusetts Institute of Technology, Cambridge USA

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Display of Multidimensional Echo Data dimensions 2 3 4 M-mode Static 2D dynamic 2D surface-rendered 3D true 3D/4D +/- color Info content: 0.2 MB 2 MB 20-100 MB Reporting: page videotapes digital loops ? print ?

History of Echo Display Dimension Display type time strip 1954 1970’s 2D movie 2000’s space Z hologram 1960’s space Y 2D still image space X 1980’s flow field 2D color movie

What is holography ? l1 l2 l2 l1 holography = recording of data by light diffraction/interference l1 l2 interference pattern object beam reference beam photosensitive substrate fix pattern in substrate l2 reference beam l1 reconstructed object

Kinds of holography optical holography digital holography Aim static 3D image change of viewing angle change of perspective Aim To explore the ability of holography to display cardiac motion space X space Y space Z Hologram TIME Conventional Holography static 3D image change of viewing angle change of perspective Dynamic Holography moving object change of viewing angle change of timepoint Kinds of holography Production of Holograms: Optical Computational technique: technique: Object ‘virtual Laser Laser optical holography object digital holography Laser beam object’ calculation of hypothetical reference interference pattern HOE beam LCD interference pattern light sensitive light sensitive substrate substrate Methods reformatting MEDIS PC optical disk HP software data acquisition Echocardiogram HP Sonos 2500 One-step digital hologram postprocessing printing filter,crop,contrast NIH image Conventional Dynamic heart hologram motion hologram conventional holograms dynamic heart motion contains multiple holograms contains perspective views multiple timeframes Viewing of dynamic heart holograms Characteristics of dynamic heart holograms: Resolution / Sharpness: currently: 640*480 pixels*32 time-frames. practically limited by computer power. theoretically limited only by wavelength of laser. no distortion Color: B/W & color images Printing time : Conventional methods: days to weeks. Prototype ‘one-step laser-printers’: minutes. additional applications of dynamic heart holograms: -2D echo + motion + color Doppler - rendered 3D + motion - true 3D + motion - true 3D + color Doppler + motion Advantages of dynamic heart holograms: display & reporting of echocardiograms: -a single page: anatomy, contractile function, valvular function & Doppler -no need for viewing stations simple archiving scheme: -a single page contains complete original image info Holographic representation of heart motion -is feasible -allows printing & display of the complete heart cycle on a two-dimensional medium. This novel technique has the potential to improve visualisation and archiving of echocardiographic imaging. Hunziker P, Circulation 1998, in print Hypothesis: Computational, dynamic holography can be applied to echo imaging of cardiac motion in a variety of clinical states

types of holography: optical vs computational real object ‘virtual object’ computation of virtual interference pattern HOE light sensitive substrate Laser LCD Laser reference beam object interference pattern light sensitive substrate illumination of real object with light necessary virtual representation of object is enough

types of holography interferometry holographic storage

types of holography display holography holographic video

conventional display holography: static representation of 3D objects multiple perspective views conventional hologram: static 3D shape

prior uses of holography in medicine Display holography Create static 3D representation from X-rays (Redman, Nature 1968) holographic interferometry: nondestructive surface testing of heart valve prostheses (Zarubin, J Heart Valve Dis 1993)

conventional holography in cardiology Excised bovine heart use ultrasound to create static, volumetric multiplexed display hologram Vannan et al. J Am Soc Echocardiogr. 1995;8:567–575

In echo, motion is key information Goal: to explore the ability of holography to display heart motion by integration of space and time dimensions into digital print holograms

Display of motion by dynamic holography static 3D image change of viewing angle change of perspective Conventional Holography moving object change of viewing angle change of timepoint Dynamic Holography

Static versus dynamic holography Conventional, static 3D hologram conventional holograms contains multiple perspective views Dynamic heart motion hologram dynamic heart motion holograms contains multiple timeframes

Methods Echocardiogram HP Sonos 2500 data acquisition optical disk reformatting PC HP software MEDIS filter,crop,contrast NIH image software postprocessing One-step digital hologram printing UNIX

Viewing of dynamic heart holograms

dynamic (2d + time) hologram from standard echo images Hunziker, Circulation 1999

Results - hologram printing pipeline real-time preprocessing printing time 10 min on prototype holographic printer ( technology similar to DVD reader/writer ) plastic sheet of 0.3mm thickness size 7x10cm resolution >>> current echo machines 640 x 480 pixels x 25 timeframes

Dynamic holographic images preserves quantitation Hunziker, Circulation 1999

dynamic (2D+time) holograms: comparative views HOCM normal MV MV prolapse myxoma

dynamic surface-rendered (3D + time ) hologram

Advantages of dynamic heart holograms display & reporting of echocardiograms: -a single page: anatomy, contractile function, valvular function & Doppler -no need for viewing stations simple archiving scheme: -a single page contains complete original image info

Summary Holographic representation of heart motion -is feasible -allows printing & display of the complete heart cycle on a two-dimensional medium -can convey 3D anatomy + motion + flow in a single printout This novel technique has the potential to improve visualisation , reporting and archiving of echocardiographic imaging.

parallax in holography -> representation of 4 kinds of image information horizontal parallax vertical parallax Smith, MIT Media Lab

Work in progress: Exploitation of independence of horizontal and vertical parallax in digital holograms => combination of true (volumetric) 3D + motion

work in progress II full color holograms 3 laser wavelengths for RGB recording full color holograms -> 3D + time + flow in a simple printout ! Hunziker et al Smith SL, MIT Media Lab

Outlook: holographic video State of the art: - a few prototypes worldwide - still low resolution - 15 fps - monochrome - need for huge bandwidths -> display of moving 3D echo in the future ?

Will display holography ever play a role in echocardiography ? Pro: -currently, working with 3D echo is tedious -> no widespread application outside the research lab. -inherent problems of 3D display on a 2D screen -hologram printer technology ~ level of DVD ROM -capability of upcoming holographic video systems Contra: availability of hologram printers will the future society be “all digital and all virtual” ?

Thanks to My teachers in echocardiography My family for support Osmund Bertel, Zurich Dieter Burckhardt, Basel Peter Buser, Basel Mike Picard, Boston Bob Levine, Boston Arthur E Weyman, Boston My family for support The Swiss National Research Foundation