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Image Processing for Interventional MRI

Image Processing for Interventional MRI. Derek Hill Professor of Medical Imaging Sciences. King’s College London. Image Processing for Interventional MRI. Derek Hill Professor of Medical Imaging Sciences. University College London. Kawal Rhode Marc Miquel Redha Berboutkah David Atkinson

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Image Processing for Interventional MRI

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  1. Image Processing for Interventional MRI Derek Hill Professor of Medical Imaging Sciences King’s College London

  2. Image Processing for Interventional MRI Derek Hill Professor of Medical Imaging Sciences University College London

  3. Kawal Rhode Marc Miquel Redha Berboutkah David Atkinson Maxime Sermesant Rado Andriantsimiavona Kate McLeish Sebastian Kozerke Reza Razavi Vivek Muthurangu Sanjeet Hegde Jas Gill Pier Lambraise Cliff Bucknall Eric Rosenthal Shaqueel Qureshi The team

  4. Context • Interventional MRI provides particular opportunities and challenges for image analysis. • Hostile environment for computers • “real time” requirements • Link between acquisition and analysis

  5. Overview • Background to XMR guided interventions • Integrating x-ray and MRI • Automatic cathether tracking • Integration of image analysis in acquisition

  6. XMR • X-ray + cylindrical bore MRI in the same room • Becoming main platform for MR guided interventions • Resection control in neurosurgery • Endovascular procedures • Not ideal for percutaneous procedures

  7. XMR suite at Guy’s(funded of JREI, Philips Medical Systems and Charitable Foundation of Guy’s & St Thomas’) Staff Patient

  8. XMR System at Guy’s Hospital • XMR = hybrid X-ray/MR imaging • Common sliding patient table • Provides path to MR-guided intervention

  9. XMR suite at Guy’s

  10. Catheter manipulation

  11. Visualizing catheters • Fast imaging (70 msec per frame) • TE = 1.3, TR = 2.6 • SSFP sequence (balanced TFE) • Acquisition: 78 x 96, 80% FOV, 80% acq, SENSE factor 2 (ie: only 25 phase encodes!) • Carbon dioxide filled balloon as contrast agent

  12. Catheter Manipulation Images acquired with standard Philips real time or interactive sequences

  13. Catheter Manipulation Miquel et al. Visualization and tracking of an inflatable balloon catheter using SSFP in a flow phantom and in the heart and great vessels of patients. Magn Reson. Med. 51(5):988-95 2004

  14. Integrating x-ray and MRI • XMR provide rapid transfer between modalities • No capability to integrate the images • X-ray and MRI provide complementary information • Combined x-ray and MR has value in complex interventions eg: electrophysiology

  15. Registration Matrix Calculation • Overall registration transform is composed of a series of stages • Calibration + tracking during intervention M1 T Scanner Space 3D Image Space X - ray Table Space M2 X - ray C - arm R*P Space M3 2D Image Space

  16. XMR Registration:Software Overview

  17. XMR Registration: Calibration • Acrylic calibration object with 14 markers • Interchangeable caps for MR and X-ray imaging • Determine geometric relationship between MR and X-ray system • Determine X-ray projection geometry MR X-ray

  18. Calibration (1) Fixing flange for sliding table. (2) Saline-filled acrylic half cylinder with 20 divot cap markers in a helical arrangement. (3) Slot in acrylic base plate to allow sliding of half cylinder. (4) & (5) End stops. (6) Fixing to allow MR surface coil attachment

  19. XMR Registration:MR Overlay on X-Ray

  20. XMR Registration:3D Reconstruction

  21. XMR Registration:Phantom Validation • T1-weighted MR volume + 5 pairs of tracked x-ray images using calibration object as a phantom • 2D RMS Error = 4.2mm (n=35), Range = 1.4 to 8.0 mm • 3D RMS Error = 4.6mm (n=17), Range = 1.7 to 9.0 mm • “Registration and Tracking to Integrate X-ray and MR Images in an XMR Facility “, Rhode et al, TMI, Nov 2003.

  22. Clinical Example • Patient undergoing electrophysiology study prior to RF ablation of heart rhythm abnormality

  23. MR Imaging - Anatomy • SSFP three-dimensional multiphase sequence • 5 phases • 256x256 matrix • 152 slices • resolution=1.33 x 1.33 x 1.4 mm • TR=3.0 ms • TE=1.4 ms • flip angle=45

  24. MR Imaging - Motion • SPAMM tagged imaging sequence • 59 phases SA & 50 phases LA • 256x256 matrix • 11 slices SA & 4 slices LA • resolution=1.33 x 1.33 x 8.0 mm • TR=11.0 ms • TE=3.5 ms • flip angle=13 • tag spacing=8 mm

  25. X-ray Imaging + Electrical Mapping • Contact electrical mapping system • Constellation catheter (Boston Scientific) LAO View AP View

  26. MR Anatomy Overlay

  27. Catheter Reconstruction

  28. Refining the Registration • Errors due to limitations of registration technique and patient motion • Basket point cloud meshed • Rigid surface-to-image registration used to realign the basket mesh

  29. Visualising the Electrical Data • Cycle 1 - normal • Cycle 2 - ectopic

  30. Instantiation of model

  31. Simulation results LV volume

  32. Catheters re-visited • Essential properties of catheters • Clearly visible • Safe • mechanically • electrically • Magnetically • Desirable properties • Automatic localization • Tip and length visible • CO2 filled balloon catheters are safe • Tip location ambiguous • Length not visible • Cannot be localized automatically

  33. Is there an image analysis solution? • Find catheter automatically in modulus image? • Is it easier to find in a phase image?

  34. Fluorine is not present in body High NMR sensitivity Safe blood subsitutes available (eg: PFOB) Better solution: change nucleus

  35. (b) (a) (c) Catheter tracking SSFP proton image plus fluorine projections Phantom setup

  36. (b) (a) (c) Catheter tracking Phantom setup Automatic superposition Of catheter tip on proton image

  37. Lumen visible

  38. Dynamic scan

  39. Catheter Tracking and Visualization Using19F Nuclear Magnetic Resonance • Sebastian Kozerke1,2, Sanjeet Hegde3, Tobias Schaeffter4, Rolf Lamerichs5, Reza Razavi3, Derek L. Hill2 Magn. Reson. Med. 2004 (in press)

  40. Image analysis combined with acquisition • Real time MRI can provide high temporal resolution, but low quality • Can we subsequently combine real time images to generate high image quality?

  41. Real time MRI with slice tracking • Real time undersampled radial acquisitions Navigator Slice tracking

  42. Registration to compensate for motion Rigid body then non-rigid registration to correct motion During scanning

  43. Demonstration on gated volunteer heart images (n=4) • Undersampled images

  44. Demonstration on gated volunteer heart images (n=4) • Combined with no registration

  45. Demonstration on gated volunteer heart images (n=4) • Combined with rigid registration

  46. Demonstration on gated volunteer heart images (n=4) • Combined with rigid then non-rigid registration

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