3D Ultrasound imaging

Transcription

1 3D Ultrasound imaging Hans Torp and Torbjørn Hergum Department of Circulation and Medical Imaging NTNU, Trondheim, Norway 1 of 45

2 Outline Introduction Transducer for 3-D cardiology Clinical examples Future directions 2 of 45

3 The heart is a pump Pump output not satisfactory? Diagnosis: what is wrong? Functional or anatomical Anatomy: leaking valves? Regional function: how well is each muscle cell contracting? 3 of 45

4 3D Cardiac Ultrasound 4 of 45 Figure by Terry Hayes

5 Why 3D? Visualization of anatomic disorders No shape-assumptions No out-of-plane Arbitrary 2D slices from 3D dataset Decreased exam time TEE en-face view of prolapsed mitral valve 5 of 45 Videos by Crosby and Jungwirth et al

6 Outline Introduction Transducer for 3-D cardiology Clinical examples Future directions 6 of 45

7 Offline 3D Gated acquisition using ECG or B-mode Assumes periodicity Probe is moved: tilt, shift, rotate, arbitrary Probe position must be known Probe w. magnetic position sensor 7 of 45 figures by Marco Voormolen

8 Tilted scanning angle 8 of 45

9 Rotating Probe 3D Transvaginal ultralyd - Nasjonalt senter for Fostermedisin - IFBT, IDI, NTNU - GE Vingmed Ultrasound 9 of 45

10 Technology OwlVision TM 3D visualization software Crown-rump length 7.5 mm 6 weeks 6 days 10 of 45

11 Technology OwlVision TM 3D visualization software 8 0 weeks CRL 14.5 mm 11 of 45

12 Fast rotating transducer 12 of 45 Courtesy of Marco Voormolen and Erasmus MC

13 2-D matrix array probe From 1D Array to 2D Array array elements array elements Challenges: Long data acquisition time, stitching data from 7 heart cycles Small element size high electrical impedance lower SNR Elevation Azimuth 13 of 45

14 Cardiac real time 3D with electronically steered beams Must fit between ribs Maintain image quality (aperture size) Squared number of channels (64 2 =4096) Squared number of beams 14 of 45

15 2D array Limiting channel count Mills cross Vernier Sparse 2D Fucused in one direction, spherical wave in the other. Swap when receiving. 1D projection ieee transactions on ultrasonics, ferroelectrics, and frequency control, vol. 49, no. 1, january 2002 Real-Time Rectilinear Volumetric Imaging Jesse T. Yen, and Stephen W. Smith Brunke and Lockwood: Broad-bandwidth Radiation Patterns, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency control, vol. 44, no. 5, september 1997 SPARSE GEOMETRIES FOR TWO-DIMENSIONAL ARRAY TRANSDUCERS IN VOLUMETRIC IMAGING Richard E. Davidsen and Stephen W. Smith 15 of 45

16 Fully sampled 2D array Enabling technologies Manufacture Interconnect Integrated electronics Post processing Very small elements: high impedance 2D system, 64 channels: 12bit/sample*40MHz*64=3.8Gb/s 3D system, 2048 channels: 12bit/sample*40MHz*2048=123Gb/s 16 of 45 Courtesy of Philips Medical and GE Vingmed

17 Beamforming Transmit Receive Delays τ Transmit Signal τ τ τ τ τ τ τ τ τ τ τ τ τ Aligned receive signals Delays lambda/2 lambda/2 Focal Point Scatterer at Focal Point 17 of 45 Courtesy of Kjell Kristoffersen and Tore Bjåstad

18 Sub-apertures 1D Projection Split array into subapertures System Delays τ τ τ τ τ τ τ Probe processing ~2 * lambda Micro-beamforming in probe handle Channel count reduced from ~3000 to ~ of 45 courtesy of Kjell Kristoffersen

19 Real time challenges Speed of sound Wide beams Fewer beams Intrinsic tradeoff between high image quality and high frame rate 2D: 100 beams / 5000 Hz = 20ms. 3D: beams / 5000 Hz = 2s. Framerate = 50Hz Framerate = 0.5Hz 19 of 45 Video by Jonas Crosby

20 Parallel beams Increase frame rate Must reduce Tx aperture Looses penetration and resolution Harmonic imaging problematic Image artifacts 20 of 45

21 Harmonic Real-time 3D, 60 frames/sec Limited field of view Thomas? 21 of 45

22 Stitching to cover the whole ventricle 22 of 45 Videos by Jonas Crosby

23 Automatic segmentation for Left ventricular volume and wall thickening 23 of 45 courtesy of Fredrik Orderud

24 3D TEE - real-time with full field of view Transesophageal probe 24 of 45 video by Philips Healthcare

25 Example: Barlow mitral valve disease post-op. 25 of 45 video by Philips Healthcare

26 3D color flow Transmitting several (~8) pulses in each direction Real time imaging a lot harder Limited ROI Stitching even more important 26 of 45

27 3D color flow A lot easier to assess valvular regurgitation Regurgitant orifice areas Multiple jets Stroke volume Regurgitant volume (more about this in the next lecture) Miniature mitral regurgitation. 27 of 45

28 My insuff. Not easy to interpret? 28 of 45

29 6-slice Mitral regurgitation 29 of 45

30 Heart attack 30 of 45US National Heart, Lung, and Blood Institute, Diseases and Conditions Index

31 Evaluating myocard function Heart muscle not functioning properly Contractility / force: ideal parameter Perfusion We typically measure displacement (and derived properties velocity, strain, strain rate) Contracting cardiac muscle cell 31 of 45 Videos by Morten Høydal and Hans Torp

32 9-slice Easier to visually assess wall motion in cut-planes than with 3D rendering 32 of 45 Illustration by GE Vingmed Ultrasound

33 Bi-plane Imaging Short- and long-axis images acquired simultaneously 33 of 45 Illustration by GE Vingmed Ultrasound

34 Outline Introduction Transducer for 3-D cardiology Clinical examples Future directions 34 of 45

35 Future directions 3D strain 3D strain during stress CMUT Real time segmentation Automatic view-detection Adaptive acquisition Correction for aberration 3D perfusion metal silicon oxide 11.4 um Silicon nitride video by Gabriel Kiss Courtesy of Svein Erik Måsøy and 35Halvard of 45 Kaupang Bhan, A. et al. Eur J Courtesy Echocardiogr of Fredrik Gabriel Kjersti 2008 Midtbø Orderud 9:761-5 Kiss

36 Summary Real time 3D ultrasound available Diagnosis of function and anatomy Image quality vs. frame rate: no ideal solution Lots of exciting topics for further research! video by Gabriel Kiss 36 of 45

37 My insuff. Questions? 37 of 45

38 The heart is a pump Pump output not satisfactory? Anatomy: leaking valves? 38 of 45

39 The heart is a pump Pump output not satisfactory? Anatomy: leaking valves? Regional function: how well is each muscle cell contracting? 39 of 45

40 Outline Introduction Transducer for 3-D cardiology Clinical examples Future directions 40 of 45

41 The heart is a pump Pump output not satisfactory? 41 of 45

42 Global function Measuring performance of the left ventricle (LV) LV function from LV volumes: Stroke volume: SV = EDV ESV [ml] Ejection fraction: EF = SV / EDV [%] Cardiac output: CO = SV HR [ml/min] 42 of 45 EDV = End Diastolic Volume ESV = End Systolic Volume HR = Heart Rate

43 Volume measurement Previously: 2D methods with abundance of assumptions Simpsons method Now: automated measurements from 3D ultrasound datasets 43 of 45 Based on illustration in Schiller NB, J Am Soc Echocardiogr 1989;2(5):358-67

44 GE Vingmed 4D Auto-LV quantification With contrast Bhan, A. et al. Eur J Echocardiogr : of 45 courtesy of Kjell Kristoffersen

45 Real-time volume measurement (RCTL) 45 of 45 courtesy of Fredrik Orderud