A Real-time Freehand 3D Ultrasound System for Image-guided Surgery
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Transcript of A Real-time Freehand 3D Ultrasound System for Image-guided Surgery
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Jacqueline Nerney Welch, Jeremy A. Johnson, Michael R. Bax, Rana Badr, Ramin Shahidi
IEEE Ultrasonics Symposium 2000
October 24, 2000
A Real-time Freehand 3D Ultrasound System for Image-guided Surgery
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Overview
• Design motivations and decisions– 3D ultrasound
– Freehand scanning
– Optical tracking
– Volume rendering
– Simultaneous acquisition and visualization
• Methods– Equipment
– Spatial calibration
– Volume construction and maintenance
• Results
• Future Work
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Ultrasound
• Ultrasound versus other imaging modalities (CT, MR, X-ray)– Least expensive
– No ionizing radiation
– Compatible with existing surgical instruments
– Widely available and commonly used
– Real-time, interactive nature
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
3D Visualization of Ultrasound
• Compared to 2D, 3D provides:– More intuitive and comprehensible images
– More accurate volume estimation
– Shorter scanning times
– Improved sharing of information
2D Ultrasound Image Volume Rendered 3D US
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
3D from Conventional 2D Ultrasound
Volume Volume Construction Construction
EngineEngine
WorkstationWorkstation
Volume Volume Rendering Rendering
EngineEngineji
k
(x,y,z)
2D Images
Position Data
US Probe
Tracking Device
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Optically Tracked Freehand Acquisition
• Freehand versus other scanning techniques (mechanical)– Greatest freedom of movement
– Compact
– Least cumbersome
– Requires probe position measurements
• Optical versus other position tracking methods (magnetic, mechanical, speckle decorrelation)– Insensitive to metallic surgical equipment
– Allows volume localization
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
• Volume rendering versus other visualization methods (slice projection, surface rendering)– Truest to the data set
– Easiest to interpret
– Segmentation not required
– Computationally expensive but feasible with current technology
Interactive Volume Rendering
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Volume Construction
Engine
Visualization
Static Volume
Simultaneous Acquisition & Visualization
(x,y,z)
ji
k
DataStorage
Acquisition
(x,y,z)
ji
k
Volume Construction
Engine
Simultaneous Acquisition & Visualization
Dynamic Volume
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Equipment
• Image Guided Technology FlashPoint™ 5000 optical tracking system with 580 mm camera
• Sonosite handheld ultrasound scanner with 5MHz linear probe
• SGI 320 Visual Workstation with a single processor running Windows NT
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Image to Volume Mapping
SSPPTTWW pTTTp
IISS pSp
WWVV pSp
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Calibration Parameters
• 6 extrinsic parameters
– Rotation (Ri , Rj , Rk)
– Translation (ti , tj , tk)
• 2 intrinsic parameters
– Image scale (si , sj)
• Can be written as
jS, v
iS, u
Slice Coordinates
Probe Tracking Device Coordinates
iP jP
kP
v
uj
i
S
PSSPSP
p
ps
s
00
0
0
x
txRx
(Ri , Rj , Rk)(ti , tj , tk)(si , sj)
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Calibration Phantom
Ultrasound Phantom(1/16” Acrylic)
Image of Phantom During Calibration
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Calibration Method
• Obtain feature positions• Align ultrasound probe• Capture US image and probe position• Localize features in image• Calculate calibration parameters
• Scale factor
• Rotation and Translation
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Volume Construction and Maintenance
Insertion of New Slices Removal of
Old Slices
Overwrite Existing Slices
Interpolate with Nearby
Slices
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Results
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Results
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Future Work
• Quantify and improve system performance– Spatial and temporal accuracy
– Data rates
• Display position and trajectory of surgical instruments
• Apply system to clinical situations
Image Guidance Laboratories, Stanford University Image Guidance Laboratories, Stanford University School of MedicineSchool of Medicine
Acknowledgements
• Dr. Thomas Krummel’s lab• DOD Graduate Research Fellowship• CBYON, Inc.