Copyright © Gabor Fichtinger, 2008 Laboratory for Percutaneous Surgery – The Perk Lab Fluoroscopy and CT Fluoroscopy and CT Imaging Imaging
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Fluoroscopy and CTFluoroscopy and CTImagingImaging
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
3D coordinate space3D coordinate space
Source-1 Source-2
X-ray film-1
X-ray coordsystem
Film-1 coordsystem
Film-2 coordsystem
X-ray film-2
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Edison in his fluoroscope, 1896Edison in his fluoroscope, 1896
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
The first commercial fluoroscopeThe first commercial fluoroscope
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
XX--ray + Television = Fluoroscopyray + Television = Fluoroscopy
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
XX--ray image intensifier tuberay image intensifier tube
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Siemens
C-arm fluoroscopy
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Fluoroscopy images
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Biplane fluoroscopy
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
• Mobile• Real-time• Inexpensive• Good bone contrast• Broad insurance coverage
• Poor soft tissue contrast• Limited rotation• Limited field of view (9-15”)• Often non-isocentric• Object truncation• High X-ray dose to all parties• Need for calibration• Poor/no joint encoding• Image warping• Loss of depth & volume
Siemens
Pros and Cons for C-arm in Surgery
LL
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Calibration = determine unknown constant Calibration = determine unknown constant parametersparameters
target
SADSDD
Beam central
Field of View (FOV)
Detector plane
X-ray source
image
Pixel size
x
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Typical calibration: Typical calibration: shoot images from various shoot images from various angles of a known object and calculate unknown Cangles of a known object and calculate unknown C--arm arm
parametersparameters
The calibration fixture:• A priori known• Precisely machined• Asymmetric• Easy to pick feature points
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Image warpingImage warping
Courtesy of Yao & Taylor
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Dewarping stepDewarping step--1: Find groove points1: Find groove points
•Find image points corresponding to the centerline of each vertical and horizontal groove
Courtesy of Yao & Taylor
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Dewarping stepDewarping step--2 : Fit 52 : Fit 5’’th order th order Bernstein Polynomial CurvesBernstein Polynomial Curves
•Fit a least square smooth curve to each vertical and horizontal groove
•5’th order Bernstein Polynomial
( ) ( )∑=
−−⎟⎟⎠
⎞⎜⎜⎝
⎛=
5
0
550 1
5;,,
k
kkk vv
kavaaB K
Courtesy of Yao & Taylor
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Dewarping stepDewarping step--3 : Unbend the plate3 : Unbend the plate’’s s imageimage
• Unbend the Bersteinpolynomial to straight lines
• Employ a two pass scan line algorithm to dewarp the image with using bilinear interpolation
Courtesy of Yao & Taylor
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Full sweep cone beamFull sweep cone beam
• May give perfect volume• Lots of shots• Lots of dose to patient• Ever faster on computer• Possible in realtime
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Cone beam CT reconstruction examplesCone beam CT reconstruction examples
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Concept of Computed Tomography (CT)Concept of Computed Tomography (CT)
Type1
Type2
Planar fan beam
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Beam configurationsBeam configurations
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Spiral CTSpiral CT
Spiral path with 4,8,16,32,64, 128, 256 rows
Scan Examples: Scan Examples: http://www.radiology.uiowa.edu/3d/http://www.radiology.uiowa.edu/3d/
SINGLE SLICE SPIRAL MULTISLICE SPIRAL
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
CT scannersCT scanners
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Examples to CT imagingExamples to CT imaging
Copyright © Gabor Fichtinger, 2008Laboratory for Percutaneous Surgery – The Perk Lab
Measuring in CT imageMeasuring in CT image
Slice thickness
543210
Slice index
Field of view X
pixe
l Y
pixel X
Field of view X