sps 4d imaging - uclouvain · denoising (bilateralfiltering) 2. inversion of psf using iterative...
TRANSCRIPT
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On the use of 4D imaging
in cancer treatmentin cancer treatment
Guillaume Janssens
October 2011
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Radiotherapy
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Radiotherapy planning is a balistic problem
TOO
LS
SURGERY RADIOTHERAPYTO
OL
STA
RG
ET
TARGET VOLUMES ???
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Different image modalities emphasize different
biological properties for defining target regions
CT vs macro
PET vs macro
macroscopy
CT imaging
PET imaging
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CT scan
Set of 1D X-ray projections (sinogram)
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CT scan
Set of 1D X-ray projections (sinogram)
2D slices reconstruction
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CT scan
3D image
(set of 2D slices)
2D slices reconstruction
Set of 1D X-ray projections (sinogram)
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Anatomy is easily identifyable on CT
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PET scan
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PET scan
� Different tracers for different
biological properties (metabolism,
hypoxia, …)
� Reconstruction based on statistics
(coincident events)
� Poor SNR (trade-off between
resolution and noise)
� SNR increases with acquisition
duration
� Point spread function (blurring by
convolution)
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Once anatomical target has been delineated, highly-
resistant regions can be segmented using PET
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Automatic segmentation of radio-resistant regions in
PET images
Metabolical image (FDG - PET)
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1. Noise reduction using bilateral filtering (edge-
preserving smoothing)
Denoising (bilateral filtering)
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2. Inversion of PSF using iterative constrained
deconvolution
« Sharpness » enhancement (deconvolution)
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3. Gradient extraction
Gradient image
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4. Watersheds and clustering
Segmentation (watersheds + clustering)
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Target volumes for planning
Target tumor volume and radio-resistant « boost » region
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3D target volume delineation workflow
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Dose planning
X-Ray dose that is planned to be delivered (tumor + boost region)
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Slow CT scans can be divided into 3D phases
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Slow CT scans can be divided into 3D phases
RCCT
(set of ten 3D images)
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Slow CT scans can be divided into 3D phases
RCCT
(set of ten 3D images)
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Breathing motion can be estimated using image
registration
RCCT
(set of ten 3D images)
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A mid-position CT can also be reconstructed
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Long PET scans can also be divided into phases
RCPET
(set of ten 3D images)
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PET scan
RCPET
(set of ten 3D images)
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Breathing motion estimation from CT can be used for
correcting PET images
Corrected PET image
PET-CT fusion
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3D target volume delineation workflow
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4D target volume delineation workflow
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Validation of 4D
treatment delivery
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Planned dose on Planned dose on
each phase
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Planned dose on Planned dose on
each phase
Delivered dose
reference phase
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Delivered vs Planned dose