Deformable Registration for Image-Guided Radiation Therapy

Transcription

1 Symposium Multimodality Imaging for Radiotherapy : State of the art, needs and perspectives 1/33 Deformable Registration for Image-Guided Radiation Therapy David Sarrut «Radiation, images, oncology» team («rayonnement, images, oncologie») Radiotherapy department, Centre Léon Bérard Creatis : UMR CNRS 5515 INSERM 630

2 2/33 Plan de l exposé [5 mn] rappel motion pb intra/inter ; sous/sur dosage ; stratégie à l'étude : réduire (contention, aide repo, blocage), quantifier résiduel (4D CT) BH, perso marges, gating, tracking, Adaptive RT conclu : need new imaging tools in TPS, one is def reg [2mn] example de recal : BH (respi) [IJRO2005] [8mn] example CT 4D [2mn] modèle 4D : pourquoi? nécessaire pour dosi 4D (intra/inter) [2mn] Euler/Lagrange [2mn] contour propagation [PMB] [2mn] bertrand's method [Miccai] [4mn] Simulation 4D from 2 BH principle straight line, warp forward mapping, inverse VF, cross dissolve /density [MedPhys] [3mn] Validation, temps calcul [2mn] Persp : controle density jacobian inter subject (F. Maes) [ZmedPhys]

3 3/33 Problem Respiration : motion during irradiation (intra-fraction) Potential consequences : tumour under dosage healthy tissue over dosage Increase dose? increase ballistic control Even more important for hadron (proton, carbon) Current TPS : static situation Future TPS : dynamic intra-fraction inter-fraction

4 4/33 State of the art, needs and perspectives Breath Hold treatment Personalized margins (adapted to motion) Gating treatment Tracking

5 5/33 State of the art, needs and perspectives Breath Hold treatment Personalized margins (adapted to motion) Gating treatment Tracking

6 6/33 State of the art, needs and perspectives Breath Hold treatment Personalized margins (adapted to motion) Gating treatment Tracking tumor Motion

7 7/33 State of the art, needs and perspectives Breath Hold treatment Personalized margins (adapted to motion) Gating treatment Tracking Interesting Interesting for for some some patient patient With With proton proton also also How How to to synchronise synchronise?? QA QA

8 8/33 State of the art, needs and perspectives Breath Hold treatment Personalized margins (adapted to motion) Gating treatment Tracking

9 9/33

10 10/33 State of the art, needs and perspectives Not a single strategy for all patients All strategies need 4D information

11 11/33 State of the art, needs and perspectives Needs : time dimension 4D information acquisition, personalized to each patient 4D model (quantification) 4D dosimetry 4D control 4D adaptive On-line Time : intra-fraction (seconds) inter-fraction (days, weeks...) Planning

12 12/33 State of the art, needs and perspectives Needs : time dimension One key tool is is Deformable Registration

13 13/33 Deformable registration Rigid : translation, rotation... (~ 6/12 parameters) Deformable : deformation, million parameters A Deformable registration B Deformation map Output Input Describe how the image A should be deformed to resemble to B

14 14/33 Deformable registration A vector each 16 mm

15 15/33 Deformable registration A vector each 10 mm

16 16/33 Deformable registration A vector each 5 mm

17 17/33 A vector each 4 mm

18 18/33 Deformable registration : examples Deformable registration in radiation therapy : why? Example 1 : Breath Hold reproducibility assessment Example 2 : 4D breathing thorax model Example 3 : 4D breathing thorax simulation

19 19/33 Example 1 : breath hold reproducibility Data : 3 CT breath-hold with ABC (Elekta) for each patient Reproducibility? Assessed with lung volume measurement and deformable registration Results Results Diff. Diff.lung lungvol. vol.<5% <5% Motion Motion<<4mm 4mm One Onepatient patient Lung Lungvol. vol.==3.9% 3.9% But Butmotion motion>>6mm 6mm!! [Sarrut et al. 2005, IJROBP ]

20 20/33 Example 2 : 4D model Data : 4D CT scan What is a model? Why need a model?

21 21/33 Example 2 : 4D model Data : 4D CT scan What is a model? Why need a model? m e Conventional CT On-board cone-beam CT

22 22/33 Example 2 : 4D model Data : 4D CT scan What is a model? Why need a model? Quantitative Quantitativedescription descriptionofofpoints pointstrajectory trajectory Density change Density change I x, y, z =ρ I x, y, z, t =ρ

23 23/33 Example 2 : 4D model Data : 4D CT scan What is a model? Why need a model? To quantify displacement & deformation To measure hysteresis / ventilation image To propagate contours on each phase To accumulate dose (4D dosimetry)

24 24/33 Example 2 : 4D dose accumulation This is the 4D model Dose end-expiration + Dose mid-expiration reference + = Dose end-inspiration 4D dose map Deformation maps 3D dose map

25 25/33 Example 2 : 4D model Method 1 : [Boldea et al. 2003, 2006] Intensity-based, non-parametric registration method Lagrange vs Euler : equivalent Relatively fast, warning to image artifact Method 2 : [Delhay et al. 2006] Intensity-based, parametric (B-spline) Longer, more robust, temporally regularized 4D adaptive Simple trajectory (straight line) : few parameters Complex trajectory : several parameters

26 26/33 Example 2 : 4D model Lagrange description Euler description

27 27/33 Example 2 : 4D model Reference CT CT10

28 28/33 Validation Errors ~ < 2.5 mm Green points : landmarks manually selected by experts Blue = automated

29 29/33 Computational time Depends on number of voxels (displacement vectors) amplitude of the displacement (number of iterations needed to converge) About 1 second/iteration/1 million vectors (PC, 2Ghz) Whole thorax (45 dm3) Small deformation 1000 iterations Large deformation 4000 iterations 5 mm3 = 0.4 m 3 min 13 min 3 mm3 = 1.6 m 15 min 1 hour

30 30/33 Example 3 : simulation Data : 2 breath-hold CT inspiration/expiration Preprocessing : modify lung density Simulation : deformable registration interpolation (straight line) density with Jacobian Expiration Inspiration [Boldea, Sarrut et al. 2003, 2005, 2006]

31 31/33 Example 3 : simulation [Sarrut et al. Med. Phys. 2006] Simulated 4D images were close to acquired 4D images (~3mm) : 4D image acquisition/reconstruction to be improved

32 32/33 Conclusion Managing time is part of the future TPS Deformable registration is a key tools [Sarrut, ZMed. Phys., Intra-fraction : Contours propagation (from phase to phase) Dynamic dosimetry (4D) On-line control? Inter-fraction Contours propagation (from session to session) Adaptive dosimetry Inter-patient Helped thorax segmentation : atlas 2006]

33 33/33 Future works Validation Public validated patient-based numerical 4D model Open access to research community 4DCT + 4D model + validation data Cone-beam 4D reconstruction needs 4D model Thorax atlas (inter-patient) Dynamic phantom for 4 dosimetry validation (Faster than reality)