Brain Tumor Radiosurgery. Gabor Fichtinger, PhD

Transcription

1 Brain Tumor Radiosurgery Gabor Fichtinger, PhD

2 Surgical CAD/CAM Preoperative Computerassisted planning Surgical Intraoperative Update Model Update Plan Surgical CAD CAM Patient-specific Model Computer- Assisted Assessment Computer- Assisted Execution Patient Atlas Surgical TQM Postoperative

3 Brain tumors The leading cause of death from childhood cancers among persons up to 19y The second leading cause of cancer-related deaths in males ages The fifth leading cause of cancer-related deaths in women ages Primary brain tumors generally do not metastasize to other parts of the body Total new cases of brain/cns tumors (malignant and non-malignant): 200,000 metastatic 43,800 primary They occur in 10-15% of people with cancer Brain is usually the final metastatic site Primary brain tumors generally do not metastasize to other parts of the body

4 Brain tumors Some are lethally aggressive (glioblastoma multiforme)

5 Brain tumors Some are small and inoperable Metastatic lung Metastatic melanoma Acoustic neuroma (benign)

6 Radiosurgery Blasting out tumors with high energy (25 MeV) X-ray

7 Medical linear accelerator

8 Linear accelerator Linear accelerator (LINAC) for electrons. A klystron (B) connected to a waveguide (C) generates traveling microwaves in the evacuated accelerator tube (D). Electrons are injected in bunches by source (A) and are accelerated by the traveling microwaves. The pulsed electron beam is spread by a scanning coil (E), exits through a thin window (F) and irradiates the target (G). (Adapted from O Donnell and Sangster.)

9 Isocentric beams

10 Radiosurgery CAD/CAM CAD CAM IMAGE MODEL PLAN REGISTER EXECUTE TQM FOLLOW UP

11 Radiosurgery CAD/CAM CAD CAM IMAGE MODEL PLAN REGISTER EXECUTE TQM FOLLOW UP

12 Base ring attachment

13 Head frame attached to base ring Graphite screws Base ring Fiducial cage

14 Repeatable head frame

15 Linac calibrated to base ring F LC

16 Head frame to image registration P1 P2 P7 P6 P3 P4 P5 Rods intersect with the CT plane Find the same triangle in image and cage Triangle defines orthonormal base F CI transformation from cage to image Linac has been calibrated to cage: F LC Robot-to-Image transformation: F LI = F LC F CI Closed form computation for L 2 P 2 found in cage coordinates Repeat for P 4 and P 6 We obtained (P 2 P 4 P 6 ) triangle F LI from single image slice Fast and robust Accuracy sub-mm & sub -degree P 1 P 2 = d 12 P 1 P 2 L d 23 = P 2 P 3 P 3 Image plane

17 CT imaging

18 Computed tomography (CT)

19 Radiosurgery CAD/CAM CAD CAM IMAGE MODEL PLAN REGISTER EXECUTE TQM FOLLOW UP

20 Segmentation

21 3D Reconstruction

22 3D Reconstruction

23 3D Reconstruction

24 3D Reconstruction

25 3D Reconstruction

26 Data fusion

27 3D Target visualization

28 Target volume in CT and MRI

29 Radiosurgery CAD/CAM CAD CAM IMAGE MODEL PLAN REGISTER EXECUTE TQM FOLLOW UP

30 Arc / beam design

31 Thick pencil beams

32 Dose from two isocenters

33 Beam collimation

34 Multi-leaf collimation Plan MLC unit, add-on to the LINAC

35 BrainLab SRS

36 Beam s eye view

37 Dose Absorption Function Dose absorption in tissue as beam penetrates The normalized function is called tissue max ratio D(d) = D 0 *DAF (d) DAF(d) Depth dose absorption profile d

38 Radial Dose Function Dose drops as we go away from beam center, mainly due to leakage around collimator edge (a.k.a. penumbra effect) D(d,r) = D 0 DAF(d) *RDF (r) Beam s cross section d r Radial dose function RDF(r) Non-flat beam 1.0 Leak Distance from beam ctr r

39 Point dose from all beams Dose in point P i from all n beams n Point dose: D i = j=1 D(dij,rij) Beam j d ij rij P i

40 3D dose matrix computation Put 3D matrix of grid points around isocenter. Cover the organs of interest. Be sensible in selecting number of points and voxel size. Compute point dose in each matrix point receive the dose matrix Beam j d ij rij P i

41 3D dose coverage

42 2D dose overlay on CT

43 Dose volume histogram (DVH)

44 BrainLab SRS

45 Inverse planning Acquire images Make 3D model Set dosimetric objectives Set constraints Set plan parameters Compute dose Analyze dose Compare to objectives Adjust plan parameters Cost function Evolutionary optimizer Satisfactory? Treat

46 Radiosurgery CAD/CAM CAD CAM IMAGE MODEL PLAN REGISTER EXECUTE TQM FOLLOW UP

47 Register plan to linac

48 Winston-Lutz QA test

49 Radiosurgery CAD/CAM CAD CAM IMAGE MODEL PLAN REGISTER EXECUTE TQM FOLLOW UP

50 Dry run first!

51 Radiosurgery CAD/CAM CAD CAM IMAGE MODEL PLAN REGISTER EXECUTE TQM FOLLOW UP

52 Follow-up CT in 20 days

53 Cyber Knife linac on serial robot

54 Gamma Knife

55 Thank You! Perk Lab: