RTTs role in lung SABR

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Darcy Terence Lyons
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1 RTTs role in lung SABR Bart van Baaren Lineke van der Weide VU Medical Centre SBRT symposium VUMC 16 December 2017

2 Flow chart lung SABR Pre-treatment imaging Treatment planning On-line imaging Treatment delivery

Pre-imaging: 4D CT Respiratory motion causes artifacts during 3D CT Errors in position, shape and volume information for the target volume and critical structures Respiratory motion

3 Pre-imaging: 4D CT Respiratory motion causes artifacts during 3D CT Errors in position, shape and volume information for the target volume and critical structures Respiratory motion may significantly influence the accuracy and reproducibility of SABR 4D CT reduces the motion artifact and allows for accurate delineation of tumor and critical structures 4D-CT 3D-CT

4 4D CT: Retrospective gating Full breathing cycle Breathing Signal Inspiration Expiration X-ray on 1 e table position 2 de table position 3 e table position 4D CT sorting program 1e fase bin 2e fase bin 3e fase bin

5 4D CT

6 4D CT

7 4D CT

8 Average-IP / MIP Each voxel has a certain intensity (Hounsfield Unit) Intensity voxels in lung vary over respiratory cycle (10 bins) Reconstruction can be made from the 10 bins Ave-IP calculates average intensity Max-IP or MIP calculates maximum intensity

9 Average-IP / MIP Average Intensity Projection Maximum Intensity Projection

10 4D CT artifact

11 A bad example Artifacts due to variations in: Amplitude Frequency

12 4D CT protocol for lung SABR 4DCT scan of whole thorax during (uncoached) breathing Head first supine positioned on thorax support with arms up Strong irregular breathing Small" 4DCT (limited to the tumor region Central tumors a second Small" 4DCT with IV contrast Note : the "small" 4DCT series must have sufficient length to match well with the "big" 4D CT.

13 Flow chart lung SABR Pre-treatment imaging Treatment planning On-line imaging Treatment delivery

14 Dose prescription

15 Planning: Contouring On the Average-IP Target: ITV = GTV+tumor motion (MIP) PTV= ITV+5mm OAR: Spinal canal Esophagus (4D) Plexus brachialis Lungs Skin Ribs PRV: + Spinal Canal+3mm + Esophagus+3mm + Plexus br.+3mm

16 MIP: ITV = GTV+resp.motion ITV in MIP

17 Contouring: PTV PTV= ITV+ 5MM

18 Contouring: body + matras Mattress in body contour

19 Contouring: virtual table Virtual Table

20 Contouring: Lungs LUNGS

21 Contouring: Ribs RIBS

22 Contouring: Spinal canal Spinal canal

23 Contouring: Ring RING

24 Contouring: Skin SKIN

25 Planning Beam settings: 2 full arcs (CW and CCW) with avoidance sector or 2 partial arcs Collimator 40 and 45 Energies: o Novalis TX 6X-SRS (1000 MU/min) o TrueBeam 10X-FFF (2400 MU/min) Isocentre middle of PTV

26 Planning: Partial arc Partial arcs Avoidance area Isocentre

27 Planning: Partial arc Avoidance area Isocentre Partial arcs

28 Planning: VMAT Optimization RapidArc PRO optimization algorithm PTV ITV Lung Contra.lat Spinal canal oesophagus

29 Planning: Dose calculation Acuros XB o grid size 0.25 cm default o grid size 0.1 cm overlap with OAR

30 Planning: Final Dose

31 Constraints 100% isodose (prescription dose) covers 95% of the PTV Max dose between 110% -140% of prescription dose Dose to ribs ALARA (preferably < 50% of dose) Total lung V20 < 5-8% Contralateral lung save as much as possible

32 Flow chart lung SABR Pre-treatment imaging Treatment planning On-line imaging Treatment delivery

33 Patient positioning Posirest lung board Knee support External reference lines and tattoos

34 Lung-protocol TrueBeam Novalis TX PTV match with CBCT Irradiation Arc 1 PTV match with CBCT (1st fraction) Irradiation Arc 2 Intrafraction monitoring through Real-time Positioning Management (RPM) (Bone match with ET) PTV match with CBCT Irradiation Arc 1 and 2 Intrafraction monitoring through ExacTrac (ET)

35 Post-treatment CBCT, SBRT lung 140 fractions (32 patients) Mean translation (±SD): 0.7 ± 1.4 mm (vertical), 0.7 ± 1.3 mm (longitudinal) +0.2 ± 1.2 mm (lateral) 3D vector: 2.1 ± 1.2 mm. Mean delivery time on TrueBeam with FFF was 4.4 ± 3.4 min (mean beam-on 1.9 ± 0.4 min) Radiother Oncol Jun;107(3): doi: /j.radonc Epub 2013 May 23. Frameless high dose rate stereotactic lung radiotherapy: intrafraction tumor position and delivery time. Peguret N1, Dahele M,

36 TrueBeam OBI 6D Couch EPID

37 TrueBeam CBCT match

38 6D-couch 55-yr old patient Multiple lesions left lung 2 lesions in 1 PTV 8 x 7,5 Gy

39 Deep Inspiration Breath Hold (DIBH) 46-yr old patient 4 lesions in lung 1 lesion close to diaphragm Tumorshift on planning-ct >3cm

40 Deep Inspiration Breath Hold (DIBH)

41 CT, Lung case

42 CBCT, Lung case

43 New plan, lung case

44 Novalis Tx, ExacTrac (ET)

45 ET Extra-cranial positioning

46 Pre-positioning Novalis TX

47 Tx CBCT match

48 Flow chart lung SABR Pre-treatment imaging Treatment planning On-line imaging Treatment delivery

49 TrueBeam RPM RPM OBI 6D Couch EPID

50 Monitoring TrueBeam 4DCT TrueBeam

51 TrueBeam FFF Treatment

52 Monitoring ExacTrac markers

53 Questions?

Which Planning CT Should be Used for Lung SBRT? Ping Xia, Ph.D. Head of Medical Physics in Radiation Oncology Cleveland Clinic

Which Planning CT Should be Used for Lung SBRT? Ping Xia, Ph.D. Head of Medical Physics in Radiation Oncology Cleveland Clinic Outline Image quality and image dose Free breathing CT, 4DCT, and synthetic