Initial Experience with a Commercial System for Volumetric Analysis of Patient Specific QA. Katja Langen Mariana Guerrero Shifeng Chen Shh..

Transcription

1 Initial Experience with a Commercial System for Volumetric Analysis of Patient Specific QA Katja Langen Mariana Guerrero Shifeng Chen Shh..Mobius3D

2 ACKOWLEDGEMENTS Dr. Katja Langen Dr. Shifeng Chen Dr. Baoshe Zhang Morgan Killefer (summer student) Dr. Huijun Xu (Physics resident) Dr. Chaitanya Kalavagunta Kalin Shipman (dosimetrist)

3 No conflict of interest. Disclaimer

4 What will I say? Mobius 3D for photon beams Current Status of Patient Specific QA at University of Maryland and why we want to change. Summary of Mobius 3D Commissioning. Our recommendation for clinical use: current status Overview of software features and challenges.

5 What will I NOT say? MobiusFX and Mobius Doselab modules Electron calcs (will work on this next),10mv not commissioned

6 Patients specific QA at UMD 3D conformal -Old fashioned Point dose hand-calc: - Simple formula with data book parameters - Issues with point location - Issues with heterogeneity corrections. - No DICOM transfer: have to type-in - In-house software: work to support

7 Patients specific QA at UMD IMRT-VMAT-SBRT -NO MORE MEASUREMENTS: In-house 3D Monte Carlo Calc on CIRS phantom + extensive weekly and monthly MLC QA. -Beam parameter comparison between planning and R&V system -Beam by Beam point dose -3D isodose comparison with Gamma analysis (3%3mm, >95% passing rate)

8 Patients specific QA at UMD IMRT-VMAT-SBRT -VERY NICE SOFTWARE BUT : -Only commissioned for 6MV. -Requires In-house support to fix problems. -Time consuming in order to add features (other energies, FFF, etc) -Goal: use Mobius3D for both 3D conformal and IMRT, VMAT and SBRT.

9 Mobius 3D Game changer in patient specific QA -Biggest asset: designed to give full 3D dose information (point dose an afterthought) -DVH comparison -Mean target doses -Gamma analysis -RTOG criteria for ROIs -Delivery time -Deliverability -Biggest liability: designed to give full 3D dose information (point dose an afterthought) We have to think differently about our second calcs!

10 Mobius 3D Commissioning: Overview TPS: Eclipse and Raystation Hallelujah! Mobius 3D comes commissioned. -Commissioning tests were done to validate the model. I - Configuration (PDDs, OF and OAR) II - Quick calcs test for TMRs and OFs. III- Phantom Plans (TPS vs Mobius vs Measurement) IV-Patient Plans Mobius recommends to keep the model as is unless large differences are seen -Small changes were made to certain output factors and the MLC dose-leaf-gap for 18MV.

11 Commissioning I Beam Configuration Parameter comparison Example: Raystation 6MV 6MV, 15MV and 18MV Compare Mobius configuration with Eclipse and Raystation configuration Excellent agreement for all energies mostly <2% except 1x1 OF Measured in phantom

12 Commissioning I Beam Configuration Parameter Summary Photon pdds agree mostly within <1-2% for both planning systems OARs and OF agree also within 1-2% for both planning systems except 1x1 field (small discrepancies in 6MV and 15MV beam were resolved by changing OF in Mobius for small field sizes)

13 Commissioning II Spot check of TMR and OF open fields with quick-calc Good Results!

14 Commissioning III Phantom test plans and measurements (Morgan Killefer and Dr. Huijun Xu s work) Made simple to complex phantom plans (12 in total) 11 plans in CIRS phantom: single beam, 4-field box, single beam 2 by2 cm, Off axis, Tangent, EDW, Conformal MLC 2field plan, Complex 1 field MLC plan, IMRT low modulation, IMRT high modulation, VMAT. 1 field in Cork phantom plan Made each plan in 2 TPS (Eclipse and RayStation), for 3 beam energies (6,15, and 18X) Compare TPS vs Mobius: -TPS 3D dose comparison with Gamma analysis -Mobius mean ion chamber dose versus TPS mean ion chamber dose vs ion chamber measured

15 Commissioning III Changes made to configuration based on results (Morgan and Huijun s work) Changed 18MV output (have to request this to Mobius) (100MU dose at 10cm for 10x10 field at 100SSD reduced by about 1%) Change two small fields (1x1 and 2x2) output factors for 15MV Change small fields (1x1 to 5x5) output factors for 6MV Slight change to the MLC dynamic leaf gap for 18MV

16 Commissioning III 3D plans compared to TPS look good

17 Commissioning III MLC, IMRT, VMAT compared to TPS

18 Commissioning III Nothing is perfect Build-up issue (high energies) Heterogeneity corrections a problem VMAT for 15X and 18X not that great (but we don t use them)

19 Commissioning IV Plan comparisons Raystation and Eclipse Using adjusted Mobius model and Mobius version Exported several RayStation plans to Mobius. Exported RapidArc plans and 3D plan from Eclipse

20 Commissioning IV Plan comparisons Eclipse- 3D conformal- IMRTplans -Point doses pretty good -Gammas 3%3mm fails for 15MV with heterogeneity corrections, may need 5%3mm as recommended by Mobius.

21 Commissioning IV Plan comparisons Eclipse- Rapidarc plans

22 Commissioning IV Mean target dose - Raystation 3D VMAT Mixed IMRT SF_IMRT all 6X except those in circles: -Red: (18/15X) -Green: Mixed energy Mean target doses show excellent agreement with TPS

23 Commissioning IVb Point dose (max of any beam)- Raystation SF=SPLIT FILED 3D VMAT Mixed IMRT SF-IMRT more 3D (not all had 3D plans had target Contours) SF-IMRT, same point dose for all fields, average among beams point dose in Air

24 Commissioning IVb Point dose (max of any beam)- Raystation in air in gradient -6.8% Be mindful of where the calc point is!!!

25 Commissioning IVb Point dose (max of any beam)- Raystation 3D VMAT Mixed IMRT SF-IMRT more 3D (not all had 3D plans had target contours SF-IMRT, same point dose for all fields point dose in gradient

26 in gradient 6.1% is max 2.3% abs mean 0.8% average Commissioning IVb Point dose (max of any beam)- Raystation

27 Commissioning IVb Gamma pass rate at 3%/3 mm-raystation 3D mixed IMRT SF-IMRT VMAT IMRT-VMAT great! Issue with 3D plans WBRT/partial brain

28 Commissioning IVb WBRT gamma issue - Raystation Cold in skull Needs 5%/3mm gamma criteria to get pass rate >95%

29 3.2 % mean target dose difference Commissioning IVb Lung, 3D, 18 X- Raystation

30 Commissioning IVb Lung, 3D, 18 X- Raystation 2% max point dose difference

31 Commissioning IVb Lung, 3D, 18 X- Raystation 3%/3 mm gamma fail 5%/3mm gamma is 95.4

32 Recommendations for clinical use for 3D Report point dose

33 Recommendations for clinical use for 3D DVH plot Target coverage stats

34 Recommendations for clinical use for 3D ROI overview

35 Recommendations for clinical use for 3D Delivery time?

36 Recommendations for clinical use for 3D Gamma pass rate?

37 Recommendations for clinical use for 3D Now Report point dose With Mobius Report point dose DVH plot (just show) Target coverage stats (within 3%) ROI overview Gamma pass rate? Delivery time? RTOG criteria?

38 Recommendations for clinical use for IMRT-SBRT-VMAT With Mobius Report point dose Gamma passing rate DVH plot (just show) Target coverage stats (within 3%) ROI overview BUT. Not READY because no plan parameter comparison!!!! We are working on a workaround!

39 Known problems/features with Mobius If target DVH has soft shoulder! -5.6 %

40 Known problems/features with Mobius If target DVH has soft shoulder! PTV1 is partially in air Reason for soft shoulder in plan See differences for doses in air between Mobius and TPS

41 Known problems/features with Mobius May not recognize target as target!

42 Known problems/features with Mobius Manually change classification

43 Known problems/features with Mobius Recalculate plan -takes 5-10 minutes

44 Known problems/features with Mobius Checks for Stray Voxels - issues Alert!

45 ? Thank you!