Computational Verification in Interventional Radiation Oncology (Brachytherapy)

Transcription

1 Computational Verification in Interventional Radiation Oncology (Brachytherapy) Prof. Dr. Dimos Baltas Abteilung Medizinische Physik & Engineering Strahlenklinik Brussels, 5- December Starkenburgring Offenbach

2 Modern Brachytherapy: Treatment Verification An Example Delivered Treatment versus Planned Treatment CT-Verification I CT-Verification II CT-Planning

3 Modern Brachytherapy: Treatment Verification An Example Delivered Treatment versus Planned Treatment Assuming that: The geometry and location of the implanted catheters The connection of channels to implanted catheters The length of the channels The source movement patterns (dwell positions and dwell times) within the implanted catheters are during treatment delivery exact as considered and planned in the RTP.

4 BRT versus ERT Similarities and Differences The Field / Beam: 2 ERT 1 BRT 3

5 BRT versus ERT Similarities and Differences Dose Shaping: Intensity Modulation (2D) MSS: Step & Shoot ERT BRT Bixel Dwell Position MUs Dwell Time

6 BRT versus ERT Similarities and Differences Beam Shaping: Plane Field Catheter/Needle/Applicator MLC 2.5 mm or 5.0 mm or 10.0 mm MSS 1.0 mm 2.5 mm 5.0 mm 10.0 mm?? mm ERT BRT

7 BRT versus ERT Similarities and Differences Dosimetric Kernel Particles (Spot) Delivery Technology IMRT (X, P) (Modulation, Dose-Volume-Prescriptions ) Dose Distribution SRS / SBRT (Inhomogeneity)

8 BRT versus ERT Similarities and Differences 10% 10% 50% 30% 30% SRS 100% 110% 50% BRT 125%

9 BRT versus ERT Similarities and Differences The Localization Process 3D-Localization of the relevant Anatomy (as in ERT) 3D-Localization of the implanted catheters (Beams) Co-Registration of Anatomy and implanted catheters

10 BRT versus ERT Similarities and Differences Beam Delivery System in BRT Beam = Catheter/Needle/Applicator MLC Settings = Source moving patterns within applicator Monitor Units = Dwell Times Thus beams become for BRT patient-dependent parameters, that requires 3D reconstruction (Localization: Imaging, ) and registration to anatomy

11 BRT versus ERT Similarities and Differences Verification We mean the process of proof that we deliver the dose we planned to the tissue (3D) within a specific accuracy and precision level. BRT (HDR) In opposite to ERT our dose delivery system (stepping source within implanted catheters) depends on the specific patient implant geometry (anatomy). This is not the case for ERT, where the performance of the dose delivery system (MLC, Dose Rate, Energy, Gantry Angle, Collimator Angle & Couch Settings) is independent of the specific patient.

12 Where are we today in ERT? Verification of individual RT-Plan via 2D/3D measurements: RTP(Phantom) + Machine as an Off-Line Pre-Treatment-Procedure Dose Reconstruction in Patient Anatomy utilising Off-Line 3D-measurements: RTP + Machine 3D-Dose Verification in Patient-customized Phantom Off-Line 3D-measurement: RTP + Machine + Set-Up Real-Time Fluence Measurement during Treatment and Dose Reconstruction Starkenburgring Offenbach

13 Example of a PCA-IMRT Offline Pre-Treatment Procedure: RTP(Phantom) + Machine 15 Starkenburgring Offenbach

14 Example of a PCA-IMRT Offline Pre-Treatment Procedure: RTP(Phantom) + Machine RTP: Automatic transfer to phantom geometry OCTAVIUS by PTW RTP Meas. Compare Gamma-3D Fluences / Intensity Maps Decision VeriSoft by PTW 16 Starkenburgring Offenbach

15 Example of Dose Reconstruction in Patient Anatomy utilising Off-Line 3D-measurements: RTP + Machine 17 Starkenburgring Offenbach

16 Example of Dose Reconstruction in Patient Anatomy utilising Off-Line 3D-measurements: RTP + Machine 18 Starkenburgring Offenbach

17 Example of Real-Time Fluence Measurement during Treatment and Dose Reconstruction: RTP + Machine + Set-Up + Patient DAVID by PTW 19 Starkenburgring Offenbach

18 Example of Real-Time Fluence Measurement during Treatment and Dose Reconstruction: RTP + Machine + Set-Up + Patient DAVID by PTW delivered RTP CT CBCT RTP Delivered DVHs 20 Starkenburgring Offenbach

19 Example of Anatomy (Target) based Verification of Positioning: Patient (PTV) + Machine + Set-Up +... (Targeting) DRR MIP EPID 21 Starkenburgring Offenbach

20 BRT versus ERT Similarities and Differences The Verification Process What is the DRR in BRT? What is the BEV in BRT? What is the EPID in BRT? What is the Fiducial in BRT? What is the measurable Beam Fluence in BRT? What is the Fingerprint of a Beam-Delivery in BRT? What is the individual plan verification process in BRT????

21 BRT versus ERT Similarities and Differences The Verification Process The majority of those tools and/or processes are not defined at all or are not implemented or are not part of the current clinical treatment planning and treatment delivery procedure (RTP)!

22 A general Concept of Verification in BRT: Computational Verification CoVer Dose Planned = Dose Delivered? can not completely be answered w/o incorporating in-situ imaging and 3D-localization techniques! If the performance of our BRT-MLC, thus the correct stepping with the correct dwell time pattern (fluence) at the correct geometrical configuration (the analogue of Gantry, Collimator, Couch Set- Up) is the appropriate (planned) can be most probably answered by applying Computational Techniques. Computational, since in BRT we have to compute firstly and on the top issues similar to a DRR, an EPID, or a Fluence profile (the Finger-Print?), which currently are not part of our standard RTP-procedure (as it is the case in ERT-RTP-Process).

23 A general Concept of Verification in BRT: Computational Verification CoVer The CoVer-Process Compute / Pre-Calculate Estimate - Define Acquire / Measure Compute Predict Compare Estimate Decide Live Process (real-time) during BRT-delivery Off-Line Process

24 A general Concept of Verification in BRT: Computational Verification CoVer (1) Compute Dose-Volume Parameters (DVHs) under consideration of uncertainties:» Implant-specific» Treatment Device-specific» Dosimetry-specific»??? (1a) Compute Dose-Volume Parameters (DVHs) under consideration of» specific possible/expectable/predictable alterations (errors?)

25 A general Concept of Verification in BRT: Computational Verification CoVer (2) Compute time-resolved information (dose-rate, dose, etc..) that can be considered as the reference information for an on-line (in-vivo) verification process. This could be the analogon to DRR or fluence profile in ERT and could be considered as the Finger-Print of the treatment delivery (?). per channel / catheter Whole treatment plan Including Uncertainties» Implant-specific» Treatment Device-specific» Dosimetry-specific»???

26 A general Concept of Verification in BRT: Computational Verification CoVer (2a) Where to be computed? Single position versus Multiple Positions 1D-Array 2D-Array??? (2b) How to be computed? Whole Treatment Plan Dedicated Verification Plan Time-resolved Channel & Dwell Position resolved???

27 A general Concept of Verification in BRT: Computational Verification CoVer (3) Map firstly Computed to Measurable Treatment-Finger-Print, e.g. time- and/or channel/adpresolved Dose or Dose Rate (3a) To be computed considering Measuring System / Detector System characteristics» Volume effect/response» Directional response» Energy response (distance)» Temperature Response»???

28 A general Concept of Verification in BRT: Computational Verification CoVer (3) Map firstly Computed to Measurable Treatment-Finger-Print, e.g. time- and/or channel/adpresolved Dose or Dose Rate (3b) To be computed considering Measuring System / Detector System related uncertainties» Geometrical (localization)» Response / dosimetric»???

29 A general Concept of Verification in BRT: Computational Verification CoVer (4) Map Computed Measurable to Measured Treatment-Finger-Print, e.g. time- and/or channel/adpresolved Dose or Dose Rate Consideration of actual performance of the measuring system/device Update of localization??? (5) Dedicated tools for (live and off-line): Pattern-analysis (e.g. AEDA*) Prediction Decision alert generation and interfacing *Kertzscher et al., 2014

30 A general Concept of Verification in BRT: Computational Verification CoVer CoVer: Open Issues - Work in Progress Interface to Afterloading device - Synchronization of time-axis - Triggering - Synchronization of system-status - Interlock-Interface -??? Interface to Detectors / Detector Systems Does it matter which Detector? Real-Time Evaluation, Prediction and Decision Tool

31 Treatment Delivery Verification: 4D Imaging +δvois + δbeams Time Period between: Plan & Delivery During Delivery +δdose

32 A general Concept of Verification in BRT: Computational Verification CoVer +δvois + δbeams + δfluence