Proton Treatment Planning Systems Daniel Yeung

Transcription

1 New Developments in Proton Treatment Planning Systems Daniel Yeung

2 Statement of Disclosure Funded Research & Development: Philips Medical Systems IBA

3 Proton Planning Systems Commercial Systems Academic Systems Analytical/Semi-Analytical CMS - Xio MGH, HCL Varian Eclipse Proton Varian EyePlan Optivus - Odyssey Dosigray Others PSI Clatterbridge Loma Linda Orsay * Under Development Philips Pinnacle* UF* Others Monte Carlo CMS*, Varian*, MGH, DKFZ,

4 Proton Pencil Beam Algorithms Hong et al, MGH 1996 Szymanowski et al, Institut Curie 2001 Beam Model dosimetry in water inhomogeneity correction water equivalent thickness (wet) HU stopping power

5 Proton Pencil Beam Algorithm Beam Model CAX Depth Dose (DD) broad beam pristine peak sobp Radial Spread (RS) multi coloumb scatter beamline: degrader, nozzle elements (wet only) compensator: material dependent scattering gpower patient: wet only gaussian kernel σ 2 = total σ line σ comp σ patient

6 Proton Pencil Beam Algorithm Dose Calculation Dose from a pencil beam Convolve DD with RS for each pencil Sum dose from all pencils

7 Bortfeld Model of Pristine Peak Analytical model of proton BP (up to ~ 200 MeV) accounts for energy spread empirical model of nuclear fragmentation (data fitting) numeric depth dose calculation of fitted BP assumption range straggling constant with depth

8 Pristine Peak - Analytical Model R=21.86 g/cm 2 V 8.0 R= g/cm 2 R=9 9.0 g/cm 2 V 8.1 For R > 15 g/cm 2, Range straggling depth R=19.8 g/cm 2 Error in Bortfeld model Eclipse Model Bortfeld Model

9 Pristine Peak Bortfeld Model R=19.8 g/cm 2 R=28.4 g/cm 2 Bortfeld Model Bortfeld - Enhanced

10 SOBP Calc vs Measurement Courtesy R. Slopsema

11 R=15.1 M=10.4 Beam Profile Calc vs Measurement d=5 mm d=10 cm 20%-8 80% Lateral Penu umbra [cm] d=15 cm 0.3 Option B5 - R=15.1 g/cm^2, M=10.4 g/cm^2, Air gap = 11.7cm, SSD=220.1, aperture: 15cmx15cm Eclipse convolved cm Measurement (av) cm Eclipse convolved cm Measurement (av) cm Eclipse convolved cm Measurement (av) cm Air Gap [cm] Courtesy R. Slopsema

12 Proton Dose Calc in water is generally accurate!

13 ok, what about Clinical Issues? Physics Clinical

14 Match & Patch Fields used to avoid OARs adjacent to target partition target into segments (sub-targets) sub-targets treated with sub-beams angle sub-beams to avoid OARs combined with other fields for dose uniformity

15 Match Fields match fields abutting each other penumbra matching penumbra Inf - LAT Sup - RAO matchline

16 Patch Fields thru beam txt t partial target t residual txt with patch lateral penumbra (t-beam) matched with distal falloff (p-beam) LPO beam (inferior) patched with SPO (superior)

17 Lacrimal Gland Carcinoma partition into sup + inf targets sup PTV 50.4 brainstem inf SPO-patch 50% LPO-Inf (spare optics & BS) PTV50.4: 5fi fields with match h& patch Target Fields PTV LAO LPO PTV(Inf) LPO-Inf PTV(Sup) LAO-match SPO-patch

18 Lacrimal Gland Carcinoma PTV Fields Inf - LPO Sup LAO match Sup SPO patch LPO LAO

19 Patch Field Selection Patch Field Angle Selection optimal geometric coverage (G = 230 ) avoid inhomogeneity along path (G = 205 ) Patch line Patch line Gantry 230 Gantry 205

20 Patch Field Beam Angle Selection Gantry 230 Gantry 205 G=230 G=205

21 Distal Blocking selective pullback of range to spare OARs pullback achieved with added compensator potential pitfalls setup error or motion may nullify sparing simple distal blocking may compromise target coverage assess robustness of approach

22 Distal Blocking added compensator Target distal block OAR range pullback

23 Distal Blocking underdose Whole BS Partial BS PTV BS RPO Field Partial BS

24 Clinical Tools It Integrate t Clinical Clii lworkflow clinical database web-based applications mu model physics qa plan evaluation quality assurance clinical efficiency & efficacy

25 Plan/Dvh Evaluation Courtesy R. Malyapa, C.McKenzie, Z. Li Dvh statistics for CTV, PTV, OARs are extracted manually from plots

26 Treatment Plans Plan, Dose, ROI Information TPS RT-PACS Clinical Information Server Active Forms Physics Q/A Forms Plan Contouring DVH Prescription SharePoint Server Clinicians Tx. Delivery Electronic Q/A Process: Upon export of tx plan to RT-PACS, clinical Q/A forms are generated. Active forms are sent via to the personnel on the list. Contents of active forms is stored in a Clinical Information Database. Courtesy V. Frouhar

27 Electronic Q/A Process: Upon expert of treatment plan to RT-PACS, appropriate clinical Q/A forms are generated. Active forms are sent via to the personnel on the list. Contents of active forms is stored in a Clinical Information Database.

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30 Integration of Clinical Workflow Patient Information R&V HIS External Connectivity Physics Calc. RX Delivery Setup Quality Assurance Clinical Data Management & Workflow Machine Data IGRT Linac TPS CT Sim PET/MR Physician Clinical Information Physicist Dosimetrist Therapist

31 Golden Beam Data TPS commissioning time consuming share beam data among gantries (institutions)? tut s)? golden beam data set accuracy requirements on modeling parameters pristine depth dose & sobp effective source size virtual sad effective sad

32 Golden Beam Data max error in penumbra of ±0.5mm in air, at isocenter Courtesy R. Slopsema

33 Golden Beam Data

34 Summary Analytical Proton Algorithms provide accurate dose model Proton specific clinical planning issues requires vigilance Dose plan is a snap shot of dose distribution Dose delivered depends on uncertainties in range, setup, organ motion, etc. Select beams and parameters to minimize uncertainties Tools to integrate clinical workflow are essential Golden beam data looks feasible

35 Thanks!