NOVEL SOFTWARE MODULES FOR TREATMENT PLANNING OF 106 RU EYE PLAQUE BRACHYTHERAPY

Transcription

1 NOVEL SOFTWARE MODULES FOR TREATMENT PLANNING OF 106 RU EYE PLAQUE BRACHYTHERAPY Gerd Heilemann, Lukas Fetty, Matthias Blaickner, Nicole Nesvacil, R. Dunavölgyi, and Dietmar Georg ESTRO 35 Forum 29 April - 03 May 2016, Turin

2 2 Treatment planning aspects 106 Ru treatment planning: Good local control, rel. low morbidity Current practice in planning: BEBIG eyephysics (Mac only) 1D depth dose based Shortcomings/limitations -> motivated development of software modules Goal: in-house software tool for treatment planning (+ tool for pro- /retrospective studies) BEBIG Plaque Simulator

3 3 The 3D eye and tumor model Houdini, SideFX (Toronto, Canada) Tumor model Dome shaped tumor Apex 3-8 mm Basal diameters 5-20 mm Eye model Anatomical model, adjustable tumor location OARs lens, ciliary body, optic nerve, macula as well as the retina and sclera Tumor location Distance to opt. nerve/macula

4 4 The 3D eye and tumor model Houdini, SideFX (Toronto, Canada) Tumor model Dome shaped tumor Apex 3-8 mm Basal diameters 5-20 mm Eye model Anatomical model, adjustable tumor location OARs lens, ciliary body, optic nerve, macula as well as the retina and sclera Tumor location Distance to opt. nerve/macula

5 5 The 3D eye and tumor model Houdini, SideFX (Toronto, Canada) Tumor model Dome shaped tumor Apex 3-8 mm Basal diameters 5-20 mm Eye model Anatomical model, adjustable tumor location OARs lens, ciliary body, optic nerve, macula as well as the retina and sclera Tumor location Distance to opt. nerve/macula

6 Dose calculation & uncertainty 6 Benchmark MCNP6 Film dosimetry (diode, µ-diamond) Manufacturer Uncertainties/Robustness MC dose calculation Eye model voxelization imperfect positioning of plaque

7 7 Treatment plan optimization A. Switching from larger plaque to smaller plaque type (for different tumor locations) B. Shifting plaque on relatively small tumors away from the critical structures

8 8 Robustness 104 Gy 20 Gy 34 Gy 6 Gy Naturally larger tumors induce larger dose change Ant: lens Post: opt. nerve & macula Cent: similar effect on lens and opt. nerve + retina mean dose Examples: Central position, 3mm apex Central position, 8mm apex

9 Plan optimization Pt. 1 9 Objective: Tumor coverage must not be compromised! Threshold base diameters (w.r.t. positional accuracy) Example: Type Shift Maximum base diameter 0 mm D basal 10 mm A apex CCA CCB 1 mm D basal 6.5 mm + A apex 2 mm D basal 3.5 mm + A apex 1 mm D basal 6.5 mm + A apex 2 mm D basal 3.5 mm + A apex 0 mm D basal 13.4 mm A apex 1 mm D basal 12 mm A apex 2 mm D basal 13 mm A apex (apex 5mm with CCA) Max. base diameter for different shifts: 1 mm : 11.5 mm 0 mm : 12.9 mm Max dose reduction: Lens (D 2% ): Gy Optic (D 2% ): 38.3 Gy Retina (D mean ): 77.3 Gy OAR name Lens Optic nerve Retina Apex (mm) Dose reduction (in Gy) D 2% D mean ant cent post ant cent post

10 Plan optimization Pt Linear fits to express dose change ΔD with respect to introduced shifts Δs: Example: G = Τ D s 5mm apex, 6 mm diameter, anterior tumor with CCA, shift away from lens by 3 mm Dose change: Reduce D max lens: > 33 Gy Increase D max opt. nerve < 0.5 Gy Apex Dose change per shift (Gy/mm) height OAR anterior middle posterior 3mm lens mm lens 11.3 Gy/mm D2 8mm lens mm 5mm 8mm makula optic nerve makula optic Gy/mm nerve makula optic nerve D2 3mm retina mm retina mean 8mm retina

11 11 Conclusion Novel software modules for 3D treatment planning of 106 Ru eye plaque brachytherapy of uveal melanomas. Application: daily treatment planning research on plan optimization performing pro- and retrospective studies provide further information on dose-response relationships prognostic values for treatment morbidity and local control. Future works involves the registration of pre- or postapplication MR images as well as a quantitative evaluation on the basis of retrospective data.

12 12 Thank you for your attention! Supported by the Austrian Science Fund (FWF), project P25936