Improving the robustness of the beam-scanning delivery in - PowerPoint PPT Presentation

Improving the robustness of the beam-scanning delivery in proton-therapy. Paul Morel March, 25 2014 LIGM - Laboratoire d’Informatique Gaspard Monge Advisors: Guillaume Blin, PhD (LIGM, Universit´ e Paris-Est Marne La Vall´ ee, France) St´ ephane Vialette, PhD (LIGM, Universit´ e Paris-Est Marne La Vall´ ee, France) Xiaodong Wu, PhD (University of Iowa, USA) Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 1 / 38

Outline: Proton-Therapy Proton-Therapy Simulator Motion Compensation Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 2 / 38

Proton-Therapy Proton-Therapy Cancer treatment relying on ionizing radiations aiming at killing cancerous cells using proton beams. Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 3 / 38

Proton-Therapy Why protons? Why protons? Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 4 / 38

Proton-Therapy Why protons? Why protons? Figure 1: Comparison of spinal fields for medullblastoma: photons (upper panels) versus protons (lower panels) [Kirsch and Tarbell, 2004] Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 5 / 38

Proton-Therapy Why not only protons? Why not only protons? Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 6 / 38

Proton-Therapy Protons therapy - an analogy Protons therapy - an analogy Water pressure = Proton energy ( depth of Bragg Peak) Water quantity = Dose = Number of protons Water drops are deposited on the way = Dose is cumulative along the way Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 7 / 38

Proton-Therapy Protons therapy - an analogy Protons therapy - an analogy Water pressure = Proton energy ( depth of Bragg Peak) Water quantity = Dose = Number of protons Water drops are deposited on the way = Dose is cumulative along the way Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 7 / 38

Proton-Therapy Protons therapy - an analogy Protons therapy - an analogy Water pressure = Proton energy ( depth of Bragg Peak) Water quantity = Dose = Number of protons Water drops are deposited on the way = Dose is cumulative along the way Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 7 / 38

Proton-Therapy Protons therapy - an analogy Protons therapy - an analogy Water pressure = Proton energy ( depth of Bragg Peak) Water quantity = Dose = Number of protons Water drops are deposited on the way = Dose is cumulative along the way Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 7 / 38

Proton-Therapy Protons therapy - an analogy Protons therapy - an analogy Water pressure = Proton energy ( depth of Bragg Peak) Water quantity = Dose = Number of protons Water drops are deposited on the way = Dose is cumulative along the way Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 7 / 38

Proton-Therapy Delivery Techniques Main Principle: Energy Layers Figure 2: Energy layers Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 8 / 38

Proton-Therapy Delivery Techniques Pencil Beam Scanning Discrete scanning : The beam is turned off between the spot positions. Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 9 / 38

Proton-Therapy Treatment Planning Treatment Planning Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 10 / 38

Proton-Therapy Treatment Planning Treatment Planning Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 11 / 38

Proton-Therapy Treatment Planning Treatment Planning Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 12 / 38

Proton-Therapy Treatment Planning Treatment Planning weight ⇔ dose ⇔ amount of protons ⇔ duration Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 13 / 38

Proton-Therapy Motion Sensitivity to motion Inter-fraction motions: loss/gain of weight, tumor swelling/shrinkage, bladder, intestinal gas... Intra-fraction motions: breathing, heart beat ... ⇒ Interplay Effect Figure 3: Results of irradiations without (left) and with (right) motion on a radiographic film.[Bert et al., 2012] ⇒ Overall treatment degraded Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 14 / 38

Proton-Therapy Motion Sensitivity to motion Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 15 / 38

Proton-Therapy Motion Motion mitigation I During treatment planning: chose beam direction, use several beams, safety margins. Motion reduction: Abdominal press Breath-Hold Anesthesia Breathing control techniques Beam-gating Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 16 / 38

Proton-Therapy Motion Motion mitigation II Rescanning (for interplay effect): One energy slice: Iso-Layered Repainting Scaled Repainting Dose per spot visit is kept under an The prescribed dose of every spots is upper limit. It is characterized by t max divided by a constant N (repainting the time limit per spot per visit. factor:number of repaintings). Applicable to the whole volume. Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 17 / 38

Proton-Therapy Motion Motion mitigation III A GPS for the body: Calypso (Varian) Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 18 / 38

Proton-Therapy Simulator Proton-Therapy Simulator Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 19 / 38

Proton-Therapy Simulator Overview Simulator overview Main objective Quantify the impact of intra-fraction motions for given treatment plans. ⇒ Choice of the most robust plan. Implemented in Python with subroutines in C. Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 20 / 38

Proton-Therapy Simulator Patient Data Patient data Patient data: conversion CT # to mass densities and structure set information. Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 21 / 38

Proton-Therapy Simulator Physical Data Physical Data Depth dose curve generated from dose distributions in a water tank simulated in RayStation (RaySearch lab.) for energies ranging from 30MeV to 225MeV (step 5MeV). Missing energies: Approximation of the depth-dose curve from computed data. Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 22 / 38

Proton-Therapy Simulator Dose calculation Dose calculation Analytical model[Hong et al., 1996],[Szymanowski and Oelfke, 2002]: Main functions Auxiliary functions � σ 2 σ tot ( z ) = size + σ pt ( z ) 2 d ( x , y , z ) = S m w C ( z ) O ( x , y , z ) ρ m σ pt ( z ) = y 0 ( rpl ( z )) w � t � t � 2 � 2 � �� � ssd 0 + rpl ( z ) y 0 ( t ) = y 0 ( R ) ∗ 0 . 69 ∗ + 0 . 33 C ( z ) = DD w ( rpl ( z ) , E 0 ) ∗ R R z x 2 + y 2 � � 1 y 0 ( R ) = 0 . 12085 × 10 − 4 ∗ R 2 + 0 . 02275 ∗ R O ( x , y , z ) = 2 π ( σ tot ( z )) 2 ∗ exp − 2( σ tot ( z )) 2 Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 23 / 38

Proton-Therapy Simulator Model evaluation Model evaluation Comparison to RayStation results: Single beamlets in water tank, energies from 30MeV to 225MeV: Dose profile and Bragg Peak: Comparison mean (mm) min(mm) max(mm) std. dev.(mm) RaySt. vs Simul. 1 . 1 0 2 . 73 1 . 15 Table 1: Absolute difference between the BP locations. Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 24 / 38

Proton-Therapy Simulator Model evaluation Model evaluation Comparison to RayStation results: Single beamlets in water tank, energies from 30MeV to 225MeV: Lateral profile at Bragg Peak: mean (mm) min(mm) max(mm) std. dev.(mm) 2 . 3 × 10 − 3 3 . 4 × 10 − 4 7 . 6 × 10 − 3 2 × 10 − 3 Table 2: Absolute difference between the std. dev. of the lateral profiles. Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 25 / 38

Proton-Therapy Simulator Model evaluation Model evaluation Treatment simulation: Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 26 / 38

Proton-Therapy Simulator Motion Motion We consider a patient moving during the treatment and being monitored: f ( x , y , z , t ) → ( x ′ , y ′ , z ′ ) Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 27 / 38

Proton-Therapy Simulator Motion Motion Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 28 / 38

Motion Compensation Compensation principle Compensation principle Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 29 / 38

Motion Compensation Approaches Studied Approaches Studied Compensated Repainting Compensated unlimited rescanning with combining these methods: Use margins for spot positions with or without map update. Figure 6: Map of original scanning positions (green) with a margin (red) for an energy layer. Paul Morel Improving the robustness in Proton-Therapy March, 25 2014 30 / 38