MISTREAT: MotIon Simulator in proton-therapy TREATment. Paul Morel - - PowerPoint PPT Presentation
MISTREAT: MotIon Simulator in proton-therapy TREATment. Paul Morel February, 27 2014 Workshop on Bioinformatics and Stringology 2014 Advisors: Guillaume Blin, PhD (LIGM, Universit e Paris-Est Marne La Vall ee, France) St ephane
Paul Morel February, 27 2014 Workshop on Bioinformatics and Stringology 2014
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)
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Radiation Therapy Cancer treatment relying on radiations aiming at killing cancerous cells. Examples of radiation therapy modalities:
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Radiotherapy External X-ray (photon) cone beam rotating around a patient. Proton-therapy External beam of protons rotating around a patient, stopping at specific angles to deliver a prescribed treatment.
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Proton-Therapy
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Proton-Therapy
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Proton-Therapy
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Proton-Therapy
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Proton-Therapy
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Proton-Therapy
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Proton-Therapy
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Proton-Therapy
Figure 1: Comparison of spinal fields for medullblastoma: photons (upper panels) versus protons (lower panels) [?]
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Proton-Therapy
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Proton-Therapy
Water pressure = Proton energy = depth of Bragg Pic Water quantity = Dose = Number of protons Some water drops are deposited on the way = Some dose too Dose is cumulative along the way
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Proton-Therapy
Water pressure = Proton energy = depth of Bragg Pic Water quantity = Dose = Number of protons Some water drops are deposited on the way = Some dose too Dose is cumulative along the way
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Proton-Therapy
Water pressure = Proton energy = depth of Bragg Pic Water quantity = Dose = Number of protons Some water drops are deposited on the way = Some dose too Dose is cumulative along the way
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Proton-Therapy
Water pressure = Proton energy = depth of Bragg Pic Water quantity = Dose = Number of protons Some water drops are deposited on the way = Some dose too Dose is cumulative along the way
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Proton-Therapy
Water pressure = Proton energy = depth of Bragg Pic Water quantity = Dose = Number of protons Some water drops are deposited on the way = Some dose too Dose is cumulative along the way
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Proton-Therapy
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Proton-Therapy
The beam is turned off between the spot positions
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Proton-Therapy
The beam is turned off between the spot positions
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Proton-Therapy Treatment Planning
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Proton-Therapy Treatment Planning
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Proton-Therapy Treatment Planning
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Proton-Therapy Treatment Planning
Plan: ... Step k: Energy, x coordinate , y coordinate, duration ...
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Proton-Therapy Treatment Planning
Plan: ... Step k: Energy, x coordinate , y coordinate, duration ...
Paul Morel MISTREAT February, 27 2014 12 / 34
Proton-Therapy Treatment Planning
Plan: ... Step k: Energy, x coordinate , y coordinate, duration ...
Paul Morel MISTREAT February, 27 2014 12 / 34
Proton-Therapy Treatment Planning
Plan: ... Step k: Energy, x coordinate , y coordinate, duration ...
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Proton-Therapy Treatment Planning
Plan: ... Step k: Energy, x coordinate , y coordinate, duration ...
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Proton-Therapy Motion
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Proton-Therapy Motion
Inter-fraction motions: loss/gain of weight, tumor swelling/shrinkage, bladder, intestinal gas... Intra-fraction motions: breathing, heart beat ... ⇒ Interplay Effect
Figure 2: Results of irradiations without (left) and with (right) motion on a radiographic film.[?]
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Proton-Therapy Motion
During treatment planning: chose beam direction, use several beams, safety margins. Motion reduction:
Abdominal press Anesthesia Fixation devices Breathing control techniques (Breath-Holding + Gating)
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Proton-Therapy Motion
During treatment planning: chose beam direction, use several beams, safety margins. Motion reduction:
Abdominal press Anesthesia Fixation devices Breathing control techniques (Breath-Holding + Gating)
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Proton-Therapy Motion
During treatment planning: chose beam direction, use several beams, safety margins. Motion reduction:
Abdominal press Anesthesia Fixation devices Breathing control techniques (Breath-Holding + Gating)
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Proton-Therapy Motion
During treatment planning: chose beam direction, use several beams, safety margins. Motion reduction:
Abdominal press Anesthesia Fixation devices Breathing control techniques (Breath-Holding + Gating)
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Proton-Therapy Motion
Rescanning (for interplay effect):
One energy slice: Iso-Layered Repainting Dose per spot visit is kept under an upper limit. It is characterized by tmax the time limit per spot per visit. Scaled Repainting The prescribed dose of every spots is divided by a constant N (repainting factor:number of repaintings). Applicable to the whole volume.
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Proton-Therapy Motion
A GPS for the body: Calypso (Varian)
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Proton-Therapy Motion
A GPS for the body: Calypso (Varian)
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Proton-Therapy Motion
A GPS for the body: Calypso (Varian)
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Proton-Therapy Simulator
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Proton-Therapy 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 is C.
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Proton-Therapy Simulator Patient Data
Patient data: conversion CT # to mass densities and structure set information.
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Proton-Therapy Simulator 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.
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Proton-Therapy Simulator Dose calculation for heterogeneous media
Analytical model[?],[?]: Main functions d(x, y, z) = Sm
w
ρm
w
C(z)O(x, y, z)
C(z) = DDw(rpl(z), E0) ∗ ssd0 + rpl(z) z 2
O(x, y, z) = 1 2π(σtot(z))2 ∗ exp
x2 + y2 2(σtot(z))2
σtot(z) =
size + σpt(z)2
σpt(z) = y0(rpl(z))
y0(t) = y0(R) ∗
t R 2 + 0.33 t R
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Proton-Therapy Simulator Model evaluation
Comparison to RayStation results: Single beamlets in water tank, energies from 30MeV to 225MeV: Dose profile of Bragg Peak: Comparison mean (mm) min(mm) max(mm)
1.1 2.73 1.15 Table 1: Absolute difference between the BP locations.
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Proton-Therapy Simulator 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)
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.
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Proton-Therapy Simulator Model evaluation
Treatment simulation:
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Proton-Therapy Simulator Motion
We consider a patient moving during the treatment and being monitored: f (x, y, z, t) → (x′, y′, z′)
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Proton-Therapy Simulator Motion
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Motion Compensation Compensation principle
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Motion Compensation Approaches Studied
Compensated Repainting Compensated unlimited rescanning with combining these methods:
Use margins for spot positions with or without map update. Figure 3: Map of original scanning positions (green) with a margin (red) for an energy layer.
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Motion Compensation Experiments for 2D Motions
Experiment: Motion parameters:
X Y Z τ : Period(s) 4 3.5 A : Ampl (cm) 2 1.5 φ : Phase (rad)
(a) 2D Motion parameters
Delivery of 1 energy layer. Noise:
Amplitude: σx = 0.25cm, σy = 0.2cm Period: σx = 0.2s, σy = 0.1s
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Motion Compensation Experiments for 2D Motions
Interest of the compensation method:
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Motion Compensation Experiments for 2D Motions
Noise added to the measure provided by motion monitor: (σ = 0cm,σ = 0.4cm,σ = 1cm in both directions)
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Conclusion
Current state: Simulate different treatment plans to render the effect of the motion. Dose distribution in the patient at each instant. Basic compensation technique: adapt the weight. Improvements for the future: Make use of all the dose information computed. Improve the compensation technique to be able to compensate at each unit of time. Offer improvements for the treatment plan.
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Bibliography
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