vmat qa assessment verification - sfpmluz2016.sfpm.fr/luz/biblio/s3/05_barbeiro.pdf · 1 2 6 3...

A R Barbeiro1, A Ureba2, J A Baeza3, R Linares4, M Perucha4, E Jiménez-

Ortega1 and A Leal1

1. Dept. Fisiología Médica y Biofísica, University of Seville

2. Medical Radiation Physics, Stockholm University, Karolinska Institutet

3. Maastro Clinic, Maastricht, The Netherlands

4. Servicio de Radiofisica, Hospital Infanta Luisa, Seville

1st Workshop: Radiotherapy Modelling - Luz Saint Sauveur, Sep 2016

A model for assessing VMAT pre-treatment verification

systems and VMAT optimization algorithms

1

2

6

3

IntroductionVMAT and QA systems, main issues and uncertainties,

rationale for a highly accurate model.

Purpose

Material and MethodsLinac modelling, MC simulation and verification, QuAArC

phantom and QuAArC model.

Results and DiscussionQuAArC implementation with clinical cases, discretization

effect and proof of concept study.

Conclusions and future work

2 | 1st Workshop SFPM: Radiotherapy Modelling

Outline

5

Complexity of IMRT techniques is increasing.

VMAT dynamic implementation:

- Dynamic MLC motion

- Dose rate

- Gantry rotation speed

Rigorous QA correct delivery and consistency

with the planning.

demanding dose

distributions;

shorter treatment

times &

fewer MUs.

New uncertainties, associated issues

Introduction

Varying

Simultaneously

during

irradiation

Webb & McQuaid

PMB(54),2009


Chandraraj et al., J Appl Clin Med Phys(12) 2011

Hammond L. et al, Clinical

Oncology(23) 2011

MatriXX, IBA

COMPASS/MatriXX,IBA

ArckChek, Sun NuclearDelta4, Scandidos

2D/3D QA systems

Boggula et al., PMB(56)

2011


Introduction

Octavius, PTW

Film & Ion chamber

PTW and Scandidos websites

Dose calculation accuracy in these conditions.

Continuous delivery of a discrete calculation.Added complexity for optimization algorithms:

- more variables;

- connectivity (more or less robust solutions);

6MeV degradado

X (cm)

10 20 30 40 50 60 70 80 90

Y (

cm)

10

20

30

40

50

60

70

80

902000

4000

6000

8000

10000

12000

14000

DAO (Direct Aperture Optimization) (RapidArc ; SmartArc) FMO (Segmentation) + arc sequencing

Connectivity?

Plan degeneration!!


Introduction

Explicit particle transport throughout the detailed

geometry of linac and patient models.

Scattered and transmitted radiation through the

beam modifiers – contribution of complex apertures.


Monte Carlo simulation – rationale

Dose calculation accuracy:

Machine Log files


Introduction

Continuous delivery of a discrete calculation:

Information recorded during irradiation: MLC leaf and/or jaws positions; gantry

angles; MU; etc.

Dose reconstruction on the patient anatomy (discretization level ≈ TPS).

(e.g. MobiusFX; MC simulation of DynaLog files for RapidArc QA with

DOSXYZnrc dynamic source, Teke et al.)

As a patient-specific QA method is controversial experimental dose

measurements.

High detection

density

High calculation

resolution

Highly accurate model based on Monte Carlo simulation of log files, andon 3D radiochromic film measurements in a specific cylindrical phantom.specific cylindrical phantom

Purpose

Log files information Full MC calculation.

Absolute and 3D relative dose measurements.

Entrance dose or fluence estimation.

QuAArC model

High spatial resolution


EGSnrc/BEAMnrc: geometry modelling and 6MV beams simulation

Materials and Methods

MLC Tilt effect

Leaf lateral view


EGSnrc/DOSXYZnrc: dose distributions calculation in a water phantom

10 | 1st Workshop SFPM: Radiotherapy Modelling%

Do

se

PDDs & OARs: MC vs. Measurements

Agreement ±2%

MLC models (leakadge, gap and tilt study): additional experimental measurements with radiochromic film.



MC showed high

agreement with film

MC simulation

TPS LINAC MOSAIQ

BEAMnrc

BEAMDOSE

Automatic MC verification of TPS (RTP files) and log files



MC simulation

TPS LINAC MOSAIQ

BEAMnrc

BEAMDOSE

Automatic MC verification of TPS (RTP files) and log files



Log file


Different discretization level

– effect in the verification

process.

MC simulation of Log files




process.


Log file analysis

MC simulation of log files

MLC leaf positions difference between RTP and LOG

dif

feren

ce (

cm

)

Mu distribution for the entire arc

RTP MULOG MU

0

-3

-2

-1

1

2

3

4

5

6


QuAArC phantom:



Big setup:

30 cm x 30 cm length

Small setup:

20 cm x 28 cm length

3D relative dose

measurements & absolute

point dose measurements

Outer film scroll:entrance dose

estimation

Inner film scroll: dose distribution



Dose processing and 3D dose reconstruction:

min𝑥

12𝐶 ∙ 𝑥 − 𝑑

2

2such that

𝐴 ∙ 𝑥 ≤ 𝑏𝐴𝑒𝑞 ∙ 𝑥 = 𝑏𝑒𝑞𝑙𝑏 ≤ 𝑥 ≤ 𝑢𝑏

Feedback process to experimentally

adjust MUs with measurements



Feedback process – proposed MU variations for IMRT and VMAT plans.

IMRT plan VMAT plan

Clinical cases planned with different conventional TPS:

- MONACO

- PINNACLE

Verified with different commercial systems:

- Delta4

- COMPASS

Some of them were not accepted during their verification (2 treatment plansfor a same case).


QuAArC model validation with clinical cases:


Final QuAArC phantom - experimental verification:


Rolled up radiochromic

EBT3 films

PMMA slices for axial films

With cork cylinders

Results


% Dose DifferenceFilm Dose Distributions

Ou

ter

Fil

m

0-1

80

º

γ (3%/3mm)

Ou

ter

Fil

m

18

0-3

60

º

In

ner

Fil

m0

-36

0º

Reproducibility of film scroll measuments in QuAArC.

High reproducibility:

γ < 1: > 99%

Results


Discretization level effect in treatment verification:

Results – QuAArC model implementation

Gantry angle (°)

Axia

l sli

ce (

mm

)

Film vs MC Log Film vs QuAArC solution

% Dose Differences – coarse discretization

% Dose Differences – fine discretization

Film vs MC Log Film vs QuAArC solution

(a) (b) (c)

(d) (e) (f)


QuAArC model implementation: coarse Vs. fine log

Results

min𝑥

12𝐶 ∙ 𝑥 − 𝑑

2

2such that



% Dose Differences Gamma Analysis (2%/2mm)Film Dose Distributions QuAArC Dose Distributions

Gantry angle (°)

Prostate VMAT Plan

Ou

ter s

croll

In

ner s

croll

Axia

l slice

(m

m)

% Dose Differences Gamma Analysis (2%/2mm)Film Dose Distributions QuAArC Dose Distributions

Gantry angle (°)

H&N VMAT Plan

Ou

ter s

croll

In

ner s

cro

llA

xia

l slice

(m

m)

PINNACLE/COMPASS Plans

Proof of concept of the feedback process Results

Prostate

case

H&N

case


DVHs PINNACLE TPS Vs. QuAArC

Results



DVHs COMPASS Vs. QuAArC

Results



% Dose DifferencesFilm Dose Distributions QuAArC Dose Distributions

Axia

l sli

ce

(m

m)

Gantry angle (°)

Plan A

In

ner s

croll

Plan B

Ou

ter s

croll

In

ner s

croll

Ou

ter s

croll

Gamma Analysis (2%/2mm)

Prostate caseMONACO/Delta4 Plans

ResultsProof of concept of the feedback process

min𝑥

12𝐶 ∙ 𝑥 − 𝑑

2

2such that



% Dose Differences Gamma Analysis (2%/2mm)

Film Dose Distributions QuAArC Dose Distributions

Axia

l sli

ce

(m

m)

Gantry angle (°)

Plan A

In

ner s

croll

Plan B

Ou

ter s

croll

In

ner s

croll

Ou

ter s

croll

MONACO/Delta4 Plans

Proof of concept of the feedback process

H&N case

Results

min𝑥

12𝐶 ∙ 𝑥 − 𝑑

2

2such that



(c) (d)

(a) (b)

ResultsDVHs for QuAArC model Vs. MONACO TPS

Delta4-Anatomy (PB) Vs. QuAArC solutions


Results


Conclusions and future work

QuAArC model showed to be consistent and robust.

Effect of dose calculation accuracy and degree of detection density was

assessed in the developed model. (more reliable solutions, DVHs)

Potentially, control and reduce VMAT uncertainties, allowing evaluation of

commercial VMAT systems and/or the optimization algorithm implemented in

TPS.

Further studies about VMAT efficiency against more established techniques in

specific cases.

QuAArC model for dose painting verification.

QuAArC is being adapted for 4D verification.

QuAArC can also be implemented without MC.

Funding: Spanish Ministry of Science and Technology and FEDER.

Radiophysics department, Virgen Macarena Hospital, Seville.

Radiophysics department, Virgen del Rocio Hospital, Seville.

Radiophysics department, Infanta Luisa Clinic, Seville.

Thank you for your attention !


Acknowledgments

vmat qa assessment verification - sfpmluz2016.sfpm.fr/luz/biblio/s3/05_barbeiro.pdf · 1 2 6 3...

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