Integration of optical tracking for organ motion compensation in scanned ion-beam therapy

31 July 2012

G Fattori[1], N Saito[2], A Pella[1], R Kaderka[2], M Seregni[1], A Constantinescu[2], P Cerveri[1,3], P Steidl[2], M Riboldi[1,3], G Baroni[1,3] and C Bert[2]

AAPM 2012 Annual Meeting

[1] Politecnico di Milano [2] GSI Helmholtzzentrum für Schwerionenforschung GmbH [3] Centro Nazionale di Adroterapia Oncologica (CNAO)

2 - 10 Presentation outline

INTRODUCTION: the role of optical tracking system in moving targets treatment Moving targets treatment in scanned IBT Optical Tracking Systems (OTS)

SYSTEMS INTEGRATION: integrated setup with GSI Therapy Control System

OTS/TCS integration RESULTS: performance and dosimetric results

Lateral target motion compensation Performance study Preliminary 3D target motion results and future works

3 - 10 Workflow of moving targets treatment with beam tracking

X-RAY STEREO PROJECTIONS

SOFT-TISSUE IMAGING

US MRI

DEPTH LATERAL

4DCT …

PHA

SE 1

4D

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G M

OTI

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4D TREATMENT PLAN (TP)

PHA

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THERAPY CONTROL SYSTEM (TCS) TR

EAT

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ICAT

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IN-BEAM PET OFFLINE PET

OPTICAL EXTERNAL SURROGATES TRACKING

ü  Non-invasive ü  High frequency ü  High accuracy ²  Surrogate signal

INTERNAL – EXTERNAL CORRELATION MODELS

ü  Periodic imaging for train/retrain

ü  Target position estimation from external signal

TARGET MOTION

4 - 10 Optical Tracking System (OTS) SMART-DX100, BTS Bioengineering Windows based workstation 3 free-standing Infrared TVC cameras 15 min calibration procedure 3D reconstruction of markers: •  3D error < 0.3 mm in 1 m3 volume •  Frequency: 100 Hz

OTS APPLICATIONS IN HIGH CONFORMAL RADIATION THERAPY

•  SETUP VERIFICATION: visual feedback during patient daily re-positioning •  REAL TIME MOTION MONITORING: continuous patient surveillance during treatment

CNAO patient positioning Ongoing studies on surface reconstruction

5 - 10 Integrated software for setup verification and motion monitoring

100

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111000 112000 113000 114000 115000 116000 117000 118000 119000

rang

e [m

m]

time [usec]

T*

T

external surrogate (y)Target surrogate (x)

MFlat signal

TREATMENT SETUP

PPS

OTS

IMAGING

NOMINAL POSITION

IN-ROOM CALIBRATION

MOTION MONITORING

Room coordinates system Visually assisted stereotactic frameless patient positioning

Tools for: §  On-line motion phase detection from external surrogates

Amplitude and phase based criteria

§  Target position estimation with correlation models State model, Artificial Neural Networks

§  Time prediction for delays compensation Polynomial data fitting: linear, 5 samples

§  Digital TCS communication UDP socket over Ethernet

SETUP VERIFICATION

6 - 10 Software implementation

Correction vector

3D DATA FLOW

Optical Tracking System Therapy Control System

BTU

Wedge range shifter

Steering magnets

Depth compensation

Lateral compensation

100 Hz frame rate

LABELLER

TARGET"

FRAMES INTERPOLATION"

POLYNOMIAL"COEFFICIENTS"

TIM

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ICAL

TH

REA

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HR

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BREATHING SIGNAL"

MOTION PHASE DETECTION"

CORRELATION MODELS" [ x y z ]

[ MP ]"

PATIENT MODEL"

MOTION PHASE TABLE"

RCS TRANSFORM MATRIX"

SHARED RESOURCES!

DIG

ITAL

CO

MM

UN

ICAT

ION

(U

DP

SOC

KET)!

Treatment plan

7 - 10 Lateral target motion compensation by beam tracking

PINPOINT I II III IV V MEDIAN DIRECT TRACKING -2.66 -1.09 0.35 -0.61 1.85 -0.61

ANN PREDICTION 2.10 0.61 -5.13 -7.30 -4.63 -4.63

STATIC DIRECT

PoliMi breathing phantom §  Planar motion §  18 mm peak to peak §  Planarity index: median

•  0.038 mm (IQR:0.09) §  Repeatability: mean ± std

•  0.18 ± 0.3 mm

Measurement tools §  Gafchromic film §  5 PTW PinPoint®

chambers

Prediction §  3 samples (30msec)

(visual inspection)

Critical point: ²  Residual interplay effect visible on

films due to non optimal systems communcation/integration

GSI TCS §  on-the-fly lateral compensation §  Digital TCS/OTS interface

DELTA % WRT STATIC IRRADIATION

ANN

8 - 10 OTS processing and communication time measurements

UDP receiver SHM reader

LED ON

2800 measures [usec] 2.5 25 MEDIAN 75 97.5 IQR DATA transfer

100 Hz

LED vs UDP 10070 12910 16450 19660 257830 6751 100%

UDP vs SHM 76 84 99 161 625.5 77 99.95%

50 Hz

LED vs UDP 10574 15520 20873 25947 44841 10428 100%

UDP vs SHM 27 28 43 49 60 21 100%

§  OTS

§  3 TVC setup §  InfraRed LED array

§  16 IR LED λ = 880 nm §  0.6 usec 10-90% switching time

§  TCS: linux based general purpose workstation

§  NI-6211 board; nsec switch time

TVC 2 Shared Memory

TVC 1

TVC 3

UDP SOCKET

4 bit TTL

“TCS” OTS

16 IR

LE

D A

RR

AY

NI-6211

Timestamps delta: §  UDP receiver Vs LED activation §  Shared Memory (SHM) reader Vs UDP receiver

SETUP

METHOD

RESULTS

9 - 10 Ongoing activities: 3D target motion

§  GSI breathing thorax phantom (Steidl et al. 2012)

§  predictors tuning for depth and lateral compensation §  Correlation model optimization

§  Retrain

§  1 Gy in cubic volume 35 mm side

§  20 PTW PinPoint® chambers

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180000 185000 190000 195000 200000 205000 210000

x co

ordi

nate

[mm

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time [msec]

ANN real TS points

Irradiation Mean ± Std.Dev NON COMPENSATED 12.23 ± 23.55 DIRECT TRACKING -0.46 ± 3.31 ANN ESTIMATED 0.6 ± 3.3

STATE MODEL 0.8 ± 3.3

Modality Retrain Median ± IQR

ANN 4 0.27 ± 0.32 STATE MODEL 13 0.33 ± 0.23

MODELS PERFORMANCE: 3D ERROR [mm]

DOSE STUDY [DELTA PERC. WRT STATIC]

10 - 10 Conclusions and future works

ü  Demonstrate the feasibility of CNAO OTS integration with GSI scanned ion-beam TCS

ü  Demonstrate the experimental use of two breathing phantoms featuring planar (PoliMI) and 3D (GSI) target motion in beam tracking experiments

ü  Demonstrate the functionality of standard digital communication protocol (UDP) for real

time OTS-TCS data stream

ü  Describe a method to qualify the OTS processing and data communication time requirements for time prediction parameters fine tuning

Future works §  Phantom: clinical breathing pattern from lung patients dataset

§  Treatment verification: in-beam PET

§  Improvements on models: reduced number of retrain with smaller dataset

11 - 10 Thank you

These activities were partially founded by the EU-FP7 ULICE project, WP 4: “Ion-therapy for intra-fractionally moving targets”.

Grant agreement number 228436