Post on 12-Jul-2015
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
IMA
GIN
G M
OTI
ON
D
ETE
CTI
ON
DO
SE
D
ELI
VE
RY
4D TREATMENT PLAN (TP)
PHA
SE N
THERAPY CONTROL SYSTEM (TCS) TR
EAT
ME
NT
VE
RIF
ICAT
ION
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
E C
RIT
ICAL
TH
REA
D!O
TS D
RIV
EN T
HR
EAD!
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
]
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