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Simona GiordanengoTorino January 12 2009
Study and development of the Dose Delivery System for the National Center of Oncological Hadrontherapy (CNAO)
2
Introduction Advanced Radiotherapy and
Hadrontherapy Dose delivery systems Active scanning system CNAO projectMy research activity CNAO Dose Delivery System (Hardware
and Software characteristics) Preliminary test of the CNAO scanning
performanceConclusions
Overview
3
Standard and advanced Radiotherapy
LINAC6 – 18 MV
Dynamic Multi-Leaf Collimator (DMLC)
To increase conformity
To increase conformity and biological effects
3D conformal Radiotherapy (3DCRT)
Intensity Modulated Radiotherapy (IMRT)
Hadrontherapy
Maximum dose rate: ~ 5 Gy/min
[Gy] = [J/Kg]
44
Tumors treatment with heavy particles
Depth dose distribution of various radiation modalities
Inelastic collision with nuclei: neutrons production and others fragments
High dE/dx High Ionization
High Dose (Gy = J/Kg )
Hadrontherapy
Standard Radiotherapy
5
Ions vs X-rays physical advantages
These are mainly dependent on the Dose Delivery These are mainly dependent on the Dose Delivery SystemSystem
Low dose on surface
High dose in depth
High precision on dose delivery
Minimal lateral scattering
Multiple Scattering
6
PatientACCELERATOR Dose Delivery
The elements and devices necessary to conform, control and adjust the beam just before the patient belong to the Dose Delivery System (DDS)
Beam line
Magnets (dipoles and quadrupoles), vacuum chambers and beam diagnostic devices characterize the beam transport system just before the Dose Delivery
The hadrontherapy “machine”
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Vacuum chamber Pencil Beam Target
Dim 1 ÷ 30 cm
FWHM 2 ÷ 10 mm
Two main methods have been successfully adopted to cover a large transversal area with a small native pencil beam: THE PASSIVE and the ACTIVE METHODS
From the original beam dimension to the target dimension through the Dose Delivery System
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Dose Delivery elements for a PASSIVE SCATTERING system
• 1st transversal beam spread
• 1st energy modulation (Spread Out Bragg Peak)• 2nd energy modulation to increase homogeneity
• 1st (X,Y) conformation
• Energy (Z) conformation
• 2nd (X,Y) conformation
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y
x
z
L L
Beam
Target
θ
Scanning magnets
YX
Beam monitors
ACTIVE BEAM DELIVERY SOLUTIONS
Two dipole magnets smear out the particles of a beam pulse
Only beam monitors between vacuum window and patient to increase efficiency and reduce unnecessary dose reduce scattering and nuclear interactions between particles and material along the beam path
Vacuum window
F = q * (v Λ B)
10
RASTER SCAN SOLUTION
The beam is moved continuously in a pre-selected pattern over the target area and a well-defined number of particles are delivered in each line element.
Scanning magnets
Scanning magnets
y
x
z
Isocenter
Scanned Field
Protons,Carbon ions
To obtain the desired field, several scanning techniques can be adopted
11
SPOT SCAN SOLUTIONS
It moves a beam spot across the field in discrete steps
Scanning magnets
Scanning magnets
y
x
z
Isocenter
Scanned Field
Very time consuming
Protons,Carbon ions
Requirements: fast system to switch on-off the beam
y
x
z
Isocenter
Scanned Field
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y
x
z
Isocenter
Scanned Field
y
x
z
Isocenter
Scanned Field
VOXEL SCAN SOLUTIONS
The beam is aimed to a voxel for the time necessary to reach the prescribed fluence then it is steered to the next
voxel without stopping the particle delivery
Scanning magnets
Scanning magnets
Protons,Carbon ions
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Scanning magnets
Scanning magnets
Synchrotron
Synchrotron
LinacLinac
2 sources2 sources
Nozzle and Nozzle and monitor systemmonitor system
Nozzle and Nozzle and monitor systemmonitor system
INFN and University of Torinocollaborate with Fondazione CNAO
z
y
x
• (X,Y) VOXEL SCANNING
• (Z) PARTICLE ENERGY VARIATION through the accelerator
E0E1 En
E0<E1<…<En
CNAO “3D” active dose delivery system
Beam ON
Beam OFF t
0.5 sec
1.5 sec
Synchrotron time structure
SLICES
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2 strip chambers 1 pixel chamber
Detectors characteristics
Intensity Measurement
Read every 1 s
Integral sensitive areaGap 5mmGas nitrogenHV 400 V
Position Measurementevery 80-100 s s precision 100 precision 100 mm# strips 128 (1.65 mm pitch)Gap 5mmGas nitrogenHV 400 V
2D Position Measurement2D Intensity MeasurementPrecision 200 Precision 200 mm# pixels 1024 (6.6 mm pitch)Gap 5mmGas nitrogenHV 400 V
2 integral chambers
15CNAO - Pavia
Main entrance
Synchrotron vault
Hospital rooms
Power plant
16
CNAOCNAOCentro Nazionale di Adroterapia OncologicaCentro Nazionale di Adroterapia Oncologica
3 treatment rooms:3 horizontal lines1 vertical line
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To treat deep tumours (range 1-30 cm):
p (E : 60-250 MeV, I :1010), C6+(E : 120-400 MeV/u, I : 4*108) Gaussian Beam : 4 10 mm (FWHM) Active Dose Delivery System Beam position step: 1 ± 0.1 mm Maximum field: 20 x 20 cm2
Patient daily fraction in ~ 2 -3 min
Synchrotron
Treatment rooms
~26 m
17
Synchrotron room
19
CNAO Dose Delivery System
Hardware and Software characteristics
20
Crate PXI -NI
Supervision System
Timing System
Control Room
Scanning Magnets
Interlock System
DATA(monitor)
Dose Delivery InterfacesDose Delivery Interfaces
Treatment Planning System
Chopper/Dump
Based on NI products and LabVIEW Real-Time Operating System
BOX 1 BOX 2
21
65341
FPGA1
65342
FPGA2
65344
FPGA4
StXStY
IM1
IM2PX
PXI trig bus
PXI data bus
MagnetsX Y
FPGA3
65343 I/OI/O I/O
Chopper
Interlock
External BUS to trasnfer data between FPGA 2-3-4
External BUS to connect FPGA1-2-3-4, interlock module and chopper module
CPUO
TT
ControlRoom
Master Timing
CRATE PXI
Supervision System and TPS
Ethernet
Optical Link
Ethernet Optical Link
22
En
• Monitor on-line the beam (fluence, position and dimension)• Set the beam position voxel by voxel through the direct connection with the scanning magnets power supplies• Correct on-line the beam position (feed-back operations) • Stop the beam slice by slice or when something is wrong
When the beam is ON the Dose Delivery has to…
BOX 1 BOX 2
PS PS
Slice
Treated Treated voxelsvoxels
PXI with FPGAs
Dose Delivery DAQ
5 ionization chambers
123 45Monitors
1-4 : Integral chamber2-3 : Strip chambers5 : Pixel chamber
Scanning magnets
IDD
IDD
IPS
IPS
23
“TREATMENT LOADING”
“START DAQ”
“SPILL ON”
“LOGFILE CREATE”
YES
NO
“DATA STORAGE”
“END of SLICE or SPILL”
NO
YES
WAIT NEXT TREATMENT
“STOP DAQ”
Slice Ended
Treat Ended
TREATMENT SEQUENCE FROM DOSE DELIVERY
Implemented with NI hardware and LabVIEW Real-Time Operating System
NI = National Instruments
z
y
x
E0E1 En
Treatment volume
24
“TREATMENT LOADING”
“START DAQ”
“SPILL ON”
“LOGFILE CREATE”
YES
NO
“DATA STORAGE”
“END of SLICE or SPILL”
NO
YES
WAIT NEXT TREATMENT
“STOP DAQ”
Slice Ended
Treat Ended
The sequential beam positions for each voxel are preventively stored in a memory and are translated in a set of strip coordinates and magnet currents
For each voxel:
(En, Np, X, Y)
(counts, xstrip, ystrip, Ix, Iy) z
y
x
E0E1 En
For the ionization chamber For the ionization chamber counts also Pressure and counts also Pressure and Temperature dosimetric Temperature dosimetric correction is done for each correction is done for each patientpatientAfter a trigger from Timing System the monitor data acquisition from FPGA starts
25
“TREATMENT LOADING”
“START DAQ”
“SPILL ON”
“LOGFILE CREATE”
YES
NO
“DATA STORAGE”
“END of SLICE or SPILL”
NO
YES
WAIT NEXT TREATMENT
“STOP DAQ”
Slice Ended
Treat Ended
Slice
TreateTreated d voxelsvoxels
En
IN REAL-TIME when SPILL is ON for each voxel FPGA1 counts particles, FPGA2 checks the beam position and compares it with the expected one FPGA4 corrects the currents set if necessary (feed-back operations).
VOXEL END FPGA1 sends a trigger to the others FPGAs which prepare themselves for the next voxel. FPGA4 transmits the new voxel currents to the magnet PS.
26
“TREATMENT LOADING”
“START DAQ”
“SPILL ON”
“LOGFILE CREATE”
YES
NO
“DATA STORAGE”
“END of SLICE or SPILL”
NO
YES
WAIT NEXT TREATMENT
“STOP DAQ”
Slice Ended
Treat Ended
SLICE and SPILL END DD stop the Beam and DAQ DD rady to start new DAQ TREATMENT END DD creates “logfiles” and send to the SS DD ready for next treatment
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Preliminary test of the CNAO scanning performance
28
Acceptance test of the communication Acceptance test of the communication between Dose Delivery and Power between Dose Delivery and Power
Supply Supply
The time response of the scanning The time response of the scanning magnet magnet fieldfield
The performance of the scanning The performance of the scanning system with a system with a realreal treatment treatment
THE AIMS OF THE MEASUREMENTS
29
Scanning Scanning MagnetMagnet
L = 4.4 mH, R = 26 mΩBmax = 0.3 T with 606 AHomogeneity better than
0.2 %
Power SupplyPower Supply
Power rated = ±550A/±660VRate 100 kA/s vbeam> 20
m/sCurrent precision = ± 100
ppmM. Incurvati et al “FAST HIGH-POWER POWER SUPPLY FOR SCANNING MAGNETS OF CNAO MEDICAL ACCELERATOR” – EPAC 08 - Genova
B
Designed and built in collaboration between OCEM S.p.A and INFN-CNAO
SCANNING CHARACTERISTICS
30
Setup for the magnetic field measurement
High Linearity Hall Probe for Room and High Linearity Hall Probe for Room and Cryogenic Temperatures Cryogenic Temperatures
Nominal control current, In : 100 mA Nominal control current, In : 100 mA Sensitivity : Sensitivity : 439 mV/T439 mV/TRange for B : Range for B : ± 3 T± 3 TLinearity : Linearity : < 0.2 %< 0.2 %Active area:Active area: 0.5x1.25 mm0.5x1.25 mm22
Band width:Band width: ~6 MHz~6 MHz
PXIPXI
FPGAFPGA7831-R7831-R
FPGA with ADCFPGA with ADC
analog channels:analog channels: 8 8 resolution :resolution : 16 bit16 bitInput signal range: Input signal range: ±10 V±10 VDAQ rate: DAQ rate: 200 kHz 200 kHz Noise : Noise : 3 counts (~0.17 3 counts (~0.17 A from PS)A from PS)
IIinin = 100mA = 100mA
VVout out x50x50
31
PXI with FPGA
PXI with FPGA
Magnet
Hall probe
40 kHz
Iref, err
Iref, Imeas, err
200 kHz
B (a.u.)
10 m Shielded cable
DATA FLOW
Dose Delivery System
4 Mbaud optical link
Power Supply
32
Acceptance test of the communication Acceptance test of the communication between Dose Delivery and Power between Dose Delivery and Power
SupplySupply
Set of different currents Set of different currents OKOK(-540 A(-540 A 540 A) 540 A)
Transmission times checkTransmission times check OKOK4 Mbaud4 Mbaud
40 kHz of data40 kHz of data
Simulation of a transmission error Simulation of a transmission error OKOK
Detection of current out of range Detection of current out of range OKOK
33
• Scan from -540 A Scan from -540 A +540 A +540 A -540 A with the -540 A with the following current steps:following current steps:
– 1 A, 2 A, 5 A, 10 A, 15 A, 20 A, 540 A 1 A, 2 A, 5 A, 10 A, 15 A, 20 A, 540 A – Δt = 2 ms, 4 ms and 10 ms (= time between two steps)Δt = 2 ms, 4 ms and 10 ms (= time between two steps)
Probe Hall in 3 different positions within the magnet (0 cm, Probe Hall in 3 different positions within the magnet (0 cm, +20 cm, +25 cm)+20 cm, +25 cm)
• Slices from treatments (scan in X and scan in Y) Slices from treatments (scan in X and scan in Y) with with ΔΔt proportional to the fluencet proportional to the fluence
Performance Tests
34
Step planned by Dose Delivery from planned coordinate
PS current Step
A
B
Beam at position A:XA coordinate A plannedIA current for PSNA # particles in A (Dose)tA time to deliver NA
Scanning parameters Position – Speed – Time – Intensity – Dose
Beam at position B:XB coordinate B plannedIB current for PSNB # particles in B (Dose)tB time to deliver NB
tA-B = step timeIA-B = current step
Beam Speed = VA-B = (XA-XB)/tA-B
Power Supply Current rate = dI/dt= (IA-IB)/tA-B
VA-B
t
IPSIDD
t
35
I_DD (A) Current set by the Dose Delivery.
Acquisition rate 40 kHz.I_PS (A) Current read by the Power Supply control loop.
Acquisition rate 40 kHz. B (a.u.) Hall probe measurement in arbitrary unit to normalize the field to the current.
Acquisition rate 200 kHz.
Scan with 10 A step every 2 ms
A
B
VA-B
36
Linearity step 10A
Power Supply non-linearity negligible
B-Idd Ips-Idd
Hysteresis
37
Beam Speed for 1 A step
ΔI/Δt = 20 kA/sec
Scanning speed measurements GENERAL REQUIREMENTS: if 2.5 A ≤ ΔI ≤ 15 A ΔI/ Δt > 100 kA/secif ΔI < 2.5A time < 200 μs
1 A in Δt ~ 50 μs << 200 μs
From linear fit between 10 %- 90 %ΔI/Δt = 0.0201 A/μs
1 A = 200 μm for C6+ (400Mev/u)
Bρ= 6.36 Tm1 A = 1 mm for p (60 Mev) Bρ= 1.14 Tm
Beam speed 4 m/sec for C6+ max EBeam speed 20 m/sec p minima E
38
2 A step in the magnet center
ΔI/Δt = 31 kA/sec
2A in Δt < 70 μs
From linear fit between 10 %- 90 % Slope = 0.0314 A/μs
ΔI/Δt = 29 kA/sec
2A in Δt < 70 μs
From linear fit between 10 %- 90 %ΔI/Δt = 0.0291 A/μs
2 A step at the magnet edge
70 μs << 200 μs required
39
10 A step in the magnet center
ΔI/Δt = ~ (6/35)*106 ~ 170 kA/sec
10 A step in the magnet edge
10 A step out of the magnet
Time Time for 20%-80% A step ( for ΔI = 6A) = 35 ± 5 us
170 kA/sec >> 100 kA/sec
required
40
Slice from Real Patient Treatment
MEASURED and PLANNED VOXELS POSITIONS
41Treatment MEDIUM , slice 9
Slice dose distributions
N particles/voxel
PLANNED
MEASURED
Maximum N particles/voxel ~ 4*104
42
Relative maximum difference0.008
Difference between the Difference between the real distribution real distribution
obtained using the obtained using the measured beam measured beam
positions and the ideal positions and the ideal distribution (from TPS) distribution (from TPS)
better than 1 %. better than 1 %. (Required 2.5 %)
43
S. Giordaengo et al.“Performance test of the scanning system for CNAO, Italian National Center of Oncological Hadrontherapy”
Soon ready to be submitted for pubblication to NIM
44
CONCLUSIONS about my activity The CNAO Dose Delivery operations defined The DD data acquisition developed A software prototype to interface the DD with several CNAO subsystems implemented and will be ready to start the DD debug soon The interface with the Supervision System successfully tested The interface with the Power Supply for scanning magnets defined, developed and successfully tested Performance test of the scanning system successfully done
FUTURE Master Timing interface test Interlock System interface test DD debug at CNAO with beam Overall software optimizations