Simona GiordanengoTorino January 12 2009

Study and development of the Dose Delivery System for the National Center of Oncological Hadrontherapy (CNAO)

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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

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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]

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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

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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

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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)

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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

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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

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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

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Synchrotron room

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CNAO Dose Delivery System

Hardware and Software characteristics

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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

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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

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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

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“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

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“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

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“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.

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“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

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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

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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

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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

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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

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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

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• 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

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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

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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

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Linearity step 10A

Power Supply non-linearity negligible

B-Idd Ips-Idd

Hysteresis

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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

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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

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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

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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

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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 %)

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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

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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