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Simona Giordanengo Torino January 12 2009

Study and development of the Dose Delivery System for the National Center of Oncological Hadrontherapy (CNAO). Simona Giordanengo Torino January 12 2009. Overview. Introduction Advanced Radiotherapy and Hadrontherapy Dose delivery systems Active scanning system CNAO project

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Simona Giordanengo Torino January 12 2009

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  1. Study and development of the Dose Delivery System for the National Center of Oncological Hadrontherapy (CNAO) Simona Giordanengo Torino January 12 2009

  2. Overview Introduction • Advanced Radiotherapy and Hadrontherapy • Dose delivery systems • Active scanning system • CNAO project My research activity • CNAO Dose Delivery System (Hardware and Software characteristics) • Preliminary test of the CNAO scanning performance Conclusions

  3. Standard and advanced Radiotherapy Dynamic Multi-Leaf Collimator (DMLC) LINAC 6 – 18 MV Maximum dose rate: ~ 5 Gy/min [Gy] = [J/Kg] • 3D conformal Radiotherapy (3DCRT) • Intensity Modulated Radiotherapy (IMRT) • Hadrontherapy To increase conformity To increase conformity and biological effects

  4. Hadrontherapy Tumors treatment with heavy particles Standard Radiotherapy High dE/dx High Ionization High Dose (Gy = J/Kg ) Inelastic collision with nuclei:  neutrons production and others fragments Depth dose distribution of various radiation modalities 4

  5. Ions vs X-rays physical advantages Multiple Scattering • Low dose on surface • High dose in depth • High precision on dose delivery • Minimal lateral scattering These are mainly dependent on the Dose Delivery System

  6. The hadrontherapy “machine” The elements and devices necessary to conform, control and adjust the beam just before the patient belong to the Dose Delivery System (DDS) ACCELERATOR Dose Delivery Beam line Patient Magnets (dipoles and quadrupoles), vacuum chambers and beam diagnostic devices characterize the beam transport system just before the Dose Delivery

  7. From the original beam dimension to the target dimension through the Dose Delivery System Target Vacuum chamber Pencil Beam FWHM 2 ÷ 10 mm Dim 1 ÷ 30 cm 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

  8. 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

  9. ACTIVE BEAM DELIVERY SOLUTIONS Two dipole magnets smear out the particles of a beam pulse y Vacuum window X F = q * (vΛB) Target Y z θ Beam x Beam monitors L L Scanning magnets 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

  10. To obtain the desired field, several scanning techniques can be adopted 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. Protons, Carbon ions y Scanned Field Scanning magnets z x Isocenter

  11. y y Scanned Field Scanned Field z z x x Isocenter Isocenter SPOT SCAN SOLUTIONS Itmoves a beam spot across the field in discrete steps Protons, Carbon ions Scanning magnets Requirements: fast system to switch on-off the beam Very time consuming

  12. y y Scanned Field Scanned Field z z x x Isocenter Isocenter 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 Protons, Carbon ions Scanning magnets

  13. 0.5 sec Beam ON t Beam OFF 1.5 sec CNAO “3D” active dose delivery system • (X,Y) VOXEL SCANNING • (Z) PARTICLE ENERGY VARIATION through the accelerator 2 sources Linac Scanning magnets SLICES Synchrotron E0<E1<…<En E0 E1 y En x Synchrotron time structure Nozzle and monitor system z INFN and University of Torino collaborate with Fondazione CNAO

  14. Detectors characteristics 2 integral chambers 2 strip chambers 1 pixel chamber Position Measurement every 80-100 s precision 100 m # strips  128 (1.65 mm pitch) Gap  5mm Gas  nitrogen HV  400 V 2D Position Measurement 2D Intensity Measurement Precision 200 m # pixels  1024 (6.6 mm pitch) Gap  5mm Gas  nitrogen HV  400 V Intensity Measurement Read every 1 s Integral sensitive area Gap  5mm Gas  nitrogen HV  400 V

  15. Power plant Synchrotron vault Main entrance Hospital rooms CNAO - Pavia

  16. CNAO Centro Nazionale di Adroterapia Oncologica • 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 ~26 m 3 treatment rooms: 3 horizontal lines 1 vertical line Treatment rooms 16

  17. Synchrotron room

  18. CNAO Dose Delivery System Hardware and Software characteristics

  19. Dose Delivery Interfaces Based on NI products and LabVIEW Real-Time Operating System DATA (monitor) Control Room Treatment Planning System BOX 1 BOX 2 Crate PXI -NI Chopper/Dump Interlock System Timing System Scanning Magnets Supervision System

  20. FPGA 1 FPGA 2 FPGA 4 FPGA 3 6534 1 6534 2 6534 4 6534 3 StX StY External BUS to connect FPGA1-2-3-4, interlock module and chopper module CRATE PXI PXI trig bus PXI data bus CPU TT O I/O I/O I/O Ethernet Ethernet Optical Link IM1 Interlock Supervision System and TPS Control Room PX IM2 Chopper Magnets X Y Optical Link Master Timing External BUS to trasnfer data between FPGA 2-3-4

  21. Monitor on-line the beam (fluence, position and dimension) • Set the beam position voxel by voxel through thedirect 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… PXI with FPGAs IDD IDD PS PS Dose Delivery DAQ IPS En IPS BOX 2 BOX 1 Slice 5 ionization chambers 1-4 : Integral chamber 2-3 : Strip chambers 5 : Pixel chamber Treated voxels Scanning magnets 5 4 1 2 3 Monitors

  22. “TREATMENT LOADING” TREATMENT SEQUENCE FROM DOSE DELIVERY Implemented with NI hardware and LabVIEW Real-Time Operating System “START DAQ” “SPILL ON” E0 E1 y En “END of SLICE or SPILL” x “STOP DAQ” “DATA STORAGE” Treatment volume z NO Slice Ended YES NO Treat Ended YES “LOGFILE CREATE” NI = National Instruments WAIT NEXT TREATMENT

  23. “TREATMENT LOADING” 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 “START DAQ” “SPILL ON” E0 E1 y “END of SLICE or SPILL” En For each voxel: x “STOP DAQ” (En, Np, X, Y) “DATA STORAGE” z (counts, xstrip, ystrip, Ix, Iy) NO Slice Ended For the ionization chamber counts also Pressure and Temperature dosimetric correction is done for each patient YES NO Treat Ended YES “LOGFILE CREATE” After a trigger from Timing System the monitor data acquisition from FPGA starts WAIT NEXT TREATMENT

  24. “TREATMENT LOADING” 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. “START DAQ” “SPILL ON” “END of SLICE or SPILL” “STOP DAQ” “DATA STORAGE” NO Slice Ended YES NO Treat Ended Treated voxels YES “LOGFILE CREATE” Slice WAIT NEXT TREATMENT En

  25. “TREATMENT LOADING” “START DAQ” “SPILL ON” • 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 “END of SLICE or SPILL” “STOP DAQ” “DATA STORAGE” NO Slice Ended YES NO Treat Ended YES “LOGFILE CREATE” WAIT NEXT TREATMENT

  26. Preliminary test of the CNAO scanning performance

  27. THE AIMS OF THE MEASUREMENTS • Acceptance test of the communication between Dose Delivery and Power Supply • The time response of the scanning magnet field • The performance of the scanning system with a real treatment

  28. SCANNING CHARACTERISTICS Power Supply Scanning Magnet Designed and built in collaboration between OCEM S.p.A and INFN-CNAO B Power rated = ±550A/±660V Rate 100 kA/s  vbeam> 20 m/s Current precision = ± 100 ppm L = 4.4 mH, R = 26 mΩ Bmax = 0.3 T with 606 A Homogeneity better than 0.2 % M. Incurvati et al “FAST HIGH-POWER POWER SUPPLY FOR SCANNING MAGNETS OF CNAO MEDICAL ACCELERATOR” – EPAC 08 - Genova

  29. Setup for the magnetic field measurement PXI FPGA 7831-R Vout x50 Iin = 100mA High Linearity Hall Probe for Room and Cryogenic Temperatures Nominal control current, In : 100 mA Sensitivity : 439 mV/T Range for B : ± 3 T Linearity : < 0.2 % Active area: 0.5x1.25 mm2 Band width: ~6 MHz FPGA with ADC analog channels: 8 resolution : 16 bit Input signal range: ±10 V DAQ rate: 200 kHz Noise : 3 counts (~0.17 A from PS)

  30. DATA FLOW 4 Mbaud optical link Iref, err PXI with FPGA 40 kHz Power Supply PXI with FPGA Iref, Imeas, err 10 m Shielded cable 200 kHz Dose Delivery System Hall probe B (a.u.) Magnet

  31. Acceptance test of the communication between Dose Delivery and Power Supply • Set of different currents OK (-540 A 540 A) • Transmission times check OK 4 Mbaud 40 kHz of data • Simulation of a transmission error OK • Detection of current out of range OK

  32. Performance Tests • Scan from -540 A  +540 A  -540 A with the following current steps: • 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) Probe Hall in 3 different positions within the magnet (0 cm, +20 cm, +25 cm) • Slices from treatments (scan in X and scan in Y) with Δt proportional to the fluence

  33. Scanning parameters Position – Speed – Time – Intensity – Dose Beam at position A: XA coordinate A planned IA current for PS NA # particles in A (Dose) tA time to deliver NA Beam at position B: XB coordinate B planned IB current for PS NB # particles in B (Dose) tB time to deliver NB A VA-B B tA-B = step time IA-B = current step Beam Speed = VA-B = (XA-XB)/tA-B Power Supply Current rate = dI/dt= (IA-IB)/tA-B IPS IDD t t Step planned by Dose Delivery from planned coordinate PS current Step

  34. Scan with 10 A step every 2 ms 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. A VA-B B

  35. Linearity step 10A Ips-Idd B-Idd Hysteresis Power Supply non-linearity negligible

  36. Scanning speed measurements GENERAL REQUIREMENTS: if 2.5 A ≤ ΔI ≤ 15 A  ΔI/ Δt > 100 kA/sec if ΔI < 2.5A  time < 200 μs Beam Speed for 1 A step From linear fit between 10 %- 90 % ΔI/Δt = 0.0201 A/μs ΔI/Δt= 20 kA/sec 1 A in Δt~ 50 μs << 200 μs Beam speed 4 m/sec for C6+ max E Beam speed 20 m/sec p minima E 1 A = 200 μm for C6+ (400Mev/u) Bρ= 6.36 Tm 1 A = 1 mm for p (60 Mev) Bρ= 1.14 Tm

  37. 2 A step in the magnet center From linear fit between 10 %- 90 % Slope = 0.0314 A/μs ΔI/Δt= 31 kA/sec 2A in Δt< 70 μs 2 A step at the magnet edge From linear fit between 10 %- 90 % ΔI/Δt= 0.0291 A/μs ΔI/Δt= 29 kA/sec 2A in Δt< 70 μs 70 μs << 200 μs required

  38. 10 A step in the magnet center Time for 20%-80% A step ( for ΔI = 6A) = 35 ± 5 us Time ΔI/Δt= ~ (6/35)*106 ~170 kA/sec 170 kA/sec >> 100 kA/sec required 10 A step in the magnet edge 10 A step out of the magnet

  39. Slice from Real Patient Treatment MEASURED and PLANNED VOXELS POSITIONS

  40. N particles/voxel Slice dose distributions MEASURED PLANNED Maximum N particles/voxel ~ 4*104 Treatment MEDIUM , slice 9

  41. Relative maximum difference 0.008 Difference between the real distribution obtained using the measured beam positions and the ideal distribution (from TPS) better than 1 %. (Required 2.5 %)

  42. 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

  43. 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

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