MATRIX an innovative Pixel Ionization Chamber for Online

MATRIX an innovative Pixel Ionization Chamber for Online Monitoring of Hadrontherapy Treatments Giuseppe Pittà TERA Foundation for Oncological Hadrontherapy Frontier. Science 2005 - 16. 09. 05 - G. P. 1

MATRIX PIXEL IONIZATION CHAMBER for on-line control system 2 D information on: DOSE delivered to patient during the irradiation BEAM POSITION treatment planning specifications Collaboration between TERA, the University of Torino, INFN - Torino and the University of Piemonte Orientale “A. Avogadro” Frontier. Science 2005 - 16. 09. 05 - G. P. 2

Structure of the detector Mylar window Front-end boards Anode Mylar window Frontier. Science 2005 - 16. 09. 05 - G. P. Cathode • • • Anode: 1024 pixels Sensitive area: 21 × 21 cm 2 Pixel dimension: 6. 5 × 6. 5 mm 2 3

Anode and Cathode Very thin ANODE GLUING Kapton: 50 mm - Copper: 17 mm The anode and the cathode are glued on the fiberglass frames with a nonconducting epoxy araldite Sensitive area: 1024 pixels Guard rind Connection with front-end boards – pads for connectors Frontier. Science 2005 - 16. 09. 05 - G. P. 4

Front-end electronics READ-OUT • • TTL digital output Maximum digital count frequency: 5 MHz Quantum of charge adjustable in the range 100 - 800 f. C Tested minimum read-out time for the full chamber: 1 ms. 1024 channels 8 electronic boards 16 TERA 06 chips Frontier. Science 2005 - 16. 09. 05 - G. P. MATRIX - Fully assembled 5

First beam tests at the cyclotron of JRC (Ispra, Italy) MATRIX Frontier. Science 2005 - 16. 09. 05 - G. P. 6

Beam tests at the cyclotron of JRC First run (end of November 2004) 2 D ma po f th eb ea m Conteggi al secondo Very low electronic noise: less than one count per second per channel Frontier. Science 2005 - 16. 09. 05 - G. P. Beam energy: 17 Me. V Beam current: 5 n. A 7

Beam tests at the cyclotron of JRC 1 2 25 cm 1 3 50 cm 2 3 100 cm l 400 mm Al exit window l Longitudinal displacements of 25, 50, 100 cm in air Simulation (SRIM) Frontier. Science 2005 - 16. 09. 05 - G. P. 8

Beam tests at the Loma Linda University Medical Center • First hospital-based proton therapy centre, built in 1993 • 160/sessions a day Frontier. Science 2005 - 16. 09. 05 - G. P. 9

MATRIX at LLUMC MATRIX HV and LV power supplies Room for proton-therapy - horizontal beam Frontier. Science 2005 - 16. 09. 05 - G. P. 10

The first measurements 5 cm diameter collimator (about 6 cm at isocenter) 14 x 14 cm square field (about 15 x 15 cm at isocenter) Frontier. Science 2005 - 16. 09. 05 - G. P. 11

Calibration No calibration • • • Calibration Data taken with the chamber in three different positions with a constant beam (base position, 90 o rotation, 6. 5 mm displacement) No assumptions on the shape of the beam Flatness of < 2% has been obtained Frontier. Science 2005 - 16. 09. 05 - G. P. 12

Stability • Constant beam intensity • Counting Vs Monitor Units • The linearity is better then 2 per mill Frontier. Science 2005 - 16. 09. 05 - G. P. 13

Bragg Peak • Ebeam = 149 Me. V Total sum (Counts) • Absorbers of water equivalent material Depth in water (mm) Frontier. Science 2005 - 16. 09. 05 - G. P. 14

Beam shape MATRIX in a rotating gantry Beam shaped for a prostate cancer Frontier. Science 2005 - 16. 09. 05 - G. P. 15

Pencil beam MATRIX in the experimental room Frontier. Science 2005 - 16. 09. 05 - G. P. Pencil beam 16

Conclusions and Outlook l The MATRIX pixel ionization chamber has been successfully constructed and tested l Several beam tests at JRC and LLUMC on – Beam shape – Calibration – Bragg Peak – Spot scanning l MATRIX is a very powerful detector that can be used for precision monitoring of dose and beam position during hadrontherapy treatments Frontier. Science 2005 - 16. 09. 05 - G. P. 17