Talk JNM2 5

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A NOVEL b PARTICLES SILICON DOSIMETER Chiara Cappellini University of Insubria-Como IEEE NSS-MIC conference Rome, 18/21 October 2004 Chiara Cappellini University of Insubria-Como The author research is supported by the European Community under under the contract G1RD-CT-2001-00561

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SUCIMA PROJECT Sucima, Silicon Ultrafast Camera for b and g sources In Medical Applications, is a research project approved by the European Commission within the 5th framework program The project is coordinated by University of Insubria and eleven partners from five European countries are involved The main goal of the project is the development of a novel type of Silicon real time, high granularity, monolithic, pixel dosimeter to be used in medical application Two are the major application foreseen by the collaboration IV-Brachytherapy IEEE NSS-MIC conference Rome, 18/21 October 2004 Chiara Cappellini University of Insubria-Como http://sucima.dipscfm.uninsubria.it Hadrotherapy

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THE HYBRID SOLUTION The final SUCIMA sensor have been manufactured in CMOS and SOI monolithic technology In order to have an early feed-back from the “medical” end users hybrid prototypes have been developed Prof. Wojtek Kucewicz New Solid State Detectors N28-2. Dr. Grzegorz Deptuch Photodetectors and Radiation imaging N41-2. Dr. Laura Badano Beam Instrumentation N46-3 In the following….. CMOS SOI Brachytherapy Hadrotherapy IEEE NSS-MIC conference Rome, 18/21 October 2004 Chiara Cappellini University of Insubria-Como

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THE SENSOR Produced by HAMAMATSU on AGILE design Dimension: 9.5 x 9.5 cm2 Thickness : 410mm 768 strips; 121 m pitch Leakage current: 0.1nA/strip @ 80 V (full depletion) 6x128 channels, pitch=100 mm 4 different gains, integrating Range: ± 405, 41000 fC (110-11000 mip) double sample&hold -> no dead-time IEEE NSS-MIC conference Rome, 18/21 October 2004 Chiara Cappellini University of Insubria-Como Barbiellini, G. and others, Nucl. Instr. and Meth. A490 (2002) 146

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SENSOR QUALIFICATION Infra red laser (l= 1024 nm) on a mm 3D movement station Sensor qualification in terms of stability, repeatability, linearity and uniformity of response IEEE NSS-MIC conference Rome, 18/21 October 2004 Chiara Cappellini University of Insubria-Como

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ASSESSMENT OF RELATIVE DOSIMETRY Acquisition of DDC in PMMA phantoms and comparison with qualified dosimeters & MC 90Sr/Y A ~ 1 mCi IEEE NSS-MIC conference Rome, 18/21 October 2004 Chiara Cappellini University of Insubria-Como According to the AAPM tg60 prescriptions PMMA

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ASSESSMENT OF RELATIVE DOSIMETRY in = 0,74 mm ext = 1,19 mm source = 0,64 mm tunnel = 1,50 mm 85 m of fall off source  10% dishomogenity Acquisition of azimuthal profiles in PMMA phantoms and comparison with qualified dosimeters IEEE NSS-MIC conference Rome, 18/21 October 2004 Chiara Cappellini University of Insubria-Como

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TOWARDS ‘ABSOLUTE’ DOSIMETRY From strips to pixels… 1D 2D To fully qualify the system it is necessary to prove the possibility of absolute dosimetry, i.e. to directly measure the dose from the energy released in the sensor. But using strip detector, the problem is how to convert the charge integrated along one strip to that released in each point of the sensor! To prove the principle, the idea is to use the signal information from the strips and the geometrical information one can get from GafChromic films IEEE NSS-MIC conference Rome, 18/21 October 2004

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1st step: digitising the Gaf… From the 2D dose map it is possible to get the integrated dose along one dimension. This information corresponds to the one returned by the strips… D = 17x3-23.96x2+24.94x-0.3941 A.U. pixel rows silicon strips IEEE NSS-MIC conference Rome, 18/21 October 2004

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3rd step: scaling factor A B 95% of the fitted function peak value = 20% of the signal  statistically significant value define a length along which we assume a uniform dose release and a “scaling factor for the strips outcome IEEE NSS-MIC conference Rome, 18/21 October 2004 Chiara Cappellini University of Insubria-Como

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4th step: scaling the strips outcome… Finally we get the released DOSE !!!  3% IEEE NSS-MIC conference Rome, 18/21 October 2004 Chiara Cappellini University of Insubria-Como

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The Dose Rate… mm 144 Ce source 90Sr source Still a systematic error… Enhanced in the edges IEEE NSS-MIC conference Rome, 18/21 October 2004 Chiara Cappellini University of Insubria-Como Blurring of the image Detection efficiency energy dependence Further investigate the acquisition geometry and the densitometer output Keep in mind…

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CONCLUSIONS Chiara Cappellini University of Insubria-Como 8 full size board have been assembled and qualified Thanks!!! The possibility of relative dosimetry has been well assessed and proved Promising results have been obtained by the geometrical analysis with Gafchromics films Measurement with the pixel sensors are scheduled in the nearest future Studies on the possibility of Radiotherapic beams profilometry have been undertaken… In this concern spectrometric measurements of the scattered radiation are also planned IEEE NSS-MIC conference Rome, 18/21 October 2004