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DITANET Workshop 08 November 2011 Alessio Bocci, CNA 1 A silicon strip detector for a novel 2D dosimetric method for complex radiotherapy treatment verication.

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Presentation on theme: "DITANET Workshop 08 November 2011 Alessio Bocci, CNA 1 A silicon strip detector for a novel 2D dosimetric method for complex radiotherapy treatment verication."— Presentation transcript:

1 DITANET Workshop 08 November 2011 Alessio Bocci, CNA 1 A silicon strip detector for a novel 2D dosimetric method for complex radiotherapy treatment verication Alessio Bocci DITANET Experienced Researcher

2 Complex radiation therapy treatments - IMRT Detectors for dosimetric applications RADIA2 project : experimental set-up Measurements and results Conclusions DITANET Workshop 08 November 2011 Alessio Bocci, CNA 2 Outline

3 Motivation and Objective Motivation: Cancer is the second most frequent cause of death in developed countries. At present, although surgery is the most effective way to remove the malignant tissue, when it is combined with radiation therapy improves the cure rate by 40% approximately. Objective Characterization of a silicon strip detector dedicated to 2D dose measurements in the axial plane of a phantom for the verification of complex radiation therapy treatment plans (i.e. IMRT) DITANET Workshop 08 November 2011 Alessio Bocci, CNA 3

4 Many beam directions and entrance points for conformal doses distributions modulating in space the fluence of each radiation field DITANET Workshop 08 November 2011 Alessio Bocci, CNA 4 Intensity Modulated Radiation Therapy

5 Dosimetry for radiotherapy verification Ionization chambers – gold standard detectors Radiographic and radiochromic films Semiconductor dosimeters: Silicon diodes DITANET Workshop 08 November 2011 Alessio Bocci, CNA 5 2D Detectors dedicated to radiotherapy verification plans verification plans

6 Film dosimetry used as 2D dosimeters : Advantages : high spatial resolution (sub-mm), good uniformity, axial plane Disadvantages : Unusable as on-line detectors and are unreliable and time consuming detectors Film dosimeters: traditional detectors for verifying treatment plans dose distribution DITANET Workshop 08 November 2011 Alessio Bocci, CNA 6 Dose distribution verification Axial plane (inferior and superior) Coronal plane (ventral and dorsal) Sagittal plane

7 IMRTLog (ONCOlog Medical) 2D array silicon diodes spatial resolution 0.5 to 1.0 cm IMRT MatriXX (Scanditronix/Wellhöfer) array of ionizations chambers MapCHECK (Sun Nuclear) silicon diodes Spatial resolution is still poor with respect to film dosimeters These devices are useful only for one irradiation angle and they can measure dose distribution only in the coronal plane of the patient DITANET Workshop 08 November 2011 Alessio Bocci, CNA 7 2D Digital Detectors in radiotherapy treatments Single silicon detectors and ionization chambers assembled for 2D detectors

8 New detection systems Traditional detectors New detection systems It is necessary to develop new detection systems that enhance the traditional ones, and that are able to verify in a simple and accurate way complex treatment planning Radiographic films DITANET Workshop 08 November 2011 Alessio Bocci, CNA 8 Film dosimeters commercial 2D commercial digital detectors New detection systems On-lineno Spatial resolution poor 2D detectors yes Not monolithic! Axial plane no inexpensive radiation hard easy to use

9 Silicon strip detectors CNA in a telescope configuration Silicon strip detectors Virgen Macarena Hospital in Seville silicon tracking detectors silicon detectors for medical applications DITANET Workshop 08 November 2011 Alessio Bocci, CNA 9 From Nuclear Physics to Medical Applications Medical applications can benefit from the developments on nuclear and high energy physics detector technology

10 Commercial silicon detector Low cost Normally used on particle detection (W1 type from Micron Semiconductor Ltd) Single sided 16 strips (3.1 mm pitch) Active area 50 x 50 mm² & 500 µm thick DITANET Workshop 08 November 2011 Alessio Bocci, CNA 10 RADIA2 Project Si-DETECTOR

11 Advantages: Linear relationship between photon energy and e/h pairs ; High sensitivity (Si eV/pair – sensitivity per unit volume: 640 nC Gy -1 /mm 3 ) (about times the sensitivity per unit volume of an ionization chamber) ; Small active volume that allows to obtain high spatial resolution ; Well developed technology for the production of segmented monolithic planar detectors ; Radiation hard material ; DITANET Workshop 08 November 2011 Alessio Bocci, CNA 11 Why Silicon detectors ? C. Talamonti et al, NIM-A 658 (2011) 84–89

12 Signals from each strip are converted to the absorbed dose Radiotherapy energies photon interactions : Compton Effect Secondary electrons from the phantom interacts centemeters away DITANET Workshop 08 November 2011 Alessio Bocci, CNA 12 Single-sided-Si-strip detectors (SSSSD) Water-equivalent phantom γ photons

13 Z. Abou-Haidar 1, M. A. G. Alvarez 1,R. Arrans 3, A. Bocci 1, M. A. Cortes-Giraldo 2, J. M. Espino 2,M. I. Gallardo 2, A. Perez Vega-Leal 4 F. J. Perez Nieto 5, J. M. Quesada 2 1.DITANET National Accelerator Centre (CNA) 2.Department of Atomic, Molecular and Nuclear Physics (FAMN), University of Seville 3. Virgen Macarena University Hospital, Seville 4. School of Engineering, University of Seville 5. Instalaciones Inabensa S.A. DITANET Workshop 08 November 2011 Alessio Bocci, CNA 13 RADIA2 Project – Collaboration A. Bocci et. al., A silicon strip detector for a novel 2D dosimetric method for radiotherapy treatment verication submitted to NIM-a (October 2011) A. Bocci et. al., Empirical characterization of a silicon strip detector for a novel 2d mapped method for dosimetric verification of radiotherapy treatments, Radiotherapy and Oncology, Volume 99, Supplement 1, May 2011, Page S172 M. A. Cortes-Giraldo et al., "Geant4 Simulation to Study the Sensitivity of a MICRON Silicon Strip Detector Irradiated by a SIEMENS PRIMUS Linac", Progress in Nuclear Science and Technology, in press (2011)

14 Siemens PRIMUS linac dual energy machine operating at 6 MV photon mode University Hospital Virgen Macarena (Seville, Spain) DITANET Workshop 08 November 2011 Alessio Bocci, CNA 14 LINAC accelerator A treatment planning system TPS (Philips Pinnacle) was used to calculate dose distributions. Calculations were compared to experimental data

15 Two phantoms prototypes were designed and built Polyethylene slab material Cylindrical phantom 1. A slab phantom for: detector characterization (sensitive area perpendicular to the beam direction) 2. A cylindrical phantom for: angular response measurements & 2D treatment plans verification in the axial plane DITANET Workshop 08 November 2011 Alessio Bocci, CNA 15 Experimental Set-up

16 Set-up 2: The active area of the detector is parallel axial plane to the beam direction (axial plane) This work is part of a more ambitious project aiming to: Employ this prototype for obtaining 2D dose maps by an in-house developed algorithm dedicated to verify IMRT treatment plans. This system is patent pending as an innovation axial plane, Since common ways to present dose distributions is a dose map in the patient axial plane, as an innovation the detector was placed in the cylindrical phantom in the axial plane, parallel to the beam axis DITANET Workshop 08 November 2011 Alessio Bocci, CNA 16 Detector in the axial plane

17 Charge integrators for each strip (electrometers) digitized (12 bits) and analyzed by a Digital signal processor (DSP) discrete electronics developed in-house A PC allows to control and to retrieve data via an RS-232 serial bus based on a LabVIEW software DITANET Workshop 08 November 2011 Alessio Bocci, CNA 17 Electronics School of Engineering, University of Seville School of Engineering, University of Seville Virgen Macarena University Hospital, Seville

18 Set-up 1: Linearity Uniformity Calibration Percent Depth Dose (PDD) Penumbra Set-up 2: TPS and Geant4 Simulations Angular measurements Final calibration DITANET Workshop 08 November 2011 Alessio Bocci, CNA 18 Measurements Detector characterization Angular response

19 Set-up 1: Linearity Linearity Uniformity Calibration Percent Depth Dose (PDD) Penumbra Set-up 2: TPS and Geant4 simulations Angular measurements Final calibration DITANET Workshop 08 November 2011 Alessio Bocci, CNA 19 Measurements Detector characterization Angular response

20 Linearity with dose better than 0.1 % for all channels Set-up 1: SSSSD perpendicular to the beam direction DITANET Workshop 08 November 2011 Alessio Bocci, CNA 20 Linearity

21 Set-up 1: Linearity Uniformity Uniformity Calibration Percent Depth Dose (PDD) Penumbra Set-up 2: TPS and Geant4 simulations Angular measurements Final calibration DITANET Workshop 08 November 2011 Alessio Bocci, CNA 21 Measurements Detector characterization Angular response

22 Uniformity better than 0.5 % for all channels Set-up 1: SSSSD perpendicular to the beam direction DITANET Workshop 08 November 2011 Alessio Bocci, CNA 22 Uniformity Non-uniformities depend by the different strip efficiency and gain of the electronics

23 Set-up 1: Linearity Uniformity Calibration Calibration Percent Depth Dose (PDD) Penumbra Set-up 2: TPS and Geant4 simulations Angular measurements Final calibration DITANET Workshop 08 November 2011 Alessio Bocci, CNA 23 Measurements Detector characterization Angular response

24 Calibration in standard condition radiation eld 10 × 10 cm 2 source-to-surface distance (SSD) = 100 cm 1.5 cm of water-equivalent solid slabs Set-up 1: SSSSD perpendicular to the beam direction DITANET Workshop 08 November 2011 Alessio Bocci, CNA 24 Calibration Monitor Units –> Voltage -> cGy

25 Set-up 1: Linearity Uniformity Calibration Percent Depth Dose (PDD) Percent Depth Dose (PDD) Penumbra Set-up 2: TPS and Geant4 simulations Angular measurements Final calibration DITANET Workshop 08 November 2011 Alessio Bocci, CNA 25 Measurements Detector characterization Angular response

26 The difference between SSSSD and ionization chamber is: 0.68 % at 10 cm and 0.73 % at 15 cm Set-up 1: SSSSD perpendicular to the beam direction DITANET Workshop 08 November 2011 Alessio Bocci, CNA 26 Percent Depth Dose Dose at different depth measured using different water-equivalent solid slabs

27 Set-up 1: Linearity Uniformity Calibration Percent Depth Dose (PDD) Penumbra Penumbra Set-up 2: TPS and Geant4 simulations Angular measurements Final calibration DITANET Workshop 08 November 2011 Alessio Bocci, CNA 27 Measurements Detector characterization Angular response

28 SSSSD penumbra value larger than the one obtained when using a single silicon detector This was mainly due to the SSSSD strips pitch of 3.1 mm Geant4 simulations gave compatible results Improvements with a future prototype (next project) Set-up 1: SSSSD perpendicular to the beam direction DITANET Workshop 08 November 2011 Alessio Bocci, CNA 28 Penumbra SSSSD: 6.17 ± 0.56 mm - single silicon diode: 3.92 ± 0.20 mm Region between 20 % and 80 % of the maximum dose levels at 1.5 cm water depth

29 Set-up 1: Linearity Uniformity Calibration Percent Depth Dose (PDD) Penumbra Set-up 2: Geant4 simulations and TPS calculations Angular measurements Final calibration DITANET Workshop 08 November 2011 Alessio Bocci, CNA 29 Measurements Detector characterization Angular response

30 DITANET Workshop 08 November 2011 Alessio Bocci, CNA 30 Geant4 simulations and TPS calculations Treatment head Geometry Model Phantom SSSSD Detector M. A. Cortés Giraldo, Ph. D. Thesis, 2011 The geometry of the Siemens treatment head at 6 MV nominal energy photons, was reproduced in detail The geometric model of the phantoms and of the SSSSD was also reproduced The absorbed dose in each strip was calculated Geant4 Simulations were also performed for calculating the dose-to-water case for comparisons with TPS calculations M. A. Cortes-Giraldo et al., "Geant4 Simulation to Study the Sensitivity of a MICRON Silicon Strip Detector Irradiated by a SIEMENS PRIMUS Linac", Progress in Nuclear Science and Technology, in press (2011)

31 Set-up 1: Linearity Uniformity Calibration Percent Depth Dose (PDD) Penumbra Set-up 2: Geant4 simulations and TPS calculations Angular measurements Final calibration DITANET Workshop 08 November 2011 Alessio Bocci, CNA 31 Measurements Detector characterization Angular response

32 DITANET Workshop 08 November 2011 Alessio Bocci, CNA 32 gantry detector Set-up 2: SSSSD parallel to the beam direction Two experimental measurements

33 DITANET Workshop 08 November 2011 Alessio Bocci, CNA 33 Angular Response Comparison between exp. data, TPS and Geant4 Set-up 2: SSSSD parallel to the beam direction Steps of 45 0 The agreement between the tendency of experimental data at dierent angles and the TPS is notable This implies that the new calibration factors are independent of the irradiation angle Constant calibration factors

34 Set-up 1: Linearity Uniformity Calibration Percent Depth Dose (PDD) Penumbra Set-up 2: Geant4 simulations and TPS calculations Angular measurements Final calibration DITANET Workshop 08 November 2011 Alessio Bocci, CNA 34 Measurements Detector characterization Angular response

35 Calibration factors: Experimental/TPS Calibration factors independent of angular irradiation and of strip number DITANET Workshop 08 November 2011 Alessio Bocci, CNA 35 Final Calibration Set-up 2: SSSSD parallel to the beam direction Constant calibration factors gantry detector

36 Relative dierence between the calibrated dose and TPS calculations are better than 2 % DITANET Workshop 08 November 2011 Alessio Bocci, CNA 36 Final Calibration Calibrated dose Set-up 2: SSSSD parallel to the beam direction gantry detector

37 Main Objective: Characterize and benchmark a new detection system based on a Si-strip detector dedicated to 2D dose measurements in the axial plane of a cylindrical phantom SSSSD characterization: results shows that the prototype is suitable for IMRT verication plans (remarkable linearity, uniformity, PDD) The angular response of the detector in the axial plane was independent of the irradiation angle and of the strip number Geant4 simulations gave compatible results with respect to TPS and to experimental data Final calibration with respect to TPS in the axial plane gives dierences smaller than 2 % for all the strips This system is patent pending OEMP PATENT number P DITANET Workshop 08 November 2011 Alessio Bocci, CNA 37 Conclusions

38 Future: work is in progress in order to obtain 2D dose maps from experimental data in the axial plane using an in-house developed algorithm based on the Radon Transform A new SSSSD prototype and a new experimental set-up has been designed to improve the spatial resolution, coupling the data acquisition system with a reconstruction algorithm and with an on-line graphical interface software Future developments DITANET Workshop 08 November 2011 Alessio Bocci, CNA 38

39 Z. Abou-Haidar 1, M. A. G. Alvarez 1,R. Arrans 3, A. Bocci 1, M. A. Cortes-Giraldo 2, J. M. Espino 2,M. I. Gallardo 2, A. Perez Vega-Leal 4 F. J. Perez Nieto 5, J. M. Quesada 2 1.DITANET National Accelerator Centre (CNA) 2.Department of Atomic, Molecular and Nuclear Physics (FAMN), University of Seville 3. Virgen Macarena University Hospital, Seville 4. School of Engineering, University of Seville 5. Instalaciones Inabensa S.A. DITANET Workshop 08 November 2011 Alessio Bocci, CNA 39 RADIA2 Project – Collaboration A. Bocci et. al., A silicon strip detector for a novel 2D dosimetric method for radiotherapy treatment verication submitted to NIM-a (October 2011) A. Bocci et. al., Empirical characterization of a silicon strip detector for a novel 2d mapped method for dosimetric verification of radiotherapy treatments, Radiotherapy and Oncology, Volume 99, Supplement 1, May 2011, Page S172 M. A. Cortes-Giraldo et al., "Geant4 Simulation to Study the Sensitivity of a MICRON Silicon Strip Detector Irradiated by a SIEMENS PRIMUS Linac", Progress in Nuclear Science and Technology, in press (2011)

40 Thank you for your attention!!!

41 Single Strip and 2D monolithic silicon detectors Research is directed towards silicon microstrip technology to improve spatial resolution Pixellated monolithic silicon detectors such as the 2D array D. Menichelli et al., Nucl. Instr. and Meth. A, 583, 109 (2007) Single crystal n-Si 128 channels 32 mm x 0.2 mm 128 phosphor implanted n+ strips on a p- type silicon wafer J. H. D. Wong et al., Medical Physics 37 (2010) 427–439 I. Redondo-Fernandez et al, NIM-a, (2007) 141– CMRP DMG 441 Si n+p diodes 50 µm epi layer growth on MCz p. Active area: 6.29 x 6.29 cm DOSI 3. European project MAESTRO DITANET Workshop 08 November 2011 Alessio Bocci, CNA 29

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