1. First DQE measurment of 500 µm thick Si hybrid pixel sensor with Photon counting readout for X-ray medical imaging M.Caria, J.Chaput, L.Sarry, B.Surre IWORID 2004 - Glasgow

2. IWORID 2004 - B.SURRE2 Introduction Aim: to measure system DQE following a standart protocole Requirements: –IEC 62220-1 –RQA 5 (~ 70 kVp) –Flat field corrected data

3. IWORID 2004 - B.SURRE3 Establishment of Standard X-ray spectrum Adjust kVp of generator to get RQA 5 spectrum such as: Spectrum Added filtration (mm Al) HVL (mm Al) RQA 3107 RQA 5217.1 RQA 7309.1 RQA 94011.5

4. IWORID 2004 - B.SURRE4 Measurement geometry

5. IWORID 2004 - B.SURRE5 Tube calibration @ RQA 5

6. IWORID 2004 - B.SURRE6 Set up ? Well known Photon counting chip = MEDIPIX 2 (chip set just above the noise) Bump bonded with 500 µm thick Si detector MUROS 2 interface Medisoft Thanks to the MEDIPIX collaboration

7. IWORID 2004 - B.SURRE7 Depletion voltage 20 % overdepletion  120 V

8. IWORID 2004 - B.SURRE8 Conversion function Pixel size 55x55 µm² Fluence: 91 #/(pixel.µGy) Slope: 5.9 count/(pixel.µGy) G=6.5%

9. IWORID 2004 - B.SURRE9 MTF (ESF) N = 1/tan( α ) = 12 Oversampling = 0.055 mm/12 Angle α

10. IWORID 2004 - B.SURRE10 SNR ? 20 flood images to compute the flat field coefficients

11. IWORID 2004 - B.SURRE11 ESF, RQA 5, 10 mAs

12. IWORID 2004 - B.SURRE12 7. Step (300 pts), RQA 5, 10 mAs Step(x)=ESF(x-x_shift)-ESF(x)

13. IWORID 2004 - B.SURRE13 DFT(Step) (300 pts), RQA 5, 10 mAs MTF(f)=|DFT(real step,f)|/|DFT(perfect step,f)|

14. IWORID 2004 - B.SURRE14 DFT(Step) (300 pts), RQA 5, 10 mAs MTF(f)=|DFT(real step,f)|/|DFT(perfect step,f)|

15. IWORID 2004 - B.SURRE15 DFT(Step) (300 pts), RQA 5, 10 mAs MTF(f)=|DFT(real step,f)|/|DFT(perfect step,f)|

16. IWORID 2004 - B.SURRE16 MTF, RQA 5, 10 mAs

17. IWORID 2004 - B.SURRE17 MTF, RQA 5, 10 mAs

18. IWORID 2004 - B.SURRE18 MTF, RQA 5, 10 mAs Presampling resolution: 7.7 lp/mm Visible detail limit = 0.3

19. IWORID 2004 - B.SURRE19 NPS @ RQA 5 dose

20. IWORID 2004 - B.SURRE20 NTF² @ RQA 5

21. IWORID 2004 - B.SURRE21 DQE @ RQA 5 DQE(f) = GxMTF²/NTF²

22. IWORID 2004 - B.SURRE22 NPS considerations & calculation Can we consider our results correct? >>> Calculations and simulations…

23. IWORID 2004 - B.SURRE23 Experimental NPS dose

24. IWORID 2004 - B.SURRE24 Simulated NPS dose

25. IWORID 2004 - B.SURRE25 NPS comparison: sim & exp

26. IWORID 2004 - B.SURRE26 1-D NPS comparison, 2 directions

27. IWORID 2004 - B.SURRE27 1-D NPS comparison

28. IWORID 2004 - B.SURRE28 1-D NPS comparison Interpolation increases the low frequencies

29. IWORID 2004 - B.SURRE29 Conlusions DQE has been calculated on 500 µm thick Si, bonded to a MEDIPIX2 chip A standard measure protocol have been used DQE is not so evident to find… How to improve this DQE ? (remember medicine) Next step: comparison with detectors of different thickness, study in parallel with detectors from the market, further calculations…

30. IWORID 2004 - B.SURRE30 Acknowledgements The MEDIPIX collaboration J.CHAPUT, M.CARIA L.SARRY You, for your attention