1. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 1 IWORID 4, September 2002 Large scale x-ray images taken with the Medipix1 chip Karl-Friedrich Pfeiffer Physikalisches Institut, Abt. 4 Universität Erlangen-Nürnberg Workgroup SPOC * Medipix Collaboration *Single PhOton Counting

2. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 2 IWORID 4, September 2002 Overview " The Medipix1 chip " Experimental setup " Large Images 1: 'Move and Tile' Measurement and Simulation " Large Images 2: 'Tile and Move' Measurement and Simulation " DQE Measurements " Summary

3. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 3 IWORID 4, September 2002 The Medipix1 chip " Pixelated solid state hybrid detector for single photon counting  64 x 64 Pixel, size 170  m  active area 10.88 x 10.88 mm 2 " Semiconductor sensor layer bump-bonded to the pixelated read-out electronics chip  Sensor layer: e.g. 300  m Si, but other materials (GaAs, Cd(Z)Te...) can be used as well " Developed within the framework of the Medipix1 collaboration

4. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 4 IWORID 4, September 2002 Experimental setup Computer 1: main control Computer 2: data acquisition Translation stages X-ray generator MUROS1 board & Medipix1 chip " Complete imaging process controlled by computer 1 " Data acquisition done with Medisoft software (developed in the Medipix collaboration) " (Semi-)automated processing of acquired data

5. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 5 IWORID 4, September 2002 Large Images 1: 'Move and Tile' " Make single exposure with single detector " Move detector to next position " Make another exposure " Repeat until the whole area is covered " Merge all single exposures to get one large tiled image

6. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 6 IWORID 4, September 2002 Large Images 1: Measurement 5x5 single exposures, 10 pixels overlap

7. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 7 IWORID 4, September 2002 Comparison Measurement - Simulation Object: „Siemensstern“ 0.05mm Pb in 2mm PMMA Ø 4.5cm " Contrast Pb -Air: 0.965 " Contrast Pb-PMMA: 0.941 Contrast ratio measurement -simulation: 0.996 0.978 " Contrast Pb -Air: 0.969 " Contrast Pb-PMMA: 0.962

8. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 8 IWORID 4, September 2002 Large Images 2: 'Tile and Move' " Tile several detectors to make an array " Take large picture (with gaps) " Move array to next position " Take another picture " Repeat to cover all gaps " Merge pictures to get one large image without gaps and with high photon statistics

9. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 9 IWORID 4, September 2002 Large Images 2: Measurement 3 images, 4 x 4 tiles each

10. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 10 IWORID 4, September 2002 Comparison Measurement - Simulation Object: „Siemensstern“ 0.05mm Pb in 2mm PMMA Ø 4.5cm " Contrast Pb -Air: 0.954 " Contrast Pb-PMMA: 0.928 Contrast ratio measurement -simulation: 0.988 0.964 " Contrast Pb -Air: 0.966 " Contrast Pb-PMMA: 0.963

11. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 11 IWORID 4, September 2002 Improved 'Tile and Move' If it is possible to tile several detecors without gaps (e.g. with the Medipix2 chip):  Tile detectors to get ’detector bars': two pictures are sufficient to cover all gaps  even faster & less dose!

12. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 12 IWORID 4, September 2002 DQE Definition " DQE: Detective Quantum Efficiency " SNR: Signal-to-Noise-Ratio 1 in: SNR of incoming radiation field (~  N ) 2 out: SNR of the image " f = f(x,y): Spatial frequency

13. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 13 IWORID 4, September 2002 Calculation of the DQE  : System gain factor MTF: Modulation Transfer Function NPS: Noise Power Spectrum : Mean photon energy  0 : Incoming energy fluence

14. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 14 IWORID 4, September 2002 DQE Measurement " MTF(f) measurement: line pair phantom " NPS out measurement: flat field images "... some lenghty calculations...  DQE(f) 15.5cm

15. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 15 IWORID 4, September 2002 MTF: results

16. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 16 IWORID 4, September 2002 First DQE results

17. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 17 IWORID 4, September 2002 Summary " There are basically two ways to get large field images: 1) 'Move and Tile': single detector, flexible, but takes quite a long time and high dose  'Lab Method' 2) 'Tile and Move': quite fast, but requires several detectors  'Standard Imaging Method'  The MTF and DQE of a Medipix1 chip with a 300  m Si sensor layer was determined " We are looking forward to the Medipix2 chip

18. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 18 IWORID 4, September 2002 Thanks to: " Prof. G. Anton 1 " Ch. Bert 1 & D. Niederlöhner 1 " J. Giersch 1 " M. Hoheisel 2 & L. Bätz 2 (for the DQE calculations) " Medipix Collaboration " B. Mikulec 3 1 Universität Erlangen 2 Siemens 3 CERN

19. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 19 IWORID 4, September 2002 Phantoms used: Siemensstern Line pair phantom

20. K.-F. Pfeiffer, PI4 Universität Erlangen-Nürnberg 20 IWORID 4, September 2002 Background picture: blown fuse