Large scale x-ray images taken with the Medipix

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

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

The Medipix 1 chip " Pixelated solid state hybrid detector for single photon counting " 64 x 64 Pixel, size 170 mm Þ 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 mm Si, but other materials (Ga. As, Cd(Z)Te. . . ) can be used as well Developed within the framework of the Medipix 1 collaboration K. -F. Pfeiffer, PI 4 Universität Erlangen-Nürnberg 3 IWORID 4, September 2002

Experimental setup Computer 1: main control Computer 2: data acquisition X-ray generator MUROS 1 board & Medipix 1 chip Translation stages " " " Complete imaging process controlled by computer 1 Data acquisition done with Medisoftware (developed in the Medipix collaboration) (Semi-)automated processing of acquired data K. -F. Pfeiffer, PI 4 Universität Erlangen-Nürnberg 4 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 K. -F. Pfeiffer, PI 4 Universität Erlangen-Nürnberg 5 IWORID 4, September 2002

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

Comparison Measurement - Simulation Object: „Siemensstern“ 0. 05 mm Pb in 2 mm PMMA Ø 4. 5 cm " " Contrast Pb -Air: 0. 965 Contrast Pb-PMMA: 0. 941 K. -F. Pfeiffer, PI 4 Universität Erlangen-Nürnberg Contrast ratio measurement -simulation: 0. 996 " " 0. 978 7 Contrast Pb -Air: 0. 969 Contrast Pb-PMMA: 0. 962 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 K. -F. Pfeiffer, PI 4 Universität Erlangen-Nürnberg 8 IWORID 4, September 2002

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

Comparison Measurement - Simulation Object: „Siemensstern“ 0. 05 mm Pb in 2 mm PMMA Ø 4. 5 cm " " Contrast Pb -Air: 0. 954 Contrast Pb-PMMA: 0. 928 K. -F. Pfeiffer, PI 4 Universität Erlangen-Nürnberg Contrast ratio measurement -simulation: 0. 988 " " 0. 964 10 Contrast Pb -Air: 0. 966 Contrast Pb-PMMA: 0. 963 IWORID 4, September 2002

Improved 'Tile and Move' If it is possible to tile several detecors without gaps (e. g. with the Medipix 2 chip): Þ Tile detectors to get ’detector bars': two pictures are sufficient to cover all gaps Þ even faster & less dose! K. -F. Pfeiffer, PI 4 Universität Erlangen-Nürnberg 11 IWORID 4, September 2002

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

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

DQE Measurement " " " MTF(f) measurement: line pair phantom NPSout measurement: flat field images. . . some lenghty calculations. . . Þ DQE(f) 15. 5 cm K. -F. Pfeiffer, PI 4 Universität Erlangen-Nürnberg 14 IWORID 4, September 2002

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

First DQE results K. -F. Pfeiffer, PI 4 Universität Erlangen-Nürnberg 16 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 Þ 'Lab Method' 2) 'Tile and Move': quite fast, but requires several detectors Þ 'Standard Imaging Method' " " The MTF and DQE of a Medipix 1 chip with a 300 mm Si sensor layer was determined We are looking forward to the Medipix 2 chip K. -F. Pfeiffer, PI 4 Universität Erlangen-Nürnberg 17 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 K. -F. Pfeiffer, PI 4 Universität Erlangen-Nürnberg 2 Siemens 3 CERN 18 IWORID 4, September 2002

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

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