Imaging spectroscopic performances for a Si based detection system

We present the imaging and spectroscopic capabilities of a system based on a single photon counting chip (PCC) bump-bonded on a Si pixel detector. The system measures the energy spectrum and the flux, produced by a standard mammographic tube. We have also made some images of low contrast details, achieving good results

Experimental study of Compton scattering reduction in digital mammographic imaging

In mammography, the first cause of image contrast reduction arises from the photons scattered inside the examined organ. The amount of Compton scattering strongly depends on the irradiation area and on the distance between the organ and the X-ray detector. We have experimentally evaluated how these geometrical conditions affect the scattering fraction. Our experimental setup includes a single photon counting device based on a silicon pixel detector as X-ray sensor; a lucite cylinder to simulate the breast tissue, and a lead collimator to define the irradiation area. We have evaluated the contrast and the signal-to-noise ratio for images acquired in different conditions

Study of GaAs detectors characteristics for medical imaging

In this work we present the results of a systematic study about SI GaAs detectors as a function of substrate and contact type, geometry and thickness. This study has been stimulated from the interest in using GaAs as a detector for medical imaging applications. GaAs detectors have been produced using crystals grown with different techniques and changing both the thickness (in the range 200 μm-1 mm) and the contacts type and geometry. We have measured the current-voltage characteristics and, using radioactive sources (109Cd, 20 keV photons, 241Am, 60 keV photons, 99mTc, 140 keV photons), we have studied the performance of our detectors in terms of charge collection efficiency and energy resolution as a function of the bias voltage. Besides we have also studied the electrical and spectroscopic properties of GaAs detectors with different types and concentrations of the dopants in the substrate. So we have found the optimal doping type and concentration to have the best spectroscopic performances and the higher breakdown voltage. Simulation programs made with Monte Carlo methods have been developed to describe the electric field distribution and the transport of charge carriers toward the electrodes in GaAs detectors. In these simulations we have considered the presence of deep energy levels in the bandgap, the thickness, the bias voltage and the charge deposition in the crystal after photon interaction

Low contrast imaging with a GaAs pixel digital detector

A digital mammography system based on a GaAs pixel detector has been developed by the INFN (Istituto Nazionale di Fisica Nucleare) collaboration MED46. The high atomic number makes the GaAs a very efficient material for low energy X-ray detection (10-30 keV is the typical energy range used in mammography). Low contrast details can be detected with a significant dose reduction to the patient. The system presented in this paper consists of a 4096 pixel matrix built on a 200 μm thick semi-insulating GaAs substrate. The pixel size is 170×170 μm2 for a total active area of 1.18 cm2 . The detector is bump-bonded to a VLSI front-end chip which implements a single-photon counting architecture. This feature allows to enhance the radiographic contrast detection with respect to charge integrating devices. The system has been tested by using a standard mammographic tube. Images of mammographic phantoms will be presented and compared with radiographs obtained with traditional film/screen systems. Monte Carlo simulations have been also performed to evaluate the imaging capability of the system. Comparison with simulations and experimental results will be shown

Visibility of tumor-like details in inline phase contrast mammography using quasi monochromatic X-ray sources

A new generation of quasi monochromatic high-flux X-ray sources, based on the X-ray radiation produced through Compton scattering between an electron beam and a laser beam, is under development. One of the possible applications of this source is inline phase contrast mammography, based on the observation of the edge-enhancement effect that can be observed at the border of structures inside the breast in images produced using a partially or totally coherent X-ray beam. In this work we present the results of a set of simulations of inline phase contrast mammography using typical inverse Compton scattering sources parameters. The simulated sample was a tumour-like mass having spherical shape, diameter between 200 mu m and 5 mm, placed inside a breast-like matrix, 4cm thick, and a standard composition of 50% glandular tissue and 50% adipose tissue. We discuss the minimum requirements for mammography using inverse Compton scattering sources and we discuss how the working parameters of the experimental setup (focal spot size, source-object distance, object-detector distance, detector point spread function, mean energy, energy bandwidth) affect the image quality, and specifically the edge-enhancement visibility. In particular, we show that the energy bandwidth does not significantly affect the visibility up to several keV. On the other hand, the edge-enhancement visibility depends substantially on other parameters such as source-object distance and detector point spread function. (C) 2009 Elsevier B.V. All rights reserved. RI Oliva, Piernicola/E-5839-201

Visibility of tumor-like details in inline phase contrast mammography using quasimonochromatic X-ray sources

A new generation of quasimonochromatic high-flux X-ray sources, based on the X-ray radiation produced through Compton scattering between an electron beam and a laser beam, is under development. One of the possible applications of this source is inline phase contrast mammography, based on the observation of the edge-enhancement effect that can be observed at the border of structures inside the breast in images produced using a partially or totally coherent X-ray beam. In this work we present the results of a set of simulations of inline phase contrast mammography using typical inverse Compton scattering sources parameters. The simulated sample was a tumour-like mass having spherical shape, diameter between 200 μm and 5 mm, placed inside a breast-like matrix, 4 cm thick, and a standard composition of 50% glandular tissue and 50% adipose tissue. We discuss the minimum requirements for mammography using inverse Compton scattering sources and we discuss how the working parameters of the experimental setup (focal spot size, source-object distance, object-detector distance, detector point spread function, mean energy, energy bandwidth) affect the image quality, and specifically the edge-enhancement visibility. In particular, we show that the energy bandwidth does not significantly affect the visibility up to several keV. On the other hand, the edge-enhancement visibility depends substantially on other parameters such as source-object distance and detector point spread function. B. Golosioa, , , P. Delogub, I. Zanetteb, P. Olivaa, A. Stefaninib, G. Stegela and M. Carpinell

A Medipix2-based imaging system for digital mammography with silicon pixel detectors

We present the first tests of a digital imaging system based on a silicon pixel detector bump bonded to an integrated circuit operating in single-photon counting mode. The X-ray sensor is a 300-mum-thick silicon, 14 x 14 mm(2) sensitive area, upon which a matrix of 256 x 256 (65536) square pixel, 55 mum in side, has been built. The readout chip, named MEDIPIX2, has been developed at CERN within the MEDIPIX2 collaboration and it is composed by a matrix of 65536 readout channels exactly with the same geometry of the detector. The spatial resolution properties of the system,have been assessed by measuring the square-wave resolution function and the first images of a standard mammographic phantom were acquired using a radiographic tube in the clinical irradiation condition