<title>Evaluation of a photon-counting mammography system</title>

Abstract

The most natural way of digital X-ray imaging is photon counting as the photon flux in itself is digital. In photon counting, the information in the X-ray flux is used more efficiently as the information carrying low-energy photons are given the same weight as higher energy photons carrying less image information. This is in contrast to all existing X-ray instruments, which are energy-integrating systems where the highest energy photons are given the highest weight. A novel technique for high resolution digital X-ray imaging, using gaseous avalanche detectors for photon counting with high signal-to-noise ratios for single X-ray photons, has been developed. The performance of this detector has been studied and compared to analogue film-screen system by imaging phantoms. Our results show that this technology can improve image quality while decreasing the glandular dose to the patient.

Digital detectors for mammography: the technical challenges

“…Data are acquired by simultaneous scanning of the breast by a highly collimated X-ray beam and by the detector [1,[26][27][28]. With this geometry, only a fraction of the emitted X-ray output is used at each step of the exposure process so that the load for the X-ray tube is higher.…”

“…With this geometry, only a fraction of the emitted X-ray output is used at each step of the exposure process so that the load for the X-ray tube is higher. Tungsten-target X-ray tubes with high heat storage capacity have been specifically designed for clinical application [26][27][28]. Because of the reduction of scattered radiation through beam collimation, these systems operate without a grid, which permits a reduction of the dose to the patient.…”

“…Counting the photons can be regarded as an X-ray imaging system that increases the contribution of low-energy photons to the formation of the image. Such a process is an improvement compared to the classical integration process [28]. Only photon-matter interactions above a given energy level are counted by the detector.…”

Musculoskeletal imaging with a prototype photon-counting detector

“…In this mode, the signal intensity in each pixel is equivalent to the number of X-ray photons detected, rather than to the photon energy deposited in the detector. Counting the photons can be regarded as an X-ray imaging system that increases the contribution of low-energy photons to the formation of the image, which results in increased contrast (actually SNR), compared to energy integration [11]. Counting only events above a given energy threshold will minimise the contribution of detector and electronic noise, providing a higher detective quantum efficiency (DQE) compared to other direct radiography techniques [12].…”

Comparative investigation of the detective quantum efficiency of direct and indirect conversion detector technologies in dedicated breast CT

“…In such a system, the x-ray photon produces electron-hole-pairs inside a sensor material, which are extracted directly from the sensor by an applied bias voltage [26,29]. Several semi-conductors have been tested as possible sensor materials to be used in mammography detectors and also in CT systems, such as cadmium telluride (CdTe), cadmium zinc telluride (CdZnTe) and silicon (Si) [25,26,30,31]. The superiority of high-Z-materials like Cd(Zn)Te over other lighter semiconducting materials such as Si regarding quantum efficiency if used as an x-ray detector are well documented in the literature and their use for digital mammography and BCT was studied [26,28,29,32].…”