A novel semiconductor pixel device and system for X-ray and gamma ray imaging

We are presenting clinical images (objects, mammography phantoms, dental phantoms, dead animals) and data from a novel X-ray imaging device and system. The device comprises a pixel semiconductor detector flip-chip joined to an ASIC circuit. CdZnTe and Si pixel detectors with dimensions of the order of 1 cm² have been implemented with a pixel pitch of 35 μm. Individual detectors comprise, therefore, tens of thousands of pixels. A novel ASIC accumulates charge created from directly absorbed X-rays impinging on the detector. Each circuit on the ASIC, corresponding to a detector pixel, is capable of accumulating thousands of X-rays in the energy spectrum from a few to hundreds of keV with high efficiency (CdZnTe). Image (X-ray) accumulation times are user controlled and range from just a few to hundreds of ms. Image frame updates are also user controlled and can be provided as fast as every 20 ms, thus offering the possibility of real time imaging. The total thickness of an individual imaging the including the mounting support does not exceed 4 mm. Individual imaging tiles are combined in a mosaic providing an imaging system with any desired shape and useful active area. The mosaic allows for cost effective replacement of individual tiles. A scanning system, allows for elimination, in the final image, of any inactive space between the imaging tiles without use of software interpolation techniques. The Si version of our system has an MTF of 20% at 14 1p/mm and the CdZnTe version an MTF of 15% at 10 1p/mm. Our digital imaging devices and systems are intended for use in X-ray and gamma-ray imaging for medical diagnosis in a variety of applications ranging from conventional projection X-ray imaging and mammography to fluoroscopy and CT scanning. Similarly, the technology is intended for use in non destructive testing, product quality control and real time on-line monitoring. The advantages over existing X-ray digital imaging modalities (such as digital imaging plates, scintillating screens coupled to CCDs etc.) include compactness, direct X-ray conversion to an immediate real time digital display, exquisite image resolution, dose reduction and large continuous imaging areas. Our measurements and images confirm that this new digital imaging system compares favourably to photoluminescence