This chapter also discusses direct conversion detectors and indirect conversion detectors.
Potential advantages of direct conversion detectors are high quantum efficiencies (QE) of 98% or higher (for 0.3 mm thick CdZnTe detector with 20 keV X-rays), improved contrast, high sensitivity and low intrinsic noise.
The detective quantum efficiency of indirect-conversion, dynamic, solid-state detectors is superior to that of both x-ray image intensifier TV systems and direct-conversion detectors.
Although organic-based direct conversion X-ray detectors have been developed, their photocurrent generation efficiency has been limited by recombination of excitons due to the intrinsically poor electrical properties of organic materials.
The proposed new NPA detector is based on direct conversion of charge in silicon and approximate matching of the detector thickness with the ranges of the observed particles.
The photon-counting detector technology enables direct conversion of individual X-ray photons into an ionisation cloud within a semi-conductor layer [39].
A new type of underwater digital X-ray linear detector array is under development for transmission imaging, based on GaAs and direct conversion of X-rays into an electrical signal.
Specification of an imaging system as 'CR' or 'DR' is not enough: more information is needed because of the varying dose efficiency (e.g., indirect versus direct conversion DR, CsI versus Gadox scintillator, dual versus single read-out CR, needle versus amorphous detector).
When interpreting and comparing these results, it is important to consider the following aspects: Specification of an imaging system as 'CR' or 'DR' is not enough: more information is needed because of the varying dose efficiency (e.g., indirect versus direct conversion DR, CsI versus Gadox scintillator, dual versus single read-out CR, needle versus amorphous detector).
In standard projection radiography indirect conversion DR detectors currently offer superior physical image quality and dose efficiency compared with direct conversion DR and modern point-scan CR.
Full field digital mammography (FFDM) systems based on an indirect conversion detector have generally poorer response, in terms of spatial resolution, with respect to detectors based on a direct conversion process [ 1].
