Le. Antonuk et al., Strategies to improve the signal and noise performance of active matrix, flat-panel imagers for diagnostic x-ray applications, MED PHYS, 27(2), 2000, pp. 289-306
Citations number
44
Categorie Soggetti
Radiology ,Nuclear Medicine & Imaging","Medical Research Diagnosis & Treatment
A theoretical investigation of factors limiting the detective quantum effic
iency (DQE) of active matrix flat-panel imagers (AMFPIs), and of methods to
overcome these limitations, is reported. At the higher exposure levels ass
ociated with radiography, the present generation of AMFPIs is capable of ex
hibiting DQE performance equivalent, or superior, to that of existing film-
screen and computed radiography systems. However, at exposure levels common
ly encountered in fluoroscopy, AMFPIs exhibit significantly reduced DQE and
this problem is accentuated at higher spatial frequencies. The problem app
lies both to AMFPIs that rely on indirect detection as well as direct detec
tion of the incident radiation. This reduced performance derives from the r
elatively large magnitude of the square of the total additive noise compare
d to the system gain for existing AMFPIs, In order to circumvent these rest
rictions, a variety of strategies to decrease additive noise and enhance sy
stem gain are proposed. Additive noise could be reduced through improved pr
eamplifier, pixel and array design, including the incorporation of compensa
tion lines to sample external line noise. System gain could be enhanced thr
ough the use of continuous photodiodes, pixel amplifiers, or higher gain x-
ray converters such as lead iodide. The feasibility of these and other stra
tegies is discussed and potential improvements to DQE performance are quant
ified through a theoretical investigation of a variety of hypothetical 200
mu m pitch designs. At low exposures, such improvements could greatly incre
ase the magnitude of the low spatial frequency component of the DQE, render
ing it practically independent of exposure while simultaneously reducing th
e falloff in DQE at higher spatial frequencies, Furthermore, such noise red
uction and gain enhancement could lead to the development of AMFPIs with hi
gh DQE performance which are capable of providing both high resolution radi
ographic images, at similar to 100 mu m pixel resolution, as well as variab
le resolution fluoroscopic images at 30 fps. (C) 2000 American Association
of Physicists in Medicine. [S0094-2405(00)01302-X].