A new and novel detector structure is now being investigated to minimize the readout noise of large area TFT arrays. A conventional TFT panel consists of orthogonal arrays of gate lines and data lines. The parasitic capacitance from the crossover of these lines results in a sizable data line capacitance. During image readout, the thermal noise of the charge integrator is greatly magnified by the ratio of the data line capacitance to the feedback capacitance of the charge amplifier. The swinging of the gate voltage will also inject charges in and out of the imaging holding pixel capacitors and contribute to the switching noise in the readout image. By redesigning the layout of the TFT arrays and by coupling linear light source to the bottom side of the TFT array in the same direction as the gate lines, the crossover of gate lines and data lines can be avoided and the data line capacitance can be greatly reduced. Instead of addressing each row of transistors by the switching of the gate control voltage, linear light source with collimators are used to optically switch on and off the amorphous silicon transistors. The transistor switching noise from the swinging of the gate voltages is reduced. By minimizing the data line capacitance and avoiding the swinging of the gate control voltage, the basic TFT readout noise is minimized and lower dose x-rays images can be obtained. This design is applicable to both Direct Conversion and Indirect Conversion panels.

Date Published: 16 March 2011
PDF: 7 pages
Proc. SPIE 7961, Medical Imaging 2011: Physics of Medical Imaging, 79610R (16 March 2011); doi: 10.1117/12.877900

Published in SPIE Proceedings Vol. 7961:
Medical Imaging 2011: Physics of Medical Imaging
Norbert J. Pelc; Ehsan Samei; Robert M. Nishikawa, Editor(s)