10th International "Hiroshima" Symposium on the Development and Application of Semiconductor Tracking Detectors, Xi'an, China

X-ray performance evaluation of a wafer-scale CMOS flat panel imager for applications in medical imaging and nondestructive testing

26 Sept 2015, 19:53

1m

Multi-function Hall (International Conference Center (Nanyang Hotel))

POSTER Pixels (incl. CCD's) - X-ray imaging After dinner POSTER session, with drinks: (All presenters are requested/encouraged to attend their posters; All participants are requested to participate the session, with drinks!)

Speaker

Bo Kyung Cha (KERI)

Description

Currently, the wafer-scale CMOS flat panel imagers have been widely used in X-ray medical imaging applications including dental CBCT, mammography as well as NDT (nondestructive testing). The CMOS active pixel sensor (APS) has many advantages such as the higher readout speed, low noise, high spatial resolution and high system integration compared to amorphous silicon TFT-based flat panel detector. Specially, the CMOS flat panel X-ray imager has the higher readout speed due to higher electrical charge mobility in single crystalline silicon. The disadvantage of current CMOS technology is the limited wafer size and less resistive to X-ray radiation damage in comparison with a-Si TFT array imager. However, the size limitation of CMOS image sensor can be solved by tiling a single panel into larger array or utilizing 12 inch-wafer scale CIS process. In this work, the 8 inch-wafer scale CMOS flat panel was fabricated using a 0.18µm 1-poly/4-metal standard CMOS image sensor (CIS) process. The CMOS APS detector with 100µm pixel size, different frame rates (30 fps in normal mode and 60 fps in binning mode) and 14.3-bit extended ADC with built-in binning mode was developed for low-dose, high resolution X-ray imaging. The various phosphor screens (or scintillators) such as Gd2O2S:Tb) and CsI:Tl with columnar structure were used in the developed CMOS flat panel detector for the X-ray photons to visible light conversion. The different scintillators and fiber-optic plate were optically combined with the CMOS sensor array to optimize the X-ray imaging characterization. The X-ray imaging performance such as X-ray sensitivity, signal to noise ratio, dynamic range and spatial resolution were measured. X-ray image with about 4.0 lp/mm spatial frequencies could be acquired. The output signal of CMOS flat panel detectors with full resolution mode linearly increased as the incident X-ray dose increases. This paper will demonstrate the significant potential of our CMOS flat panel imager for medical imaging and NDT applications with high-resolution and high-frame rate.