A United Kingdom consortium (MI3) is founded to develop advanced CMOS image sensors for scientific applications. “Vanilla,” a 520×520 array of active pixels with 25-µm pitch is fabricated in the 0.35-µm 4M2P (4 metal, 2 poly) CMOS process and uses a 3.3-V supply. It has flushed reset circuitry to attain low reset noise and random pixel access for high-speed region-of-interest (ROI) readout. “OPIC” is a 64×72 test structure array of digital pixels with 30-µm pitch, fabricated in 0.25-µm 5M1P (5 metal 1 poly) CMOS process with a 3.3/2.5-V supply. It can perform thresholding via an in-pixel comparator for sparse readout at a high frame rate. Characterization of both sensors is performed under optical illumination and x-ray exposure. For x-ray characterization, both sensors were coupled to a structured thallium-doped cesium iodide (CsI:Tl) scintillator via a fiber optic plate. Vanilla has been found to exhibit 34±3e− read noise and a spectral response of 225±5 mA/W at 500 nm and can read a 6×6 ROI at 24,395 frames/s. OPIC has 46±3e− read noise and can perform sparse readout at up to 3700 frames/s. Based on these results, Vanilla could be employed for applications where only a small portion of the image contains relevant information, while OPIC is suited to high-speed imaging applications.
The properties of dual energy contrast enhanced breast imaging have been analyzed by imaging a 4 cm breast equivalent phantom consisting of adipose and glandular equivalent plastics. This phantom had superimposed another thin plastic which incorporated a 2 mm deep cylinder filled with iodinated contrast media. The iodine projected thicknesses used for this study was 3 mg/cm2. Low and high energy spectra that straddle the iodine K-edge were used. Critical parameters such as the energy spectra and exposure are discussed, along with post processing by means of nonlinear energy dependent function. The dual energy image was evaluated using the relative contrast to noise ratio of a 2.5 mm x 2.5 mm region of the image at the different iodine concentrations incorporating different breast composition with respect to the noniodinated areas. Optimum results were achieved when the low and high-energy images were used in such a way that relative contrast to noise ratio of the iodine with respect to the background tissue was maximum. A figure of merit suggests that higher noise levels can be tolerated at the benefit of lower exposure. Contrast media kinetics of a phantom incorporating a water flow of 20.4 ml/min through the plastic cylinder suggests that time domain imaging could be performed with this approach. The results suggest that optimization of dual energy contrast enhanced mammography has the potential to lead to the development of perfusion digital mammography.
A UK consortium (MI3) has been founded to develop advanced CMOS pixel designs for scientific applications.
Vanilla, a 520x520 array of 25&mgr;m pixels benefits from flushed reset circuitry for low noise and random pixel access
for region of interest (ROI) readout. OPIC, a 64x72 test structure array of 30&mgr;m digital pixels has thresholding
capabilities for sparse readout at 3,700fps. Characterization is performed with both optical illumination and
x-ray exposure via a scintillator. Vanilla exhibits 34±3e- read noise, interactive quantum efficiency of 54% at
500nm and can read a 6x6 ROI at 24,395fps. OPIC has 46±3e- read noise and a wide dynamic range of 65dB
due to high full well capacity. Based on these characterization studies, Vanilla could be utilized in applications
where demands include high spectral response and high speed region of interest readout while OPIC could be
used for high speed, high dynamic range imaging.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.