David M. Binkley

Bio: David M. Binkley is an academic researcher from University of North Carolina at Charlotte. The author has contributed to research in topics: CMOS & Flicker noise. The author has an hindex of 21, co-authored 50 publications receiving 1978 citations. Previous affiliations of David M. Binkley include North Carolina State University & University of California, Los Angeles.

MicroPET: a high resolution PET scanner for imaging small animals

Abstract: MicroPET is a high resolution positron emission tomography (PET) scanner designed for imaging small laboratory animals. It consists of a ring of 30 position-sensitive scintillation detectors, each with an 8/spl times/8 array of small lutetium oxyorthosilicate (LSO) crystals coupled via optical fibers to a multi-channel photomultiplier tube. The detectors have an intrinsic resolution averaging 1.68 mm, an energy resolution between 15 and 25% and 2.4 ns timing resolution at 511 keV. The detector ring diameter of microPET is 17.2 cm with an imaging field of view of 112 mm transaxially by 18 mm axially. The scanner has no septa and operates exclusively in 3D mode. Reconstructed image resolution 1 cm from the center of the scanner is 2.0 mm and virtually isotropic, yielding a volume resolution of 8 mm/sup 3/. For comparison, the volume resolution of state-of-the-art clinical PET systems is in the range of 50-75 mm/sup 3/. Initial images of phantoms have been acquired and are reported. A computer controlled bed is under construction and will incorporate a small wobble motion to improve spatial sampling. This is projected to further enhance spatial resolution. MicroPET is the first PET scanner to incorporate the new scintillator LSO and to our knowledge is the highest resolution multi-ring PET scanner currently in existence.

Tradeoffs and Optimization in Analog CMOS Design

Abstract: The selection of drain current, inversion coefficient, and channel length for each MOS device in an analog circuit results in significant tradeoffs in performance. The selection of inversion coefficient, which is a numerical measure of MOS inversion, enables design freely in weak, moderate, and strong inversion and facilitates optimum design. Here, channel width required for layout is easily found and implicitly considered in performance expressions. This paper gives hand expressions motivated by the EKV MOS model and measured data for MOS device performance, inclusive of velocity saturation and other small-geometry effects. A simple spreadsheet tool is then used to predict MOS device performance and map this into complete circuit performance. Tradeoffs and optimization of performance are illustrated by the design of three, 0.18-mum CMOS operational transconductance amplifiers optimized for DC, balanced, and AC performance. Measured performance shows significant tradeoffs in voltage gain, output resistance, transconductance bandwidth, input-referred flicker noise and offset voltage, and layout area.

A 100-ps time-resolution CMOS time-to-digital converter for positron emission tomography imaging applications

Abstract: An integrated CMOS subnanosecond time-to-digital converter (TDC) has been developed and evaluated for positron emission tomography (PET) front-end applications. The TDC architecture combines an accurate digital counter and an analog time interpolation circuit to make the time interval measurement. The dynamic range of the TDC is programmable and can be easily extended without any timing resolution degradation. The converter was designed to operate over a reference clock frequency range of 62.5 MHz up to 100 MHz and can have a bin size as small as 312.5 ps LSB with 100-ns conversion times. Measurements indicate the TDC achieves a DNL of under /spl plusmn/0.20 LSB and INL less than /spl plusmn/0.30 LSB with an rms timing resolution of 0.312 LSB (97.5 ps), very close to the theoretical limit of 0.289 LSB (90 ps). The design is believed to be the first fully integrated CMOS subnanosecond TDC used in PET medical imaging and the first realization of a CMOS TDC that achieves an rms timing resolution below 100 ps within a 100-ns conversion time.

A CAD methodology for optimizing transistor current and sizing in analog CMOS design

Abstract: A computer-aided design (CAD) methodology for optimizing MOS transistor current and sizing is presented where drain current ID, inversion level (represented by inversion coefficient IC), and channel length L are selected as three independent degrees of design freedom resulting in an optimized selection of channel width for layout. At a given drain current I/sub D/ in saturation, a selected MOS inversion coefficient IC and channel length L define a point on an operating plane illustrating dramatic tradeoffs in circuit performance. Operation in the region of low inversion coefficient IC and long channel length L results in optimal DC gain and matching compared to the region of high inversion coefficient IC and short channel length L where bandwidth is optimal. A design methodology is presented here to enable optimum design choices throughout the continuum of inversion level IC (weak, moderate, or strong inversion) and available channel length L. The methodology is implemented in a prototype CAD system where a graphical view permits the designer to explore optimum tradeoffs against preset goals for circuit transconductance g/sub m/, output conductance g/sub ds/, drain-source saturation voltage, gain, bandwidth, white and flicker noise, and DC matching for a 0.5-/spl mu/m CMOS process. The design methodology can be readily extended to deeper submicron MOS processes through linkage to the EKV or BSIM3 MOS models or custom model equations.

A miniaturized neuroprosthesis suitable for implantation into the brain

Abstract: This paper presents current research on a miniaturized neuroprosthesis suitable for implantation into the brain. The prosthesis is a heterogeneous integration of a 100-element microelectromechanical system (MEMS) electrode array, front-end complementary metal-oxide-semiconductor (CMOS) integrated circuit for neural signal preamplification, filtering, multiplexing and analog-to-digital conversion, and a second CMOS integrated circuit for wireless transmission of neural data and conditioning of wireless power. The prosthesis is intended for applications where neural signals are processed and decoded to permit the control of artificial or paralyzed limbs. This research, if successful, will allow implantation of the electronics into the brain, or subcutaneously on the skull, and eliminate all external signal and power wiring. The neuroprosthetic system design has strict size and power constraints with each of the front-end preamplifier channels fitting within the 400 /spl times/ 400-/spl mu/m pitch of the 100-element MEMS electrode array and power dissipation resulting in less than a 1/spl deg/C temperature rise for the surrounding brain tissue. We describe the measured performance of initial micropower low-noise CMOS preamplifiers for the neuroprosthetic.

Cognitive control signals for neural prosthetics

Abstract: In an embodiment, the invention relates to neural prosthetic devices in which control signals are based on the cognitive activity of the prosthetic user. The control signals may be used to control an array of external devices, such as prosthetics, computer systems, and speech synthesizers. Data obtained from monkeys' movement intentions were recorded, decoded with a computer algorithm, and used to position cursors on a computer screen. Not only the intended goals, but also the value of the reward the animals expected to receive at the end of each trial, were decoded from the recordings. The results indicate that brain activity related to cognitive variables can be a viable source of signals for the control of a cognitive-based neural prosthetic.

Noise in RF-CMOS mixers: a simple physical model

Abstract: Flicker noise in the mixer of a zero- or low-intermediate frequency (IF) wireless receiver can compromise overall receiver sensitivity. A qualitative physical model has been developed to explain the mechanisms responsible for flicker noise in mixers. The model simply explains how frequency translations take place within a mixer. Although developed to explain flicker noise, the model predicts white noise as well. Simple equations are derived to estimate the flicker and white noise at the output of a switching active mixer. Measurements and simulations validate the accuracy of the predictions, and the dependence of mixer noise on local oscillator (LO) amplitude and other circuit parameters.

High-resolution 3D Bayesian image reconstruction using the microPET small-animal scanner

Abstract: A Bayesian method is described for reconstruction of high-resolution 3D images from the microPET small-animal scanner. Resolution recovery is achieved by explicitly modelling the depth dependent geometric sensitivity for each voxel in combination with an accurate detector response model that includes factors due to photon pair non-collinearity and inter-crystal scatter and penetration. To reduce storage and computational costs we use a factored matrix in which the detector response is modelled using a sinogram blurring kernel. Maximum a posteriori (MAP) images are reconstructed using this model in combination with a Poisson likelihood function and a Gibbs prior on the image. Reconstructions obtained from point source data using the accurate system model demonstrate a potential for near-isotropic FWHM resolution of approximately 1.2 mm at the center of the field of view compared with approximately 2 mm when using an analytic 3D reprojection (3DRP) method with a ramp filter. These results also show the ability of the accurate system model to compensate for resolution loss due to crystal penetration producing nearly constant radial FWHM resolution of 1 mm out to a 4 mm radius. Studies with a point source in a uniform cylinder indicate that as the resolution of the image is reduced to control noise propagation the resolution obtained using the accurate system model is superior to that obtained using 3DRP at matched background noise levels. Additional studies using pie phantoms with hot and cold cylinders of diameter 1-2.5 mm and 18FDG animal studies appear to confirm this observation.

Nanoplatforms for targeted molecular imaging in living subjects.

Abstract: Molecular or personalized medicine is the future of patient management and molecular imaging plays a key role towards this goal. Recently, nanoplatform-based molecular imaging has emerged as an interdisciplinary field, which involves chemistry, engineering, biology, and medicine. Possessing unprecedented potential for early detection, accurate diagnosis, and personalized treatment of diseases, nanoplatforms have been employed in every single biomedical imaging modality, namely, optical imaging, computed tomography, ultrasound, magnetic resonance imaging, single-photon-emission computed tomography, and positron emission tomography. Multifunctionality is the key advantage of nanoplatforms over traditional approaches. Targeting ligands, imaging labels, therapeutic drugs, and many other agents can all be integrated into the nanoplatform to allow for targeted molecular imaging and molecular therapy by encompassing many biological and biophysical barriers. In this Review, we will summarize the current state-of-the-art of nanoplatforms for targeted molecular imaging in living subjects.