Design, analysis and evaluation of sigma-delta based beamformers for medical ultrasound imaging applications

The inherent analogue nature of medical ultrasound signals in conjunction with the abundant merits provided by digital image acquisition, together with the increasing use of relatively simple front-end circuitries, have created considerable demand for single-bit ��������� beamformers in digital ultrasound imaging systems. Furthermore, the increasing need to design lightweight ultrasound systems with low power consumption and low noise, provide ample justification for development and innovation in the use of single-bit ��������� beamformers in ultrasound imaging systems. The overall aim of this research program is to investigate, establish, develop and confirm through a combination of theoretical analysis and detailed simulations, that utilize raw phantom data sets, suitable techniques for the design of simple-to-implement hardware efficient ��������� digital ultrasound beamformers to address the requirements for 3D scanners with large channel counts, as well as portable and lightweight ultrasound scanners for point-of-care applications and intravascular imaging systems. In addition, the stability boundaries of higher-order High-Pass (HP) and Band-Pass (BP) ������� modulators for single- and dual- sinusoidal inputs are determined using quasi-linear modeling together with the describing-function method, to more accurately model the ��������� modulator quantizer. The theoretical results are shown to be in good agreement with the simulation results for a variety of input amplitudes, bandwidths, and modulator orders. The proposed mathematical models of the quantizer will immensely help speed up the design of higher order HP and BP ������� modulators to be applicable for digital ultrasound beamformers. Finally, a user friendly design and performance evaluation tool for LP, BP and HP ��������� modulators is developed. This toolbox, which uses various design methodologies and covers an assortment of ��������� modulators topologies, is intended to accelerate the design process and evaluation of ��������� modulators. This design tool is further developed to enable the design, analysis and evaluation of ��������� beamformer structures including the noise analyses of the final B-scan images. Thus, this tool will allow researchers and practitioners to design and verify different reconstruction filters and analyze the results directly on the B-scan ultrasound images thereby saving considerable time and effort.

Theranostic Fibers for Simultaneous Imaging and Drug Delivery

New methods for creating theranostic systems with simultaneous encapsulation of therapeutic, diagnostic, and targeting agents are much sought after. This work reports for the first time the use of coaxial electrospinning to prepare such systems in the form of core���shell fibers. Eudragit S100 was used to form the shell of the fibers, while the core comprised poly(ethylene oxide) loaded with the magnetic resonance contrast agent Gd(DTPA) (Gd(III) diethylenetriaminepentaacetate hydrate) and indomethacin as a model therapeutic agent. The fibers had linear cylindrical morphologies with clear core���shell structures, as demonstrated by electron microscopy. X-ray diffraction and differential scanning calorimetry proved that both indomethacin and Gd(DTPA) were present in the fibers in the amorphous physical form. This is thought to be a result of intermolecular interactions between the different components, the presence of which was suggested by infrared spectroscopy. In vitro dissolution tests indicated that the fibers could provide targeted release of the active ingredients through a combined mechanism of erosion and diffusion. The proton relaxivities for Gd(DTPA) released from the fibers into tris buffer increased (r1 = 4.79���9.75 s���1 mM���1; r2 = 7.98���14.22 s���1 mM���1) compared with fresh Gd(DTPA) (r1 = 4.13 s���1 mM���1 and r2 = 4.40 s���1 mM���1), which proved that electrospinning has not diminished the contrast properties of the complex. The new systems reported herein thus offer a new platform for delivering therapeutic and imaging agents simultaneously to the colon.