Compound ultrasound (US) images benefit from reduced speckle noise, at the expense of blurring. The purpose of this
work was to evaluate several different methods for reducing the effects of blurring on compounded ultrasound images.
We evaluated 3 different approaches: unsharp masking (USM), Gaussian deconvolution (GD), and system measured
point-spread-function (PSF) deconvolution (PD). The compounded images are created from summation of
approximately 300 B-Mode US images. We applied the different de-blurring methods to these images and examined the
images subjectively as well as measured resolution with an autocorrelation metric. Overall, these methods improved
resolution by 1.25 (USM), 1.09 (GD), and 1.27 (PD). Unsharp masking was the best trade-off between runtime
performance and image quality.
Volume data reconstruction from cone-beam projections can be time consuming, typically reconstructing parallel axial
slices. We present a system for performing fast, arbitrary-orientation CT slice reconstruction using commodity graphics
processing units (GPUs). For 1024x1024 voxel slice reconstruction we have achieved a 89-fold performance
improvement over a CPU implementation with comparable image quality.
The purpose of this project was to design, build, and characterize the performance of a volume breast ultrasound (VBUS) scanner that images the pendant breast. VBUS scanner design includes a: 1) clinical ultrasound scanner and transducer; 2) scanning table with a hole for the pendant breast; 3) rotational gantry; 4) probe mounting assembly; 5) compressionless breast stabilization device; 6) acquisition, control, reconstruction, and display software. Performance assessment characterized a variety of parameters including: spatial resolution, uniformity, and distortion using high and low contrast test objects in both horizontal and vertical scanning modes. The VBUS scanner modules have been constructed and initial performance evaluated. Approximately 300 scans are acquired over 360 degrees in 18 seconds. Reconstruction requires 25 ms per slice. Test object images depicted hyper- and hypo-echoic masses and demonstrated good resolution, soft tissue contrast and reduced speckle compared to conventional US images. Although scanner performance is satisfactory, additional developments including reduced spacing transducer - scanned object spacing and corrections for sound velocity and aberrations will improve operation. Future work will continue system optimization.
While mammography is the gold standard for breast cancer screening worldwide, it is widely recognized that mammography has limitations, especially in women with dense breasts. In response to the need for a more sensitive approach to breast cancer screening, a CT scanner specifically for breast imaging in the pendant geometry was designed, fabricated, and is currently in clinical evaluation. The spatial resolution and noise properties are discussed, and breast images from a normal volunteer and a patient with breast cancer demonstrate very promising breast CT image quality from a qualitative perspective.
A pendant-geometry, cone-beam breast CT scanner has been constructed and is undergoing thorough testing in our facility. The system is capable of acquiring 30 frames/sec in 2×2 binning mode (1024×768 pixels) using a flat panel detector coupled to a thallium-doped cesium iodide scintillator. The DQE of the detector system for RQA5 and RQA9 x-ray beam qualities were computed, and the low frequency DQE values were 65% and 57% respectively at approximately 16 μR/frame. The results also shown that minor improvements in DQE are achieved for exposures greater than 16 μR/frame. It is expected that the scanner will be available for the imaging of human volunteers in the first half of 2004.
Visualization of volumetric medical data is challenging. Rapid-prototyping (RP) equipment producing solid object prototype models of computer generated structures is directly applicable to visualization of medical anatomic data. The purpose of this study was to develop methods for transferring 3D Ultrasound (3DUS) data to RP equipment for visualization of patient anatomy. 3DUS data were acquired using research and clinical scanning systems. Scaling information was preserved and the data were segmented using threshold and local operators to extract features of interest, converted from voxel raster coordinate format to a set of polygons representing an iso-surface and transferred to the RP machine to create a solid 3D object. Fabrication required 30 to 60 minutes depending on object size and complexity. After creation the model could be touched and viewed. A '3D visualization hardcopy device' has advantages for conveying spatial relations compared to visualization using computer display systems. The hardcopy model may be used for teaching or therapy planning. Objects may be produced at the exact dimension of the original object or scaled up (or down) to facilitate matching the viewers reference frame more optimally. RP models represent a useful means of communicating important information in a tangible fashion to patients and physicians.
This paper considers the propagation of a pulse through a theoretical fractal network. The temporal and spectral features resulting from the decorrelation of a pulse as it transits the network including the effeci of perturbations are discussed. Application to naturally occurring networks such as the His-Purkinje system of the myocardium are considered. Both the fractal dimension (DF) and the power spectrum [P(w)are descriptive of the organizational features of the network. DF describes the geometric structure based on segment length generation and scaling factors. P(w) measures the heterogeneity of the pathways present in the network which in turn reflects the distribution of the segment length variations throughout the network. We show a direct relation between structural heterogeneity and the spectral features. Variation of perturbation size and location shows that changes in geometry occur across many size scales consistent with a fractal structure. Furthermore both location and size of the perturbation are important determinants of the extent of spectral changes produced. Simulation of the His-Purkinje conduction system demonstrates QRS complexes in good agreement with clinical observations. Additionally simulation of conduction defects in the network shows that network perturbations are reflected in the QRS and more importantly in P(w). Our results suggest that characterizing perturbations in terms of their functional wavelength (frequency) rather than their geometric dimension may be a useful method for assessing the extent of performance degradation in the system under study.
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