Signal-to-noise measurements utilizing a novel dual-energy multimedia detector

Dual-energy measurements are presented utilizing a novel slot-scan digital radiographic imaging detector, operating on gaseous solid state ionization principles. The novel multimedia detector has two basic functional components: a noble gas-filled detector volume operating on gas microstrip principles, and a solid state detector volume. The purpose of this study is to investigate the potential use of this multimedia detector for enhanced dual-energy imaging. The experimental results indicate that the multimedia detector exhibits a large subtracted signal-to-noise ratio. Although the intrinsic merit of this device is being explored for medical imaging, potential applications of the multimedia detector technology in other industrial areas, such as aerospace imaging, aviation security, and surveillance, are also very promising

Design, Development, and Characterization of a Prototype Digital Mammography System

Breast cancer is a major health concern in the United States. Mammography is the gold standard for screening breast cancer and screen-film technology is still widely used in the screening for breast cancer. However, screen-film systems have limited dynamic range and contrasts compared to digital systems, and do not offer integrated image processing capabilities. Recently, digital mammography has seen an upsurge in clinical adoption but current digital mammography systems are limited in terms of their spatial resolution. Therefore, high-resolution digital mammography systems with superior signal-to-noise ratio and contrast characteristics need to be explored. A monolithic, single module high-resolution (39 um) digital x-ray platform (Fairchild Imaging Inc., Milpitas, CA) was developed and characterized for digital mammography. The architecture was extended to a large area (16 x 24-cm) multi-module solid-state imager with variable resolution (39 and 78-um). In addition, a four module (16 x 16-cm) imaging architecture with 78-um pixel was explored for high-resolution contrast enhanced digital mammography for the detection of malignancy-associated angiogenesis. Simulations based on the cascaded linear systems framework were performed in order to characterize the physical properties of the imaging platforms such as the modulation transfer function (MTF), noise power spectra (NPS), and detective quantum efficiency (DQE). Experimental measurements of imager performance was also conducted and compared to model predicted results. Further, perceptual analysis of the prototype imaging platform for digital mammography was performed. Various imaging platforms were successfully developed and investigated to identify essential parameters for high-resolution digital x-ray breast imaging. The single module prototype exhibited physical characteristics that are favorable for digital mammography. Good agreement between model and experimental results were observed demonstrating the utility of such models for further system improvement. The large area 16 x 24-cm prototype demonstrated superior contrast-detail characteristics compared to a clinical FFDM system (100 um pixel) at both 39 and 78-um pixel sizes. Both experimental and theoretical results pointed towards the feasibility of contrast enhanced mammography at mean x-ray glandular dose levels substantially lower than mammography under the conditions investigated. Qualitative analysis of contrast enhanced digital mammography indicated favorable image quality.Ph.D.Committee Chair: Andrew Karellas, Ph.D.; Committee Member: Ernest V. Garcia, Ph.D.; Committee Member: John N. Oshinski; Committee Member: Xiaoping P. Hu, Ph.D

Evaluation of an improved algorithm for producing realistic 3D breast software phantoms: application for mammography

PURPOSE: This work presents an improved algorithm for the generation of 3D breast software phantoms and its evaluation for mammography. METHODS: The improved methodology has evolved from a previously presented 3D noncompressed breast modeling method used for the creation of breast models of different size, shape, and composition. The breast phantom is composed of breast surface, duct system and terminal ductal lobular units, Cooper\u27s ligaments, lymphatic and blood vessel systems, pectoral muscle, skin, 3D mammographic background texture, and breast abnormalities. The key improvement is the development of a new algorithm for 3D mammographic texture generation. Simulated images of the enhanced 3D breast model without lesions were produced by simulating mammographic image acquisition and were evaluated subjectively and quantitatively. For evaluation purposes, a database with regions of interest taken from simulated and real mammograms was created. Four experienced radiologists participated in a visual subjective evaluation trial, as they judged the quality of the simulated mammograms, using the new algorithm compared to mammograms, obtained with the old modeling approach. In addition, extensive quantitative evaluation included power spectral analysis and calculation of fractal dimension, skewness, and kurtosis of simulated and real mammograms from the database. RESULTS: The results from the subjective evaluation strongly suggest that the new methodology for mammographic breast texture creates improved breast models compared to the old approach. Calculated parameters on simulated images such as beta exponent deducted from the power law spectral analysis and fractal dimension are similar to those calculated on real mammograms. The results for the kurtosis and skewness are also in good coincidence with those calculated from clinical images. Comparison with similar calculations published in the literature showed good agreement in the majority of cases. CONCLUSIONS: The improved methodology generated breast models with increased realism compared to the older model as shown in evaluations of simulated images by experienced radiologists. It is anticipated that the realism will be further improved using an advanced image simulator so that simulated images may be used in feasibility studies in mammography

Flat-panel digital mammography system: contrast-detail comparison between screen-film radiographs and hard-copy images

PURPOSE: To compare the contrast-detail (CD) characteristics of screen-film (SF) and postprocessed digital images by using a phantom-based method. MATERIALS AND METHODS: Images of a CD phantom with polymerized methyl methacrylate were acquired with SF and full-field digital mammography systems at matched exposure conditions. A four-alternative forced-choice experiment was conducted with seven observers participating in the study. Each observer was required to identify randomly located disks in phantom images from which detection curves were computed. The CD diagrams for the SF and digital systems were estimated from the detection curves and compared at 50% and 62.5% threshold levels. Furthermore, a theoretic model was used to estimate the CD performance of the SF and digital systems. RESULTS: Analysis of covariance for mixed models was used with the natural logarithm of disk thickness as the dependent variable, the natural logarithm of disk diameter as the covariate, and the observer as a random factor. The results of statistical analysis indicated significant differences between the CD characteristics of SF and digital mammographic images at both 50% (PCONCLUSION: The authors conclude that digital CD curves, on average, exhibit threshold contrast characteristics that are lower (better) than those of SF mammography

Imaging nanoprobe for prediction of outcome of nanoparticle chemotherapy by using mammography

PURPOSE: To prospectively predict the effectiveness of a clinically used nanochemotherapeutic agent by detecting and measuring the intratumoral uptake of an x-ray contrast agent nanoprobe by using digital mammography. MATERIALS AND METHODS: All animal procedures were approved by the institutional animal care and use committee. A long-circulating 100-nm-scale injectable liposomal probe encapsulating 155 mg/mL iodine was developed. Preliminary studies were performed to identify the agent dose that would result in adequate tumor enhancement without enhancement of the normal vasculature in rats. This dose was used to image a rat breast tumor (n = 14) intermittently for 3 days by using a digital mammography system; subsequently, the animals were treated with liposomal doxorubicin. The predictive capability of the probe was characterized by creating good- and bad-prognosis subgroups, on the basis of tumor enhancement found during imaging, and analyzing the tumor growth after treatment of the animals in these two subgroups. RESULTS: A dose of 455 mg of iodine per kilogram of body weight was found to produce an undetectable signal from the blood while achieving enough intratumoral accumulation of the probe to produce adequate signal for detection. The good- and bad-prognosis subgroups demonstrated differential tumor growth rates (P \u3c .003). An inverse linear relationship between the contrast enhancement rate constant during imaging and the tumor growth rate constant during treatment was found (slope = -0.576, R(2) = 0.838). CONCLUSION: In this animal model, quantitative measurement of vascular permeability enabled prediction of therapeutic responsiveness of tumors to liposomal doxorubicin