TOWARD A MORE CLARIFIED DETECTIVE QUANTUM EFFICIENCY METHODOLOGY: STUDY OF THE DQE THEORY AND APPLICATIONS

Detective quantum efficiency (DQE) is widely accepted as the golden rule to objectively evaluate the performance of x-ray imaging systems. It provides a comprehensive characterization of an x-ray imaging system, because it combines several important image-quality-related measurements such as contrast, resolution, and noise, and because it measures the efficiency of the utilization of x-ray in the imaging process. Despite its importance, the current DQE methodology is imperfect in general agreement. The focus of this dissertation is to investigate the DQE methodology for digital x-ray imaging systems, in an effort to clarify some confusing aspects of the current DQE methodology. Through a detailed theoretical derivation of the DQE methodology for digital x-ray imaging, a more clarified understanding of the DQE theory is provided. Besides the re-visited DQE theory, techniques to determine the constituent parts of DQE, including the photon fluence, Modulation Transfer Function (MTF), and Noise Power Spectrum (NPS) are also discussed in this dissertation.The dissertation is structured as follows. After a brief introduction of the current DQE theory in Chapter 1, the DQE theory for digital x-ray imaging systems is revisited in detail in Chapter 2, with experimental results for the demonstration purpose. In Chapter 3, DQE theory for the magnification radiography is provided, and the theory is supported by experimental results. In Chapter 4, the measurements of x-ray photon fluence and spectral composition are discussed in detail, and uncertainty analysis is conducted to investigate the impact of the calibration uncertainty on the two measurements. In Chapter 5, an innovative alignment procedure that was designed to reduce the error in the spectral measurements and imaging experiments is introduced. MTF measurement techniques are covered in Chapter 6, and NPS measurement techniques are discussed in Chapter 7. As an example application of the DQE methodology, a study about the impact of additive noise on the imaging performance of a CCD based x-ray system is also reported in Chapter 7. In Chapter 8, a DQE analysis on an innovative dual detector x-ray imaging system is detailed, as another example application of DQE. Finally, a summary of this dissertation is provided in Chapter 9

Emerging technologies for the non-invasive characterization of physical-mechanical properties of tablets

The density, porosity, breaking force, viscoelastic properties, and the presence or absence of any structural defects or irregularities are important physical-mechanical quality attributes of popular solid dosage forms like tablets. The irregularities associated with these attributes may influence the drug product functionality. Thus, an accurate and efficient characterization of these properties is critical for successful development and manufacturing of a robust tablets. These properties are mainly analyzed and monitored with traditional pharmacopeial and non-pharmacopeial methods. Such methods are associated with several challenges such as lack of spatial resolution, efficiency, or sample-sparing attributes. Recent advances in technology, design, instrumentation, and software have led to the emergence of newer techniques for non-invasive characterization of physical-mechanical properties of tablets. These techniques include near infrared spectroscopy, Raman spectroscopy, X-ray microtomography, nuclear magnetic resonance (NMR) imaging, terahertz pulsed imaging, laser-induced breakdown spectroscopy, and various acoustic- and thermal-based techniques. Such state-of-the-art techniques are currently applied at various stages of development and manufacturing of tablets at industrial scale. Each technique has specific advantages or challenges with respect to operational efficiency and cost, compared to traditional analytical methods. Currently, most of these techniques are used as secondary analytical tools to support the traditional methods in characterizing or monitoring tablet quality attributes. Therefore, further development in the instrumentation and software, and studies on the applications are necessary for their adoption in routine analysis and monitoring of tablet physical-mechanical properties

Compact multi-aperture imaging with high-angular-resolution

Previous reports have demonstrated that it is possible to emulate the imaging function of a single conventional lens with an NxN array of identical lenslets to provide an N-fold reduction in imaging-system track length. This approach limits the application to low-resolution imaging. We highlight how using an array of dissimilar lenslets, with an array width that can be much wider than the detector array, high-resolution super-resolved imaging is possible. We illustrate this approach with a ray-traced design and optimization of a long-wave infrared system employing a 3x3 array of free-form lenslets to provide a four-fold reduction in track length compared to a baseline system. Simulations of image recovery show that recovered image quality is comparable to that of the baseline system

Digital Color Imaging

This paper surveys current technology and research in the area of digital color imaging. In order to establish the background and lay down terminology, fundamental concepts of color perception and measurement are first presented us-ing vector-space notation and terminology. Present-day color recording and reproduction systems are reviewed along with the common mathematical models used for representing these devices. Algorithms for processing color images for display and communication are surveyed, and a forecast of research trends is attempted. An extensive bibliography is provided

Marshall Space Flight Center Research and Technology Report 2019

Today, our calling to explore is greater than ever before, and here at Marshall Space Flight Centerwe make human deep space exploration possible. A key goal for Artemis is demonstrating and perfecting capabilities on the Moon for technologies needed for humans to get to Mars. This years report features 10 of the Agencys 16 Technology Areas, and I am proud of Marshalls role in creating solutions for so many of these daunting technical challenges. Many of these projects will lead to sustainable in-space architecture for human space exploration that will allow us to travel to the Moon, on to Mars, and beyond. Others are developing new scientific instruments capable of providing an unprecedented glimpse into our universe. NASA has led the charge in space exploration for more than six decades, and through the Artemis program we will help build on our work in low Earth orbit and pave the way to the Moon and Mars. At Marshall, we leverage the skills and interest of the international community to conduct scientific research, develop and demonstrate technology, and train international crews to operate further from Earth for longer periods of time than ever before first at the lunar surface, then on to our next giant leap, human exploration of Mars. While each project in this report seeks to advance new technology and challenge conventions, it is important to recognize the diversity of activities and people supporting our mission. This report not only showcases the Centers capabilities and our partnerships, it also highlights the progress our people have achieved in the past year. These scientists, researchers and innovators are why Marshall and NASA will continue to be a leader in innovation, exploration, and discovery for years to come

Signal, noise power spectrum, and detective quantum efficiency of indirectâ detection flatâ panel imagers for diagnostic radiology

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135120/1/mp8243.pd