Improved coronary calcium detection and quantification with low-dose full field-of-view photon-counting CT:a phantom study

OBJECTIVE: The aim of the current study was to systematically assess coronary artery calcium (CAC) detection and quantification for spectral photon-counting CT (SPCCT) in comparison to conventional CT and, in addition, to evaluate the possibility of radiation dose reduction. METHODS: Routine clinical CAC CT protocols were used for data acquisition and reconstruction of two CAC containing cylindrical inserts which were positioned within an anthropomorphic thorax phantom. In addition, data was acquired at 50% lower radiation dose by reducing tube current, and slice thickness was decreased. Calcifications were considered detectable when three adjacent voxels exceeded the CAC scoring threshold of 130 Hounsfield units (HU). Quantification of CAC (as volume and mass score) was assessed by comparison with known physical quantities. RESULTS: In comparison with CT, SPCCT detected 33% and 7% more calcifications for the small and large phantoms, respectively. At reduced radiation dose and reduced slice thickness, small phantom CAC detection increased by 108% and 150% for CT and SPCCT, respectively. For the large phantom size, noise levels interfered with CAC detection. Although comparable between CT and SPCCT, routine protocols CAC quantification showed large deviations (up to 134%) from physical CAC volume. At reduced radiation dose and slice thickness, physical volume overestimations decreased to 96% and 72% for CT and SPCCT, respectively. In comparison with volume scores, mass score deviations from physical quantities were smaller. CONCLUSION: CAC detection on SPCCT is superior to CT, and was even preserved at a reduced radiation dose. Furthermore, SPCCT allows for improved physical volume estimation. KEY POINTS: • In comparison with conventional CT, increased coronary artery calcium detection (up to 156%) for spectral photon-counting CT was found, even at 50% radiation dose reduction. • Spectral photon-counting CT can more accurately measure physical volumes than conventional CT, especially at reduced slice thickness and for high-density coronary artery calcium. • For both conventional and spectral photon-counting CT, reduced slice thickness reconstructions result in more accurate physical mass approximation

Mass Spectrometric and Molecular Analyses of Biological Agents In Environmental Compartments

abstract: This thesis discusses the use of mass spectrometry and polymerase chain reaction (PCR), among other methods, to detect biomarkers of microorganisms in the environment. These methods can be used to detect bacteria involved in the degradation of environmental pollutants (bioremediation) or various single-celled pathogens, including those posing potential threats as bioterrorism agents. The first chapter introduces the hurdles in detecting in diverse environmental compartments in which they could be found, a select list of single-celled pathogens representing known or potential bioterrorism agents. These hurdles take the form of substances that interfere either directly or indirectly with the detection method. In the case of mass spectrometry-based detection, many of these substances (interferences) can be removed via effective sample pretreatment. Chapters 2 through 4 highlight specific methods developed to detect bioremediation or bioterrorism agents in environmental matrices. These methods are qualitative mass spectrometry, quantitative PCR, and quantitative mass spectrometry, respectively. The targeted organisms in these methods include several bioremediation agents, e.g. Pseudomonas putida F1 and Sphingomonas wittichii RW1, and bioterrorism agents, e.g. norovirus and Cryptosporidium parvum. In Chapter 2, I identify using qualitative mass spectrometry, biomarkers for three bacterial species involved in bioremediation. In Chapter 3, I report on a new quantitative PCR method suitable for monitoring of a key gene in yet another bioremediation agent, Sphingomonas wittichii RW1; furthermore, I apply this method to track the efficacy of bioremediation in bioaugmented environmental microcosms. In Chapter 4, I report on the development of new quantitative mass spectrometry methods for two organisms, S. wittichii RW1 and Cryptosporidium parvum, and evaluate two previously published methods for their applicability to the analysis of complex environmental samples. In Chapter 5, I review state-of-the-art methods for the detection of emerging biological contaminants, specifically viruses, in environmental samples. While this summary deals exclusively with viral pathogens, the advantages and remaining challenges identified are also applicable to all single-celled organisms in environmental settings. The suggestions I make at the end of this chapter are expected to be valid not only for future needs for emerging viruses but also for bacteria, eukaryotic pathogens, and prions. In general, it is advisable to continue the trend towards quantification and to standardize methods to facilitate comparison of results between studies.Dissertation/ThesisPh.D. Biological Design 201

Signal procession of single measurand for dynamical system identification /

Accurate damage inspection and reliable health monitoring of dynamical systems rely on accurate dynamical data computation. In theory, if all three variables (i.e., displacement, velocity, and acceleration) of each point on a dynamical system are available from measurement, system identification/damage detection methods can be easily and accurately performed. In the experiment, however, there is often only one variable is measured because collocating three different sensors at a point is too difficult even if the sensors are small enough not to affect the system's dynamic characteristics. Numerical investigations reveal that velocity is the best choice because the corresponding acceleration and displacement can be estimated by numerical differentiation and integration and because today's laser vibrometers can provide very accurate measurements of velocities. Therefore, with the velocity signal as the single measurand, efficient and accurate numerical computation methods are needed to compute the corresponding displacement and acceleration signals. Ideally, an intelligent structure will be able to realize real-time monitoring that the occurrence of damage can be identified at a very early stage. Then, by localizing the existed damage, a detailed analysis of the damaged structure section can be carried out such as determine the severity of the damage or the remaining service life of the structure. Two direct time-domain methods and two indirect time-domain methods for system identification are reviewed in this thesis. The feasibility of using these system identification methods for level 1 damage detection has been discussed in this thesis. While some of the methods can realize a realtime monitoring and quick feedback, some can only realize periodic inspections or cannot reflect small change in modal parameters. Two origin methods as stiffness-characteristic matrix method (stiffness-CMM) and mass characteristic matrix method (mass-CMM) for damage localization are proposed in this thesis, and it is the concentration of the thesis. Different from traditional damage detection methods, proposed methods do not require the corresponding intact beam structure for comparison. While measured signals only processed in the spatial domain, a weighting matrix developed from the finite element model of the beam structure is used for computing the damage index on each measured location. The largest (filtered) damage index indicate the actual damage location. Two different weighting matrixes are used in proposed methods and the mass-CMM is more robust to measuring noise. Application of the two methods is demonstrated through numerical examples. In addition, experimental vibration data of damaged beam structure measured using a PSV-200 scanning laser vibrometer are also used to verify the accuracy of these methods.Dr. P. Frank Pai, Dissertation Supervisor.|Dr. Ming Xin, Dissertation Co-Supervisor.|Includes vita.Includes bibliographical references (pages 216-223)

Simultaneous measurement of the trace elements Al, As, B, Be, Cd, Co, Cu, Fe, Li, Mn, Mo, Ni, Rb, Se, Sr, and Zn in human serum and their reference ranges by ICP-MS

The goal of this article was to establish reference ranges of the concentration of trace elements in human serum and to compare these results with those reported by other authors. We describe the sample preparation and measurement conditions that allow the rapid, precise, and accurate determination of Al, As, B, Be, Cd, Co, Cu, Fe, Li, Mn, Mo, Ni, Rb, Se, Sr, and Zn in human serum samples (n=110) by inductively coupled plasma-mass spectrometry (ICP-MS). Accuracy and precision were determined by analyzing three reconstituted reference serum samples by comparison with other methods and by the standard addition procedure. The advantages of the ICP-MS method include short time of analysis of the elements mentioned, low detection limit, high precision, and high accuracy. Disadventages include a high risk of contamination due to the presence of some of the elements of interest in the environment, the relatively delicate sample handling, and the high cost of the equipmen

Comparison of different exoplanet mass detection limit methods using a sample of main-sequence intermediate-type stars

The radial velocity (RV) technique is a powerful tool for detecting extrasolar planets and deriving mass detection limits that are useful for constraining planet pulsations and formation models. Detection limit methods must take into account the temporal distribution of power of various origins in the stellar signal. These methods must also be able to be applied to large samples of stellar RV time series We describe new methods for providing detection limits. We compute the detection limits for a sample of ten main sequence stars, which are of G-F-A type, in general active, and/or with detected planets, and various properties. We use them to compare the performances of these methods with those of two other methods used in the litterature. We obtained detection limits in the 2-1000 day period range for ten stars. Two of the proposed methods, based on the correlation between periodograms and the power in the periodogram of the RV time series in specific period ranges, are robust and represent a significant improvement compared to a method based on the root mean square of the RV signal. We conclude that two of the new methods (correlation-based method and local power analysis, i.e. LPA, method) provide robust detection limits, which are better than those provided by methods that do not take into account the temporal sampling.Comment: 18 pages, 15 figures Accepted in Astronomy & Astrophysic

Morton Neuroma: Evaluated with Ultrasonography and MR Imaging

Objective The purpose of this study was to compare the diagnostic accuracy of both ultrasonography (US) and magnetic resonance imaging (MRI) for the assessment of Morton neuroma. Materials and Methods Our study group was comprised of 20 neuromas from 17 patients, and the neuromas were confirmed on surgery following evaluation with US, MRI, or both US and MRI. The diagnostic criterion for Morton neuroma, as examined by US, was the presence of a round or ovoid, well-defined, hypoechoic mass. The diagnostic criterion, based on MR imaging, was a well defined mass with intermediate to low signal intensity on both the T1- and T2-weighted images. The retrospective comparison between the sonographic and MR images was done by two experienced radiologists working in consensus with the surgical and pathologic correlations. Results The detection rate of Morton neuroma was 79% for 14 neuromas from 11 patients who had undergone US followed by an operation. The detection rate was 76% for 17 neuromas from 15 patients who had undergone MRI and a subsequent operation. The mean size of the examined neuromas was 4.9 mm on the US images and it was 5.1 mm on the MRI studies. Ten neuromas (71%) were 5 mm or less as measured by US, and three neuromas were not detected, whereas on the MRI analysis, 10 neuromas (59%) were 5 mm or less and four neuromas were not visualized. Among the patients examined during postoperative follow-up, symptoms were completely relieved in 85% and the symptoms were partially relieved in 15%. Conclusion US and MR imaging are comparable modalities with high detection rate for the evaluation of Morton neuroma.ope

The Filament Sensor for Near Real-Time Detection of Cytoskeletal Fiber Structures

A reliable extraction of filament data from microscopic images is of high interest in the analysis of acto-myosin structures as early morphological markers in mechanically guided differentiation of human mesenchymal stem cells and the understanding of the underlying fiber arrangement processes. In this paper, we propose the filament sensor (FS), a fast and robust processing sequence which detects and records location, orientation, length and width for each single filament of an image, and thus allows for the above described analysis. The extraction of these features has previously not been possible with existing methods. We evaluate the performance of the proposed FS in terms of accuracy and speed in comparison to three existing methods with respect to their limited output. Further, we provide a benchmark dataset of real cell images along with filaments manually marked by a human expert as well as simulated benchmark images. The FS clearly outperforms existing methods in terms of computational runtime and filament extraction accuracy. The implementation of the FS and the benchmark database are available as open source.Comment: 32 pages, 21 figure