Multi-Modal X-ray Imaging and Analysis for Characterization of Urinary Stones

Backgound: The composition of stones formed in the urinary tract plays an important role in their management over time. The most common imaging method for the non-invasive evaluation of urinary stones is radiography and computed tomography (CT). However, CT is not very sensitive, and cannot differentiate between all critical stone types. In this study, we propose the application, and evaluate the potential, of a multi-modal (or multi-contrast) X-ray imaging technique called speckle-based imaging (SBI) to differentiate between various types of urinary stones. Methods: Three different stone samples were extracted from animal and human urinary tracts and examined in a laboratory-based speckle tracking setup. The results were discussed based on an X-ray diffraction analysis and a comparison with X-ray microtomography and grating-based interferometry. Results: The stones were classified through compositional analysis by X-ray diffraction. The multi-contrast images obtained using the SBI method provided detailed information about the composition of various urinary stone types, and could differentiate between them. X-ray SBI could provide highly sensitive and high-resolution characterizations of different urinary stones in the radiography mode, comparable to those by grating interferometry. Conclusions: This investigation demonstrated the capability of the SBI technique for the non-invasive classification of urinary stones through radiography in a simple and cost-effective laboratory setting. This opens the possibility for further studies concerning full-field in vivo SBI for the clinical imaging of urinary stones

The Drosophila melanogaster model of human uric acid nephrolithiasis as a novel in vivo drug screening platform

Nephrolithiasis involves the supersaturation of a stone-forming solute in urine leading to the formation of a calculus. The development of novel therapeutic agents for this multifactorial urological disorder has been hindered by lack of a practical pre-clinical model. Currently established medical treatments can possess unfavorable side effect profiles and inconsistent efficacies in certain metabolic milieus. Here, Drosophila melanogaster ̶ an emerging model for calcium oxalate nephrolithiasis ̶ was investigated as a potential disease model and high throughput drug discovery platform for human uric acid nephrolithiasis. Through disruption of the Uro gene and purine-rich dietary manipulation, we successfully demonstrate the formation of uric acid calculi in fly malpighian tubules as confirmed by ex vivo confocal microscopy, qRT-PCR and scanning electron microscopy. Flies treated with standardized concentrations of drug candidates through a novel assay identified several compounds with potential anti-lithogenic effects underscoring the power of D. melanogaster as a high throughput tool in drug screening for nephrolithiasis

Electrical Characterization and Detection of Blood Cells and Stones in Urine

Urine contains an immense amount of information related to its physical, chemical, and biological components; hence, it is a promising tool in detecting various diseases. Available methods for detecting hematuria (blood in the urine) are not accurate. Results are influenced by many factors, such as, health and vitals of the patients, settings of the equipment and laboratories, which leads to false positive or false negative outputs. This necessitates the development of new, accurate, and easy-access methods that save time and effort. This study demonstrates a label-free and accurate method for detecting the presence of red and white blood cells (RBCs and WBCs) in urine by measuring the changes in the dielectric properties of urine upon increasing concentrations of both cell types. The current method could detect changes in the electrical properties of fresh urine over a short time interval, making this method suitable for detecting changes that cannot be recognized by conventional methods. Correcting these changes enabled the detection of a minimum cell concentration of 10² RBCs per ml which is not possible by conventional methods used in the labs except for the semi-quantitative method that can detect 50 RBCs per ml, but it is a lengthy and involved procedure, not suitable for high volume labs. This ability to detect a very small amount of both types of cells makes the proposed technique an attractive tool for detecting hematuria, the presence of which is indicative of problems in the excretory system. Furthermore, urolithiasis is also a very common problem worldwide, affecting adults, kids, and even animals. Calcium oxalate is the major constituent of urinary tract stones in individuals, primarily due to the consumption of high oxalate foods. The occurrence of urinary oxalate occurs by endogenous synthesis, especially in the upper urinary tract. In a normal, healthy individual, the excretion of oxalate ranges from 10 to 45 mg/day, depending on the age and gender, but the risk of stone formation starts at 25 mg/day depending on the health history of the individual. This study also addresses the detection of the presence of calcium oxalate in urine following the same label-free approach. This can be done by measuring the changes in the dielectric properties of urine with increasing concentrations of calcium oxalate hydrate (CaC₂O₄.H₂O). The current method could detect dynamic changes in the electrical properties of urine over a time interval in samples containing calcium oxalate hydrate even at a concentration as low as 10 μg/mL of urine, making this method suitable for detecting changes that cannot be recognized by conventional methods. The ability to detect a very small amount of stones makes it an attractive tool for detecting and quantifying stones in kidneys. Using a non-invasive method which also works as a precautionary measure for early detection of some severe ailments, holds a good scope. It forms the basis of the cytological examinations and molecular assays for the diagnosis of several diseases. This method can be considered a point-of-care test because the results can be instantaneously shared with the members of the medical team. Based on these results, it is anticipated that the present approach to be a starting point towards establishing the foundation for label-free electrical-based identification and quantification of an unlimited number of nano-sized particles

Dark-field computed tomography reaches the human scale

X-ray computed tomography (CT) is one of the most commonly used three-dimensional medical imaging modalities today. It has been refined over several decades, with the most recent innovations including dual-energy and spectral photon-counting technologies. Nevertheless, it has been discovered that wave-optical contrast mechanisms—beyond the presently used X-ray attenuation—offer the potential of complementary information, particularly on otherwise unresolved tissue microstructure. One such approach is dark-field imaging, which has recently been introduced and already demonstrated significantly improved radiological benefit in small-animal models, especially for lung diseases. Until now, however, dark-field CT could not yet be translated to the human scale and has been restricted to benchtop and small-animal systems, with scan durations of several minutes or more. This is mainly because the adaption and upscaling to the mechanical complexity, speed, and size of a human CT scanner so far remained an unsolved challenge. Here, we now report the successful integration of a Talbot–Lau interferometer into a clinical CT gantry and present dark-field CT results of a human-sized anthropomorphic body phantom, reconstructed from a single rotation scan performed in 1 s. Moreover, we present our key hardware and software solutions to the previously unsolved roadblocks, which so far have kept dark-field CT from being translated from the optical bench into a rapidly rotating CT gantry, with all its associated challenges like vibrations, continuous rotation, and large field of view. This development enables clinical dark-field CT studies with human patients in the near future

Context-sensitive imaging for single, dual and multi energy computed tomography

In clinical routine, a case-adapted CT examination is usually conducted for each medical indication in order to allow for a comprehensive high-quality diagnosis of a patient. Therefore, image reading requires the transition between various image stacks, since each medical question implicitly requires organ-dependent reconstructions, display settings, multi planar reformations and image analysis tools. In particular, if dual or multi energy CT data are available, various spectral evaluation methods yield material-specific or functional information. However, the interpretation of this large amount of data is a time-consuming and tedious task. Hence, the purpose of this thesis is to evaluate the potential benefit of the incorporation of patient-specific anatomical priors, which are gained from an automatic multi-organ segmentation, in order to discover novel opportunities to improve the clinical workflow. In this thesis, a new paradigm is proposed which combines competing image properties resulting from different reconstruction algorithms and display settings into a context-sensitive CT imaging by means of anatomical prior information. With the incorporation of anatomical prior knowledge, which is obtained using an automatic multi-organ segmentation approach, various desired image characteristics are combined into a single context-sensitive CT image formation and presentation. The comparison with conventional CT images reveals an improved spatial resolution in highly attenuating materials as well as in air-filled body regions. Simultaneously, the compound image maintains a low noise level in soft tissue resulting in a superior soft tissue contrast compared to conventional images. Furthermore, the novel CT imaging framework allows for the combination of mutually exclusive display settings for the presentation of context-sensitive images to the radiologists. By exploiting anatomical prior information, numerous DECT applications can be integrated into one single DE analysis tool. Moreover, the tools can be chosen and applied to different organs simultaneously without any user interaction. The prior-based DE scheme performs all organ-specific feasible methods instantaneously without the need of a manual selection. Exploiting the anatomical priors, DECT analysis and evaluations are automated and standardized. The iodine quantification accuracy is significantly improved using patient-specific calibrations. The evaluation method and the presentation of the data to the radiologist can be realized via color overlays, pop up menus, volume rendering etc. Furthermore, the method can readily be generalized to the cases of multi energy CT data as it is not limited to the processing of DECT data. The principle of incorporation anatomical prior knowledge is then extended to provide a novel pseudo material decomposition that decomposes dual energy data into more than three basis materials. The method consists of multiple three-material decompositions, where the basis materials are automatically adjusted to the organ of interest based on the automatic segmentation. Moreover, a patient-specific calibration is introduced to improve the volume fraction and material quantification accuracy. An organ-adapted basis material triplet is automatically assigned to each anatomical region resulting in overlapping triangles in the dual energy space. The basis materials are calibrated by evaluating ROIs to improve the volume fraction accuracy. Besides presenting evermore increasing material images to the radiologists, the volume fractions are rescaled to organ-dependent material scores and visualized via pie charts to be later correlated with different diagnoses. The prior-based pseudo multi material decomposition is evaluated using phantom and patient data. The materials are quantified according to the anatomical structure they belong to. Overall, the proposed method provides physically plausible volume fractions that bear the potential to improve the material quantification for diagnosis and e.g. tumor treatment monitoring. In addition, the iodine quantification accuracy and the volume fraction accuracy are evaluated depending on different material calibration methods in conventional DECT applications as well as in the novel pseudo multi material decomposition. The accuracy using default parameters or simulation-based calibrations is compared against the accuracy obtained using patient-specific ROIs. All patient-specific calibrations can be performed directly from the patient data itself, such that almost no user interaction is required. It turns out that a patient-specific calibration is superior compared to a default or simulation based calibration. The new paradigm offers the possibility to display evermore complex information in CT imaging in order to significantly improve the workflow of radiologists. In the clinical routine, e.g. during case presentations and discussions, the fast switching between different image stacks is time-consuming and can be avoided in the future since the CS images merge advantageous image properties resulting from various reconstructions and display settings. The results of the DE evaluation can be dynamically superimposed by color overlays. This superposition provides a comprehensive quantitative analysis of the patient data that can be interpreted as an additional image dimension. By means of the combined DECT evaluation scheme, the radiologists might be assisted in finding a precise diagnosis. In summary, diagnostic accuracy could be increased with the CS imaging by improving the sensitivity for incidental findings: e.g. small nodules can be diagnosed in the lung parenchyma, even if the radiologist is mainly focused on assessing soft tissue. The possibility to robustly decompose DECT data into more than three basis materials opens up for novel clinical evaluation to quantify e.g. fat content and iodine content in the liver simultaneously and to assess long term material scores using pie chart visualizations

Application of Dual-Energy Computed Tomography to the Evalution of Coronary Atherosclerotic Plaque

Atherosclerotic coronary artery disease is responsible for around 50 of cardiovascular deaths in USA. Early detection and characterization of coronary artery atherosclerotic plaque could help prevent cardiac events. Computed tomography (CT) is an excellent modality for imaging calcifications and has higher spatial resolution than other common non-invasive modalities (e.g MRI), making it more suitable for coronary plaque detection. However, attenuation-based classification of non-calcified plaques as fibrous or lipid is difficult with conventional CT, which relies on a single x-ray energy. Dual-energy CT (DECT) may provide additional attenuation data for the identification and discrimination of plaque components. The purpose of this research was to evaluate the feasibility of DECT imaging for coronary plaque characterization and further, to explore the limits of CT for non-invasive plaque analysis. DECT techniques were applied to plaque classification using a clinical CT system. Saline perfused coronary arteries from autopsies were scanned at 80 and 140 kVp, prior to and during injection of iodinated contrast. Plaque attenuation was measured from CT images and matched to histology. Measurements were compared to assess differences among plaque types. Although calcified and non-calcified plaques could be identified and differentiated with DECT, further characterization of non-calcified plaques was not possible. The results also demonstrated that calcified plaque and iodine could be discriminated. The limits of x-ray based non-calcified plaque discrimination were assessed using microCT, a pre-clinical x-ray based high spatial resolution modality. Phantoms and tissues of different composition were scanned using different tube voltages (i.e., different energies) and resulting attenuation values were compared. Better vessel wall visualization and increase in tissue contrast resolution was observed with decrease in x-ray energy. Feasibility of calcium quantification from contrast-enhanced scans by creating virtual n

Application of Dual-Energy Computed Tomography to the Evalution of Coronary Atherosclerotic Plaque

Atherosclerotic coronary artery disease is responsible for around 50 of cardiovascular deaths in USA. Early detection and characterization of coronary artery atherosclerotic plaque could help prevent cardiac events. Computed tomography (CT) is an excellent modality for imaging calcifications and has higher spatial resolution than other common non-invasive modalities (e.g MRI), making it more suitable for coronary plaque detection. However, attenuation-based classification of non-calcified plaques as fibrous or lipid is difficult with conventional CT, which relies on a single x-ray energy. Dual-energy CT (DECT) may provide additional attenuation data for the identification and discrimination of plaque components. The purpose of this research was to evaluate the feasibility of DECT imaging for coronary plaque characterization and further, to explore the limits of CT for non-invasive plaque analysis. DECT techniques were applied to plaque classification using a clinical CT system. Saline perfused coronary arteries from autopsies were scanned at 80 and 140 kVp, prior to and during injection of iodinated contrast. Plaque attenuation was measured from CT images and matched to histology. Measurements were compared to assess differences among plaque types. Although calcified and non-calcified plaques could be identified and differentiated with DECT, further characterization of non-calcified plaques was not possible. The results also demonstrated that calcified plaque and iodine could be discriminated. The limits of x-ray based non-calcified plaque discrimination were assessed using microCT, a pre-clinical x-ray based high spatial resolution modality. Phantoms and tissues of different composition were scanned using different tube voltages (i.e., different energies) and resulting attenuation values were compared. Better vessel wall visualization and increase in tissue contrast resolution was observed with decrease in x-ray energy. Feasibility of calcium quantification from contrast-enhanced scans by creating virtual n

Aerospace medicine and biology: A continuing bibliography with indexes

This bibliography lists 148 reports, articles and other documents introduced into the NASA scientific and technical information system in December 1984

The study of renal function and toxicity using zebrafish (Danio rerio) larvae as a vertebrate model

Zebrafish (Danio rerio) is a powerful model in biomedical and pharmaceutical sciences. The zebrafish model was introduced to toxicological sciences in 1960, followed by its use in biomedical sciences to investigate vertebrate gene functions. As a consequence of many research projects in this field, the study of human genetic diseases became instantly feasible. Consequently, zebrafish have been intensively used in developmental biology and associated disciplines. Due to the simple administration of medicines and the high number of offspring, zebrafish larvae became widely more popular in pharmacological studies in the following years. In the past decade, zebrafish larvae were further established as a vertebrate model in the field of pharmacokinetics and nanomedicines. In this PhD thesis, zebrafish larvae were investigated as an earlystage in vivo vertebrate model to study renal function, toxicity, and were applied in drug-targeting projects using nanomedicines. The first part focused on the characterization of the renal function of three-to four-dayold zebrafish larvae. Non-renal elimination processes were additionally described. Moreover, injection techniques, imaging parameters, and post-image processing scripts were established to serve as a toolbox for follow-up projects. The second part analyzed the impact of gentamicin (a nephrotoxin) on the morphology of the pronephros of zebrafish larvae. Imaging methodologies such as fluorescent-based laser scanning microscopy and X-ray-based microtomography were applied. A profound comparison study of specimens acquired with different laboratory X-ray-based microtomography devices and a radiation facility was done to promote the use of X-ray-based microtomography for broader biomedical applications. In the third part, the toxicity of nephrotoxins on mitochondria in renal epithelial cells of proximal tubules was assessed using the zebrafish larva model. Findings were compared with other teleost models such as isolated renal tubules of killifish (Fundulus heteroclitus). In view of the usefulness and high predictability of the zebrafish model, it was applied to study the pharmacokinetics of novel nanoparticles in the fourth part. Various in vivo pharmacokinetic parameters such as drug release, transfection of mRNA/pDNA plasmids, macrophage clearance, and the characterization of novel drug carriers that were manipulated with ultrasound were assessed in multiple collaborative projects. Altogether, the presented zebrafish model showed to be a reliable in vivo vertebrate model to assess renal function, toxicity, and pharmacokinetics of nanoparticles. The application of the presented model will hopefully encourage others to reduce animal experiments in preliminary studies by fostering the use of zebrafish larvae