Tiefenverteilung von Radionukliden in Fichtenwald- und Hochmoorböden

In der Umwelt vorkommende Radionuklide wurden als Tracer für Migrationsverhalten verwendet. Low-level-γ-Spektrometrie und zusätzliche Plutoniumanalysen ermöglichten den Nachweis sehr geringer Konzentrationen radioaktiver Nuklide. Der atmosphärische Eintrag wurde über Regenwasser- und Staubfilterproben gemessen. Untersuchungen an Filterstäuben ermöglichten eine nachträgliche Charakterisierung der Eintragssituation vor und nach dem Tschernobyl-Unfall im Freiberger Raum. Die Radionuklidtiefenverteilungen in Fichtenwald- und Hochmoorböden und deren weiterführende Analyse erlaubten Aussagen zum Stofftransport und zu bodenbildenden Prozessen. Die Migrationsdynamik in weitgehend ungestörten Hochmooren unterscheidet sich von der anthropogen überprägter Moore. Die Eignung verschiedener Radionuklide zur Datierung bzw. zeitlichen Markierung von Moorbodenschichten und damit zur Verwendung in der Moorstratigraphie wurde geprüft. Eine gute Übereinstimmung der Ergebnisse verschiedener Datierungs- und Markierungsmethoden zeigte sich v. a. für die Profile der ungestörten, rezent wachsenden ombrogenen Hochmoore

Molecular Imaging of Pulmonary Tuberculosis in an Ex-Vivo Mouse Model Using Spectral Photon-Counting Computed Tomography and Micro-CT

Assessment of disease burden and drug efficacy is achieved preclinically using high resolution micro computed tomography (CT). However, micro-CT is not applicable to clinical human imaging due to operating at high dose. In addition, the technology differences between micro-CT and standard clinical CT prevent direct translation of preclinical applications. The current proof-of-concept study presents spectral photon-counting CT as a clinically translatable, molecular imaging tool by assessing contrast uptake in an ex-vivo mouse model of pulmonary tuberculosis (TB). Iodine, a common contrast used in clinical CT imaging, was introduced into a murine model of TB. The excised mouse lungs were imaged using a standard micro-CT subsystem (SuperArgus) and the contrast enhanced TB lesions quantified. The same lungs were imaged using a spectral photoncounting CT system (MARS small-bore scanner). Iodine and soft tissues (water and lipid) were materially separated, and iodine uptake quantified. The volume of the TB infection quantified by spectral CT and micro-CT was found to be 2.96 mm(3) and 2.83 mm(3), respectively. This proof-of-concept study showed that spectral photon-counting CT could be used as a predictive preclinical imaging tool for the purpose of facilitating drug discovery and development. Also, as this imaging modality is available for human trials, all applications are translatable to human imaging. In conclusion, spectral photon-counting CT could accelerate a deeper understanding of infectious lung diseases using targeted pharmaceuticals and intrinsic markers, and ultimately improve the efficacy of therapies by measuring drug delivery and response to treatment in animal models and later in humans

Tiefenverteilung von Radionukliden in Fichtenwald- und Hochmoorböden

In der Umwelt vorkommende Radionuklide wurden als Tracer für Migrationsverhalten verwendet. Low-level-γ-Spektrometrie und zusätzliche Plutoniumanalysen ermöglichten den Nachweis sehr geringer Konzentrationen radioaktiver Nuklide. Der atmosphärische Eintrag wurde über Regenwasser- und Staubfilterproben gemessen. Untersuchungen an Filterstäuben ermöglichten eine nachträgliche Charakterisierung der Eintragssituation vor und nach dem Tschernobyl-Unfall im Freiberger Raum. Die Radionuklidtiefenverteilungen in Fichtenwald- und Hochmoorböden und deren weiterführende Analyse erlaubten Aussagen zum Stofftransport und zu bodenbildenden Prozessen. Die Migrationsdynamik in weitgehend ungestörten Hochmooren unterscheidet sich von der anthropogen überprägter Moore. Die Eignung verschiedener Radionuklide zur Datierung bzw. zeitlichen Markierung von Moorbodenschichten und damit zur Verwendung in der Moorstratigraphie wurde geprüft. Eine gute Übereinstimmung der Ergebnisse verschiedener Datierungs- und Markierungsmethoden zeigte sich v. a. für die Profile der ungestörten, rezent wachsenden ombrogenen Hochmoore

Tiefenverteilung von Radionukliden in Fichtenwald- und Hochmoorböden

In der Umwelt vorkommende Radionuklide wurden als Tracer für Migrationsverhalten verwendet. Low-level-γ-Spektrometrie und zusätzliche Plutoniumanalysen ermöglichten den Nachweis sehr geringer Konzentrationen radioaktiver Nuklide. Der atmosphärische Eintrag wurde über Regenwasser- und Staubfilterproben gemessen. Untersuchungen an Filterstäuben ermöglichten eine nachträgliche Charakterisierung der Eintragssituation vor und nach dem Tschernobyl-Unfall im Freiberger Raum. Die Radionuklidtiefenverteilungen in Fichtenwald- und Hochmoorböden und deren weiterführende Analyse erlaubten Aussagen zum Stofftransport und zu bodenbildenden Prozessen. Die Migrationsdynamik in weitgehend ungestörten Hochmooren unterscheidet sich von der anthropogen überprägter Moore. Die Eignung verschiedener Radionuklide zur Datierung bzw. zeitlichen Markierung von Moorbodenschichten und damit zur Verwendung in der Moorstratigraphie wurde geprüft. Eine gute Übereinstimmung der Ergebnisse verschiedener Datierungs- und Markierungsmethoden zeigte sich v. a. für die Profile der ungestörten, rezent wachsenden ombrogenen Hochmoore

Resources in Antarctica: With the World’s dwindling natural resources, is there a chance for exploitation in Antarctica?

Pressure on global resources increases daily as the worlds human population and its demand for energy, raw materials, food, water and health care increases almost exponentially. Naturally such growth puts pressure on resources and is therefore inevitable that relatively untouched areas Of the world such as Antarctica come under the spotlight. From an almost unlimited number Of potential resources for exploitation, the syndicate chose to concentrate on five areas considered to be the most significant in terms Of their current and fu ture relevance. W•hilst the pressure to exploit some resources seems distant in terms Of time and economic viability, exploitation has already begun in the Southern Ocean and coastal waters Of Antarctica. Fishing, bioprospecting and the potential Of iceberg utilisation are all activities which can occur With minimal environmental impact if they are well managed. Prospecting and extraction Of Oil and mineral resources are likely to cause significant problems for otherwise pristine areas. Above all, the exploitation Of Antarctic resources poses the greatest threat to the current stability Of the ATS and the Wider Antarctic political framework. The increasing global pressure to use resources Of any kind from Antarctica, underlines the need to strengthen existing Treaty and Protocol statements and intentions, in order to provide the world With a single Antarctic voice With which to guide its future approach to this unique region Of the planet. Pressure on global resources increases daily as the worlds human population and its demand for energy, raw materials, food, water and health care increases almost exponentially. Naturally such growth puts pressure on resources and is therefore inevitable that relatively untouched areas Of the world such as Antarctica come under the spotlight. From an almost unlimited number Of potential resources for exploitation, the syndicate chose to concentrate on five areas considered to be the most significant in terms Of their current and fu ture relevance. W•hilst the pressure to exploit some resources seems distant in terms Of time and economic viability, exploitation has already begun in the Southern Ocean and coastal waters Of Antarctica. Fishing, bioprospecting and the potential Of iceberg utilisation are all activities which can occur With minimal environmental impact if they are well managed. Prospecting and extraction Of Oil and mineral resources are likely to cause significant problems for otherwise pristine areas. Above all, the exploitation Of Antarctic resources poses the greatest threat to the current stability Of the ATS and the Wider Antarctic political framework. The increasing global pressure to use resources Of any kind from Antarctica, underlines the need to strengthen existing Treaty and Protocol statements and intentions, in order to provide the world With a single Antarctic voice With which to guide its future approach to this unique region Of the planet

Measuring Identification and Quantification Errors in Spectral CT Material Decomposition

Material decomposition methods are used to identify and quantify multiple tissue components in spectral CT but there is no published method to quantify the misidentification of materials. This paper describes a new method for assessing misidentification and mis-quantification in spectral CT. We scanned a phantom containing gadolinium (1, 2, 4, 8 mg/mL), hydroxyapatite (54.3, 211.7, 808.5 mg/mL), water and vegetable oil using a MARS spectral scanner equipped with a poly-energetic X-ray source operated at 118 kVp and a CdTe Medipix3RX camera. Two imaging protocols were used; both with and without 0.375 mm external brass filter. A proprietary material decomposition method identified voxels as gadolinium, hydroxyapatite, lipid or water. Sensitivity and specificity information was used to evaluate material misidentification. Biological samples were also scanned. There were marked differences in identification and quantification between the two protocols even though spectral and linear correlation of gadolinium and hydroxyapatite in the reconstructed images was high and no qualitative segmentation differences in the material decomposed images were observed. At 8 mg/mL, gadolinium was correctly identified for both protocols, but concentration was underestimated by over half for the unfiltered protocol. At 1 mg/mL, gadolinium was misidentified in 38% of voxels for the filtered protocol and 58% of voxels for the unfiltered protocol. Hydroxyapatite was correctly identified at the two higher concentrations for both protocols, but mis-quantified for the unfiltered protocol. Gadolinium concentration as measured in the biological specimen showed a two-fold difference between protocols. In future, this methodology could be used to compare and optimize scanning protocols, image reconstruction methods, and methods for material differentiation in spectral CT

Assessment of Material Identification Errors, Image Quality, and Radiation Doses Using Small Animal Spectral Photon-Counting CT

Photon-counting CT offers the potential to provide new diagnostic information. In this study, we sought to determine the interplay between material identification errors, image quality indicators, and radiation doses using photon-counting spectral CT, and to determine whether this relationship is replicated in spectral CT scans of mice. Custom-built Perspex phantoms were used to measure signal-to-noise ratio (SNR) and spatial resolution, and to measure radiation dose using thermoluminescent dosimeters. A multicontrast calibration phantom containing inserts with different concentrations of gadolinium (1, 2, 4, and 8 mg/mL), hydroxyapatite rods (0, 54.3, 104.3, 211.7, 402.3, and 808.5 mg/mL) along with water and lipid was used to assess material identification errors. Image acquisition was performed using the MARS photon-counting scanner with four energy channels (30-45, 45-60, 60-78, and 78-118 keV) at four different tube currents (24, 34, 44, and 55 mu A). As increased tube current showed no significant effect on material characterization, small animal dosimetry was performed with 24-mu A tube current using two noncontrast mice and one mouse injected with gadolinium. Results demonstrated that a tube current increase from 24 to 54 mu A improved the SNR and spatial resolution by <10%, gadolinium identification by <20% (for 1 mg/mL) but radiation dose increased by >160%. Imaging results of the mice showed no obvious artefacts, and the mean absorbed dose measured for the three mice was 27.3 +/- 2.4 mGy. The results suggest that the energy resolving capability of photon-counting CT maintains diagnostically relevant image quality with high levels of material discrimination at reduced radiation dose

Beam profile assessment in spectral CT scanners.

In this paper, we present a method that uses a combination of experimental and modeled data to assess properties of x-ray beam measured using a small-animal spectral scanner. The spatial properties of the beam profile are characterized by beam profile shape, the angular offset along the rotational axis, and the photon count difference between experimental and modeled data at the central beam axis. Temporal stability of the beam profile is assessed by measuring intra- and interscan count variations. The beam profile assessment method was evaluated on several spectral CT scanners equipped with Medipix3RX-based detectors. On a well-calibrated spectral CT scanner, we measured an integral count error of 0.5%, intrascan count variation of 0.1%, and an interscan count variation of less than 1%. The angular offset of the beam center ranged from 0.8° to 1.6° for the studied spectral CT scanners. We also demonstrate the capability of this method to identify poor performance of the system through analyzing the deviation of the experimental beam profile from the model. This technique can, therefore, aid in monitoring the system performance to obtain a robust spectral CT; providing the reliable quantitative images. Furthermore, the accurate offset parameters of a spectral scanner provided by this method allow us to incorporate a more realistic form of the photon distribution in the polychromatic-based image reconstruction models. Both improvements of the reliability of the system and accuracy of the volume reconstruction result in a better discrimination and quantification of the imaged materials