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Cancer is a leading cause of morbidity and mortality worldwide, with approximately 14 million new cases and 8.2 million cancer related deaths in 2012 [1]. Moreover, the global cancer burden is expected to exceed 20 million new cancer cases by 2025. Understanding the spatial and temporal behaviour of cancer is a crucial precondition to achieve a successful treatment. Because no two cancer cases are the same, every patient should receive a treatment plan designed specifically for her case, in order to improve the patient’s survival chances.
We report on investigations that illustrate the interaction between the specific immune system and a young avascular tumor growing due to a diffusive nutrient supply. We formulate a hybrid cellular automata-partial differential equation (CA-PDE) model which includes cell cycle dynamics and allows for tracking the spatial and temporal evolution of this elaborate biological system. We present results of two dimensional numerical simulations that, specifically in this work, include special cases of the spherical and papillary tumor growth, the infiltration of immune system cells into the tumor and the escape of tumor cells from the regime of the immune cells.
We report on the suitability of two different ranges of Hounsfield units (HU) in computed tomography (CT) for the quantification of metallic components of active implantable medical devices (AIMD). The conventional Hounsfield units (CHU) range, which is traditionally used in radiology, is well suited for tissue but suspected inappropriate for metallic materials. Precise HU values are notably beneficial in radiotherapy (RT) for accurate dose calculations, thus for the safety of patient carrying implants. Some of today’s CT machines offers an extended Hounsfield units (EHU) range. This study presents CT acquisitions of a water phantom containing various metallic discs and an implantable-cardioverter defibrillator (IPG). We show that the comparison of HU values at EHU and CHU ranges clearly reveals the superiority and accuracy of EHU. Some geometrical discrepancies perpendicular to slices are observed. At EHU metal artifact reduction algorithms (MAR) underestimates HU values rendering MAR potentially inappropriate for RT.
In this paper, the effect of computed tomography (CT) values of metals in 12-bit and 16-bit extended Hounsfield Unit (EHU) scale on dose calculations in radiotherapy treatment planning systems (TPS) were quantified. Dose simulations for metals in water environment were performed with the software PRIMO in 6MV photon mode. The depth dose profiles were analysed and the relative dose differences between the metals determined with 12-bit and 16-bit CT imaging, respectively, were calculated. Maximum dose differences of ΔAl= 3.0%, ΔTi= 4.5%, ΔCr= 6.2% and ΔCu= 11.6% were measured. In order to increase the accuracy of dose calculation on patients with implants, CT imaging in the EHU scale is recommended.
Bereits im April 2012 wurde im HZwei Magazin ein Stackkonzept für PEM-Brennstoffzellen vorgestellt, bei dem im Gegensatz zu der heute üblichen bipolaren Zellenanordnung mit mechanischer Verpressung Einzelzellen über ein Hydraulikmedium verpresst werden. Die Vorteile der homogenen Verpressung und Temperierung der Zellen wurden hierbei herausgestellt. Zwischenzeitlich ist basierend auf diesem Ansatz das Labormuster eines PEM-Elektrolyseurs entwickelt worden, bei dem der produzierte Wasserstoff oder auch der Sauerstoff mit hohen Ausgangsdrücken, z.B. auf einem für Power-2-Gas-Anlagen günstigem Druckniveau, direkt bereitgestellt werden kann.
The aim of this phantom study is to examine radiation doses of dual- and single-energy computed tomography (DECT and SECT) in the chest and upper abdomen for three different multi-slice CT scanners. A total of 34 CT protocols were examined with the phantom N1 LUNGMAN. Four different CT examination types of different anatomic regions were performed both in single- and dual-energy technique: chest, aorta, pulmonary arteries for suspected pulmonary embolism and liver. Radiation doses were examined for the CT dose index CTDIvol and dose-length product (DLP). Radiation doses of DECT were significantly higher than doses for SECT. In terms of CTDIvol, radiation doses were 1.1–3.2 times higher, and in terms of DLP, these were 1.1–3.8 times higher for DECT compared with SECT. The third-generation dual-source CT applied the lowest dose in 7 of 15 different examination types of different anatomic regions.
Cardiac and liver computed tomography (CT) perfusion has not been routinely implemented in the clinic and requires high radiation doses. The purpose of this study is to examine the radiation exposure and technical settings for cardiac and liver CT perfusion scans at different CT scanners. Two cardiac and three liver CT perfusion protocols were examined with the N1 LUNGMAN phantom at three multi-slice CT scanners: a single-source (I) and second- (II) and third-generation (III) dual-source CT scanners. Radiation doses were reported for the CT dose index (CTDIvol) and dose–length product (DLP) and a standardised DLP (DLP10cm) for cardiac and liver perfusion. The effective dose (ED10cm) for a standardised scan length of 10 cm was estimated using conversion factors based on the International Commission on Radiological Protection (ICRP) 110 phantoms and tissue-weighting factors from ICRP 103. The proposed total lifetime attributable risk of developing cancer was determined as a function of organ, age and sex for adults. Radiation exposure for CTDIvol, DLP/DLP10 cm and ED10 cm during CT perfusion was distributed as follows: for cardiac perfusion (II) 144 mGy, 1036 mGy·cm/1440 mGy·cm and 39 mSv, and (III) 28 mGy, 295 mGy·cm/279 mGy·cm and 8 mSv; for liver perfusion (I) 225 mGy, 3360 mGy·cm/2249 mGy·cm and 54 mSv, (II) 94 mGy, 1451 mGy·cm/937 mGy·cm and 22 mSv, and (III) 74 mGy, 1096 mGy·cm/739 mGy·cm and 18 mSv. The third-generation dual-source CT scanner applied the lowest doses. Proposed total lifetime attributable risk increased with decreasing age. Even though CT perfusion is a high-dose examination, we observed that new-generation CT scanners could achieve lower doses. There is a strong impact of organ, age and sex on lifetime attributable risk. Further investigations of the feasibility of these perfusion scans are required for clinical implementation.