The use of 3D printing for rapid tooling and manufacturing has promised to produce components with complex geometries according to computer designs. Due to the intrinsically limited mechanical properties and functionalities of printed pure polymer parts, there is a critical need to develop printable polymer composites with high performance. 3D printing offers many advantages in the fabrication of composites, including high precision, cost effective and customized geometry. This article gives an overview on 3D printing techniques of polymer composite materials and the properties and performance of 3D printed composite parts as well as their potential applications in the fields of biomedical, electronics and aerospace engineering. Common 3D printing techniques such as fused deposition modeling, selective laser sintering, inkjet 3D printing, stereolithography, and 3D plotting are introduced. The formation methodology and the performance of particle-, fiber- and nanomaterial-reinforced polymer composites are emphasized. Finally, important limitations are identified to motivate the future research of 3D printing.

3D printing of polymer matrix composites: A review and prospective

Additive manufacturing (AM) is poised to bring about a revolution in the way products are designed, manufactured, and distributed to end users. This technology has gained significant academic as well as industry interest due to its ability to create complex geometries with customizable material properties. AM has also inspired the development of the maker movement by democratizing design and manufacturing. Due to the rapid proliferation of a wide variety of technologies associated with AM, there is a lack of a comprehensive set of design principles, manufacturing guidelines, and standardization of best practices. These challenges are compounded by the fact that advancements in multiple technologies (for example materials processing, topology optimization) generate a "positive feedback loop" effect in advancing AM. In order to advance research interest and investment in AM technologies, some fundamental questions and trends about the dependencies existing in these avenues need highlighting. The goal of our review paper is to organize this body of knowledge surrounding AM, and present current barriers, findings, and future trends significantly to the researchers. We also discuss fundamental attributes of AM processes, evolution of the AM industry, and the affordances enabled by the emergence of AM in a variety of areas such as geometry processing, material design, and education. We conclude our paper by pointing out future directions such as the "print-it-all" paradigm, that have the potential to re-imagine current research and spawn completely new avenues for exploration. The fundamental attributes and challenges/barriers of Additive Manufacturing (AM).The evolution of research on AM with a focus on engineering capabilities.The affordances enabled by AM such as geometry, material and tools design.The developments in industry, intellectual property, and education-related aspects.The important future trends of AM technologies.

The status, challenges, and future of additive manufacturing in engineering

Additive manufacturing processes take the information from a computer-aided design (CAD) file that is later converted to a stereolithography (STL) file. In this process, the drawing made in the CAD software is approximated by triangles and sliced containing the information of each layer that is going to be printed. There is a discussion of the relevant additive manufacturing processes and their applications. The aerospace industry employs them because of the possibility of manufacturing lighter structures to reduce weight. Additive manufacturing is transforming the practice of medicine and making work easier for architects. In 2004, the Society of Manufacturing Engineers did a classification of the various technologies and there are at least four additional significant technologies in 2012. Studies are reviewed which were about the strength of products made in additive manufacturing processes. However, there is still a lot of work and research to be accomplished before additive manufacturing technologies become standard in the manufacturing industry because not every commonly used manufacturing material can be handled. The accuracy needs improvement to eliminate the necessity of a finishing process. The continuous and increasing growth experienced since the early days and the successful results up to the present time allow for optimism that additive manufacturing has a significant place in the future of manufacturing.

/pdf/a-review-of-additive-manufacturing-2g0afwxkp6.pdf

A Review of Additive Manufacturing

Rationale and Objectives:To characterize and compare commercially available contrast media (CM) for magnetic resonance imaging (MRI) in terms of their relaxivity at magnetic field strengths ranging from 0.47 T to 4.7 T at physiological temperatures in water and in plasma. Relaxivities also were quan

Comparison of magnetic properties of MRI contrast media solutions at different magnetic field strengths.

Nearing 30 years since its introduction, 3D printing technology is set to revolutionize research and teaching laboratories. This feature encompasses the history of 3D printing, reviews various printing methods, and presents current applications. The authors offer an appraisal of the future direction and impact this technology will have on laboratory settings as 3D printers become more accessible.

https://www.egr.msu.edu/eceshop/testingfacility/connex/papers/ac403397r.pdf

Evaluation of 3D printing and its potential impact on biotechnology and the chemical sciences.

Fragestellung. Mit der Verfugbarkeit neuartiger Kontrastmittel – proteininteragierend oder hoher konzentriert – stellt sich die Frage, ob und wie sich diese von den Standardkontrastmitteln hinsichtlich der vaskularen Kontrastierung unterscheiden. 
Methodik. In einer intraindividuellen Vergleichsstudie des Abdomens (1,5 T-MRTSystem) wurden 5 Probanden mit einer multiphasischen MRA jeweils mit 3 verschiedenen MR-Kontrastmitteln (Gadopentetat-Dimeglumin 0,5 M;Gadobenat-Dimeglumin 0,5 M und Gadobutrol 1,0 M) untersucht. Dosis (0,15 mmol/kg Korpergewicht) und Flussrate (3,0 ml/s) waren fur alle 3 Kontrastmittel identisch. Die Untersuchungen wurden geblindet qualitativ und quantitativ evaluiert. 
Ergebnisse. Das proteininteragierende Gadobenat-Dimeglumin erzielte im Vergleich mit den anderen Kontrastmitteln signifikant hohere Signalintensitaten in den arteriellen Gefasen (p = 0,05). Es wurde aufgezeigt, dass zwischen Gadopentetat-Dimeglumin und Gadobutrol 1,0 M keine signifikante Differenz in der vaskularen Kontrastierungseigenschaften besteht. 
Schlussfolgerung. Gadobenat-Dimeglumin hat sich als vorteilhaftes Kontrastmittel fur die multiphasische MRA herausgestellt. Hoher konzentrierte Gd-Chelate fuhren unter standardisierter Bildgebung nicht automatisch zu verbesserten Kontrastierungseffekten.

Intraindividueller Vergleich dreier Kontrastmittel (Gd-DTPA, Gd-BOPTA und Gd-BT-DO3A) mit der multiphasischen MR-Angiographie

Magnetic resonance angiography is undergoing rapid development as a non-invasive technique to reliably assess renal artery stenosis. Invasive X-ray angiography is currently the gold standard imaging technique and gives excellent spatial resolution. However, its disadvantages include a necessary exposure to radiation and the need for iodinated contrast media. While magnetic resonance angiography does not have these disadvantages, its spatial resolution is inherently lower. On the other hand, magnetic resonance angiography enables true three-dimensional imaging. The use of rapid imaging techniques allows multiple image acquisition within one breath-hold thereby permitting the visualization of distinct vascular phases. The limitation in spatial resolution can be overcome readily by combining morphologic imaging with functional information on the hemodynamic relevance. This can be achieved by means of magnetic resonance phase contrast flow measurements. The use of such a combined approach enables the grading of vascular stenosis based on the combination of morphology and functional information. Magnetic resonance angiography is already able to demonstrate a clinical utility equivalent to that of invasive procedures, indicating that it is likely to become a premier method for the diagnosis and follow up of renovascular disease. Index terms: Magnetic resonance-Angiography-Renal artery stenosis-Contrast agents.

Non-invasive assessment of renal artery stenosis: current concepts and future directions in magnetic resonance angiography.

Benign prostate hyperplasia (BPH) is a major disease and its non-surgical therapy a major area of interest. The purpose of this study was to establish perfusion parameters in beagles with BPH using dynamic contrast-enhanced (DCE) MRI and to investigate changes due to the effects of finasteride treatment. Twelve male beagles (mean age 4.4 +/- 0.9,years) were divided into a control and treatment group that received a daily dose of 1 mg/kg finasteride. DCE MRI was carried out in a clinical scanner using a 3D spoiled gradient echo sequence prior to and during treatment. 0.2 mmol/kg contrast agent (gadoteridol) was administered with an injection rate of 0.2 ml/s followed by a 15 ml flush of saline. Contrast enhancement was evaluated by pharmacokinetic mapping of a two-compartment model with colour overlay images in addition to regional ROI analysis. Quantitative parameters were defined by the amplitude of contrast enhancement A, the exchange rate k(ep) and the time to maximum signal enhancement. Dynamic contrast-enhanced MRI investigations of the prostate revealed two distinct zones, an inner, periurethral zone and an outer, parenchymal zone. The periurethral zone is highly vascularized, whereas the parenchymal zone is moderately vascularized when compared to other parenchymal organs. During treatment, in the parenchymal zone the intensity of enhancement (amplitude A) and the time to maximum signal enhancement increased, while the exchange rate k(ep) decreased. Dynamic contrast-enhanced MRI of BPH reveals distinct differences between individual zones within the prostate. Moreover, changes during successful treatment suggest increased blood volume per volume of tissue and decreased vessel leakiness.

Benign prostate hyperplasia: evaluation of treatment response with DCE MRI

AIM

To identify morphologic factors affecting aortic expansion in patients with uncomplicated type B aortic dissections.

METHODS

Computed tomography data of 24 patients (18 male; median age: 61 years), diagnosed with acute uncomplicated type B aortic dissections between 2002 and 2013, were retrospectively reviewed. All patients had at least two computed tomography angiography scans and six months of uneventful follow-up. Computed tomography scans were assessed by two independent readers with regard to presence and number of entry tears. Thoracic and abdominal aortic diameters were derived using image processing software.

RESULTS

Twenty-two of 24 patients showed aortic expansion over a median computed tomography angiographic follow-up of 33.2 months. Annual rates showed an increase of 1.7 mm for total aortic diameter, 2.1 mm for the false and a decrease of -0.4 mm for the true lumen. In three patients (12.5%), aortic diameter exceeded 60 mm during follow-up, and all three patients underwent thoracic endovascular aortic repair. Patients with a maximum aortic diameter  2 entries vs. ≤2 entries: -7.8 mm(2) vs. +37.5 mm(2); p = 0.0369). Median size of entry tears was 12 mm (range: 2-53 mm).

CONCLUSIONS

The results presented herein suggest that uncomplicated type B aortic dissection patients with more than two entry tears and/or an initial maximum aortic diameter of<4 cm are at risk for aortic dilatation and, therefore, may require stricter follow-up including the possible need for early intervention.

Morphologic predictors of aortic expansion in chronic type B aortic dissection

Modern imaging modalities, especially noninvasive cross-sectional imaging techniques, have advanced dramatically in recent years and are now the backbone of pre- and postoperative evaluation of aortic pathologies. The planning in particular, but also the aftercare following endovascular aortic reconstructions, make heavy demands on physicians. It is necessary to select the method of examination that is best suited to the pathology concerned and to apply it to the patient in an individual manner. Ultrasound is the examination of choice for screening and follow-up of infrarenal aneurysms. Transesophageal echocardiography and magnetic resonance angiography are used in diagnosis, in intraoperative navigation during the implantation of endografts and in follow-up of patients with thoracic aortic aneurysms and aortic dissections who have undergone conservative treatment, with very high sensitivity and specificity. The use of MRA is restricted by the long time needed for an examination, metal artifacts and limited availability. DSA has been largely superseded in the diagnosis of aortic pathologies by CTA, but as yet retains its role in intraoperative imaging of the anchorage regions of endoprostheses. Selective demonstration of postoperative internal leaks with subsequent therapeutic embolization is a further area of use for DSA. CTA, including so-called image postprocessing, has taken over the prime role in imaging of the aorta. Disease-specific diagnostic algorithms are useful and necessary in day-to-day clinical practice.

/pdf/klinische-anforderungen-an-die-bildgebung-der-aorta-3ts7vyyfil.pdf

H. von Tengg-Kobligk

Papers

Intraindividueller Vergleich dreier Kontrastmittel (Gd-DTPA, Gd-BOPTA und Gd-BT-DO3A) mit der multiphasischen MR-Angiographie

Non-invasive assessment of renal artery stenosis: current concepts and future directions in magnetic resonance angiography.

Benign prostate hyperplasia: evaluation of treatment response with DCE MRI

Morphologic predictors of aortic expansion in chronic type B aortic dissection

Klinische Anforderungen an die Bildgebung der Aorta