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Liney G.P.,Ingham Institute | Liney G.P.,University of New South Wales | Liney G.P.,University of Wollongong | Holloway L.,Ingham Institute | And 9 more authors.
British Journal of Radiology | Year: 2015

Objective: Diffusion-weighted imaging (DWI) is an important technique for the localization of prostate cancer, and its response assessment during treatment with radiotherapy (RT). However, it has known limitations in terms of distortions and artefacts using standard acquisition techniques. This study evaluates two alternative methods that offer the promise of improved image quality and the potential for more reliable and consistent diffusion data. Methods: Three DWI techniques were investigated; singleshot echoplanar imaging (EPI), EPI combined with reduced volume excitation (ZOOMit; Siemens Healthcare, Erlangen, Germany) and read-out segmentation with navigator-echo correction (RESOLVE; Siemens Healthcare). Daily measurements of apparent diffusion coefficient (ADC) value were made in a quality assurance phantom to assess the repeatability of each sequence. In order to evaluate the geometric integrity of these sequences, ten normal volunteers were scanned, and the prostate was contoured to compare its similarity with T2weighted images. Results: Phantom ADC values were significantly higher using the standard EPI sequence than those of the other two sequences. Differences were also observed between sequences in terms of repeatability, with RESOLVE and EPI performing better than ZOOMit. Overall, the RESOLVE sequence provided the best agreement for the in vivo data with smaller differences in volume and higher contour similarity than T2weighted imaging. Conclusion: Important differences have been observed between each of the three techniques investigated with RESOLVE performing the best overall. We have adopted this sequence for routine RT simulation of prostate patients at Liverpool Cancer Therapy Centre. Advances in knowledge: This work will be of interest to the increasing number of centres wanting to incorporate quantitative DWI in a clinical setting. © 2015 The Authors. Published by the British Institute of Radiology. Source

News Article | April 8, 2016
Site: http://www.techtimes.com/rss/sections/science.xml

Researchers found that new composite metal foams (CMFs) have excellent thermal protection compared to plain metal, turning armor piercing bullet into dust. North Carolina State University researchers studied lightweight CMFs and found that the air pockets inside the metal foams are effective heat blockers. This makes CMFs a promising tool for use in transport and storage of hazardous materials, explosives, nuclear elements, and other heat sensitive materials. It could also prove beneficial for space exploration. Mechanical and aerospace engineering professor at NC State Afsaneh Rabiei shared that this property can be attributed to the hollow spheres in the CMFs, which is composed of stainless steel, carbon steel, or titanium implanted in a metallic matrix of aluminum, metallic alloys, and steel. "The presence of air pockets inside CMF make it so effective at blocking heat, mainly because heat travels more slowly through air than through metal," said Rabiei. The researchers employed two technologies in creating CMFs. One is by making a cast of low melting point matrix material using aluminum to surround the hollow spheres, which has a higher melting point like steel. Another technique is by having prefabricated hollow spheres covered with baked matrix powder, which creates a steel-steel CMF. To prove the heat and fire protection capability of CMFs, the researchers subjected samples of 2.5-inch x 2.5-inch steel-steel CMF that have 0.75 inch thickness to an 800 degree Celsius (1,472 degrees Fahrenheit) fire for 30 minutes. The researchers monitored the material and measured the length of time to reach the other side of the sample. The stainless steel sample only took 4 minutes to breach the 800 degree mark but for the CMF, it took 8 minutes to reach the same temperature. According to Rabiei, CMFs thermal conductivity could prevent accidents from leading to explosions. The research also found that CMFs made up of stainless steel has an 80 percent less expansion at 200 degrees Celsius. The expansion during high heat exposure is constant compared to conventional bulk metals and alloys. Researchers concluded that CMF has excellent thermal insulation, good flame retardant performance, and superior thermal stability when compared to conventional materials available in the market today. In Rabiei's previous study published in the journal Radiation Physics and Chemistry, lightweight metal foams have previously been proven to efficiently block neutron radiation, gamma rays, and X-ray, which can pave the way for more studies that focus on nuclear safety, healthcare applications, and space exploration. © 2016 Tech Times, All rights reserved. Do not reproduce without permission.

Adolfsson E.,Linkoping University | Carlsson Tedgren A.,Swedish Radiation Safety Authority | Alm Carlsson G.,Radiation Physics | Gustafsson H.,Linkoping University | Lund E.,Radiation Physics
Radiation Measurements | Year: 2014

Clinical applications of electron paramagnetic resonance (EPR) dosimetry systems demand high accuracy causing time consuming analysis. The need for high spatial resolution dose measurements in regions with steep dose gradients demands small sized dosimeters. An optimization of the analysis was therefore needed to limit the time consumption. The aim of this work was to introduce a new smaller lithium formate dosimeter model (diameter reduced from standard diameter 4.5 mm to 3 mm and height from 4.8 mm to 3 mm). To compensate for reduced homogeneity in a batch of the smaller dosimeters, a method for individual sensitivity correction suitable for EPR dosimetry was tested. Sensitivity and repeatability was also tested for a standard EPR resonator and a super high Q (SHQE) one. The aim was also to optimize the performance of the dosimetry system for better efficiency regarding measurement time and precision. A systematic investigation of the relationship between measurement uncertainty and number of readouts per dosimeter was performed. The conclusions drawn from this work were that it is possible to decrease the dosimeter size with maintained measurement precision by using the SHQE resonator and introducing individual calibration factors for dosimeter batches. It was also shown that it is possible reduce the number of readouts per dosimeter without significantly decreasing the accuracy in measurements. © 2014 Elsevier Ltd. All rights reserved. Source

Worrall M.,Radiation Physics | Sutton G.D.,Radiation Physics
Journal of Radiological Protection | Year: 2015

Any institution wishing to perform an internal cross calibration of its diagnostic dosemeters should first quantify the uncertainty associated with this to demonstrate that it remains appropriate for the measurements being undertaken. An uncertainty budget for internal cross calibration that covers a range of locally used dosemeters has been derived using the methodology of the International Atomic Energy Agency. The specific internal cross calibration protocol requirements necessary for this uncertainty budget to be valid are discussed. The final quantified uncertainty is 5.31%; this is dominated by the 5% uncertainty associated with the calibration of the reference instrument. The next largest contributions are from differences in temperature and pressure and dosemeter energy dependence. It has been demonstrated that with careful adherence to a well designed internal cross calibration protocol, dosemeters can be calibrated in-house against a calibrated reference dosemeter with very little increase in the associated calibration uncertainty. © 2015 IOP Publishing Ltd. Source

McVey S.,Radiation Physics | Sandison A.,Radiation Physics | Sutton D.G.,Radiation Physics
Journal of Radiological Protection | Year: 2013

The International Commission on Radiological Protection (ICRP) has recently issued a proposal to reduce the occupational eye dose limit from 150 to 20 mSv. A series of experiments has been performed to determine the level of protection from scattered radiation afforded to the interventional radiology operator by protective lead glasses, taking into account variation in operator position and angle of head rotation. The lenses of the glasses have a lead equivalence of 0.75 mm lead with 0.5 mm lead present in the side shields. Our results have led us to propose the use of a general dose reduction factor of 5 when using eyewear with this lead equivalence and construction. We have also concluded that the forehead of the wearer provides the most robust position to site a dosemeter that will be used to estimate the dose to both eyes as part of a personal monitoring regime. We have confirmed that backscatter from the head itself is the limiting factor for the dose reduction potential of lead eyewear. © 2013 IOP Publishing Ltd. Source

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