Efficient FPGA implementation of high-throughput mixed radix multipath delay commutator FFT processor for MIMO-OFDM

This article presents and evaluates pipelined architecture designs for an improved high-frequency Fast Fourier Transform (FFT) processor implemented on Field Programmable Gate Arrays (FPGA) for Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM). The architecture presented is a Mixed-Radix Multipath Delay Commutator. The presented parallel architecture utilizes fewer hardware resources compared to Radix-2 architecture, while maintaining simple control and butterfly structures inherent to Radix-2 implementations. The high-frequency design presented allows enhancing system throughput without requiring additional parallel data paths common in other current approaches, the presented design can process two and four independent data streams in parallel and is suitable for scaling to any power of two FFT size N. FPGA implementation of the architecture demonstrated significant resource efficiency and high-throughput in comparison to relevant current approaches within literature. The proposed architecture designs were realized with Xilinx System Generator (XSG) and evaluated on both Virtex-5 and Virtex-7 FPGA devices. Post place and route results demonstrated maximum frequency values over 400 MHz and 470 MHz for Virtex-5 and Virtex-7 FPGA devices respectively

Natural-based nanocomposites for bone tissue engineering and regenerative medicine: a review

Tissue engineering and regenerative medicine has been providing exciting technologies for the development of functional substitutes aimed to repair and regenerate damaged tissues and organs. Inspired by the hierarchical nature of bone, nanostructured biomaterials are gaining a singular attention for tissue engineering, owing their ability to promote cell adhesion and proliferation, and hence new bone growth, compared with conventional microsized materials. Of particular interest are nanocomposites involving biopolymeric matrices and bioactive nanosized fi llers. Biodegradability, high mechanical strength, and osteointegration and formation of ligamentous tissue are properties required for such materials. Biopolymers are advantageous due to their similarities with extracellular matrices, specifi c degradation rates, and good biological performance. By its turn, calcium phosphates possess favorable osteoconductivity, resorbability, and biocompatibility. Herein, an overview on the available natural polymer/calcium phosphate nanocomposite materials, their design, and properties is presented. Scaffolds, hydrogels, and fi bers as biomimetic strategies for tissue engineering, and processing methodologies are described. The specifi c biological properties of the nanocomposites, as well as their interaction with cells, including the use of bioactive molecules, are highlighted. Nanocomposites in vivo studies using animal models are also reviewed and discussed.  The research leading to this work has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no REGPOT-CT2012-316331-POLARIS, and from QREN (ON.2 - NORTE-01-0124-FEDER-000016) cofinanced by North Portugal Regional Operational Program (ON.2 - O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF)

PROPELLER Magnetic Resonance Echo Planar Imaging

我們提出一種適合在高磁場下使用的擴散張量影像技術。運用平面回訊影像(EPI)做為螺旋槳式(PROPELLER) k空間軌跡的讀取模組，因此稱為螺旋槳式平面回訊影像。因為平面回訊影像對於磁場不均造成的的偏振現象非常敏感，我們提出的螺旋槳式平面回訊影像技術包含了一系列的修正方法。在3T高磁場下的實驗結果顯示，與單次激發的平面回訊影像相較，螺旋槳式平面回訊影像有效減低了影像幾何失真的問題；螺旋槳式快速自旋回訊影像(FSE)造成的高特定射頻吸收率(SAR)的問題也得到改善。螺旋槳式平面回訊影像的自我導航相位修正能力對於擴散張量影像也非常的有效。平面回訊影像減少了資料擷取時間，所以可以在較短時間內得到較多資料而提高訊雜比。因此與常用的單次激發平面回訊影像比較，在同樣的掃描時間下，螺旋槳式平面回訊影像的高訊雜比在擴散張量影像的臨床應用上有較大的優勢。A technique suitable for diffusion tensor imaging at high field strengths is presented in this thesis. The method is based on PROPELLER k-space trajectory using EPI as the signal readout module, hence dubbed PROPELLER EPI. The implementation of PROPELLER EPI included a series of correction schemes to reduce possible errors associated with the intrinsically higher sensitivity of EPI to off-resonance effects. Experimental results on a 3.0 Tesla MR system showed that the PROPELLER EPI images exhibit substantially reduced geometric distortions compared with single-shot EPI, at a much lower RF specific absorption rate than the original version of PROPELLER fast spin-echo technique. For diffusion tensor imaging, the self-navigated phase correction capability of the PROPELLER EPI sequence was shown to be effective for in vivo imaging. The reduced data acquisition window also allows more signal averages to be performed to achieve higher signal-to-noise ratio when compared with single-shot EPI at identical total scan time, an advantage beneficial for routine diffusion tensor imaging applications in clinical practice.Abstract 中文摘要 Chapter 1 Introduction Reference 1-5 Chapter 2 Principles of EPI 2.1 EPI sequence 2-3 2.2 EPI Artifacts 2-7 2.2.1 N/2 ghost 2-8 2.2.2 Chemical shift 2-10 2.2.3 Field inhomogeneity 2-11 2.2.4 T2* blurring 2-14 2.3 Other EPI techniques 2-15 2.3.1 Segmented EPI 2-15 2.3.2 EPI with parallel imaging 2-16 2.3.3 Field map correction 2-18 References 2-22 Chapter 3 PROPELLER with EPI read out 3.1 PROPELLER principles 3-2 3.2 PROPELLER with EPI read out 3-5 3.2.1 Spatial registration 3-8 3.2.2 Phase correction 3-9 3.2.3 Further reduction of off-resonance effects via triangular windowing 3-9 3.2.4 Density compensation and data combination 3-12 3.2.5 Off-resonance correction with field map 3-12 3.2.6 Parallel imaging 3-14 3.3 Imaging experiments 3-16 3.4 Discussions 3-27 References 3-31 Chapter 4 Application: Diffusion Tensor Images 4.1 Diffusion weighted imaging 4-4 4.2 Diffusion Tensor imaging 4-8 4.3 Experiments: PROPELLER DTI v.s. conventional DTI 4-11 4.4 Discussions 4-22 References 4-25 Chapter 5 Conclusion References 5-

Autosegmentation of Prostate Zones and Cancer Regions from Biparametric Magnetic Resonance Images by Using Deep-Learning-Based Neural Networks

The accuracy in diagnosing prostate cancer (PCa) has increased with the development of multiparametric magnetic resonance imaging (mpMRI). Biparametric magnetic resonance imaging (bpMRI) was found to have a diagnostic accuracy comparable to mpMRI in detecting PCa. However, prostate MRI assessment relies on human experts and specialized training with considerable inter-reader variability. Deep learning may be a more robust approach for prostate MRI assessment. Here we present a method for autosegmenting the prostate zone and cancer region by using SegNet, a deep convolution neural network (DCNN) model. We used PROSTATEx dataset to train the model and combined different sequences into three channels of a single image. For each subject, all slices that contained the transition zone (TZ), peripheral zone (PZ), and PCa region were selected. The datasets were produced using different combinations of images, including T2-weighted (T2W) images, diffusion-weighted images (DWI) and apparent diffusion coefficient (ADC) images. Among these groups, the T2W + DWI + ADC images exhibited the best performance with a dice similarity coefficient of 90.45% for the TZ, 70.04% for the PZ, and 52.73% for the PCa region. Image sequence analysis with a DCNN model has the potential to assist PCa diagnosis

Potential Use of Environmental Biological Samples for Retrospective Electron Paramagnetic Resonance Dosimetry of Radiation Accidents

Retrospective dosimetry is one of the most important tools of accident dosimetry for environmental dose estimation when large-scale radiological incidents and nuclear mass-casualty events occur. Electron paramagnetic resonance (EPR) dosimetry is a physical method for the retrospective assessment of absorbed dose based on the measurement of stable radiation-induced radicals in materials. Different from the fast disappearance of radials in aqueous systems, the radials can persist indefinitely in some organized matrices. Therefore, environmental materials contained in creatures from sea or land can be potentially used as environmental dosimeters for a retrospective dose analysis. This study aims to assess the EPR signals of free radicals from environmental biological samples, potentially for the retrospective dose estimation. The evaluated samples involve ox bone, cyclina shell, clam shell, chitin from squid, and human tissue (enamel and fingernail). First, we dehydrate and grind these materials to the powder with different sizes. Subsequently, all materials were irradiated with different doses ranging from 5 Gy to 50 Gy using 6 MV linear accelerator, and EPR spectra of these materials were obtained from the calculation of peak-to-peak amplitudes. The dose-response curve of EPR signals versus irradiated dose for the six materials shows good linearity (R2~0.99). For the grain-size experiment, the ox bone and tooth with 0.5 mm, the chitin with 0.1 mm, and the others with 1 mm have the strongest signal. For the storage temperature experiment, the optimal temperature of storage is at −20 °C for tooth, fingernail, ox bone, and chitin, at 45 °C for clam shell and cyclina shell where the signal fading is minimal. In conclusion, the developed dose-response curves of the six materials may potentially help a fast, rough retrospective dose reconstruction under the environment when radiation accidents occur

Patent foramen ovale closure in non-elderly and elderly patients with cryptogenic stroke: a hospital-based cohort study

IntroductionThe efficacy of patent foramen ovale (PFO) closure in the elderly population is unclear. We aimed to investigate the efficacy and safety of PFO closure in non-elderly and elderly patients.MethodsPatients over 18 years of age with cryptogenic stroke (CS) or transient ischemic attack and PFO were prospectively enrolled and classified into two groups according to treatment: (1) closure of PFO (the PFOC group) and (2) medical treatment alone (the non-PFOC group). The primary outcome was a composite of recurrent cerebral ischemic events and all-cause mortality during the follow-up period. A modified Ranking Scale [mRS] at 180 days was recorded. The safety outcomes were procedure-related adverse events and periprocedural atrial fibrillation. The results between the PFOC and non-PFOC groups in non-elderly (<60 years) and elderly (≥60 years) patients were compared.ResultsWe enrolled 173 patients, 78 (45%) of whom were elderly. During a mean follow-up of 2.5 years, the incidence of primary outcome was significantly lower in the PFOC group (6.2% vs. 17.1%, hazard ratio[HR] = 0.35, 95% CI 0.13–0.97, p = 0.043) in adjusted Cox regression analysis. Compared with the non-PFOC group, the PFOC group had a numerically lower risk of the primary outcome in both the elderly (HR 0.26, 95% CI 0.07–1.01, p = 0.051) and the non-elderly (HR 0.61, 95% CI 0.11–3.27, p = 0.574) groups. In addition, patients with PFO closure in the elderly group had a lower median mRS at 180 days (p = 0.002). The rate of safety outcome was similar between the non-elderly and elderly groups.DiscussionPFO closure was associated with a reduced risk of the primary outcome in patients with PFO and CS in our total cohort, which included non-elderly and elderly patients. Compared to those without PFO closure, elderly patients with PFO closure had a better functional outcome at 180 days. PFO closure might be considered in selected elderly patients with PFO

Reconstruction of MRI data encoded by multiple nonbijective curvilinear magnetic fields

Parallel imaging technique using localized gradients (PatLoc) uses the combination of surface gradient coils generating nonbijective curvilinear magnetic fields for spatial encoding. PatLoc imaging using one pair of multipolar spatial encoding magnetic fields (SEMs) has two major caveats: (1) The direct inversion of the encoding matrix requires exact determination of multiple locations which are ambiguously encoded by the SEMs. (2) Reconstructed images have a prominent loss of spatial resolution at the center of field-of-view using a symmetric coil array for signal detection. This study shows that a PatLoc system actually has a higher degree of freedom in spatial encoding to mitigate the two challenges mentioned above. Specifically, a PatLoc system can generate not only multipolar but also linear SEMs, which can be used to reduce the loss of spatial resolution at the field-of-view center. Here, we present an efficient and generalized image reconstruction method for PatLoc imaging using multiple SEMs without explicitly identifying the locations where SEM encoding is not unique. Reconstructions using simulations and empirical experimental data are compared with those using conventional linear gradients to demonstrate that the general combination of SEMs can improve image reconstructions