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"Du, P"
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Highly accelerated whole-brain T2 mapping using non-cartesian acquisition and model-based implicit neural representation reconstruction
•Development of a novel T2-prepared stack-of-stars imaging sequence that can achieve whole-brain scan in 70 s for T2 mapping.•Introduction of a signal evolution model to account for incomplete magnetization recovery, enabling efficient data acquisition without compromising mapping accuracy.•Integration of implicit neural representation for direct, unsupervised reconstruction of T2 maps from undersampled k-space data, without requiring fully sampled training datasets.•Reformulation of the T2 mapping problem into a function optimization framework, guided by a physical model and leveraging the flexibility of neural networks for precise parametric quantification.
To propose a technique for highly accelerated T2 mapping of the whole brain.
A pulse sequence with T2 preparation and a highly undersampled golden-angle stack-of-stars trajectory is used for data acquisition. A multiresolution hash encoding implicit neural representation, embedded with a physical model of signal evolution, is employed for unsupervised reconstruction. By rotating the trajectory at different kz encodings and effective echo times (TEeff) during acquisition, undersampling is applied to three dimensions, i.e., (kx, ky, TEeff) domain. In the phantom experiment, T2 quantification using this T2-prepared stack-of-stars acquisition was compared with that using a Cartesian multi-echo spin-echo acquisition. In the human experiments, T2 quantification using the undersampled acquisition was validated in comparison with those using the fully sampled acquisition and multi-echo spin-echo.
In phantom test, T2 quantification using the proposed reconstruction agreed well (slope = 0.999, R2 > 0.99) with that obtained by fitting the NUFFT-reconstructed results for the fully sampled T2-prepared stack-of-stars acquisition. In human experiments, T2 quantification using a 20-fold acceleration agreed well with that using fully sampled data (NRMSE = 0.0066) in retrospectively undersampled reconstruction. No significant difference in T2 values was found between our technique and the reference method in prospective experiments, and our technique showed good inter-scan reproducibility and intra-scan repeatability.
Using the proposed technique, whole-brain T2 mapping can be acquired in 70 s with a 20-fold acceleration.
Journal Article
Whole brain multiparametric mapping in two minutes using a dual-flip-angle stack-of-stars blipped multi-gradient-echo acquisition
•A dual-flip-angle blipped multi-gradient-echo (DFA-mGRE) sequence with a stack-of-stars (SOS) trajectory was developed to accelerate the acquisition for fast simultaneous three-dimensional (3D) multiparametric mapping of whole brain myelin water fraction (MWF), T1, proton density (PD), R2*, magnetic susceptibility (QSM), and B1 transmit field (B1+).•A novel joint-sparsity-constrained multicomponent T2*-T1 spectrum estimation (JMSE) algorithm was proposed to improve the quantification of MWF by correcting for the T1 saturation effect and B1+/B1− inhomogeneities.•By integrating the DFA-mGRE SOS sequence, the JMSE algorithm, the tissue-prior-based B1+ estimation algorithm, and the subspace-based reconstruction, our technique can provide robust multiparametric mapping of 3D whole brain MWF, T1, PD, R2*, QSM, and B1+ with a two-minute scan.
A new MRI technique is presented for three-dimensional fast simultaneous whole brain mapping of myelin water fraction (MWF), T1, proton density (PD), R2*, magnetic susceptibility (QSM), and B1 transmit field (B1+). Phantom and human (N = 9) datasets were acquired using a dual-flip-angle blipped multi-gradient-echo (DFA-mGRE) sequence with a stack-of-stars (SOS) trajectory. Images were reconstructed using a subspace-based algorithm with a locally low-rank constraint. A novel joint-sparsity-constrained multicomponent T2*-T1 spectrum estimation (JMSE) algorithm is proposed to correct for the T1 saturation effect and B1+/B1− inhomogeneities in the quantification of MWF. A tissue-prior-based B1+ estimation algorithm was adapted for B1 correction in the mapping of T1 and PD. In the phantom study, measurements obtained at an acceleration factor (R) of 12 using prospectively under-sampled SOS showed good consistency (R2 > 0.997) with Cartesian reference for R2*/T1app/M0app. In the in vivo study, results of retrospectively under-sampled SOS with R = 6, 12, 18, showed good quality (structure similarity index measure > 0.95) compared with those of fully-sampled SOS. Besides, results of prospectively under-sampled SOS with R = 12 showed good consistency (intraclass correlation coefficient > 0.91) with Cartesian reference for T1/PD/B1+/MWF/QSM/R2*, and good reproducibility (coefficient of variation < 7.0 %) in the test-retest analysis for T1/PD/B1+/MWF/R2*. This study has demonstrated the feasibility of simultaneous whole brain multiparametric mapping with a two-minute scan using the DFA-mGRE SOS sequence, which may overcome a major obstacle for neurological applications of multiparametric MRI.
Journal Article
في بنية الحدث التركيبية والدلالية
عرف البحث اللساني تحولات نوعية كانت نتيجة الاهتمام بالآلة الصورية المسؤولة عن التمظهرات المتنوعة والتوليد اللامحدود للعبارات اللغوية. ومن هنا كانت ضرورة بناء نماذج صورية من أجل رصد التنوع والتعدد والتوسع اللغوي. وهكذا، تعددت النماذج واختلفت خلفياتها النظرية. غير أن الغاية تظل هي رصد المفاهيم والتصورات وكيفية بنائها ذهنيا وعلاقة المقولات النحوية بها. وفي هذا الإطار، يقدم هذا الكتاب ترجمة لمجموعة من النصوص اللسانية لمجموعة من الباحثين يحتلون مكانة مرموقة في البحث اللساني. وتتضمن هذه النصوص نظريات وافتراضات مختلفة تسعى إلى تحليل مجموعة من القضايا، كالتعدد الدلالي، والحدث، والجهة والزمن، ظلت محط نقاش بين اللسانيين. وكانت الغاية من ترجمة هذه النصوص هي تقريب وتمكين القارئ العربي من تنوع وثراء المعرفة اللسانية التي عرفت تراكمات قيمة.
Book
Medicinal plant cultivation for sustainable use and commercialisation of high-value crops
Many traditional healing systems are based on natural biological resources, and there is a general shift in most par ts of the world towards natural medicine, with direct implications on the demand and supply of medicinal plants. This review highlights the economic impor tance of medicinal plants, their contribution to healthcare systems, and potential oppor tunities for rural economic development through cultivation. A systematic literature review with specific search terms related to medicinal plants was used to collect scientific and non-scientific information from peer-reviewed literature and grey literature databases. The findings indicate that trade in medicinal plants is increasing, and although they are considered minor crops compared to major food crops, their value is among the highest in the list of traded plants globally. The trade also serves as a revenue source for many rural livelihoods, with women playing a significant role. Medicinal plants contribute to primary health care in many developing countries, and they are also an essential source of modern drug discovery. Cultivation of medicinal plants offers emerging rural farmers an oppor tunity to grow these plants as new and alternative crops, thus reducing unsustainable wild harvesting and competition with established commercial farmers who mostly focus on food crops. Fur thermore, medicinal plant cultivation should be promoted as one of the options for local economic development and sustainability through job creation, the revival of the rural economy, and income generation for small businesses, such as the transpor t businesses, involved in the value chain. Land accessibility, financial resources, and direct market access for rural communities can elevate their contribution to the industry. Formalisation of the lower levels of the medicinal plant trade is also recommended.
Journal Article
Antioxidant, Antimicrobial and Phytochemical Variations in Thirteen Moringa oleifera Lam. Cultivars
A study was undertaken to assess variation in antioxidant, antimicrobial and phytochemical properties of thirteen Moringa oleifera cultivars obtained from different locations across the globe. Standard antioxidant methods including the DPPH scavenging, ferric reducing power (FRAP) and β-carotene-linoleic acid model were used to evaluate the activity. Variation in the antioxidant activity was observed, with TOT4951 from Thailand being the most active, with activity five times higher than that of ascorbic acid (reference compound). A different trend was observed for the activity in the FRAP and β-carotene-linoleic acid assays. Antimicrobial activity was tested against Gram-positive (Staphylococcus aureus) and Gram-negative (Klebsiella pneumoniae) strains using the microdilution method. Acetone extracts of all cultivars exhibited good antibacterial activity against K. pneumoniae (MIC values of 0.78 mg/mL). The remaining extracts exhibited weak activity against the two microorganisms. For the antifungal activity, all the extracts exhibited low activity. Variations were observed in the total phenolic and flavonoid contents. Cultivars TOT5169 (Thailand) and SH (South Africa) exhibited highest amounts of total phenolic compounds while TOT5028 (Thailand) exhibited the lowest amounts of five times lower than the highest. The information offer an understanding on variations between cultivars from different geographical locations and is important in the search for antioxidant supplementation and anti-ageing products.
Journal Article
Rosette‐scan tomographic single‐pixel imager
Spin‐scan tomographic scanning imagers utilise a reticle with a fixed number of thin slits and nutating optics, and have produced images and video at both infrared and optical wavelengths. However, the fixed nature of these systems reduces their versatility by restricting changes that can be made after manufacture. An alternative rosette‐scan tomographic scanning imager based on similar concepts is proposed to overcome this limitation. A single thin‐slit reticle is rotated to be perpendicular to the line scan angle of each rosette petal, thereby allowing tomographic reconstruction. The parameters of the proposed system can be dynamically changed to achieve different trade‐offs between resolution and frame rate. Initial results obtained from a proof‐of‐concept prototype demonstrate the feasibility of this approach.
Journal Article