1,350 research outputs found
Hybrid time-domain and continuous-wave diffuse optical tomography instrument with concurrent, clinical magnetic resonance imaging for breast cancer imaging
Diffuse optical tomography has demonstrated significant potential for clinical utility in the diagnosis and prognosis of breast cancer, and its use in combination with other structural imaging modalities improves lesion localization and the quantification of functional tissue properties. Here, we introduce a hybrid diffuse optical imaging system that operates concurrently with magnetic resonance imaging (MRI) in the imaging suite, utilizing commercially available MR surface coils. The instrument acquires both continuous-wave and time-domain diffuse optical data in the parallel-plate geometry, permitting both absolute assignment of tissue optical properties and three-dimensional tomography; moreover, the instrument is designed to incorporate diffuse correlation spectroscopic measurements for probing tissue blood flow. The instrument is described in detail here. Image reconstructions of a tissue phantom are presented as an initial indicator of the system's ability to accurately reconstruct optical properties and the concrete benefits of the spatial constraints provided by concurrent MRI. Last, we briefly discuss how various data combinations that the instrument could facilitate, including tissue perfusion, can enable more comprehensive assessment of lesion physiology
Multi-modal diffuse optical techniques for breast cancer neoadjuvant chemotherapy monitoring (Conference Presentation)
We present high spatial density, multi-modal, parallel-plate Diffuse Optical Tomography (DOT) imaging systems for
the purpose of breast tumor detection. One hybrid instrument provides time domain (TD) and continuous wave
(CW) DOT at 64 source fiber positions. The TD diffuse optical spectroscopy with PMT- detection produces lowresolution
images of absolute tissue scattering and absorption while the spatially dense array of CCD-coupled
detector fibers (108 detectors) provides higher-resolution CW images of relative tissue optical properties.
Reconstruction of the tissue optical properties, along with total hemoglobin concentration and tissue oxygen
saturation, is performed using the TOAST software suite. Comparison of the spatially-dense DOT images and MR
images allows for a robust validation of DOT against an accepted clinical modality. Additionally, the structural
information from co-registered MR images is used as a spatial prior to improve the quality of the functional optical
images and provide more accurate quantification of the optical and hemodynamic properties of tumors. We also
present an optical-only imaging system that provides frequency domain (FD) DOT at 209 source positions with full
CCD detection and incorporates optical fringe projection profilometry to determine the breast boundary. This
profilometry serves as a spatial constraint, improving the quality of the DOT reconstructions while retaining the
benefits of an optical-only device. We present initial images from both human subjects and phantoms to display the
utility of high spatial density data and multi-modal information in DOT reconstruction with the two systems
Four small puzzles that Rosetta doesn't solve
A complete macromolecule modeling package must be able to solve the simplest
structure prediction problems. Despite recent successes in high resolution
structure modeling and design, the Rosetta software suite fares poorly on
deceptively small protein and RNA puzzles, some as small as four residues. To
illustrate these problems, this manuscript presents extensive Rosetta results
for four well-defined test cases: the 20-residue mini-protein Trp cage, an even
smaller disulfide-stabilized conotoxin, the reactive loop of a serine protease
inhibitor, and a UUCG RNA tetraloop. In contrast to previous Rosetta studies,
several lines of evidence indicate that conformational sampling is not the
major bottleneck in modeling these small systems. Instead, approximations and
omissions in the Rosetta all-atom energy function currently preclude
discriminating experimentally observed conformations from de novo models at
atomic resolution. These molecular "puzzles" should serve as useful model
systems for developers wishing to make foundational improvements to this
powerful modeling suite.Comment: Published in PLoS One as a manuscript for the RosettaCon 2010 Special
Collectio
An effective all-atom potential for proteins
We describe and test an implicit solvent all-atom potential for simulations
of protein folding and aggregation. The potential is developed through studies
of structural and thermodynamic properties of 17 peptides with diverse
secondary structure. Results obtained using the final form of the potential are
presented for all these peptides. The same model, with unchanged parameters, is
furthermore applied to a heterodimeric coiled-coil system, a mixed alpha/beta
protein and a three-helix-bundle protein, with very good results. The
computational efficiency of the potential makes it possible to investigate the
free-energy landscape of these 49--67-residue systems with high statistical
accuracy, using only modest computational resources by today's standards
Tumor Necrosis Factor-Alpha G308α Gene Polymorphism and Essential Hypertension: A Meta-Analysis Involving 2244 Participants
BACKGROUND: The tumor necrosis factor-alpha (TNFα) G308A gene polymorphism has been implicated in susceptibility to essential hypertension (EH), but study results are still controversial. OBJECTIVE AND METHODS: The present meta-analysis is performed to investigate the relationship between the TNFα G308A gene polymorphism and EH. Electronic databases were searched and seven separate studies on the association of the TNF α G308A gene polymorphism with EH were analyzed. The meta-analysis involved 1092 EH patients and 1152 controls. The pooled odds ratios (ORs) and their corresponding 95% confidence interval (CI) were calculated by a fixed or random effect model. RESULTS: A significant relationship between the TNFα G308A gene polymorphism and EH was found in an allelic genetic model (OR: 1.45, 95% CI: 1.17 to 1.80, Pâ=â0.0008), a recessive genetic model (OR: 3.181, 95% CI: 1.204 to 8.408, Pâ=â0.02), and a homozygote model (OR: 3.454, 95% CI: 1.286 to 9.278, Pâ=â0.014). No significant association between them was detected in both a dominant genetic model (OR: 1.55, 95% CI: 0.99 to 2.42, Pâ=â0.06) or a heterozygote genetic model (OR: 1.45, 95% CI: 0.90 to 2.33, Pâ=â0.13). CONCLUSION: The TNFα G308A gene polymorphism is associated with EH susceptibility
A highly compact packaging concept for ultrasound transducer arrays embedded in neurosurgical needles
State-of-the-art neurosurgery intervention relies heavily on information from tissue imaging taken at a pre-operative stage. However, the data retrieved prior to performing an opening in the patientâs skull may present inconsistencies with respect to the tissue position observed by the surgeon during intervention, due to both the pulsing vasculature and possible displacements of the brain. The consequent uncertainty of the actual tissue position during the insertion of surgical tools has resulted in great interest in real-time guidance techniques. Ultrasound guidance during neurosurgery is a promising method for imaging the tissue while inserting surgical tools, as it may provide high resolution images. Microfabrication techniques have enabled the miniaturisation of ultrasound arrays to fit needle gauges below 2 mm inner diameter. However, the integration of array transducers in surgical needles requires the development of advanced interconnection techniques that can provide an interface between the microscale array elements and the macroscale connectors to the driving electronics. This paper presents progress towards a novel packaging scheme that uses a thin flexible printed circuit board (PCB) wound inside a surgical needle. The flexible PCB is connected to a probe at the tip of the needle by means of magnetically aligned anisotropic conductive paste. This bonding technology offers higher compactness compared to conventional wire bonding, as the individual electrical connections are isolated from one another within the volume of the paste line, and applies a reduced thermal load compared to thermo-compression or eutectic packaging techniques. The reduction in the volume required for the interconnection allows for denser wiring of ultrasound probes within interventional tools. This allows the integration of arrays with higher element counts in confined packages, potentially enabling multi-modality imaging with Raman, OCT, and impediography. Promising experimental results and a prototype needle assembly are presented to demonstrate the viability of the proposed packaging scheme. The progress reported in this work are steps towards the production of fully-functional imaging-enabled needles that can be used as surgical guidance tools
A search for the decay modes B+/- to h+/- tau l
We present a search for the lepton flavor violating decay modes B+/- to h+/-
tau l (h= K,pi; l= e,mu) using the BaBar data sample, which corresponds to 472
million BBbar pairs. The search uses events where one B meson is fully
reconstructed in one of several hadronic final states. Using the momenta of the
reconstructed B, h, and l candidates, we are able to fully determine the tau
four-momentum. The resulting tau candidate mass is our main discriminant
against combinatorial background. We see no evidence for B+/- to h+/- tau l
decays and set a 90% confidence level upper limit on each branching fraction at
the level of a few times 10^-5.Comment: 15 pages, 7 figures, submitted to Phys. Rev.
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