Dimensionality reduced plug and play priors for improving photoacoustic tomographic imaging with limited noisy data

The reconstruction methods for solving the ill-posed inverse problem of photoacoustic tomography with limited noisy data are iterative in nature to provide accurate solutions. These methods performance is highly affected by the noise level in the photoacoustic data. A singular value decomposition (SVD) based plug and play priors method for solving photoacoustic inverse problem was proposed in this work to provide robustness to noise in the data. The method was shown to be superior as compared to total variation regularization, basis pursuit deconvolution and Lanczos Tikhonov based regularization and provided improved performance in case of noisy data. The numerical and experimental cases show that the improvement can be as high as 8.1 dB in signal to noise ratio of the reconstructed image and 67.98% in root mean square error in comparison to the state of the art methods.     

Joint aperture detection for speckle reduction and increased collection efficiency in ophthalmic MHz OCT

Joint-aperture optical coherence tomography (JA-OCT) is an angle-resolved OCT method, in which illumination from an active channel is simultaneously probed by several passive channels. JA-OCT increases the collection efficiency and effective sensitivity of the OCT system without increasing the power on the sample. Additionally, JA-OCT provides angular scattering information about the sample in a single acquisition, so the OCT imaging speed is not reduced. Thus, JA-OCT is especially suitable for ultra high speed in-vivo imaging. JA-OCT is compared to other angle-resolved techniques, and the relation between joint aperture imaging, adaptive optics, coherent and incoherent compounding is discussed. We present angle-resolved imaging of the human retina at an axial scan rate of 1.68 MHz, and demonstrate the benefits of JA-OCT: Speckle reduction, signal increase and suppression of specular and parasitic reflections. Moreover, in the future JA-OCT may allow for the reconstruction of the full Doppler vector and tissue discrimination by analysis of the angular scattering dependence.OCIS codes: (170.4500) Optical coherence tomography, (170.3880) Medical and biological imaging, (120.3890) Medical optics instrumentation, (030.6140) Speckle     

Imaging of the atlas (C1) and axis (C2)

In imaging the atlantoaxial region in injured patients, the initial modality is plain radiography. The lateral C-spine as well as the open-mouth view are essential in this regard. On these views, it is not only important to examine the bony contour but also to look for indirect signs of injury such as prevertebral soft-tissue swelling, air in the prevertebral space, an increased width of the anterior atlantodental interval, and overriding of the C1-C2 joint on one side (the so-called wink sign of atlantoaxial rotatory subluxation). In patients in whom there is a high index of suspicion for occult trauma, but without fractures suggested or adequately visualized on routine films, or in those with severe cranial trauma, further studies should be pursued. CT scan is the modality of choice in optimally imaging the bony contours of the axis and atlas. It has limitations in visualizing transversely oriented fractures such as high dens fractures, transverse fractures of the facet joints (although widening of the facet joint is an indirect indication of facet fracture), or transverse arch fractures. Plain tomography may better demonstrate such transverse fractures but has several disadvantages. Plain tomography is often not as readily available as CT; it requires that the patient be placed in lateral decubitus position to obtain lateral tomograms, which may be contraindicated in such clinical circumstances; and it is not as easy to appreciate three-dimensional relationships on plain tomography as it is on CT. CT clearly defines the location of displaced bone fragments in relationship to the spinal canal as well as often demonstrating disc injuries. Ligamentous injury, though potentially visualized directly on MR imaging, is more commonly addressed with flexion-extension films. Flexion-extension studies should, obviously, be performed only in awake, oriented patients who are without neurologic deficit, and the studies should be done with close physician supervision and stopped at the first onset of pain. MR imaging may be helpful in demonstrating soft-tissue injuries such as hemorrhage, disc herniation, nerve root impingement, and direct spinal cord damage.     

Joint PET-MRI image reconstruction using a patch-based joint-dictionary prior

For simultaneous positron-emission-tomography and magnetic-resonance-imaging (PET-MRI) systems, while early methods relied on independently reconstructing PET and MRI images, recent works have demonstrated improvement in image reconstructions of both PET and MRI using joint reconstruction methods. The current state-of-the-art joint reconstruction priors rely on fine-scale PET-MRI dependencies through the image gradients at corresponding spatial locations in the PET and MRI images. In the general context of image restoration, compared to gradient-based models, patch-based models (e.g., sparse dictionaries) have demonstrated better performance by modeling image texture better. Thus, we propose a novel joint PET-MRI patch-based dictionary prior that learns inter-modality higher-order dependencies together with intra-modality textural patterns in the images. We model the joint-dictionary prior as a Markov random field and propose a novel Bayesian framework for joint reconstruction of PET and accelerated-MRI images, using expectation maximization for inference. We evaluate all methods on simulated brain datasets as well as on in vivo datasets. We compare our joint dictionary prior with the recently proposed joint priors based on image gradients, as well as independently applied patch-based priors. Our method demonstrates qualitative and quantitative improvement over the state of the art in both PET and MRI reconstructions.     

Hierarchical Bayesian regularization of reconstructions for diffuse optical tomography using multiple priors

Diffuse optical tomography (DOT) is a non-invasive brain imaging technique that uses low-levels of near-infrared light to measure optical absorption changes due to regional blood flow and blood oxygen saturation in the brain. By arranging light sources and detectors in a grid over the surface of the scalp, DOT studies attempt to spatially localize changes in oxy- and deoxy-hemoglobin in the brain that result from evoked brain activity during functional experiments. However, the reconstruction of accurate spatial images of hemoglobin changes from DOT data is an ill-posed linearized inverse problem, which requires model regularization to yield appropriate solutions. In this work, we describe and demonstrate the application of a parametric restricted maximum likelihood method (ReML) to incorporate multiple statistical priors into the recovery of optical images. This work is based on similar methods that have been applied to the inverse problem for magnetoencephalography (MEG). Herein, we discuss the adaptation of this model to DOT and demonstrate that this approach provides a means to objectively incorporate reconstruction constraints and demonstrate this approach through a series of simulated numerical examples.     

Bayesian analysis of the neuromagnetic inverse problem with l(p)-norm priors

Magnetoencephalography (MEG) allows millisecond-scale non-invasive measurement of magnetic fields generated by neural currents in the brain. However, localization of the underlying current sources is ambiguous due to the so-called inverse problem. The most widely used source localization methods (i.e., minimum-norm and minimum-current estimates (MNE and MCE) and equivalent current dipole (ECD) fitting) require ad hoc determination of the cortical current distribution (l(2)-, l(1)-norm priors and point-sized dipolar, respectively). In this article, we perform a Bayesian analysis of the MEG inverse problem with l(p)-norm priors for the current sources. This way, we circumvent the arbitrary choice between l(1)- and l(2)-norm prior, which is instead rendered automatically based on the data. By obtaining numerical samples from the joint posterior probability distribution of the source current parameters and model hyperparameters (such as the l(p)-norm order p) using Markov chain Monte Carlo (MCMC) methods, we calculated the spatial inverse estimates as expectation values of the source current parameters integrated over the hyperparameters. Real MEG data and simulated (known) source currents with realistic MRI-based cortical geometry and 306-channel MEG sensor array were used. While the proposed model is sensitive to source space discretization size and computationally rather heavy, it is mathematically straightforward, thus allowing incorporation of, for instance, a priori functional magnetic resonance imaging (fMRI) information.     

Systematic regularization of linear inverse solutions of the EEG source localization problem

Distributed linear solutions of the EEG source localization problem are used routinely. Here we describe an approach based on the weighted minimum norm method that imposes constraints using anatomical and physiological information derived from other imaging modalities to regularize the solution. In this approach the hyperparameters controlling the degree of regularization are estimated using restricted maximum likelihood (ReML). EEG data are always contaminated by noise, e.g., exogenous noise and background brain activity. The conditional expectation of the source distribution, given the data, is attained by carefully balancing the minimization of the residuals induced by noise and the improbability of the estimates as determined by their priors. This balance is specified by hyperparameters that control the relative importance of fitting and conforming to prior constraints. Here we introduce a systematic approach to this regularization problem, in the context of a linear observation model we have described previously. In this model, basis functions are extracted to reduce the solution space a priori in the spatial and temporal domains. The basis sets are motivated by knowledge of the evoked EEG response and information theory. In this paper we focus on an iterative "expectation-maximization" procedure to jointly estimate the conditional expectation of the source distribution and the ReML hyperparameters on which this solution rests. We used simulated data mixed with real EEG noise to explore the behavior of the approach with various source locations, priors, and noise levels. The results enabled us to conclude: (i) Solutions in the space of informed basis functions have a high face and construct validity, in relation to conventional analyses. (ii) The hyperparameters controlling the degree of regularization vary largely with source geometry and noise. The second conclusion speaks to the usefulness of using adaptative ReML hyperparameter estimates.     

Debunking Myths in Nursing Theory and Research

This article examines myths that persist in the traditional male-defined scientific enterprise. Science per se is not rejected, but specific ways of confronting the myths are explored. The methods for debunking the myths derive from the concept of future search, wherein health and the values of nursing for the future direct the discovery of knowledge. The alternatives include a more ethical and responsible use of the methods of science as well as specific alternatives to science derived from Carper's (1978) patterns of knowing in nursing.
The nursing literature has reflected growing recognition of the limitations of the scientific method in addressing problems in nursing (Gorenberg, 1983; Munhall, 1982; Newman, 1979; Smith, M. C, 1984; Vredevoe, 1984; Webster, Jacox, & Baldwin, 1981). Taken together, the literature leaves the impression that we should perhaps forsake the scientific method; alternatives for acquiring knowledge in nursing are not adequately described, and the alternatives that are suggested are not clearly alternatives to the scientific method.
A fundamental issue that is lacking in most critiques of the scientific method is recognition that science is based on a male world view and that the myths sustained by this partial world view have perpetuated erroneous knowledge about the world. The purposes of this article are (a) to present an analysis of myths of science that arise from the partial male world view, (b) to propose methods for debunking these myths to attain a more whole science consistent with the essence of nursing, and (c) to propose alternative approaches to science where an alternative is indicated.     

具有多种浏览器的数字化人脑图谱

目的：用计算机技术实现基于MR图像的数字化人脑解剖图谱。方法：首先对获取的MR图像进行边缘提取、去除非脑组织等操作,再提取感兴趣区,分别用虚拟现实建模语言（VRML）和移动立方体法（maching cubes)获得可视化显示,并对图谱加解剖标识,用一种基于点约束的变形算法－薄板样条法（thin-plate splines）使基于MR图像的图谱与Talairach标准图谱对准,实现图谱到Talairach标准空间的映射,结果：基于中国人（男、女各一）头部MR体数据集,实现具有多种浏览功能的人脑图谱。该图谱将各种功能集成于一个人机交互式界面中,可以任意选取感兴趣区放大、旋转观察,对人脑的各个组成部分的名称及其上下级层次结构深入了解,逼真的3D显示图像对脑内部深层结构产生直观的印象,结论：具有多种浏览功能的数字化人脑图谱是人脑解剖教学、神经外科手术计划和引导及人脑组织分类的重要工具,本图谱可认为是数字化中国人脑图谱的雏形。     

The relationship of computed tomography and ultrasonography in diagnosis of abdominal disease.

A detailed comparison of computed tomography and ultrasonography of the abdomen is presented from a theoretical point of view. The advantages and limitations of both modalities are discussed in terms of scan content, resolution, plane of interrogation, dynamic imaging, examination time, imaging problems, automation, contrast administration, puncture guidance, examination availability, hazards, personnel and space requirements, and cost. Analysis of these factors leads the authors to conclude that ultrasound should be the procedure of choice for sectional imaging of the abdomen. Computed tomography should be reserved for those situations in which the ultrasound examination is not diagnostic (i.e., skeletal system, lungs, mediastinum).     

Interdisciplinary cooperation in an integrated psychiatric rehabilitation program.

The development of psychiatry is at present stormy with discussions dividing, polarising and partly paralysing. Current experience shows that psychotherapeutic approaches are not alternatives to psychopharmacological ones but necessary complements. An integrated therapy which treats the patient as a social, psychological and organic entity has not yet been spread to the poorly-equipped psychiatric periphery but is mainly restricted to the modern richly-endowed psychiatric centers. Modern psychiatric rehabilitation principles according to this integrated synoptic view seem however to be applicable even to custodial-treated patients at peripheral psychiatric institutions. In this article we present the special psycho-social, epidemiological, administrative and economical structure of the island of Gotland due to its geographical isolation. We describe the construction and forming of a rehabilitation program under greatly limited economical conditions. The program combines communication-oriented group therapy with consequent pharmacotherapy and a structured ergotherapeutic and ADL-therapeutic program and is applied to a primarily unselected sample of patients. We also describe the education and supervision of the staff as well as the components of our program. Positive results in spite of limited resources have been achieved. Problems are discussed.     

Singular value decomposition metrics show limitations of detector design in diffuse fluorescence tomography

The spatial resolution and recovered contrast of images reconstructed from diffuse fluorescence tomography data are limited by the high scattering properties of light propagation in biological tissue. As a result, the image reconstruction process can be exceedingly vulnerable to inaccurate prior knowledge of tissue optical properties and stochastic noise. In light of these limitations, the optimal source-detector geometry for a fluorescence tomography system is non-trivial, requiring analytical methods to guide design. Analysis of the singular value decomposition of the matrix to be inverted for image reconstruction is one potential approach, providing key quantitative metrics, such as singular image mode spatial resolution and singular data mode frequency as a function of singular mode. In the present study, these metrics are used to analyze the effects of different sources of noise and model errors as related to image quality in the form of spatial resolution and contrast recovery. The image quality is demonstrated to be inherently noise-limited even when detection geometries were increased in complexity to allow maximal tissue sampling, suggesting that detection noise characteristics outweigh detection geometry for achieving optimal reconstructions.     

Association between generalized joint laxity and knee joint movement in female university students

[Purpose] This study investigated the association between generalized joint laxity and knee joint movement in female university students. [Participants and Methods] The study included 21 female university students. Generalized joint laxity was measured using the Beighton criteria for joint hypermobility. Acceleration and angular velocities of the tibia during knee extension were measured along three axes using a triaxial accelerometer. Sampling data were expressed as root mean squares. The Mann–Whitney U test was used to determine differences in the acceleration and angular velocities along each axis between the generalized joint laxity and non-generalized joint laxity groups. Spearman’s rank correlations were used to confirm the association between these parameters. [Results] The rotational angular velocity was greater in the generalized joint laxity than in the non-generalized joint laxity group, and we observed a significant correlation between Beighton scores and the X-axis angular velocity. Furthermore, rotational angular velocity was positively correlated with anterior–posterior acceleration and extension angular velocity. [Conclusion] These findings suggest that rotational angular velocity of the tibia during knee extension is associated with generalized joint laxity in female university students.     

Characterization of structural-prior guided optical tomography using realistic breast models derived from dual-energy x-ray mammography

Multi-spectral near-infrared diffuse optical tomography (DOT) is capable of providing functional tissue assessment that can complement structural mammographic images for more comprehensive breast cancer diagnosis. To take full advantage of the readily available sub-millimeter resolution structural information in a multi-modal imaging setting, an efficient x-ray/optical joint image reconstruction model has been proposed previously to utilize anatomical information from a mammogram as a structural prior. In this work, we develop a complex digital breast phantom (available at http://openjd.sf.net/digibreast) based on direct measurements of fibroglandular tissue volume fractions using dual-energy mammographic imaging of a human breast. We also extend our prior-guided reconstruction algorithm to facilitate the recovery of breast tumors, and perform a series of simulation-based studies to systematically evaluate the impact of lesion sizes and contrasts, tissue background, mesh resolution, inaccurate priors, and regularization parameters, on the recovery of breast tumors using multi-modal DOT/x-ray measurements. Our studies reveal that the optical property estimation error can be reduced by half by utilizing structural priors; the minimum detectable tumor size can also be reduced by half when prior knowledge regarding the tumor location is provided. Moreover, our algorithm is shown to be robust to false priors on tumor location.OCIS codes: (170.3010) Image reconstruction techniques, (100.3190) Inverse problems, (170.3830) Mammography, (110.3080) Infrared imaging, (200.4560) Optical data processing     

Cardiac myxoma: a contemporary multimodality imaging review

Cardiac myxoma (CM) is by far the most common primary benign cardiac tumor, typically arising in the left atrium with an attachment point in the fossa ovalis region. Although the etiology of CM remains unclear, we know that this endocardial-based mass originates from undifferentiated mesenchymal cells. Continuous technical improvements in the field of echocardiography since the 1960s has profoundly changed the diagnostic approach by allowing a good tumor detection as well as the preoperative planning by providing crucial information concerning the attachment point location. However, echocardiography has its limitations among which lack of tissue characterization and restricted field of view can arise diagnosis difficulties in atypical presentations. With the widespread and routine use of echocardiography and chest computed tomography (CT), incidental detection of CM is not infrequent. As a consequence, it has become mandatory for cardiologists and radiologists evolving in a multimodality imaging world to be familiar with the wide range of presentations of this tumor. The authors present here a review of the common and less common aspects of CM using the main imaging modalities available: echocardiography, cardiovascular magnetic resonance imaging, CT, positron emission tomography and coronary angiography.     

Relation between spasticity,weakness and contracture of the elbow flexors and upper limb activity after stroke: An observational study

Purpose. Understanding the relationship between the motor impairments and their impact on physical activity will allow rehabilitation after stroke to be based on scientific principles. The aims of this study were to determine: (i) the relative contribution of weakness and spasticity to contracture, and (ii) the relative contribution of all three impairments to limitations in physical activity during the first 12 months after stroke.

Method. This longitudinal observational study charted the evolution of weakness (loss of maximal force), spasticity (stretch-evoked EMG) and contracture (loss of joint range) of the elbow flexors and limitations in upper limb activity (Motor Assessment Scale) for a year after stroke in 27 subjects who had suffered a first stroke. Spasticity was measured as abnormal reflex activity, weakness was measured as loss of maximum isometric torque, contracture was measured as the difference in range of motion between the affected and intact side, and limitations in physical activity were measured on a clinical scale.

Results. The major independent contributors to contracture were spasticity for the first four months after stroke (p = 0.0001 – 0.10) and weakness thereafter (p = 0.01 – 0.05). However, the major and only independent contributor to limitations in physical activity throughout the year was weakness (p = 0.0001 – 0.05).

Conclusions. For the first time, from a longitudinal study, the findings show that spasticity can cause contracture after stroke, consistent with the prevailing clinical view. However, weakness is the main contributor to activity limitations.     

Relation between spasticity, weakness and contracture of the elbow flexors and upper limb activity after stroke: An observational study

Purpose. Understanding the relationship between the motor impairments and their impact on physical activity will allow rehabilitation after stroke to be based on scientific principles. The aims of this study were to determine: (i) the relative contribution of weakness and spasticity to contracture, and (ii) the relative contribution of all three impairments to limitations in physical activity during the first 12 months after stroke.

Method. This longitudinal observational study charted the evolution of weakness (loss of maximal force), spasticity (stretch-evoked EMG) and contracture (loss of joint range) of the elbow flexors and limitations in upper limb activity (Motor Assessment Scale) for a year after stroke in 27 subjects who had suffered a first stroke. Spasticity was measured as abnormal reflex activity, weakness was measured as loss of maximum isometric torque, contracture was measured as the difference in range of motion between the affected and intact side, and limitations in physical activity were measured on a clinical scale.

Results. The major independent contributors to contracture were spasticity for the first four months after stroke (p = 0.0001 - 0.10) and weakness thereafter (p = 0.01 - 0.05). However, the major and only independent contributor to limitations in physical activity throughout the year was weakness (p = 0.0001 - 0.05).

Conclusions. For the first time, from a longitudinal study, the findings show that spasticity can cause contracture after stroke, consistent with the prevailing clinical view. However, weakness is the main contributor to activity limitations.     

High-speed spectral domain optical coherence tomography using non-uniform fast Fourier transform

The useful imaging range in spectral domain optical coherence tomography (SD-OCT) is often limited by the depth dependent sensitivity fall-off. Processing SD-OCT data with the non-uniform fast Fourier transform (NFFT) can improve the sensitivity fall-off at maximum depth by greater than 5dB concurrently with a 30 fold decrease in processing time compared to the fast Fourier transform with cubic spline interpolation method. NFFT can also improve local signal to noise ratio (SNR) and reduce image artifacts introduced in post-processing. Combined with parallel processing, NFFT is shown to have the ability to process up to 90k A-lines per second. High-speed SD-OCT imaging is demonstrated at camera-limited 100 frames per second on an ex-vivo squid eye.     

A new distraction arthroplasty device using magnetic force; a cadaveric study

Background

It is difficult for an articular cartilage injury to repair spontaneously. There are many procedures for treating cartilage injury, however there is no standard procedure for middle-aged patients who have diffuse knee osteoarthritis, especially of the lateral compartment. Therefore, Ochi developed a new distraction device that uses magnetic power to enlarge a joint space and promote cartilage regeneration with microfracture. The purpose of this study is to evaluate this new distraction arthroplasty system by using the cadaveric knee.

Methods

This study used ten knees from six cadavers that were embalmed by Thiel's methods. The medial and lateral joint space was measured by AP radiographic view before and after distraction, and after weight-bearing to evaluate the joint distraction. The contact pressure of the medial and lateral compartments at the knee extension position by using a prescale film system was measured before and after weight-bearing with a 15 or 30-kg weight-bearing load to evaluate the effectiveness of this device.

Findings

The lateral joint space significantly increased from the pre-distraction to the post-distraction; however, it did not change significantly between post-distraction and post-weight-bearing.With a 15 or 30-kg weight-bearing load, the contact pressure of the lateral compartment significantly decreased from the pre-distraction to the post-distraction.

Interpretation

The most important advantage of this device is that it maintains a continuous distraction tension and enables almost the full range of motion of the knee. We believe that joint distraction by using magnetic force can be a promising option for cartilage injury in middle-aged patients.