Detection of bone metastases using diffusion weighted magnetic resonance imaging: comparison with C-methionine PET and bone scintigraphy

Purpose

We evaluated the ability of diffusion-weighted imaging (DWI) to detect bone metastasis by comparing the results obtained using this modality with those obtained using ¹¹C-methionine (MET) positron emission tomography (PET) and bone scintigraphy.

Materials and methods

This retrospective study involved 29 patients with bone metastasis. DWI was obtained using a single-shot echo planar imaging (EPI) sequence with fat suppression using a short inversion time inversion recovery sequence. The detection capabilities of DWI for bone metastases were compared with those of whole body MET PET (in 19 patients) and 99mTc-methylene diphosphonate bone scintigraphy (in 15 patients).

Results

Among the 19 patients who were diagnosed using DWI and PET, the PET identified 39 bone metastases, while the DWI identified 60 metastases out of 69 metastases revealed with conventional magnetic resonance imaging (MRI). Among the 15 patients who were diagnosed using DWI and bone scintigraphy, the bone scintigraphy identified 18 bone metastases, while the DWI identified 72 metastases out of 78 metastases revealed with conventional MRI. The overall bone metastasis detection rates were 56.5% for PET, 23.1% for bone scintigraphy and 92.3% for DWI.

Conclusion

DWI is a very sensitive method for detecting bone metastasis and is superior to MET PET and bone scintigraphy in terms of its detection capabilities.     

Accurate step wedge calibration for densitometry of electrophoresis gels

Accurate step wedge calibration is important for reliable quantitative densitometry of electrophoresis gels. In this work, we outline the theory and verified by experiment, the effect that the nonlinear response of detectors at low irradiance levels has on accurate optical density (OD) calibration of step wedges. It was found that OD value departures from stated do exist and thus supports the case of calibration. Halogen broadband light was shown to be generally unsuited as light source for step wedge calibration even though applied at highest illumination before saturation, unless correction approaches which add complexity to the process are applied. Monochromatic light was determined best suited for use, provided that the irradiance level was high enough for the calibration to be conducted fully in the detector’s linear range.     

Dual-modality and dual-energy gamma ray densitometry of petroleum products using an artificial neural network

The prediction of volume fractions in order to measure the multiphase flow rate is a very important issue and is the key parameter of multi-phase flow meters (MPFMs). Currently, the gamma ray attenuation technique is known as one of the most precise methods for obtaining volume fractions. The gamma ray attenuation technique is based on the mass attenuation coefficient, which is sensitive to density changes; density is sensitive in turn to temperature and pressure fluctuations. Therefore, MPFM efficiency depends strongly on environmental conditions. The conventional solution to this problem is the periodical recalibration of MPFMs, which is a demanding task. In this study, a method based on dual-modality densitometry and artificial intelligence (AI) is presented, which offers the advantage of the measurement of the oil–gas–water volume fractions independent of density changes. For this purpose, several experiments were carried out and used to validate simulated dual modality densitometry results. The reference density point was established at a temperature of 20 °C and pressure of 1 bar. To cover the full range of likely density fluctuations, four additional density sets were defined (at changes of ±4% and ±8% from the reference point). An annular regime with different percentages of oil, gas and water at different densities was simulated. Four features were extracted from the transmission and scattered detectors and were applied to the artificial neural network (ANN) as inputs. The input parameters included the ²⁴¹Am full energy peak, ¹³⁷Cs Compton edge, ¹³⁷Cs full energy peak and total scattered count, and the outputs were the oil and air percentages. A multi-layer perceptron (MLP) neural network was used to predict the volume fraction independent of the oil and water density changes. The obtained results show that the proposed ANN model achieved good agreement with the real data, with an estimated root mean square error (RMSE) of less than 3.     

Detection of magnetic nanoparticles with magnetoencephalography

Superconducting quantum interference devices (SQUIDs) have been widely utilized in biomedical applications due to their extremely high sensitivity to magnetic signals. The present study explores the feasibility of a new type of nanotechnology-based imaging method using standard clinical magnetoencephalographic (MEG) systems equipped with SQUID sensors. Previous studies have shown that biological targets labeled with non-toxic, magnetized nanoparticles can be imaged by measuring the magnetic field generated by these particles. In this work, we demonstrate that (1) the magnetic signals from certain nanoparticles can be detected without magnetization using standard clinical MEG, (2) for some types of nanoparticles, only bound particles produce detectable signals, and (3) the magnetic field of particles several hours after magnetization is significantly stronger than that of un-magnetized particles. These findings hold promise in facilitating the potential application of magnetic nanoparticles to in vivo tumor imaging. The minimum amount of nanoparticles that produce detectable signals is predicted by theoretical modeling and computer simulation.     

Detection of hydrogen peroxide with graphyne

The effect of hydrogen peroxide on the electronic properties of graphyne has been investigated to explore the possibility of using graphyne based biosensor. We have used density functional theory to study the electronic properties of γ-graphyne in the presence of different number of hydrogen peroxide. The optimal adsorption position, orientation, and distance of hydrogen peroxide adsorbed on the graphyne sheet have been determined by calculating adsorption energy. It is found that γ-graphyne which is an intrinsic semiconductor becomes an n-type semiconductor due to the presence of hydrogen peroxide. The energy band gap of γ-graphyne is decreased by increasing the number of hydrogen peroxide. The results demonstrate that γ-graphyne is a promising candidate for biosensor application because of its electrical sensitivity to hydrogen peroxide.     

Detection of casimir photons with electrons

We propose a method for the detection of a dynamical Casimir effect. Assuming that the Casimir photons are being generated in an electromagnetic cavity with a vibrating wall (dynamical Casimir effect), we consider electrons passing through the cavity to be interacting with the intracavity field. We show that the dynamical Casimir effect can be observed via the measurement of the change in the average or in the variance of the electron’s kinetic energy. We point out that the enhancement of the effect due to finite temperatures makes it easier to detect the Casimir photons.     

Effects of recombinant human erythropoietin on the haemopoietic bone marrow monitored by magnetic resonance spectroscopy in patients with end-stage renal disease

Volume selective magnetic resonance (MR) proton spectroscopy was used to investigate changes in the haemopoietic bone marrow in patients with end-stage renal disease undergoing treatment with recombinant human erythropoietin (rHuEPO). Significant changes could be detected in the spectra 14 days after the beginning of treatment, before any response was seen in the haemoglobin concentration of peripheral blood. The spectral changes indicate an alteration in cellular composition of haemopoietic bone marrow with an increase in the amount of haemopoietic active tissue. One patient showed a major change in the spectrum four days after treatment began, indicating that MR spectroscopy may detect early changes in the cellular composition of the bone marrow. This noninvasive method may be useful in evaluating treatment effects of recombinant human haemopoietic growth factors in the bone marrow, as well as investigating bone marrow response from different modes of rHuEPO administration.     

Infrared study of the interaction of acrylic bone cement with bone structurein vitro

Infrared Spectroscopy was used for the characterization of some commercial bone cements and investigation of their inter-action with compact bone in vitro. The IR spectra of the cements and their mixtures with bone powder were recorded at various periods ranging from day one to 8 weeks. The quantitative analysis of the IR spectra of the mixtures provided a strong evidence that a certain reaction takes place between the acrylic resin and bone powder. It was found that the rate of reaction depends on the concentration of the bone powder and time. In any event, the rate of reaction showed a maximum value at 45-days for all concentrations. It was concluded that, a bond is formed between the cement and the bone powder, and this bond is not perfect.     

基于TDLAS平衡差分技术的CO气体检测

利用可调谐半导体激光吸收光谱(TDLAS)结合平衡差分探测技术测量了1.578 μm附近的CO气体3-0带P(4)跃迁在不同压强和不同浓度下的吸收光谱信号。由于平衡差分探测方法可以有效地抑制激光光强波动、温度漂移和机械振动等共模噪声,从而提高了光谱探测灵敏度。通过与直接吸收信号相比,平衡差分的信噪比提高了3.4倍,探测极限为87 ppmv。测量了浓度为1%压强为40,55,70和85 Torr时的CO气体,结果显示在70 Torr时其光谱信号最强。并且,利用直接吸收和平衡差分技术测量了不同浓度的CO气体在总压强在70 Torr时的光谱信号,发现平衡差分技术光谱强度与浓度的关系线性度符合较好,其测量误差小于5%。为了进一步验证系统的稳定性,连续采集了324 s的光谱信号,最后通过Allan方差分析,发现本实验系统的最佳探测时间为38 s,探测极限为47.8 ppmv。     

Detection of methane with mid-infrared polarization spectroscopy

We report on the application of polarization spectroscopy in the mid-infrared spectral region for the detection of methane by probing its asymmetric ro-vibrational transitions. Tunable infrared laser radiation, near 3.4 m, was obtained from difference-frequency generation in a LiNbO₃ crystal. Infrared polarization spectroscopy (IRPS) spectra of the P, Q and R branches of the ₃ band, recorded with both linearly and circularly polarized pump beams, are presented. The experiments were performed in an atmospheric pressure gas jet with methane diluted with Ar. An IRPS spectrum with signal-to-noise ratio better than 10⁴ was observed. The dependence of the IRPS signal intensity on the methane mole fraction and on the pumping laser power density was investigated. PACS 33.20.Ea; 52.35.Mw     

Detection of influential nodes with multi-scale information

The identification of influential nodes in complex networks is one of the most exciting topics in network science. The latest work successfully compares each node using local connectivity and weak tie theory from a new perspective. We study the structural properties of networks in depth and extend this successful node evaluation from single-scale to multi-scale. In particular, one novel position parameter based on node transmission efficiency is proposed, which mainly depends on the shortest distances from target nodes to high-degree nodes. In this regard, the novel multi-scale information importance (MSII) method is proposed to better identify the crucial nodes by combining the network's local connectivity and global position information. In simulation comparisons, five state-of-the-art algorithms, i.e. the neighbor nodes degree algorithm (NND), betweenness centrality, closeness centrality, Katz centrality and the k-shell decomposition method, are selected to compare with our MSII. The results demonstrate that our method obtains superior performance in terms of robustness and spreading propagation for both real-world and artificial networks.     

Detection of plasma waves with FIR lasers

FIR laser and detection techniques are reviewed. Results from various plasma experiments are shown to illustrate the sensitivity and resolution of FIR laser scattering and the nature of coherent and turbulent wave phenomena.     

利用PVDF传感器检测激光超声的实验研究

简要介绍了激光超声技术以及声表面波的基本特点、激光超声产生和接收的基本原理及激光超声技术的应用。概述了聚偏二氟乙烯（PVDF）压电薄膜材料的结构、性质和应用，以及薄膜压电性产生的机理。对PVDF换能器的设计思路和实验方法进行了简单讨论。具体实验采用脉冲激光器激发声表面波，利用PVDF传感器接收实验信号，调试实验信号，得出波形，并对实验现象作出初步分析。证实了该实验装置应用于激光超声无损检测的可行性与可靠性。     

Detection of multipartite entanglement with two-body correlations

We show how to detect entanglement with criteria built from simple two-body correlation terms. Since many natural Hamiltonians are sums of such correlation terms, our ideas can be used to detect entanglement by energy measurement. Our criteria can straightforwardly be applied for detecting different forms of multipartite entanglement in familiar spin models in thermal equilibrium. PACS 03.65.Ud; 03.67.Mn; 05.50.+q     

Detection of explosives with laser-induced breakdown spectroscopy

Our recent work on the detection of explosives by laser-induced breakdown spectroscopy (LIBS) is reviewed in this paper. We have studied the physical mechanism of laser-induced plasma of an organic explosive, TNT. The LIBS spectra of TNT under single-photon excitation are simulated using MATLAB. The variations of the atomic emission lines intensities of carbon, hydrogen, oxygen, and nitrogen versus the plasma temperature are simulated too. We also investigate the time-resolved LIBS spectra of a common inorganic explosive, black powder, in two kinds of surrounding atmospheres, air and argon, and find that the maximum value of the O atomic emission line SBR of black powder occurs at a gate delay of 596 ns. Another focus of our work is on using chemometic methods such as principle component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) to distinguish the organic explosives from organic materials such as plastics. A PLS-DA model for classification is built. TNT and seven types of plastics are chosen as samples to test the model. The experimental results demonstrate that LIBS coupled with the chemometric techniques has the capacity to discriminate organic explosive from plastics.     

Feasibility of bone assessment with leaky Lamb waves in bone phantoms and a bovine tibia

In this study, the effect of cortical thickness variation on the propagation of leaky Lamb waves is investigated by using an axial transmission technique commonly used to characterize long bones. Three Lucite plates with thicknesses of 1, 3, and 5 mm as bone phantoms and one bovine tibia with a cortical thickness of 2 mm were used at various low frequencies. Experimental measurements in bone phantoms show that the peak frequency and amplitude of excited Lamb modes strongly depend on the thickness of the Lucite plate. In the bovine tibia, the S0 and A0 Lamb modes are consistently observed in the frequency-thickness region from 0.2 to 1.0 MHz mm, and can be effectively launched at a frequency of 200 kHz, suggesting 200 kHz to be the optimal signal frequency for in vivo clinical applications. It can be also seen that both modes are affected by the frequency-thickness product, but the effect is greater for the A0 mode. Hence, the A0 Lamb mode seems more sensitive to cortical thickness change due to aging and osteoporosis. This study suggests that the use of leaky Lamb waves is feasible for ultrasonic bone assessment.     

Atmospheric Gas Detection with Broadband Sources

We investigate a new experimental method for detecting molecules from the ultraviolet to the near infrared range using ultrashort laser pulses. Two types of sources are used: a white light continuum generated by 200khz Ti: Sapphire regenerative amplifier system, and a near-gaussian femtosecond pulse (100 fs) generated by an optical parametric amplifier and tunable from 0.45 to 2.4 m. Up to now, this technique has only been performed in the visible domain. Both broadband sources allow the detection of the oxygen and the water vapor bands. Moreover, a new extraction method has been implemented, which provides the molecules' concentration by using a nonlinear fit technique.     

用于压缩光探测的高共模抑制比平衡零拍探测器

根据光电二极管的等效电路图,基于自减方案的平衡零拍探测器的光电管(ETX500)产生的光电流的位相差异主要由等效电容引起,通过给两个光电管施加不同的偏置电来补偿等效电容的差异获得高共模抑制比的平衡零拍探测器,在探测器中安装任意两个ETX500,获得了63.8dB的高共模抑制比,并且当激光功率达到探测器的饱和功率54 mW时,激光光场的噪声谱在2 MHz处高于电子学噪声37dB,该探测器能很好地满足压缩态探测对低噪声、线性增益及高共模抑制比的要求。     

同步辐射应用于软X射线探测器的标定

介绍同步辐射(SR)在惯性约束聚变(ICF)研究中的应用.北京同步辐射光源(BSRF)在专用光运行模式下,束流强度35—110mA,贮存环电子能量2GeV.标定前,首先采用1000PL/mm透射光栅作色散元件,对光源进行单色性研究,用面阵软X光CCD对光斑进行均匀性研究.在3W1B束线上,可用能区50—1550eV,通过不同材料前置滤片抑制高次谐波,获得单色性好于95%的单色光.几年来,对十余种ICF实验诊断用软X光探测元器件及设备进行了能量响应绝对标定.大量实验标定数据被用于ICF实验诊断,提高了ICF实验数据的精度