Position Of Tracer Research Articles

Recent Progress on Mass Spectrum Based Approaches for Absorption, Distribution, Metabolism, and Excretion Characterization of Traditional Chinese Medicine

The absorption, distribution, metabolism, and excretion (ADME) of traditional Chinese medicine (TCM) components are closely related to their therapeutic efficacy, toxic effects, and drug interactions. Based on the study of the whole process of ADME in TCM, it is important to screen out the key pharmacokinetic index components (pharmacokinetics PK/toxicokinetics TK makers), which can be beneficial for their clinical application or drug development. Although the detection of traditional small molecular drug's in vivo ADME process can be achieved by radioisotope methods, this approach might not be useful for the case of TCM. In detail, it is very difficult to label and trace each component in complex Chinese medicine, while it is also difficult to accurately follow the position of tracer in the whole in vivo process. In short, it is a tough task to obtain the ADME information of Chinese medicine, especially in the case of a clinical study. We searched several scientific databases, including Pubmed, ACS, ScienceDirect, Springer, Wiley, etc., by using "Chinese medicine" and "in vivo metabolism" as keywords. By summarizing the current reports as well as our recent progress in this field, this review aims to summarize current research methods and strategies for ADME study of TCM based on high-resolution mass spectrometry-based data acquisition and data mining technology which is an important approach but has not been systematically reviewed. With the development of various hybrid tandem high-resolution mass spectrometry (Q-TOF, LTQ FT, Q-Exactive), liquid chromatography-high resolution mass spectrometry (LC-HRMS) has become the mainstream method in studying ADME process of TCM. This review aims to comprehensively summarize current research technologies and strategies based on high-resolution mass spectrometry, with emphasis on the following three aspects: (1) comprehensive and automatic acquisition technologies for the analysis of in vivo TCM components (i.e., BE-DDA); (2) quick and comprehensive identification techniques for analyzing in vivo chemical substances and metabolites of TCM (i.e., PATBS or metabolomic analysis); (3) efficient correlation determination between in vivo or in vitro compounds and their metabolic transformation (i.e., MTSF). To the best of our knowledge, this is a pioneering review for systematically summarizing the analysis methods and strategies of ADME in TCM, which can help understand the whole ADME process, therapeutic molecular basis, or toxic substances of TCM. Furthermore, this review can also provide a feasible strategy to screen out PK/TK markers of TCM, while this information can be helpful to elucidate the pharmacodynamics or toxicity mechanisms of Chinese medicines and be useful in their future drug development. At the same time, we also hope that this review can provide ideas for further improvement of TCM analysis methods and help rational clinical use of TCM and the development of new drugs.

Evaluation of a Wireless Tongue Tracking System on the Identification of Phoneme Landmarks.

Evaluate the accuracy of a tongue tracking system based on the localization of a permanent magnet to generate a baseline of phoneme landmarks. The positional variability of the landmarks provides an indirect measure of the tracking errors to estimate the position of a small tracer attached on the tongue. The creation of a subject-independent (universal) baseline was also attempted for the first time. 2,500 tongue trajectories were collected from 10 subjects tasked to utter 10 repetitions of 25 phonemes. A landmark was identified from each tongue trajectory, and tracking errors were calculated by comparing the distance of each repetition landmark to a final landmark set as their mean position. In the subject-dependent baseline, the tracking errors were found to be generally consistent across all phonemes, and subjects, with less than 25% of the errors reported to be greater than 5.8mm (median: 3.9mm). However, the inter-subject variability showed that current limitations of our system resulted in appreciable errors (median: 55mm, Q3: 65mm). The tracking errors reported in the subject-dependent case demonstrated the potential of our system to generate a baseline of phoneme landmarks. We have identified areas of improvement that will reduce the gap between the subject-dependent, and universal baseline, while lowering tracking errors to be comparable to the gold standard. Creating a baseline of phoneme landmarks can help people affected by speech sound disorders to improve their intelligibility using visual feedback that guides their tongue placement to the proper position.

Sentinel lymph node fingerprinting

Background. When locating the sentinel lymph node (SLN), surgeons use state-of-the-art imaging devices, such as a 1D gamma probe or less widely spread a 2D gamma camera. These devices project the 3D subspace onto a 1D respectively 2D space, hence loosing accuracy and the depth of the SLN which is very important, especially in the head and neck area with many critical structures in close vicinity. Recent methods which use a multi-pinhole collimator and a single gamma detector image try to gain a depth estimation of the SLN. The low intensity of the sources together with the computational cost of the optimization process make the reconstruction in real-time, however, very challenging.Results. In this paper, we use an optimal design approach to improve the classical pinhole design, resulting in a non-symmetric distribution of the pinholes of the collimator. This new design shows a great improvement of the accuracy when reconstructing the position and depth of the radioactive tracer. Then, we introduce our Sentinel lymph node fingerprinting (SLNF) algorithm, inspired by MR-fingerprinting, for fast and accurate reconstruction of the tracer distribution in 3D space using a single gamma detector image. As a further advantage, the method requires no pre-processing, i.e. filtering of the detector image. The method is very stable in its performance even for low exposure times. In our ex vivo experiments, we successfully located multiple Technetium 99m (Tc-99m) sources with an exposure time of only one second and still, with a very small L2-error.Conclusion. These promising results under short exposure time are very encouraging for SLN biopsy. Although, this device has not been tested on patients yet, we believe: that this approach will give the surgeon accurate 3D positions of the SLN and hence, can potentially reduce the trauma for the patient.

Flow through porous media: a momentum tracer approach

The flow of a fluid through a spatially periodic porous medium is studied using the momentum tracer approach, that is by monitoring the temporal spread of an instantaneous source of momentum (the “momentum tracer”), following its initial introduction into the interstitial fluid. The fluid flow is described macroscopically by a Brinkman-like effective equation, containing three effective tensorial quantities, namely the permeability dyadic, the generalized viscosity tetradic and a coupling triadic term. These phenomenological coefficients are shown to be expressible in terms of the solution of the characteristic eigenvalue problem associated with the (tensorial) Stokes operator, defined within the interstitial region of a single unit cell of the periodic porous medium. The phenomenological coefficients are shown to be independent of the initial position of the momentum tracer as well as of the choice of weight function used in averaging the microscale momentum density over the unit cell. Finally, we show that the analytical expressions for the phenomenological coefficients identically satisfy the symmetry requirements that can be obtained by applying the reciprocal theorem at the macro-scale level.

Experimental characterization of the chaotic dynamics of cohesionless particles: application to a V-blender

So far, most of the investigations of the dynamics of granular material in blenders have been done in 2D tumblers due to the current lack of accurate measurement methods for the investigation of complex 3D flows. However, recent advances in the field of non-intrusive methods have paved the way to the characterization of the chaotic dynamics in 3D blenders. This work aims to present such an analysis in the case of a V-blender using radioactive particle tracking (RPT). Special attention is given to the chaotic properties of mixing by performing a time-series analysis of the position of a single tracer in motion in this blender. An original investigation of the mixing properties is also presented. More generally, this work shows that the mixing properties of a blender can be characterized by using tools of dynamical systems theory through a time-series analysis of data obtained from non-intrusive measurements.

Experimental investigation of particle contact time at the wall of gas fluidized beds

The contact time of particles at the walls of gas fluidized beds has been studied using a radioactive particle tracking technique to monitor the position of a radioactive tracer. The solids used were sand or FCC particles fluidized by air at room temperature and atmospheric pressure at various superficial velocities, covering both bubbling and turbulent regimes of fluidization. Based on the analysis of tracer positions, the motion of individual particles near the walls of the fluidized bed was studied. The contact time, contact distance and contact frequency of the particles at the wall were evaluated from these experimental data. It was found that in a bed of sand particles, the mean wall contact time of the fluidized bed of sand particles decreases by increasing the gas velocity in the bubbling and increases in the turbulent fluidization. In other words, the particle–wall contact time is minimum at the onset of turbulent fluidization in the bed of sand particles. However, the mean wall contact time is almost constant in both regimes of fluidization in the bed of FCC particles. All the existing models in the literature predict a decreasing contact time when the gas velocity in the bed is increased. It was also shown that the contact distance increases monotonously by increasing the gas velocity in the bed of sand particles, while it is almost constant for the bed of FCC particles. Contact frequency has a trend similar to that of the contact time for both sand and FCC particles.

Monitoring the particle–wall contact in a gas fluidized bed by RPT

Particle–wall contact behavior of the solids in a gas–solid fluidized bed was experimentally studied using the radioactive particle tracking (RPT) technique in which the position of a radioactive tracer is monitored when moving freely in the bed. The solids were sand particles, fluidized by air at room temperature and atmospheric pressure at various superficial velocities, covering both bubbling and turbulent regimes of fluidization. The motion of individual particles near the wall of the bed was studied based on the position of the tracer. The contact time, contact distance and contact frequency of the particles at the wall were evaluated. It was found that the distribution functions of these three parameters become wider by increasing the superficial gas velocity. Axial profiles of contact time and contact distance were also studied in this work. Axial profiles of the overall heat transfer coefficient in the fluidized bed were estimated based on the formulas reported in the literature and the experimental particle–wall contact time evaluated in the present study. Based on such profiles, in order to benefit from the maximum heat transfer coefficient along the bed, it is recommended to place the heat exchanging surface in the middle of the bed, i.e., not very close to the gas distributor as well as far from the top of the dense bed.

Measurement of in-cylinder flow by visualization of tracers in colour layer: examination of principle and measurement of three dimensional position of tracer

Measurement of in-cylinder flow by visualization of tracers in colour layer: examination of principle and measurement of three dimensional position of tracer