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Biomedical subjects

M Fink

Publications and source records attributed to M Fink.

At least 37 records · Page 2Linked to original sources
PubMed2003

Effect of acupuncture on the neutrophil respiratory burst: a placebo-controlled single-blinded study.

OBJECTIVES: Little is known about the influence of acupuncture treatment on the phagocytic immune system. This trial was performed to examine whether multiple acupuncture treatment affects the respiratory burst (RB) of neutrophils, a recognised measure of their cytotoxicity. DESIGN: Placebo-controlled single-blinded study. INTERVENTIONS: Eleven volunteers were treated bilaterally with standard needles (real) at acupoint LI11, 11 volunteers with placebo needles (placebo) at the same point. Treatments were performed for 30 min each twice a week for 4 weeks, eight times in all. The standard needles were manipulated until needle sensation (DEQI) developed. Before the treatment course (baseline), 48 h after the fourth (follow-up 1) and 48 h after the last treatment (follow-up 2) blood samples were drawn. MAIN OUTCOME MEASURES: RB and plasma beta-endorphin at each time point. RESULTS: In the real group there was a highly significant increase in the RB at follow-ups 1 (P=0.004) and 2 (P=0.007). Beta-endorphin levels decreased, but not significantly. In the placebo group there was a significant increase in the RB at follow-up 2 (P=0.048). In addition, at follow-up 2 a significant drop in beta-endorphin levels was observed (P=0.015). CONCLUSIONS: The RB of neutrophils is significantly activated by a course of several acupuncture treatments. In addition, psychological effects and a placebo that was not totally inert may contribute to the findings in the placebo group which may be mediated by the opiate endorphin system.

Acupuncture Therapy↗
PubMed2003

Comorbidity of internal derangement of the temporomandibular joint and silent dysfunction of the cervical spine.

The aim of this evaluation was to examine correlations between internal derangement of the temporomandibular joint (TMJ) and cervical spine disorder (CSD). A prospective controlled clinical study was carried out. Thirty patients with signs and symptoms of internal derangement but without any subjective neck problems and 30 age- and gender-matched control subjects without signs and symptoms of internal derangement were examined. The investigation of the temporomandibular system was carried out using a 'Craniomandibular Index'. Afterwards an examiner-blinded manual medical investigation of the craniocervical system was performed. This included muscle palpation of the cervical spine and shoulder girdle as well as passive movement tests of the cervical spine, to detect restrictions in the range of movement as well as segmental intervertebral dysfunction. The internal derangement of the TMJ was significantly associated with 'silent' CSD (t-test, P < 0.05). Patients with raised muscle tenderness of the temporomandibular system exhibited significantly more often pain on pressure of the neck muscles than patients without muscle tenderness of the temporomandibular system (t-test, P < 0.05). As a result of the present study, for patients with internal derangement of the TMJ an additional examination of the craniocervical system should be recommended.

Adolescent↗
PubMed2003

Experimental demonstration of noninvasive transskull adaptive focusing based on prior computed tomography scans.

Developing minimally invasive brain surgery by high-intensity focused ultrasound beams is of great interest in cancer therapy. However, the skull induces strong aberrations both in phase and amplitude, resulting in a severe degradation of the beam shape. Thus, an efficient brain tumor therapy would require an adaptive focusing, taking into account the effects of the skull. In this paper, we will show that the acoustic properties of the skull can be deduced from high resolution CT scans and used to achieve a noninvasive adaptive focusing. Simulations have been performed with a full 3-D finite differences code, taking into account all the heterogeneities inside the skull. The set of signals to be emitted in order to focus through the skull can thus be computed. The complete adaptive focusing procedure based on prior CT scans has been experimentally validated. This could have promising applications in brain tumor hyperthermia but also in transcranial ultrasonic imaging.

Acoustics↗
PubMed2003

Imaging in the presence of grain noise using the decomposition of the time reversal operator.

In this paper, we are interested in detecting and imaging defects in samples of cylindrical geometry with large speckle noise due to the microstructure. The time reversal process is an appropriate technique for detecting flaws in such heterogeneous media as titanium billets. Furthermore, time reversal can be iterated to select the defect with the strongest reflectivity and to reduce the contribution of speckle noise. The DORT (the French acronym for Decomposition of the Time Reversal Operator) method derives from the mathematical analysis of the time reversal process. This detection technique allows the determination of a set of signals to be applied to the transducers in order to focus on each defect separately. In this paper, we compare three immersion techniques on a titanium sample, standard transmit/receive focusing, the time reversal mirror (TRM), and the DORT method. We compare the sensitivity of these three techniques, especially the sensitivity to a poor alignment of the array with the front face of the sample. Then we show how images of the sample can be obtained with the TRM and the DORT method using backpropagation algorithm.

Journal Article↗
PubMed2003

Measurement of elastic nonlinearity of soft solid with transient elastography.

Transient elastography is a powerful tool to measure the speed of low-frequency shear waves in soft tissues and thus to determine the second-order elastic modulus mu (or the Young's modulus E). In this paper, it is shown how transient elastography can also achieve the measurement of the nonlinear third-order elastic moduli of an Agar-gelatin-based phantom. This method requires speed measurements of polarized elastic waves measured in a statically stressed isotropic medium. A static uniaxial stress induces a hexagonal anisotropy (transverse isotropy) in solids. In the special case of uniaxially stressed isotropic media, the anisotropy is not caused by linear elastic coefficients but by the third-order nonlinear elastic constants, and the medium recovers its isotropic properties as soon as the uniaxial stress disappears. It has already been shown how transient elastography can measure the elastic (second-order) moduli in a media with transverse isotropy such as muscles. Consequently this method, based on the measurement of the speed variations of a low-frequency (50-Hz) polarized shear strain waves as a function of the applied stress, allows one to measure the Landau moduli A, B, C that completely describe the third-order nonlinearity. The several orders of magnitude found among these three constants can be justified from the theoretical expression of the internal energy.

Elasticity↗
PubMed2002

Overcoming the diffraction limit in wave physics using a time-reversal mirror and a novel acoustic sink.

In recent years, time-reversal (TR) mirrors have been developed that create TR waves for ultrasonic transient fields propagating through complex media. A TR wave back propagates and refocuses exactly at its initial source. However, because of diffraction, even if the source is pointlike the wave refocuses on a spot size that cannot be smaller than half a wavelength. Here, by using a TR interpretation of this limit, we show that this latter limitation can be overcome if the source is replaced by its TR image. This new device acts as an acoustic sink that absorbs the TR wave. Here we report the first experimental result obtained with an acoustic sink where a focal spot size of less than 1/14th of one wavelength is recorded.

Journal Article↗
PubMed2002

Detection of cracks in a thin air-filled hollow cylinder by application of the DORT method to elastic components of the echo.

The DORT method (Decomposition de l'Opérateur de Retournement Temporel in French) is a scattering analysis technique which uses arrays of transducers. This method is efficient for detection of selective focusing on point-like scatterers. It has been also applied to analyze the scattering by an air-filled cylindrical steel shell immersed in water. It was shown that the diagonalization of the time reversal operator allows us to separate the different elastic components of the scattered field. Here, we apply the method to detect flaws in hollow cylinders. In this case, the dominant components are the three circumferential waves (A0, A1 and S0 Lamb modes). Each Lamb mode corresponds to an invariant of the time reversal operator. The dispersion curves of these waves are calculated from these invariants. Resonance frequencies of the shell are deduced from the frequency dependence of the eigenvalues of the time reversal operator. It is shown that the presence of a crack (0.2 mm in depth) affects significantly the eigenvalue distribution of the time reversal operator. Thus, the DORT method offers a new means for detecting defects in a shell.

Journal Article↗
PubMed2002

Acupuncture in chronic epicondylitis: a randomized controlled trial.

OBJECTIVE: To evaluate the clinical efficacy of acupuncture in the treatment of chronic lateral epicondylitis. METHODS: In a randomized, investigator- and patient-blinded, controlled clinical study, 23 patients were treated with real acupuncture and 22 patients received sham acupuncture. Patients each received 10 treatments, with two treatments per week. The primary outcome variables were maximal strength, pain intensity (verbal rating scale) and disability scale (Disabilities of the Arm, Shoulder and Hand questionnaire). Patients were examined at baseline (1 week before the start of treatment) and at follow-up 2 weeks and 2 months after the end of treatment. RESULTS: There was no significant difference between the groups at baseline for any outcome parameter. Two weeks and 2 months after the end of treatment, there were significant reductions in pain intensity and improvements in the function of the arm and in maximal strength in both treatment groups. At the 2-week follow-up these differences were significantly greater for all outcome parameters in the group treated with real acupuncture. At 2 months the function of the arm was still better in this group than in the sham acupuncture group; however, the differences in pain intensity and maximal strength between the groups were no longer significant. CONCLUSION: In the treatment of chronic epicondylopathia lateralis humeri, acupuncture in which real acupuncture points were selected and stimulated was superior to non-specific acupuncture with respect to reduction in pain and improvement in the functioning of the arm. These changes are particularly marked at early follow-up.

Acupuncture↗
PubMed2002

Chronic epicondylitis: effects of real and sham acupuncture treatment: a randomised controlled patient- and examiner-blinded long-term trial.

OBJECTIVE: The clinical long-term effectiveness of real and sham acupuncture treatment on differentiated pain measurement was evaluated in chronic lateral epicondylitis, an example of a tendomyotic disorder. METHODS: Randomised, examiner- and patient-blinded controlled clinical study. OUTCOME MEASUREMENT: pain at rest, pain on movement, pain on exertion, frequency and duration of pain. Real acupuncture (n = 23) was tested versus invasive sham acupuncture (n = 22). Ten treatments were given (2 treatments/week). Patients were examined at baseline (E1) as well as 2 weeks (E2), 2 months (E3) and 1 year (E4) after the end of treatment. In the treatment with real acupuncture, acupuncture points were selected and mechanically stimulated while in the sham group non-acupuncture points were selected. RESULTS: There was no significant difference between the groups at baseline for any outcome parameter. Two weeks, 2 months and 1 year after the end of treatment there were significant reductions in all pain variables compared to baseline. At the first follow-up, significant group differences were registered for pain on motion and pain on exertion in favour to the real acupuncture group. These differences in pain intensity between the groups were no longer significant at the 2 months and 12 months follow-ups. CONCLUSION: The results suggest that, in the treatment of chronic epicondylitis, the selection of so-called real acupuncture points gives better results than invasive sham acupuncture at early follow-up. This additional effect can be interpreted as a specific effect of real acupuncture.

Acupuncture Therapy↗
PubMed2001

Sensitivity to perturbations of a time-reversed acoustic wave in a multiple scattering medium.

We present experimental results on the robustness of acoustic time-reversal focusing in a multiple scattering medium undergoing perturbations. Time reversal in such a medium can be viewed as a correlation technique, analogous to diffusive wave spectroscopy. Moreover, the recent introduction of telecommunication techniques based on time reversal in changeable media naturally raises the question of sensitivity to a perturbation of the medium. We consider the situation where the reversibility of an acoustic wave generated by a linelike source is gradually destroyed when a perturbation is added, either locally (by removing scatterers) or globally (by changing the temperature) to the multiple scattering medium.

Journal Article↗
PubMed2001

Observation of a coherent backscattering effect with a dipolar source for elastic waves: highlight of the role played by the source.

We report an experimental evidence of the role played by the source on the coherent backscattering effect (CBE) for elastic waves. The experiment is carried out in a chaotic cavity consisting of a silicon plate whose shape is a quarter stadium. With a monopolar source, it has already been shown that the time-integrated squared amplitude at the point source is twice as large as at the other points around the source. Here, by using a dipolar source, we show that we instead obtain two peaks with the same axis as the dipole one's. The shape of this "bicone" is well explained with a modal theory assuming that the source may be modeled by two sources with opposite phases. Then, the theory is generalized to any multipolar emitter and/or receiver. Particularly, we study CBE when emitter and receiver are reciprocal.

Journal Article↗
PubMed2001

Random multiple scattering of ultrasound. I. Coherent and ballistic waves.

This is the first article in a series of two dealing with the statistical moments of ultrasonic waves transmitted through a disordered medium with resonant multiple scattering. Only the first-order moment is considered here. An ultrasonic pulsed wave is transmitted from a point source to a 128-element receiving array through two-dimensional samples with various thicknesses. The samples consist of random collections of parallel steel rods immersed in water. Experimental results show that the ensemble-averaged transmitted wave forms ("coherent wave") exhibit a time-dependent frequency spectrum. Within the independent scattering approximation, this is well explained by individual resonances of the scatterers. The coherent wave only appears after ensemble averaging and has to be distinguished from the "ballistic wave," i.e., the first well-defined pulse that crosses the sample, which can be measured on every realization of disorder. A physical interpretation is given, which is based on the separation of the coherent wave between a rigid and a resonant contribution.

Journal Article↗
PubMed2001

Random multiple scattering of ultrasound. II. Is time reversal a self-averaging process?

This is the second article in a series of two dealing with the statistical moments of ultrasonic waves transmitted through a disordered medium with resonant multiple scattering. Second-order moments in time and space are considered here. An ultrasonic pulsed wave is transmitted from a point source to a 128-element receiving array through two-dimensional samples with various thicknesses. The samples consist of random collections of parallel steel rods immersed in water. The scattered waves are recorded, time reversed, and sent back into the medium. The time-reversed waves are converging back to their source and the quality of spatial and temporal focusing on the source is related to the second-order moments of the scattered wave (correlation) in time and in space. Experimental results show that it is possible to obtain a robust estimation on a single realization of disorder, taking advantage of the wide frequency bandwidth. The spatial resolution of the system is only limited by the correlation length of the scattered field, and no longer by the array aperture. As the sample thickness is increased, the quality of focusing saturates, which we believe is linked to the Thouless factor g. In the thickest sample, g approximately 30, which is still well above the localization threshold.

Journal Article↗
PubMed2001

Breaking of time reversal invariance in nonlinear acoustics.

Time-reversal invariance of nonlinear acoustic wave propagation is experimentally investigated. Reversibility is studied for propagation shorter or longer than shock formation distance. In the first case, time-reversal invariance holds and a sinusoid distorted by nonlinearities during forward propagation progressively recovers its initial shape after the time-reversal operation. In the second case, reversibility is broken locally at the shock front as a time-reversal operation transforms a stable compression shock into an unstable expansion shock. Achieving experimentally the time-reversal process with a time-reversal mirror made of reversible piezoelectric transducers for very broadband signals, would require transducers with huge bandwidths. To date, such transducers remain unavailable. In order to overcome this technical limitation, we restricted ourselves in this study to one-dimensional (1D) propagation, for which an experimental ersatz of a time-reversal mirror can be used. Indeed, in a 1D case, the time-reversal operation applied on a plane wave can be mimicked for an antisymmetric wave form by a reflection of the plane wave onto a pressure-release interface.

Journal Article↗
PubMed2001

Scattering of sound by a vorticity filament: an experimental and numerical investigation.

A vorticity filament is investigated experimentally using the transmission of an ultrasonic wave through the flow. The analysis of the wave-front distortion provides noninvasive measurements of the vortex circulation and size. The latter is estimated by analytical calculations of the scattering of a plane wave by a vorticity filament. The case of a cylindrical wave incident on a vortex leads to similar experimental results which are successfully compared to a parabolic equation simulation. Finally, a finite-difference code based on linear acoustics is presented, in order to investigate the structure of the scattered wave numerically.

Journal Article↗
PubMed2001

The many varieties of catatonia.

About 10% of patients with severe acute psychiatric illness exhibit a cluster of motor signs (mutism, negativism, rigidity, posturing, stereotypy, staring, etc.) that are identified as the syndrome of catatonia. Catatonia responds to sedative anticonvulsant treatment (barbiturates, benzodiazepines) and to electroconvulsive therapy. These treatments raise seizure thresholds. The commonality in response indicates that catatonia, malignant catatonia, neuroleptic malignant syndrome, toxic serotonin syndrome, delirious mania, catatonic excitement, benign stupor, and oneirophrenia are best evaluated as diverse manifestations of one syndrome for clinical and neuroscience research purposes.

Acute Disease↗