RESUMO
The rise of shear strain value under temperature increase in biological tissue samples in vitro and tissue phantoms was studied and the range of shear modulus and viscosity calculated. It has been shown that the acoustic radiation force-based methods with the usage of ultrasound Doppler probing provides the potential ability of noninvasive real-time monitoring of tissues' ultrasound thermal destruction process. At that, the thermal destruction is possible under action of wave beam that creates the radiation force and local tissue displacements so that tissue ablation and acoustic remote palpation could be realized by means of the same ultrasound transducer. The experiments were performed using gelatin-based tissue-mimicking phantoms and freshly excised samples of bovine muscle tissue. It was determined also that fluctuating pattern of detected displacement amplitude variation is the indicator of the phase transitions beginning in the heated field of soft tissue or tissue phantom.
Assuntos
Hipertermia Induzida/métodos , Terapia por Ultrassom/métodos , Animais , Bovinos , Elasticidade , Humanos , Palpação , Imagens de Fantasmas , Estresse Mecânico , Ultrassonografia Doppler/métodos , ViscosidadeRESUMO
Shear wave elasticity imaging (SWEI), an emerging acoustic technology for medical diagnostics, is based on remote generation of shear waves in tissue by radiation force in the focal region of an ultrasonic beam. In this study, the feasibility of Doppler ultrasonic technique to visualize the remotely induced shear waves was demonstrated. The generation of shear displacement in the focal region of a pulsed 1-MHz ultrasound beam with pulse duration of approximately about 2 ms and intensity levels on the order of 145 W/cm2, and consequent propagation of shear wave in tissue-mimicking and muscle tissue in vitro, were measured. The analysis of temporal behavior of shear displacement within the focal plane allowed estimation of shear wave velocities. The velocities were 4 and 7 m/s in hard phantom and tissue containing phantom, respectively. The measured shear displacements on the order of micrometers in gel-based phantoms are in reasonable agreement with theoretical estimates derived from an earlier developed model of shear wave generation by radiation force of focused ultrasound. The study revealed significant dependence of shear strain on the medium viscosity. The complex oscillatory character of shear strain relaxation in viscoelastic phantom and muscle tissue in vitro was observed.
Assuntos
Elasticidade , Gelatina/química , Glicerol/química , Músculos/fisiologia , Ultrassom , Animais , Bovinos , Humanos , Modelos Teóricos , Imagens de Fantasmas , ViscosidadeRESUMO
Influence of visible light on Mg-ATPase and Ca-ATPase activity of thymocytes plasma membranes was investigated. It has been shown that illumination of the membranes at lambda = 518 nm 1.8 times increased Mg-ATPase activity and illumination at lambda = 445.5 nm 1.9 times increased Ca-ATPase activity.
Assuntos
ATPase de Ca(2+) e Mg(2+)/efeitos da radiação , ATPases Transportadoras de Cálcio/efeitos da radiação , Cálcio/efeitos da radiação , Luz , Magnésio/efeitos da radiação , Animais , ATPase de Ca(2+) e Mg(2+)/química , Cálcio/química , ATPases Transportadoras de Cálcio/química , Bovinos , Membrana Celular/enzimologia , Técnicas In Vitro , Cinética , Magnésio/química , Timo/enzimologiaRESUMO
Ultrasound effect on gramicidin incorporation into a bilayer lipid membrane has been investigated. The observed increase in the channel opening frequency points to the incorporation rate growth due to the thickness diminishing of near-membrane non-stirred layers. The dependence of ultrasound intensity on the layer thickness is presented.
