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Theranostic systems in sonography
Říkovská, Klára ; Pekař, Miloslav (referee) ; Mravec, Filip (advisor)
This work deals with preparation of microbubble suspension from a mixture of phospholipids, palmitic acid and polyethylene glycol. Properties of prepared systems were studied using bubble tensiometry and dynamic light scattering method and were compared with commercial contrast agent SonoVue®. Suspensions were prepared in various conditions including different atmosphere and increased temperature in some steps of preparation and different solution. Effect of polyethylene glycol addition on surface activity of the system was studied. Surface activity of phospholipids was insignificant. Surface tension decreased with increasing concentration and molecular weight of polyethylene glycol in the system. Effect of different atmosphere and increased temperature showed no substantial trend. It emerged that dynamic light scattering is not suitable for this type of samples because of high polydispersity and phase separation of the system.
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Study of surface tension of systems applied in ultrasonography.
Říkovská, Klára ; Pekař, Miloslav (referee) ; Mravec, Filip (advisor)
Surface tension of sonography systems was investigated using several experiments. These experiments were comprised of measurements of surface tension using BPA-800P tensiometer. The influence of surface tension of commercial substance SonoVue®, which contains in its structure two types of phospholipids, was studied more detailed. Other phospholipids were studied to comparison with SonoVue®. All substances were dissolved in saline (0,15 M NaCl). Effect of gas type on microbubbles formation and surface tension was investigated. Some samples were studied using du Nüy ring method. It was found that gas constructing the microbubbles (air or SF6) has no impact to the surface tension value. Production of foam on the surface of solutions has an impact on the value of the surface tension. This foam degreases the surface tension. Gas pressure is significant to comparison of measured data.
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Preventing microbubble conjunctions by gas flow excited by a fluidic oscillator
Tesař, Václav
Recently demonstrated was efficient generation of desirable small-size microbubbles in liquids by applying oscillation to the air flow supplied into the aerator - preferably by means of a simple and inexpensive fluidic oscillator. It remained unexplained what the oscillation actually does with the bubbles. In this paper was established that microbubbles are produced in a process consisting of several discrete steps, in each growing in size. Oscillation of the gas flow can eliminate this growth and keep the resultant bubbles small. Two alternative mechanisms were identified than can suppress the growth.
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Mechanism of Multiple Microbubble Conjunctions
Tesař, Václav ; Šonský, Jiří
In typical generation of microbubbles by blowing the gas through tiny holes in an aerator, the size of bubbles is much larger than hole exit diameter. Explanation for this discrepancy was found by analysing high-speed camera images of bubble generation. Primary microbubbles, of initial size corresponding to the aerator exits, tend to remain near the location of their formation at the aerator exit - and coalesce there with subsequently formed other primary microbubbles. Typically, this coalescence is repeated several times before the increased final size and position of the resultant larger bubble reaches the limit for separation and ascent.
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Integral fluidic generator of microbubbles
Tesař, Václav ; Jílek, Miroslav
Very small gas bubbles dispersed in liquid are desirable in many applications. If smaller than 1 mm in diameter, they are called microbubbles. Until recently, the advantages they offer have been little usedbecause of generally low efficiency of microbubble generation methods. A solution was found in pulsating the gas flow into the submerged aerator by a fluidic oscillator. At present, the oscillator and aerator are separate devices. The flow pulsation is strongly damped in the connecting tubes. New solution presented in this paper relies on oscillator robustness and no need for maintenance, which allows integrating it with the aerator into a single body submerged in the liquid. Small bubble size requires driving frequency much higher than has been so far applied. The present paper shows some of the ways leading to high frequencies – in particular the use of dominant third harmonic of the basic switching frequency.
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Near-exit coalescence – a so far unknown limit to microbubble smallness
Tesař, Václav ; Šonský, Jiří
Gas bubbles in a liquid are required in applications to be of the smallest possible bubble size. Authors studied microbubble formation using a high-speed camera and discovered that bubbles increase their volume near the aerator exits by mutual coalescence. This effect presents a limit to how small microbubbles can be produced. The discovered conjunction effects are very fast and this is probably the reason why they have so far escaped attention.
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Interesting properties of microbubbles
Tesař, Václav
Paper investigates properties of very small, sub-millimetre sized gas bubbles in liquids,which are generated by oscillation produced by a fluiidic no-moving-part oscillato in the gas supply into the aerator. Of particular interest is the tendency of microbubbles to coalesce already while in immediate neighbourhood of the aerator exit. Another investigated property is oscillation driven by released surface energy. Autorr derived an equation describing the natural frequencty of the oscillation and with the help of this equation found interesting parameters of the processes, such as the amount of outside water that takes part in the oscillation and has a decisive role in the inertial properties of the variations of the microbubble shape.
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Contrast medium in the ultrasonography
BLECHA, Dalibor
Ultrasound method belongs to the most extended and easily available modern investigative diagnostic techniques. It is the step number one in the investigative diagnostic algorithm. The beginning of this method dates back to the early fifties of the twentieth century. With respect to the fact that the usage of ultrasound contrast agents and the development of an {\clqq}optimal`` contrast agent has not finished, I refer to some limitations and obstacles. Although this process is similar for all contrast agents in all fields of modern imaging methods. Implementing new findings and observations into a clinical practice is connected with lots of difficulties and obstacles that restrain their success. In the same way as the contrast agents found their application in various modern imaging techniques, the ultrasound contrast agents are also expected to find their place in the ultrasonography. This fact acknowledges my hypothesis and points at application of ultrasound method as the first choice.
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