Ultrasound dosimetry

Biological Effects and Exposure Criteria for Ultrasound Biological Effects of Magnetic Fields Microprocessors in Dosimetry Efficacy Studies... 

Mark G, Schuchmann MN, Schuchmann H-P, von Sonntag C (1990) The photolysis of potassium peroxodisulphate in aqueous solution in the presence of tert-butanol a simple actinometer for 254 nm radiation. J Photochem Photobiol A Chem 55 157-168 Mark G, Korth H-G, Schuchmann H-P, von Sonntag C (1996) The photochemistry of aqueous nitrate revisited. J Photochem Photobiol A Chem 101 89-103 Mark G, Tauber A, Laupert R, Schuchmann H-P, Schulz D, Mues A, von Sonntag C (1998) OH-radical formation by ultrasound in aqueous solution, part II. Terephthalate and Fricke dosimetry and the influence of various conditions on the sonolytic yield. Ultrason Sonochem 5 41-52 MarkG, Schuchmann H-P, von Sonntag C (2000) Formation of peroxynitrite by sonication of aerated water. J Am Chem Soc 122 3781-3782... 

A very important point occurs in the transmission of acoustic power into a liquid which is termed the cavitation threshold. When very low power ultrasound is passed through a liquid and the power is gradually increased, a point is reached at which the intensity of sonication is sufficient to cause cavitation in the fluid. It is only at powers above the cavitation threshold that the majority of sonochemical effects occur because only then can the great energies associated with cavitational collapse be released into the fluid. In the medical profession, where the use of ultrasonic scanning techniques is widespread, keeping scanning intensities below the cavitation threshold is of vital importance. As soon as the irradiation power used in the medical scan rises above this critical value, cavitation is induced and, as a consequence, unwanted even possibly hazardous chemical reactions may occur in the body. Thus, for both chemical and medical reasons there is a considerable drive towards the determination of the exact point at which cavitation occurs in liquid media, particularly in aqueous systems. Historically, therefore, the determination of the cavitation threshold was one of the major drives in dosimetry. 

Utilization of ultrasound in the field of sonoelectrochemistry is well documented [ 11 ]. It is clear that both acoustic streaming and cavitation near or at the surface of an electrode accounts for increased mass transfer [130]. The relative contribution from each process cannot be easily estimated, but both are certainly related to the amount of dissipated power. Any dosimetry technique depending on the measurement of the mass transfer coefficient at an electrode surface should allow local and, by integration through space, overall power determination. Up to now attempts to establish quantitative correlations have failed. 

The reaction can easily be monitored by HPLC, NMR, or by simple weighing of the addition product [197]. The rate increase with ultrasound not only depends on the mechanical effects (mass transfer improvement) but also on some electronic effects as it has recently been shown that the reaction mechanism involves a single electron transfer step which can be stimulated by ultrasound [198]. Hence the development of this chemical probe could provide a very good dosimetry system since it involves both the mechanical and sonochemical effect of ultrasound. 

Berlan, J., Mason, T.J., 1996. Dosimetry for power ultrasound and sonochemistry, in... 

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