If cavitation in the vasculature of the lung is the physical mechanism responsible for lung hemorrhage, then addition of cavitation nuclei to the blood should enhance the bioeffect. To test the cavitation hypothesis, the extent of lung hemorrhage in mice injected with the echocontrast agent, Albunex(R), was compared to lung hemorrhage in animals injected with saline. Animals were exposed for 5 minutes to 1.1-MHz pulsed ultrasound (10 µs pulse length, 100-Hz pulse repetition frequency) at a peak positive pressure at the surface of the animal of 2 MPa. This exposure is approximately twice the threshold pressure amplitude for lung hemorrhage. Lesion areas did not differ significantly in the two groups of animals and were approximately equal to the lesion area in uninjected mice from an earlier study where acoustic exposures were the same. Neither this study nor a related study of hemolysis in vivo suggests that use of Albunex in echocardiographic procedures increases the risk of bioeffects.
"The mechanism known as inertial cavitations of micro-bubbles has been widely researched. However several studies have ruled out the inertial cavitations from being the mechanism of the US-induced lung haemorrhage  . "
[Show abstract][Hide abstract] ABSTRACT: The possibility of the ultrasound-induced lung haemorrhage occurring in adult human during diagnostic ultrasound examination is studied here. This study is based on the hypothetical alveolar resonance mechanism of the ultrasound-induced lung haemorrhage. The alveolar wall is initially modelled here as a square membrane with fixed-boundary, and then theoretically subjected to vibration analysis. The equation of threshold pressure for the occurrence of ultrasound-induced lung haemorrhage is derived. A comparison test against past experimental data validates the use of the square membrane model of the alveolar wall in studying the ultrasound induced lung haemorrhage. This study predicts that the ultrasound-induced lung haemorrhage in adult human can be prevented if the ultrasound frequency is kept above 1.69 MHz while the Mechanical Index does not exceed 1.9.
Polish Journal of Medical Physics And Engineering 03/2013; 18(2):59-71. DOI:10.2478/v10013-012-0008-9
"Lung hemorrhage is also possible with present diagnostic ultrasound machines (AIUM, 2000). The MI does not apply to this bioeffect, because it does not depend on the inertial cavitation mechanism (Raeman et al. 1997; O'Brien et al. 2000). Data on lung hemorrhage has been used to propose a complex new index for this bioeffect, which includes timing parameters (Church and O'Brien, 2007). "
[Show abstract][Hide abstract] ABSTRACT: This study was performed to examine the frequency dependence of glomerular capillary hemorrhage (GCH) induced by contrast-aided diagnostic ultrasound (DUS) in rats. Diagnostic ultrasound scanners were used for exposure at 3.2, 5.0 and 7.4 MHz, and previously published data at 1.5 and 2.5 MHz was also included. A laboratory exposure system was used to simulate DUS exposure at 1.0, 1.5, 2.25, 3.5, 5.0 and 7.5 MHz, with higher peak rarefactional pressure amplitudes (PRPAs) than were available from our DUS systems. The right kidneys of rats mounted in a water bath were exposed to intermittent image pulse sequences at 1 s intervals during infusion of diluted ultrasound contrast agent. The percentage of GCH was zero for low PRPAs, and then rapidly increased with increasing PRPAs above an apparent threshold, pt. The values of pt were approximately proportional to the ultrasound frequency, f, such that pt /f was approximately 0.5 MPa/MHz for DUS and 0.6 MPa/MHz for laboratory system exposures. The increasing thresholds with increasing frequency limited the GCH effect for contrast-aided DUS, and no GCH was seen for DUS at 5.0 or 7.4 MHz for the highest available PRPAs. (E-mail: [email protected]
Ultrasound in medicine & biology 06/2008; 34(10):1678-87. DOI:10.1016/j.ultrasmedbio.2008.03.001 · 2.21 Impact Factor
"Current output levels of diagnostic imaging devices are within the threshold for ultrasound-induced lung hemorrhage. For conditions investigated in Raeman et al. (1997), the presence of contrast agents in the vasculature does not increase the sensitivity of the lung to ultrasound-induced damage. Transient opening of the blood brain barrier with ultrasound and contrast agents was investigated by Hynynen et al. (2001). "
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