Effects of ambient pressure variation on the subharmonic response from contrast microbubbles: Effects of encapsulation

2013 ◽  
Vol 134 (5) ◽  
pp. 3992-3992
Author(s):  
Nima Mobaderasny ◽  
Kausik Sarkar
Keyword(s):  
Ambient Pressure ◽  
Pressure Variation ◽  
Subharmonic Response ◽  
Contrast Microbubbles

scholarly journals Improvement of Detection Sensitivity of Microbubbles as Sensors to Detect Ambient Pressure

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4083 ◽  
Author(s):  
Fei Li ◽  
Deyu Li ◽  
Fei Yan
Keyword(s):  
Scattering Amplitude ◽  
Ambient Pressure ◽  
Pressure Variation ◽  
Detection Sensitivity ◽  
Mechanical Index ◽  
Pressure Sensitivity ◽  
Acoustic Parameters ◽  
Promising Tool ◽  
Noninvasive Estimation ◽  
The Media

Microbubbles are considered a promising tool for noninvasive estimation of local blood pressure. It is reported that the subharmonic scattering amplitude of microbubbles decreases by 9 to 12 dB when immersed in the media under an ambient pressure variation from 0 to 180 mmHg. However, the pressure sensitivity still needs to be improved to satisfy clinical diagnostic requirements. Here, we investigated the effects of acoustic parameters on the pressure sensitivity of microbubbles through measuring the acoustic attenuation and scattering properties of commercially available SonoVue microbubbles. Our results showed that the first harmonic, subharmonic, and ultraharmonic amplitudes of microbubbles were reduced by 6.6 dB, 10.9 dB, and 9.3 dB at 0.225 mechanical index (MI), 4.6 dB, 19.8 dB, and 12.3 dB at 0.25 MI, and 18.5 dB, 17.6 dB, and 12.6 dB at 0.3 MI, respectively, when the ambient pressure increased from 0 to 180 mmHg. Our finding revealed that a moderate MI (0.25–0.4) exciting microbubbles could significantly improve their sensitivities to detect ambient pressure.

scholarly journals Observation of Pressure Variation in the Cavitation Region of Submerged Journal Bearings

1982 ◽  
Vol 104 (2) ◽  
pp. 157-163 ◽  
Author(s):  
I. Etsion ◽  
L. P. Ludwig
Keyword(s):  
Journal Bearing ◽  
Reverse Flow ◽  
Ambient Pressure ◽  
Journal Bearings ◽  
Pressure Variation ◽  
Pressure Measurements ◽  
Pressure Profiles ◽  
Cavitation Region ◽  
Cavitation Pressure ◽  
Visual Observations

Visual observations and pressure measurements in the cavitation zone of a submerged journal bearing are described. Tests were performed at various shaft speeds and ambient pressure levels. Some photographs of the cavitation region are presented showing strong reverse flow at the downstream end of the region. Pressure profiles are presented showing significant pressure variations inside the cavitation zone, contrary to common assumptions of constant cavitation pressure.

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