Experimental verification of acoustic saturation

Yang

Ultrasound in Medicine & Biology

et al. 2006

The objective of this study was to assess the threshold and superthreshold behavior of ultrasound (US)-induced lung hemorrhage in adult rabbits to gain greater understanding about species dependency. A total of 99 76 ± 7.6-d-old 2.4 ± 0.14-kg New Zealand White rabbits were used. Exposure conditions were 5.6-MHz, 10-s exposure duration, 1-kHz PRF and 1.1-μs pulse duration. The in situ (at the pleural surface) peak rarefactional pressure, p r(in situ) , ranged between 1.5 and 8.4 MPa, with nine acoustic US exposure groups plus a sham exposure group. Rabbits were assigned randomly to the 10 groups, each with 10 rabbits, except for one group that had nine rabbits. Rabbits were exposed bilaterally with the order of exposure (left then right lung, or right then left lung) and acoustic pressure both randomized. Individuals involved in animal handling, exposure and lesion scoring were blinded to the exposure condition. Probit regression analysis was used to examine the dependence of the lesion occurrence on in situ peak rarefactional pressure and order of exposure (first vs. second). Likewise, lesion depth and lesion root surface area were analyzed using Gaussian tobit regression analysis. Neither probability of a lesion nor lesion size measurements was found to be statistically dependent on the order of exposure after the effect of p r(in situ) was considered. Also, a significant correlation was not detected between the two exposed lung sides on the same rabbit in either lesion occurrence or size measures. The p r(in situ) threshold estimates (in MPa) were similar to each other across occurrence (3.54 ± 0.78), depth (3.36 ± 0.73 and surface area (3.43 ± 0.77) of lesions. Using the same experimental techniques and statistical approach, great consistency of thresholds was demonstrated across three species (mouse, rat and rabbit). Further, there were no differences in the biologic mechanism of injury induced by US and US-induced lesions were similar in morphology in all species and age groups studied. The extent of US-induced lung damage and the ability of the lung to heal led to the conclusion that, although US can produce lung damage at clinical levels, the degree of damage does not appear to be a significant medical problem.

Section: Exposimetrymentioning

confidence: 99%

Threshold estimation of ultrasound-induced lung hemorrhage in adult rabbits and comparison of thresholds in mice, rats, rabbits and pigs

Yang

Ultrasound in Medicine & Biology

et al. 2006

“…Water-based (degassed water, 22 • C) pulse-echo ultrasonic field distribution measurements were performed according to established procedures [19], [27] (Table I). An automated procedure, based on established standards [28], [29], was used to routinely calibrate the ultrasound fields [19], [30], [31]. Briefly, the source transducer's drive voltage was supplied by a RAM5000 (Ritec, Inc., Warwick, RI).…”

Section: A Exposimetrymentioning

confidence: 99%

Superthreshold behavior and threshold estimation of ultrasound-induced lung hemorrhage in pigs: Role of age dependency

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

et al. 2003

Self Cite

Age-dependent threshold and superthreshold behavior of ultrasound-induced lung hemorrhage were investigated with 116 2.1 0.3-kg neonate crossbred pigs (4.9 1.6 days old), 103 10 1.1-kg crossbred pigs (39 5 days old), and 104 20 1.2-kg crossbred pigs (58 5 days old). Exposure conditions were: 3.1 MHz, 10-s exposure duration, 1-kHz pulse repetition frequency (PRF), and 1.2-s pulse duration. The in situ (at the pleural surface) peak rarefactional pressure ranged between 2.2 and 10.4 MPa with either eight or nine acoustic pressure groups for each of the three pig ages (12 pigs/exposure group) plus sham exposed pigs. There were no lesions in the shams. Pigs were exposed bilaterally with the order of exposure (left then right lung, or right then left lung) and acoustic pressure both randomized. Pig age was not randomized. Individuals involved in animal handling, exposure, and lesion scoring were blinded to the exposure condition. Logistic regression analysis was used to examine the dependence of the lesion incidence rates on in situ peak rarefactional pressure, left versus right lung exposure, order of exposure (first versus second), and age in three age groups. Likewise, lesion depth and lesion root surface area were analyzed using Gaussian tobit regression analysis. A significant threshold effect on lesion occurrence was observed as a function of age; younger pigs were less susceptible to lung damage given equivalent in situ exposure. Overall, the oldest pigs had a significantly lower threshold (2.87 0.29 MPa) than middle-aged pigs (5.83 0.52 MPa). The oldest pigs also had a lower threshold than neonate pigs (3.60 0.44 MPa). Also, an unexpected result was observed. The ultrasound exposures were bilateral, and the threshold results reported above were based on the lung that was first exposed. After the first lung was exposed, the pig was turned over and the other lung was exposed to the same acoustic pressure. There was a significant decrease (greater than the confidence limits) in occurrence thresholds: 3.60 to 2.68, 5.83 to 2.97, and 2.87 to 1.16 MPa for neonates, middle-aged, and oldest pigs, respectively, in the second lung exposed. Thus, a subtle effect in lung physiology resulted in a major effect on lesion thresholds.

“…An automated procedure based on established standards [27], [28] was used to routinely calibrate the ultrasound fields [19], [25], [26]. Briefly, the source transducer's drive voltage was supplied by a RAM5000 (Ritec, Inc., Warwick, RI) that had the capability to deliver up to a 5-kW single-cycle pulse into a 50-Ω load (Fig.…”

Section: A Exposimetrymentioning

confidence: 99%

Superthreshold behavior and threshold estimates of ultrasound-induced lung hemorrhage in adult rats: role of beamwidth

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

Frizzell

et al. 2001

Self Cite

It is well documented that ultrasound-induced lung hemorrhage can occur in mice, rats, rabbits, pigs, and monkeys. The objective of this study was to assess the role of the ultrasound beamwidth (beam diameter incident on the lung surface) on lesion threshold and size. A total of 144 rats were randomly exposed to pulsed ultrasound at three exposure levels and four beamwidths (12 rats per group). The three in situ peak rarefactional pressures were about 5, 7.5, and 10 MPa. The four 19-mm-diameter focused transducers had measured pulse-echo -6-dB focal beamwidths of 470 m (2.8 MHz; f/1), 930 m (2.8 MHz; f/2), 310 m (5.6 MHz; f/1), and 510 m (5.6 MHz; f/2). Exposure durations were 10 s, pulse repetition frequencies were 1 kHz, and pulse durations were 1.3 s (2.8 MHz; f/1), 1.2 s (2.8 MHz; f/2), 0.8 s (5.6 MHz; f/1) and 1.1 s (5.6 MHz; f/2). The lesion surface area and depth were measured for each rat as well as the percentage of rats with lesions per group. Logistic regression analysis and Gaussian-Tobit analysis methods were used to analyze the data. The effects of in situ peak rarefactional pressure and beamwidth were highly significant, but ultrasonic frequency was not significant. In addition, the estimated interaction between in situ peak rarefactional pressure and beamwidth was positive and highly significant. The ultrasound beamwidth incident on the lung surface was shown to strongly affect the percentage and size of ultrasound-induced lung hemorrhage lesions. Even though ultrasonic frequency was an experimental variable, it was not shown to affect the lesion percentage or size.