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Superthreshold Behavior of Ultrasound‐Induced Lung Hemorrhage in Adult Rats
Author(s) -
O'Brien William D.,
Simpson Douglas G.,
Frizzell Leon A.,
Zachary James F.
Publication year - 2005
Publication title -
journal of ultrasound in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 91
eISSN - 1550-9613
pISSN - 0278-4297
DOI - 10.7863/jum.2005.24.3.339
Subject(s) - medicine , lung , ultrasound , pulmonary hemorrhage , pathology , radiology
Objective The purpose of this study was to augment and reevaluate the ultrasound‐induced lung hemorrhage findings of a previous 5 × 3 factorial design study (Ultrasound Med Biol 2001; 27:267–277) that evaluated the role of pulse repetition frequency (PRF: 25, 50, 100, 250, and 500 Hz) and exposure duration (ED; 5, 10, and 20 s) on ultrasound‐induced lung hemorrhage at an in situ (at the pleural surface) peak rarefactional pressure [p r(in situ) ] of 12.3 MPa; only PRF was found to be significant. However, saturation (response plateau) due to the high p r(in situ) might have skewed the results. In this follow‐up 3 × 3 factorial design study, a wider range of PRFs and EDs were used at a lower p r(in situ) . Methods Sprague Dawley rats (n = 198) were divided into 18 ultrasonically exposed groups (10 rats per group) and 6 sham groups (3 per group). The 3 × 3 factorial design study (PRF: 17, 170, and 1700 Hz; ED: 5, 31.6, and 200 s) was conducted at 2 frequencies (2.8 and 5.6 MHz). The p r(in situ) was 6.1 MPa. Logistic regression analysis evaluated lesion occurrence, and Gaussian tobit analysis evaluated lesion depth and surface area. Results Frequency did not have a significant effect, so the analysis combined results for the 2 frequencies. For lesion occurrence and sizes, the main effects for PRF and ED were not significant. The interaction term was highly significant, indicating a strong dependence of lesion occurrence and size on the total number of pulses (PRF × ED). Conclusions The results of both studies are consistent with the hypothesis that the total number of pulses is an important factor in the genesis of ultrasound‐induced lung hemorrhage.