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Intravenous microbubble oscillation in the presence of ultrasound has the potential to yield a wide range of therapeutic benefits. However, the likelihood of vessel damage caused by mechanical effects has not been quantified as a function of the numerous important parameters in therapeutic ultrasound procedures. In this study, we examined the effects of microbubbles injected into the vasculature of the earthworm. It was found that the elastic properties of earthworm blood vessels are similar to those of arteries in older humans, and that earthworms are well suited to the large number of experiments necessary to investigate safety of procedures involving microbubble oscillation in sonicated vessels. Microbubbles were infused into earthworm vessels, and the rupture time during sonication was recorded as a function of ultrasound frequency, pulse repetition frequency and acoustic pressure. A modified mechanical index (MMI) was defined that successfully captured the trends in rupture probability and rupture time for the different parameter values, creating a database of vessel rupture thresholds. In the absence of bubbles, the product of MMI squared and rupture time was approximately constant, indicating a possible radiation-force effect. The MMI was an effective correlating parameter in the presence of bubbles, though the mathematical dependence is not yet apparent. The results of the study are expected to be valuable in designing more refined studies in vertebrate models, as well as informing computational models. [ABSTRACT FROM AUTHOR]

Purpose: To measure gamma and alpha brain wave activity as a measurement of concentration and stress levels during surgical simulator performance of laparoscopic tasks to determine if expert surgeons have different brain activity patterns compared with intermediate and novice surgeons. Materials and Methods: After obtaining Institutional Review Board approval, 1st and 2nd year medical students, urology residents (PGY2-PGY5), and attending urologists from one institution were recruited. Participants were stratified by level of experience and performed laparoscopic tasks on the EDGE laparoscopic simulator. Subjects were evaluated for concentration and stress levels using the electroencephalography (EEG) data extracted from the MUSE™ headband. The MUSE software developer kit (SDK) allowed quantification of gamma and alpha waves during each task. An analysis of variance was used to compare concentration and stress levels between groups. Results: A total of 19 participants were recruited for the study and stratified by surgical experience into novice, intermediate, and expert laparoscopy groups: 6 medical students, 9 urology residents, and 4 attending urologists, respectively. Concentration and stress were quantified by calculating the area under the curve of the gamma and alpha EEG wave tracings. Stress was significantly lower in the attending urologists compared with the residents and medical students during the laparoscopic suturing and trended toward significance in the peg transfer task ( P = 0.0003, P = 0.069). Concentration was significantly higher in the expert group compared with the less experienced groups during both the peg and suture tasks ( P = 0.036, P = 0.0039). Conclusions: EEG brain activity in more experienced surgeons reveals a significant increase in concentration levels with a decrease in stress during simulated laparoscopic tasks compared with novices. This information may correlate with increased proficiency as well as provide objective feedback of progress along the learning curve with the MUSE SDK. [ABSTRACT FROM AUTHOR]

Background: Safety analyses of transcranial therapeutic ultrasound procedures require knowledge of the dependence of the rupture probability and rupture time upon sonication parameters. As previous vessel-rupture studies have concentrated on a specific set of exposure conditions, there is a need for more comprehensive parametric studies. Methods: Probability of rupture and rupture times were measured by exposing the large blood vessel of a live earthworm to high-intensity focused ultrasound pulse trains of various characteristics. Pressures generated by the ultrasound transducers were estimated through numerical solutions to the KZK (Khokhlov-Zabolotskaya-Kuznetsov) equation. Three ultrasound frequencies (1.1, 2.5, and 3.3 MHz) were considered, as were three pulse repetition frequencies (1, 3, and 10 Hz), and two duty factors (0.0001, 0.001). The pressures produced ranged from 4 to 18 MPa. Exposures of up to 10 min in duration were employed. Trials were repeated an average of 11 times. Results: No trends as a function of pulse repetition rate were identifiable, for either probability of rupture or rupture time. Rupture time was found to be a strong function of duty factor at the lower pressures; at 1.1 MHz the rupture time was an order of magnitude lower for the 0.001 duty factor than the 0.0001. At moderate pressures, the difference between the duty factors was less, and there was essentially no difference between duty factors at the highest pressure. Probability of rupture was not found to be a strong function of duty factor. Rupture thresholds were about 4 MPa for the 1.1 MHz frequency, 7 MPa at 3.3 MHz, and 11 MPa for the 2.5 MHz, though the pressure value at 2.5 MHz frequency will likely be reduced when steep-angle corrections are accounted for in the KZK model used to estimate pressures. Mechanical index provided a better collapse of the data (less separation of the curves pertaining to the different frequencies) than peak negative pressure, for both probability of rupture and rupture time. Conclusion: The results provide a database with which investigations in more complex animal models can be compared, potentially establishing trends by which bioeffects in human vessels can be estimated. [ABSTRACT FROM AUTHOR]