| Background and objectiveThe detecting of intracardic pressure is valuable of evaluating cardiac function and instructing treatment in cardiac surgeries. Nowadays we measure the reversion of valves and obtain the Peak pressure gradient and Mean pressure gradient using the Bernoulli's equation to detecting of intracardic pressure noninvasivly. But for patients with no valve reversion we can only use the catheter as an invasive way which may be result in some serious outcomes like infection, painfulness and rupture of the catheter. It also demands the eminant equipment and skilled operat -or. So the application of the two methods is restricted.Backscatter technology, an acoustic density analyzing technology, one of the tissue evaluation ways, is developing quickly recent years and applied in researchs ofcardiac and others. Microbubble of contrast agent is a good scatter and in vitro experiments it appears that the acoustic density decreases as the surrounding pressure increasing. This phenomenon is attribute to compression or rupture of the microbubbles. This experiment plans to verify the feasibility of detecting the intracardic pressure noninvasivly with the contrast agent and backscatter technology.Material and methods1. Preparation of contrast agentThe mixture of twenty milliliter mixture of 5% Dextron and 20% albumin which are mixed as a proportion of 12 to 1 and ten milliliter octafluoropropane are sonicated by the Misonix sonicator 3000 at 90W for 110 second.The finished product is preserved under 4 .2. Simulative experiment in vitroPrepare an obturation container so that we can adjust the pressure with a sphygmomanometer. Under the mode of AD of Hp sonos 5500 machine, keep the parameter of TGC and LGC stably at Gain 50% and depth 5cm. The probe is 3cm to the base of the container. Add 0.5ml contrast agent into the container.mixed gently. Fifteen seconds later, save the map in MO from beginning to 7.5 minute with a interval of 30 seconds under the pressure of 0, 40, 80, 120, 160, 200mmHg individually. Then save the map in MO under the pressure of 0, 40, 80, 120, 160, 200mmHg individually under the parameter of MI at 0.4,0.6 and 0.8, frequency at 2,2.5, 3, 3.5, 4MHZ and 7, 17, 27, 37掳C of surrounding. The course is repeated for three times.3. Experiment in vivoFive rabbits are intubated from carotid to left ventricle under the supervise of ultrosound after anaesthesia. The pressure of LV is recorded by a pressure transducer. Inject contrast agent from the marginal vein, save the map after the emergence of contrast agent in LV and record the curve of LV pressure.Inject contrast agent when the pressure decreases by using Urapidil and save the maps.4. Data analysisWe analyse the data in a specified ROI of 21*21 piexl under the depth of 1, 2, 3, 4 and 5cm individually and record the mean level of intergrated backscatter(IBS). We deal the data of MI, temperature, frequency, depth, pression and the intergrated backscatter with multianalysis of SAS software and observe whether it is correlation between the time and IBS. We also use the Medlab system to obtain the intracardiac pressure and observe whether it is related with the IBS value.Results1. The contrast agent we prepared is well-preportioned, stable and safe.2. Simulative experiment in vitro: 1) IBS value decreases with the pressure of container increasing from 0 to 200mmHg. 2) IBS value increases with the MI increasing from 0.2 to 0.8. 3) IBS value decreases with the temperature increasingabove 7 and IBS value of the group of 7 is less than other groups. 4) IBS value increases with the sampling depth change from 1 to 5cm. 5) IBS value reach the maxmum around the frequency of 3.5MHZ when the pressure changes. 6) IBS value decreases with time going up and the decreasing range and velocity under high pressure are more than those under low pressure. 7) Multivariate analysis of MI, temperature, frequency, depth, pressure and the intergrated backscatter indicates pressure and temperature have negativ... |
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