Nonlinear Acoustic Shadow Method to Reduce Reverberation Artifact

A novel technique for reducing reverberation artifact in acoustic shadow imaging using nonlinear ultrasound interaction, called nonlinear acoustic shadow method, has been developed and experimentally studied. In this technique, the conventional acoustic shadow method is modified by using the secondary wave generated by nonlinear interaction of two primary sound waves emitted from parametric array. Either conventional or nonlinear acoustic shadow imaging is carried out for aluminum square cylinder and the size of the shadow is compared. The result shows that the nonlinear acoustic shadow method reduces reverberation artifact inside the square cylinder and has better accuracy in the size measurement than conventional acoustic shadow method.

开腹手术所致手术中氧化应激反应的预防

背景有观点认为，各种活性氧成分早期即参与了手术应激和损伤，但尚未得到证实；医疗手段对氧化应激反应的作用也不明确。方法测定血中氢过氧化物的水平，作为细胞损伤的氧化应激指标；同时测定血浆铁还原能力，作为总抗氧化能力的指标。拟行乙状结肠切除术的患者分为4组：七氰烷麻醉下开腹乙状结肠切除术组；七氟烷麻醉下腹腔镜乙状结肠切除术组；丙泊酚麻醉下开腹乙状结肠切除术组；丙泊酚麻醉下腹腔镜乙状结肠切除术组。结果七氟烷开腹乙状结肠切除术组患者的血浆铁还原能力显着降低，由387mmol／L降至153mmol／L，氢过氧化物水平没有变化，这表明手术中患者的氧化应激反应有所增加。氢过氧化物，是一种典型的细胞氧化产物，它并没有明显变化，可能是由于手术中增加的氧化应澈反应还不足以损伤细胞。七氟烷腹腔镜乙状结肠切除术组中，氢过氧化物水平和铁还原能力都没有明显改变，表明腹腔镜手术不会增加手术的氧化应激反应。丙泊酚麻醉2个组，氢过氧化物术毕都明显下降，分别为120±73UCarr和144±107UCarr（1UCarr=0．8mg／L H2O2）。结论开腹手术会增加手术中的氧化应激反应，腹腔镜手术则不会；丙泊酚作为抗氧化剂能够有效地减少手术中的氧化应激反应。