问题 单项选择题 A1型题

高度怀疑眼内磁性异物时,哪种检查应为禁忌()。

A.B超

B.UBM

C.MRI

D.X线照片

E.CT检查

答案

参考答案:C

解析:该题是基本概念题,备选答案是眼科常用的影像学检查。MRI是利用人体内的氢原子中的质子在强磁场内被相适应频率的射频脉冲激发,质子吸收能量产生共振。射频脉冲终止后质子恢复原态时释放出能量,即MRI信号,通过接收线圈接收并经计算机转换成MRI图像。凡球内、眶内及体内存留磁性金属异物及治疗性磁性物体者禁用,佩戴心脏起搏器者为绝对禁忌。

选择题
单项选择题

The great advance (91) rocket theory 40 years ago showed that liquid-fuel rockets were far (92) in every respect to the skyrocket with its weak solid fuel, the only kind of rocket then known. (93) , during the last decade, large solid-fuel rockets with (94) fuels about as powerful as liquid fuels have (95) their appearance, and it is a favorite layperson’s question to (96) which one is "better". The question is meaningless. (97) might as well ask whether a gasoline or a diesel engine is "better". It all (98) on the purpose. A liquid-fuel rocket is complicated, (99) has the advantage that it can be controlled beautifully. The burning of the rocket engine can be stopped completely; it can be reignited when (100) . (101) , the thrust can be made to vary by adjusting the speed of the fuel pumps. A solid-fuel rocket, on the other hand, is rather (102) in construction, (103) hard to build when a really (104) size is desired. But once you have a solid-fuel rocket, it is ready for action (105) very short notice. A liquid-fuel rocket has to be fueled first and cannot be (106) readiness for very long after it has been fueled. (107) , once a solid-fuel rocket has been ignited, it will keep burning. It cannot be stopped and reignited (108) desired (it could conceivably be stopped and reignited after a pre-calculated time of burning has elapsed, and its thrust cannot be varied. Because a solid-fuel rocket can be kept ready for a long time, most military missiles (109) solid fuels, but human-piloted spaceflight needs the fine adjustments that can (110) be provided by liquid fuels.

A.For example

B.However

C.In addition

D.Meanwhile