That is done using ultrasound, which is generated by a box called a pulse-generator that is similar in size to a pacemaker box, but is inserted lower down in the chest (see illustration).

这个问题可以通过使用超声波来解决，也就是利用一个大小和心脏起搏器差不多，名为“脉冲发生器”的盒子来完成，但是它需要被放在胸腔下部(如上图所示)。

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Corduroy blinked.There was a chair and a chest of drawers, and alongside a girl-size bed stood a little bed just the right size for him.

小熊眨着眼睛，房间里有一把椅子和一个有抽屉的柜子，和女孩床并列的还有一张刚好容得下他的小床。

youdao

Corduroy blinked. There was a chair and a chest of drawers, and alongside a girl-size bed stood a little bed just the right size for him.

小熊眨着眼睛，房间里有一把椅子和一个有抽屉的柜子，和女孩床并列的还有一张刚好容得下他的小床。

youdao

For this scene and a specific, the emergency room, they didn't have - like a child gauge chest(ph) tube, but they can't leave the child bleed in his chest till he dies so they use the adult-size chest tube.

NPR: Doctor Takes Camera 'Inside the Red Zone' of War

So at depth they've really scrunched up into this area of my chest and reduced in size dramatically.

BBC: Breakfast with Frost

After a fainting spell, a patient would hold a pager-size communicator over his chest and press a button to freeze the recording, so a doctor could upload the data for analysis.

FORBES: Magazine Article