Finally, I know the truth. Why are you taking off your clothes?

Prevent foreign bodies on clothes in vitro from causing artifacts, leading to misdiagnosis and missed diagnosis.

1. This is a normal chest X-ray. This is the standard film after removing the bra. There is no foreign body in the lung field we see. The lungs, heart and bones are clearly visible.

2, this is not a bra photo. Comparing the first one, we see that the red arrow is a necklace worn around the neck, and the yellow arrow refers to the buttons and rims of the bra. These foreign bodies in vitro overlap with the bones and lungs we want to observe. If there are lesions in these parts, these foreign bodies in vitro will block the lesions, leading to missed diagnosis and misdiagnosis.

However, not all female patients have to take off their bras when they come to radiology. But which part to shoot requires that there is no foreign body such as metal in that part. For example, if you want to shoot the chest, you need to have no X-ray-opaque objects such as metal on the chest, such as metal buttons on bras and clothes. At this time, you need to take off your clothes and bra. But if you want to pat your legs, just make sure that there is no metal in the corresponding leg parts, and you don't need to take off your bra. General materials will not leave traces on the film, except special keys.

For CT, the principle is the same. Where to shoot? There can't be anything metal in that part. For example, oropharyngeal CT scan, if there are metal dentures, they need to be removed, otherwise there will be metal artifacts. CT said the word "metal artifact".

For MR examination, it is a completely different concept. There is a magnetic field formed by a huge magnet in the magnetic vibration room. Precession hydrogen nuclei (H+) in human tissues are nutated by magnetic pulse to generate radio frequency signals, which are imaged by computer. Because there are huge magnets in the computer room, all items with magnetism and metal can't enter the computer room, such as bank cards, keys, earrings and necklaces. If you bring it in, the bank card will be demagnetized, and metal objects will be sucked into the machine and can't be pulled out. At this time, the whole computer room needs to be powered off, so that the machine can be used again after degaussing and debugging.

In this process, the loss is huge. It is especially important to note that if there is a metal implant in the body, try not to do it, otherwise it will cause the metal implant in the body to move and cause soft tissue damage. Therefore, magnetic resonance imaging requires patients to change all their clothes and tell doctors whether they have a history of metal implantation. Magnetic resonance examination is much stricter than X-ray and CT.

References:

Baidu Encyclopedia/Medical Imaging