Imaging - opaque/hyperdense etc

[Lothric]

Hey,

I have a problem with associating imaging with specific conditions. For example, I wrote that demyelination is always hyperintense on MRI but this is wrong as it can be hypointense too depending on what type of MRI is taken. Does this apply for CT/simple x-ray too?

For example, a tumor of liver is always radiolucent or hypodense. Can it be hyperdense/opaque too? When saying radiolucent etc. Is this assuming there is a contrast too?

MRI with contrast Is always hyperintense. With CT or x-ray it may still be radiolucent/hypodense?

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[073116]

Hey,

I have a problem with associating imaging with specific conditions. For example, I wrote that demyelination is always hyperintense on MRI but this is wrong as it can be hypointense too depending on what type of MRI is taken. Does this apply for CT/simple x-ray too?

Dude it's just terms - if you understand the principle behind them - you can use them accordingly. Usually term "intensity" is used for MRI - like hypo- or hyperintense (or low and high signal). For CT/x-ray images are usually described using radiodense or opaque/lucent etc. It doesn't matter essentially what you chose to use as long as you match image to proper wording. Like for T1 MRI and T2 MRI you can switch terms used.

For example, a tumor of liver is always radiolucent or hypodense. Can it be hyperdense/opaque too? When saying radiolucent etc. Is this assuming there is a contrast too?

No, with contrast it can't be radiolucent. It will be opaque/dense. However, tumor can be anything really - it can be more or less dense compared to liver tissue (different types of tumor) and hence will be more opaue or lucent. Once again - it doesn't matter what term you use as long as it matches the image in question: e.g. if tumor is denser than liver - it should be called opaque/dense/radioopaque.

P.S. Contrast is used to help differentiate tissues, to help better visualize form, shape of tumor or other structures like small/large intestines etc. It just so happens that most contrasts used are opaque/dense as they consist of heavier atoms (as compared to usual body carbon, hydrogen, nitrogen etc).

MRI with contrast Is always hyperintense. With CT or x-ray it may still be radiolucent/hypodense?

For CT/x-ray contrast will always be radioopaque/opaque or dense. The basic principle is that contrast will attain/accumulate x-rays and image will be whiter (usually non attenuated x-rays that were not stopped by any mass that they went through - will hit the film and convert silver to black dots. With digital it's now a bit different - you can reverse it or make it any color and call it opposite like in MRI (T1, T2 etc), but it's agreed to call it opaque/radiodense/radioopaque for whiter image (meaning x-rays were attenuated and didn't reach the "film").

 

[Lothric]

Hi,

If contrast agents cause increased opacity then how come that on angiography the contrast agents make the vessels darker? Shouldnt they become more opaque?