Why are MRI images reversed?

[yhboi69]

Hello everyone. For the life of me I can’t figure out why left on an MRI is the patients right and vice versa. If we look at he images below, this is how I see it. I have flipped the image so the liver is on the right.



So how exactly does an MRI produce an image which is in that orientation? Thank you!

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[libertyyne]

IIRC convention is you are looking at the patient from their feet up .

 

[Brawndo2016]

In all forms of cross sectional axial imaging you view the images as though you are standing at the patient's feet.

 

[yhboi69]

Aah yes so that’s what my lecturers meant all this time. I see it now thank you very much!

 

[Ho0v-man]

Every image presented for interpretation must be in the anatomic position, axial, sagittal, coronal or otherwise. This way no matter what is presented, right and left are always in the same position so the interpreter doesn’t have to re-orient him/herself each time.

 

[CherryRedDracul]

You flipped the patient's left and right AND put the patient prone in the second image, FYI.

But yes, cross sectional imaging is looked at as if you were looking from the foot of the patient's bed, so to speak. Plain films, in general, are looked at as if you were facing the person/body part.

It gets a little more wonky in nuclear medicine where, in some studies, the image's left corresponds to the patient's left.

 

[DeucesHigh3]

Hello everyone. For the life of me I can’t figure out why left on an MRI is the patients right and vice versa. If we look at he images below, this is how I see it. I have flipped the image so the liver is on the right.



So how exactly does an MRI produce an image which is in that orientation? Thank you!

Also, FYI those are pics from a contrast enhanced CT, not an MR.

 

[CaptainSSO]

Looks like acute chole.

 

[libertyyne]

Looks like acute chole.

Does the a swath of the liver appear hypodense/increased opacity in acute chole?

 

[DeucesHigh3]

Does the a swath of the liver appear hypodense/increased opacity in acute chole?

Nah. You will see some pericholecystic fluid which is hypoattenuating, but the liver parenchyma itself remains normal in appearance (except for maybe a thin rim of hyperemia as seen on a contrast study or HIDA scan). I guess the only exception would be if things go really bad, and a hepatic abscess develops, which is also hypoattenuating.

This picture is showing a very distended gallbladder, and the arrow is pointing to some adjacent fat stranding.

 

[libertyyne]

Nah. You will see some pericholecystic fluid which is hypoattenuating, but the liver parenchyma itself remains normal in appearance (except for maybe a thin rim of hyperemia as seen on a contrast study or HIDA scan). I guess the only exception would be if things go really bad, and a hepatic abscess develops, which is also hypoattenuating.

This picture is showing a very distended gallbladder, and the arrow is pointing to some adjacent fat stranding.

I guess i was noticing the difference in attenuation between the yellow star and black star.

 

[DeucesHigh3]

I guess i was noticing the difference in attenuation between the yellow star and black star.

Ah, there's the confusion. Gold star is liver. Black star is gallbladder. Red arrow is infiltration of the surrounding fat.

 

[libertyyne]

Ah, there's the confusion. Gold star is liver. Black star is gallbladder. Red arrow is infiltration of the surrounding fat.

Wow that looks like it is massive for being a gallbladder.

 

[evilbooyaa]

Wow that looks like it is massive for being a gallbladder.

Welcome to fat fertile forty female (whatever the fifth F is) gallbags.

That pic looks pretty solid for acute cholecystitis.

Otherwise - yes to what everybody else said: Looking at the patient from their feet up, this is a CT (not MRI).

 

[siliso]

Imagine the patient with their feet pointed toward you. The logic is that Right means the patient’s Right: the liver is on the right side of the patient. The spleen on their left side. It does make it funny now when I point out the rightmost person X in a photo who is to everyone nonmedical the leftmost. But if I asked the people posing for the picture, they would all have agreed that person X was to their right.