QUESTION: Dear Delia I have asked Lauren these question but she could not answer, iam hoping you can. I have attached MRI Image of spinal needle in subdural space. Could you tell me if this metal foreign body would cause burning or nerve damage after having 4 MRI preformed with needle in subdural space?Would you agree that needle is in subdural space on image or there about? The needle has been removed.If you can not answer questions can Micheal K please. I didn't think the questions would be that hard to answer if so please explain Thank you Tanya

ANSWER: Hello, Tanya.

I see the artifact from the metallic needle at the level of your sacrum. The artifact makes it impossible to see exactly where the tip of the needle is, and it appears that the contrast is in the spinal canal.

However, I cannot answer your question, either. I am an MRI technologist and not qualified to diagnose disease. For a second opinion, I recommend you see another physician or have these films ready by another radiologist.

Michael K is a radiologist and is better qualified to diagnose disease. He does not have the ability to answer questions posed to me. If you'd like his opinion, please direct your question to him.

Sorry I couldn't have been of more help. I hope you feel better soon.


---------- FOLLOW-UP ----------

QUESTION: Dear Delia          Dr Michael k is on vacation.Could you please estimate the length of needle on MRI by the scale in real life or your way of measuring needle in life.I have read it has a formula but i don't know it, could you please tell me measurement of length.       
Thank you Tanya

Sorry, Tanya. It is impossible to measure the size of any metallic foreign body with MRI. In MRI, you do not see metal directly. You only see the artifact that the metallic object creates in the magnetic field.

Do you see the dark spot with a white rim near the bottom quarter of this image? That is the artifact created by the metallic needle. The dark artifact protrudes into the white fat layer behind the spine. Do you see how the anatomy in front of this artifact is smeared, like it's being sucked into the darker area?

A ferrous object diverts magnetic flux lines to go around the object, which causes this type of artifact. Because the flux lines are diverted, the image around a ferrous object is distorted.

Because you cannot see a ferrous metallic image directly and because an MR image is distorted near a metallic object, the metallic object cannot be measured with MRI.

Hope this help,


All Answers

Answers by Expert:

Ask Experts


Delia White


I am not qualified to interpret diagnostic imaging or to diagnose disease. Please consult a physician for that information. I am the photographer. I can tell you what to expect during most MRI, CT and X-ray procedures.


I now have more than 30 years experience in diagnostic imaging. My specialty is MRI. I am also very familiar with CT and the way we used to take x-rays (everything's digital now)!

I received my Bachelor of Science degree in Radiologic Technology.

©2017 All rights reserved.