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Radiology/MRI vs. CT w/contrast for planning


I am preparing to have radiosurgery for three small brain metastases lesions - 5.5 mm, 8.5 mm and 5 mm - from inflammatory breast cancer. My insurance covered the MRI during planning, but because I changed medications and my doctor went on vacation, another MRI is needed because it has been over a month. However, insurance will not cover it.
They are suggesting a CT w/contrast. Since we are dealing in millimeters here, and radiating a margin of 1 mm of healthy tissue around the lesions, I don't want room for ANY error. Is a CT w/contrast comparable imaging to use for such critical planning? I can always pay cash for the MRI, $1,100, for something this critical. It is my brain, after all. Please advise. Thank you.

Hello, Leslie.

CT is very accurate, as is MRI. One difference is the technology used to create the images. CT uses x-ray, so you will receive a dose of ionizing radiation with CT. MRI uses sound waves within a magnetic field to create those images. There is no exposure to ionizing radiation with MRI.

One modality might be chosen over the other if the patient had a condition that would prevent one or the other. For example, if a patient is allergic to the contrast used in CT, an MRI might be a good substitute. On the other hand, if a patient has a pacemaker or is claustrophobic, or their insurance doesn't cover an MRI, a CT might do the trick. It's all up to the physician to decide.

Since I am not a physician, I am not qualified to treat disease. So, I would tend to go with what your physicians are recommending. If you're not sure about this decision, I'd advise you to get a second opinion.

I'm so sorry you are having to go through this. I hope you feel better soon.

Hope this helps,


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Delia White


Please do not ask me to diagnose or interpret images. I am not qualified to do so. I will reject all questions asking for my interpretation of images. I am the photographer, not the physician. I cannot "read" x-rays. Please consult a physician for that information. 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 and am registered as an X-ray, CT and MRI Technologist.

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