Dr. Varun Chaudhry
Radiodiagnosis
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Patient's Query
Hi doctor,
I just had a CTA of the brain and neck. So I had multidetector volumetric CT acquisition of head from skull base to the vertex, which produced axial, coronal, and sagittal images. The intravenous multidetector CT angiography of the aortic arch to vertex was obtained. I was in the CT scan room for five minutes with the ceiling all red. I heard CT scan going. Then after five minutes, the contrast went on. I was in there for 10 to 15 minutes. Is that normal? How much radiation is that?
Hi,
Welcome to icliniq.com.
Thanks for your query, and I hope you are doing well. A CT (computed tomography) angiogram of the head and neck is a lengthy procedure as we have to plan the pre and post-contrast sequences from upper chest to vertex. Usually, the radiation dose is 6 to 10 mSv (mSv is millisievert which is a radiation unit). The average limit for a person of the general public per year is 20 mSv. So 10 to 15 minutes for a CT angiogram is a bit long, but different places and different scanners have different acquisition times. You can find many articles on the internet if you wish to please go through them. I hope this helps. Thanks.
Patient's Query
Hi doctor,
Thanks for the reply.
While I was inside, the top of the CT turned red, and I could hear it making sounds for about five minutes. Could they have been calibrating it? After five minutes, they said, you will now feel the dye coming. After that, I could feel the dye and be in there for about three minutes. Do you think radiation was coming out in the initial five minutes? Thank you.
Hi,
Welcome back to icliniq.com.
I do not think you would have got the radiation in the five minutes when it went red. The gantry has a magnet, and it always makes some noise when the scanner is on. That does not mean you would have received radiation during this period. They also do some planning sequences before contrast administration which gives negligible radiation. So I think most of the radiation you would have got would be when scanning you while giving you contrast. Thanks.
Patient's Query
Hello doctor,
Thanks for the reply.
I was receiving an angiogram of the head and neck. I need to reword. While I was having the CT angiogram of head and neck with contrast, they moved me into the CT scan back and forth. Then it became on, and the inside in the ceiling, there was red radiation over me for five minutes. Could they have been calibrating? Why was the red radiation switched on? Then they said I would feel the contrast. After that, I was out in two minutes. Was the red color of the ceiling due to radiation? Do you think I got radiation the whole time?
Hi,
Welcome back to icliniq.com.
As I said in the previous reply, when the red light was on, they might have done some planning sequences, which gives negligible radiation usually. It is not usual for a CT head and neck to keep giving radiation for this long. But each scanner is different, and it may be worth checking with the radiographer or the hospital where you were scanned. Thanks.
Patient's Query
Hi doctor,
Thanks for the reply.
Does the red light in the CT scan ceiling mean radiation? It looked electrical. How much extra radiation could planning sequences involve? Is it normal? How much radiation would I have been exposed? Could you guess it? Please explain. Thank you.
Hi,
Welcome back to icliniq.com.
It depends on the scanner type as different scanners have different mechanisms. Unfortunately, I could not guess your exposure rate. But I suggest you, please discuss with the people or the center that scanned you. They will also tell you how much radiation you have got since most modern scanners record the scan dose. Planning sequences gives a negligible dose. I hope this helps you.
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Radiodiagnosis
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