CT scan versus MRI (Can I have an MRI instead of a CT?)

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CT scan versus MRI (Can I have an MRI instead of a CT?)

I had a Hepatic flexure tumour (adenocarcinoma) discovered in my large intestine, subsequent Right Hemicolectomy then 14 cycles of Chemotherapy and have had 3 CT scans (Chest/Abdo)and another one is coming up soon to monitoring for any abnormalities. Been in the clear for just over 2 years. I'm a bit worried about the safety of having additional CT scans with the high doses of radiation that goes with them. I have read some scientific reports saying that the huge dose of radiation that you get with a CT scan may increase your risk of additional cancers developing later in life (I'm 34). Is anyone being monitored post bowel cancer with a MRI which is magnetic rather than radiation (CT)? I'd much prefer to lay in a small tube for an hour than to end up glowing in the dark after one too many CT scans. The Dr's always quote that its the same radiation as going on a few overseas plane trip's but I'm not so sure. I don't want to incease my future risk if a MRI will give the same infomation. Ant thoughts? Thanks
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Re: CT scan versus MRI (Can I have an MRI instead of a CT?)

Hi MeAgain, This is something I am pondering, (I am also 34 this year), I have a brain tumour which requires MRI's every 3 months, but also a facial tumour (which is benign), but for that the surgeon orders CT scans every 3-6months (sometimes more often) if I get additonal vertigo or more pain etc from that particular tumour as apparently it obtains a better picture of that particular tumour with better bone definition with a CT - however, my argument to him is that this may not necessarily be very good for my 'more malignant' brain tumour and may infact bring this tumour out of remission, and could he take that into consideration and just use the MRI scans already taken by the neuro guys. I did curtail the CT last visit - but I have the same discussion every revisit. I think the best thing would be just to ask your doctors advice, and why they believe one test is better than the other - also the cost factor may be their only concern - tell them you are willing to pay the difference (on average $500 out of pocket expense for MRI) if you so wish. Best of luck with your journey - I know how these little things can play on your mind, Nicole
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Re: CT scan versus MRI (Can I have an MRI instead of a CT?)

I am in a similar situation with CT scans every 12 months now for bowel cancer. Personally, I am claustrophobic and the thought of an MRI absolutley freaks me out. Maybe I am naieve but I have faith in the knowledge of my doctors when the dangers are weighed against each other. As we all know, in a perfect world none of us would be in the situation to have to ponder these things. In saying that, it is something that I may discuss with my doctors. S
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Re: CT scan versus MRI (Can I have an MRI instead of a CT?)

I have had this discussion with my doc's several times and they have always told me that for my cancer a CT is more valuable but I think I will ask again next time. I'd hate to think it comes down to cost Nicole but I have a feeling you may be right. There has been a lot in the news in the last week hasn't there on the concerns of overusing CT's and the risks involved. Thanks MeAgain for bringing it up, I hope you get some answers from your Doc's too. Sharon
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Re: CT scan versus MRI (Can I have an MRI instead of a CT?)

Sorry, Didnt mean to imply that cost would be the only deciding factor (sorry ;)) - but it was one of the things my 'face' guy brings up, when he forgets that I already have the MRI's every three months for the brain tumour - although once you reach the maximum medicare level thing it is cheaper of course (onlytwo to three MRI's each year and you are there)- unless you only have to pay for them in QLD?? I know unless you are hospitalised at the time you have to pay for an MRI, but CT's are bulkbilled. I think this is an excellent topic - it has been in the news this week. A lot of people at work etc, talk back radio etc have been saying that's it, I am never having a CT scan ever - I don't know about you guys - I was initially not diagnosed when I first started showing symptoms for both of my tumours (they didnt use contrast) with CT, but then was diagnosed three months later by CT scan (using contrast) - so very, very valuable tool (the media can really beat things up -I think we really need to trust in our doctors judgement) - and one tumour requires monitoring with CT better and the other tumour MRI is better - so have had many of both in the last 18 months. Hopefully your doctors do explain to your satisfaction why they feel one test is better than the other for your particular tumour, Nicole
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Re: CT scan versus MRI (Can I have an MRI instead of a CT?)

Hi there, Yes CT's can deliver a significant dose of radiation, but so can a whole range of other things, including just living. It is one of those thing where we have to balance cost versus benefit. There are also a lot of assumptions being made that people don't get told. The big assumption is that there is a linear relationship between radiation dose received and cancer risk. That appears to hold true for high doses of radiation and the evidence for this comes from atomic bomb survivors and nuclear accident survivors. When it is low doses the evidence is less clear. Most dose response curves for radiation or chemical expose look like a flattened letter 'S'. At low dose there is little response, then it goes through a region where the response is linear, then it flattens off. The problem is that you can't predict from the linear part of the curve, what will happen down at low dose, and collecting data at low dose is difficult and takes a long time. All of us are exposed to radiation all the time - it is called the background radiation. It ranges, depending on where you live, from 1 - 3 milli Sieverts a year. (A Sievert is the measure of the biological effects of radiation - shortened to Sv). Flying from Sydney to Singapore delivers about 17 micro Sv. From Sydney to London about 60 micro Sv. Flights crews build up about 5 milli Sv for each 1000 hours of flying. A standard chest X-ray is about 0.1 milli Sv, or 100 micro Sv. A full body CT is about 10 milli Sv (3 - 4 times background radiation) and a mammogram is about 3 milli Sv. Balanced against that is the benefit is terms of better imaging and diagnosis. Does this increase cancer risk. The correct answer is that we do not know, it might, so it pays to be cautious. Is MRI safe - again we do not know as MRI involves fluctuating magnetic field and radio-frequency radiation. At this stage there is no good evidence that these may have cancerous side effects, but many people believe that they could. So it plays to be cautious there as well. So, as said before, there is huge benefit from these procedures, but there is also some risk. The question is more like, 'if these procedures can help give me a good quality of life for the next ten, twenty, thirty or forty years, with some small risk of a second cancer in that time, whereas the alternative is to die from cancer in five years, which will I choose?' . To me that's a bit of a no-brainer. Cheers Sailor Even with the best charts, we are cautious about fixing our position, for it is so easy to goof. And the easiest way of all is by taking a mark, assuming it is the right one, and ignoring any others that may be in sight. 
Patrick Ellam
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Regular Contributor

Re: CT scan versus MRI (Can I have an MRI instead of a CT?)

Always Sailor the voice of wisdom and perspective. Never baffling us with science, just presenting it as it is. S
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New Contributor

Re: CT scan versus MRI (Can I have an MRI instead of a CT?)

Thanks for your replies, you have put my mind somewhat at rest. It humbling to think that you have put so much thought into your answers, I really appreciate it. I wish i could be so articulate. I will discuss my options with my Dr's next time i see them, but how does everyone else contact them between appointments? I only ever see them now after a blood test or scan.
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