joanneire Member Posts: 75 Member
edited March 2014 in Colorectal Cancer #1
Sorry this is probably a silly question but what is the difference between CT scans and PET scans (or is there one?). My boyfriend is having CT scans only (well along with blood markers)Thanks, Jo


  • steved
    steved Member Posts: 834 Member
    No such thing as a silly question here. CT looks mainly at structures in teh body (bit like a digital xray and similar to an MRI) so is good at seeing things that shouldn't be there. It sees most stuff bigger than a centimetre (so misses very small things). A PET scan looks at metabolic activity in the strucure in teh body by injecting a subsatnce that active tissues take up and use. Thereby it looks for bits of tissue that are being more active than they should (which is exactly what cancer cells are). #It can be very sensitive in finding bits of cancer int eh body but can also give very nonspecific results- ie findings that look not quite right but aren't clearly cancer.
    You will find mixed attitudes to the scans here on the board. Some have had very importnat revelations from PET scans and some less good. The research evidence at the moment is that PET scans don't improve teh outcome of follow up in colorectal cancer but then they are fairly new. Many docs aren't doing them and they certainly aren't routinely used outside the US. If you have concerns that your boyfriend should have one discuss it through with him and see if he wants to bring it up with his docs. There is no definite answer on it at present (I'm not having them and having looked at teh evidence for them I am happy witht that but I accept that for some they are an important aspect of follow up).
    Hope this helps,
  • alihamilton
    alihamilton Member Posts: 347 Member
    As Steve says, not a silly question at all. My understanding is similar to Steve's and my husband had a PET scan when the CT scan showed something in the liver. The PET scan was able to determine that there was nothing malignant there. I think they can also do a combination CT/PET. The PET scan is much more expensive which is probably one reason why they are not routinely given. But, in any case, the CT scan is enough to show if there is something suspicious. If there is nothing showing on the CT, a PET is not necessary.

    Hope this helps.