Imaging

by an active member of our forums who has worked in nuclear medicine in a large Canadian hospital for 14 years

This article was posted as a response to the question :

Dear girls, MRI's, CT scans, PET scans, do these particular procedures detect without a doubt any lurking cells, more so than for example a bone scan would show. I was wondering, what arthritis looks like, compared to cancer on a bone scan,how can they tell. The docs must be 100% on their interpretations surely, any thoughts much appreciated, just wondered,. never asked at the time after my bone scan, the doc never mentioned hotspot, just that the bonescan showed up arthritis, but when I read up on bone scans arthritis can show as a hotspot......


MRI's and CT's and bone scans are all useful tools in seeing if there are any residual cancer cells remaining in your body. However, each imaging modality shows different things and some are better at answering a particular question.

Bone scans, show anything that can affect the bones. For example, arthritis, an old injury or fractures and of course any cancer that has spread to the bones. Your bones are constantly growing and remodeling all of the time. When you have a bone scan, we inject you with a radioactive analog of phosphate and your bones are unable to tell the difference between this radioactive phosphate and the normal dietary phosphate. Your bones need phosphate to grow and repair themselves.

You have osteoblasts which are cells that build up and repair the bones and osteoclasts which break down the bones. In a normal healthy individual, the osteoclasts and osteoblasts are in sync so bone is repaired and rebuilt as it needs to be. In a patient with cancer that has spread to the bone, the osteoclasts and osteoblasts are not in sync and the bone is destroyed faster than it can be rebuilt. Having said this, not all bone secondaries appear as hot spots on a scan. A lot of them do, however some secondaries appear as cold spots. The difference being if the cancer cells are attacking the osteoclastic or osteoblastic cells.

Radiologists and nuclear medicine physicians are highly trained and you can tell the difference between arthritis and secondaries in the bone.

Arthritis will appear in the hips, knees, feet and spine and areas of the bone where there is increased wear and tear. The appearance of a bone secondary is very different than that of an arthritis. Bone secondaries appear in the axial skeleton. Meaning they appear in most commonly in the long bones, the ribs, spine, hips, legs, skull, and arms. They have a very different appearance than that of arthritis or a fracture.

So, bottom line is if your bone scan has been reported as arthritis, you can rest assured that it really is probably just arthritis. As I am one of the biggest worriers, I totally understand how you are feeling and hope I was able to alleviate your fears. As I am in the bone scan biz, the one thing, I can stress is, if you are ever told that there is an area of concern on your bone scan and it is followed up by xrays and the xrays come back normal INSIST that you are followed very closely. Have them repeat the bone scan in 2 months. Any secondary in the bone will appear much earlier on a bone scan than it will on an xray. I have seen it many times where a person will present with a single spot on a bone scan and they will then have an xray. The xray will come back normal and the patient will be reassured that all is well........and then whammo, they start having pain in other spots and a further bone scan shows that there is massive spread everywhere. It breaks my heart to see this but I have seen it and if I can prevent one person from having to go down that road, then I have to do it.

The difference between CT and nuclear medicine is that CT shows anatomy and can give precise dimensions of lesions and tumours. CT is better at showing tumours in liver and lungs and brain and gives very clear pictures. CT's are excellent for looking at soft tissues. Nuclear medicine looks at physiology meaning how the body is functioning. For example with the bones, we see if the cancer has spread to the bones.

We also do many other scans in nuclear medicine. A lot of you willl be familiar with the MUGA scans that we do to check the function of your heart and we calculate the ejection fraction to make sure that the chemo isn't having a nasty affect on your heart.

MRI's take pictures by aligning the hydrogen ions in your body with the use of a big magnet. These pictures also take a close look at the anatomy and can give measurements to tumours and can be used to look at soft tissues as well as bones.