Blog About Health & Medicine

The substance used for bone scans is taken out of the blood by bone-forming cells, and concentrates especially in areas where the bone cells are very active. In this type of scan, abnormalities show up not as ‘holes’ but as ‘hot spots’—areas where more than the usual amount of radioactive substance collects. This is because bone cells are especially active around abnormalities such as fractures, infections, or cancer deposits. The scan picks up the problem indirectly by showing the bone cell reaction rather than the abnormality itself. The amount of radiation involved in taking a scan of all the bones in the body is actually quite a bit less than if all those bones were X-rayed.

Various radio-isotopic methods can be used to get ‘pictures’ of most organs. For different organs we use different substances, choosing one that will be concentrated in the particular organ we wish to study. In all cases the radioactivity does not stay in the body for long. It is passed out through the urine, faeces or air from our lungs. The amount of radioactivity involved in each test is very small, and doesn’t pose any danger to anyone you go near or touch. If you want exact details, ask the people who are doing the test. They should tell you how long it takes your body to get rid of the particular substance being used and which way it is eliminated.

One drawback with these tests is that you only ’see’ the parts of the organ that are functioning normally. The ‘holes’ or ‘hot spots’ can be due to any one of many things that interfere with that organ’s function. Cancer is only one of many possible reasons for abnormalities in these scans.

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Lymphangiography is another means of showing up lymph nodes. For this a liquid form of contrast is injected into the tiny lymph channels and gradually works its way up through them. For example, if the ‘dye’ is injected into lymph channels in the foot, within a few hours X-rays will show it in the channels as far up as the groin and abdominal cavity. The next day the nodes themselves will be filled with the contrast material, sometimes right up into the chest. Their size and internal structure can then be checked. Unfortunately, because lymph nodes which are packed with cancer don’t function normally, the contrast may not get into the worst affected nodes. This can be a major drawback of this test. It is less likely to happen with lymphomas than with other types of cancer. Combining both methods by doing a CT scan after injecting the contrast actually gives the maximum information.

The biggest drawback of lymphangiography is that it can be used to show up only certain groups of nodes. Unless the nodes we want to ’see’ are fed by channels which are accessible (to have the contrast injected into them) we cannot show them up by this method.

Thus, lymphangiography cannot be used to show the lymph nodes from many of the internal organs such as the bowel, bladder, womb etc. Often it is only during an operation that we can easily find out for sure whether or not these are affected.

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