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What is nuclear medicine?

Nuclear medicine includes all activities and treatments during which radioactive material is introduced or produced in the human body for diagnostic or therapeutic purposes.

Diagnostics

How much heart muscle tissue has been affected by the heart attack? Is the left kidney still functioning properly after the car accident? Nuclear medicine can answer these questions reliably and quickly.

The patient is injected with a nuclear pharmaceutical - a low-radioactive substance. Sophisticated instruments and equipment will detect the radiation emitted in the body, and convert the signals into images. From these images the medical questions can be answered.

A nuclear pharmaceutical is a physiologically active carrier to which a radioisotope is attached. It is possible to manufacture chemical or biological carriers which migrate to a particular part of the human body. Calcium for example, is a 'bone seeker', and iodine concentrates in the thyriod gland. The radioisotope attached to these compounds emits radiation so that the relevant organ and its functioning can be 'observed'. Radiation is easy to detect. Even radiation which is many times weaker than natural background radiation can be measured. The location in the patient's body which emits the radiation can thus be very accurately pinpointed.

A baby's left kidney is enlarged. This had already been established by means of echography before the child's birth. With technetium-99m an accurate diagnosis ould be made: a drain obstruction. The obstruction was removed by surgery.
(With thanks to Kennemer Gasthuis, Haarlem, the Netherlands).

So we see that radioactive preparations can be very useful for diagnostic examination if we choose them in such a way that they emit sufficient radiation to be easily detectable in the body, but only for a long enough time to enable completion of the examination. Nuclear pharmaceuticals for diagnosis must therefore have a rather short halt-life, preferably no longer than a few hours.

Useful radioisotopes for diagnostic purposes are technetium-99m, gallium-67, indium-111, jodium-123, jodium-131, thallium-201, krypton-81m.

Therapeutics

Tissue dies rather quickly after receiving a large dose of radiation. This aspect of radiation can be utilized for treating tumors. The radiation can be emitted by an external source, or alternatively by an internal source. It is possible to insert a small radioactive source through body openings, via the bloodstream or by means of surgery into a tumour and leave it there for a period lasting from days to weeks until sufficient dose has been given off. A patient may also be administered a radioactive preparation - to be swallowed or injected - which will concentrate in the tumour. Nuclear pharmaceuticals which are used for therapy must have a rather longer half-life.

Useful radioisotopes for the therapeutical purposes are iodine-131 (in NaI or metaiobenzylguanidine, MIBG), phosphorus-32, irridium-192, gold-198.
Radioactive sources which are placed in the body near the tumour for local irradiation of that tumour, are also called nuclear pharmaceuticals. Irridium-192 sources are normally used for that purpose.

Palliatives

A specific therapeutical application of nuclear pharmaceuticals is pain relief for terminal patients with disseminated bone cancer. Injections which rhenium-186 - a bone seeker which numbs the neural ends in bones - will spare a patient much pain and degradation towards the end of his or her life. Strontium-89 is also often used for palliative purposes.

  
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Update 18 June 2004