What do radioactive isotopes have

Both bone and soft tissue can be imaged successfully with this system. A radiopharmaceutical is given orally, injected or inhaled, and is detected by a gamma camera which is used to create a computer-enhanced image that can be viewed by the physician. Nuclear imaging measures the function of a part of the body by measuring blood flow, distribution or accumulation of the radioisotope , and does not provide highly-resolved anatomical images of body structures. It highlights the almost microscopic remodelling attempts of the skeleton as it fights the invading cancer cells.

A widely-used nuclear imaging technique for detecting cancers and examining metabolic activity in humans and animals. A small amount of short-lived, positron-emitting radioactive isotope is injected into the body on a carrier molecule such as glucose.

Glucose carries the positron emitter to areas of high metabolic activity, such as a growing cancer. The positrons, which are emitted quickly, form positronium with an electron from the bio-molecules in the body and then annihilate, producing a pair of gamma rays.

Special detectors can track this process, enabling the detection of cancers or abnormalities in brain function. A CT scan, sometimes called CAT Computerised Axial Tomography scan, uses special X-ray equipment to obtain image data from hundreds of different angles around, and 'slices' through, the body.

The information is then processed to show a 3-D cross-section of body tissues and organs. Since they provide views of the body slice by slice, CT scans provide much more comprehensive information than conventional X-rays.

CT imaging is particularly useful because it can show several types of tissue - lung, bone, soft tissue and blood vessels - with greater clarity than X-ray images. Though a CT scan uses radiation, it is not a nuclear imaging technique, because the source of radiation - the X-rays - comes from equipment outside the body as opposed to a radiopharmaceutical inside the body. PET scans are frequently combined with CT scans, with the PET scan providing functional information where the radioisotope has accumulated and the CT scan refining the location.

The primary advantage of PET imaging is that it can provide the examining physician with quantified data about the radiopharmaceutical distribution in the absorbing tissue or organ.

Radioisotopes Different isotopes of the same element have the same number of protons in their atomic nuclei but differing numbers of neutrons. How do radioisotopes occur? Radioactive decay Atoms with an unstable nucleus regain stability by shedding excess particles and energy in the form of radiation.

How are radioisotopes used? Radioisotope Half-life Use Hydrogen-3 tritium Carbon 5, years Used to measure the age of organic material up to 50, years old. Chlorine , years Used to measure sources of chloride and the age of water up to 2 million years old. Lead Chromium Manganese Produced in reactors. Cobalt 5. Also used to irradiate fruit fly larvae in order to contain and eradicate outbreaks, as an alternative to the use of toxic pesticides.

Zinc Produced in cyclotrons. Technetiumm 6. Produced in 'generators' from the decay of molybdenum, which is in turn produced in reactors.

Caesium Ytterbium Iridium Also used to trace sand to study coastal erosion. Gold 2. Also used to trace factory waste causing ocean pollution, and to study sewage and liquid waste movements.

The atomic number defines the chemical element that the atom belongs to. Thus, regardless of the number of neutrons they have, all atoms whose nuclei have one proton are hydrogen atoms. All of those with eight protons are oxygen atoms, etcetera.

The mass number is the whole number that is closest to the mass expressed in atomic mass units of the atom in question. That is, they have the same atomic number Z but different mass numbers A. For instance, carbon is presented in nature as a mix of three isotopes with mass numbers 12, 13 and 12 C, 13 C and 14 C.

The global amounts of carbon in each are respectively Most chemical elements possess more than one isotope, as is the case of tin, the element with the highest number of stable isotopes.

In practice the technique was an enormous challenge: the goal was to draw off that very small portion of uranium atoms that were lighter than their brethren. The difficulties were so enormous the plan was abandoned in Again, the basic idea was very simple: the rate at which gas passed diffused through a filter depended on the weight of the gas molecules: lighter molecules diffused more quickly.

Gas molecules that contained U would diffuse slightly faster than gas molecules containing the more common but also heavier U This method also presented formidable technical challenges, but was eventually implemented in the gigantic gas diffusion plant at Oak Ridge, Tennessee.

In this process, the uranium was chemically combined with fluorine to form a hexafluoride gas prior to separation by diffusion. This is not a practical method for extracting radioisotopes for scientific and medical use. It was extremely expensive and could only supply naturally occurring isotopes. A more efficient approach is to artificially manufacture radioisotopes.

This can be done by firing high-speed particles into the nucleus of an atom. When struck, the nucleus may absorb the particle or become unstable and emit a particle. In either case, the number of particles in the nucleus would be altered, creating an isotope. One source of high-speed particles could be a cyclotron. A cyclotron accelerates particles around a circular race track with periodic pushes of an electric field. The particles gather speed with each push, just as a child swings higher with each push on a swing.

When traveling fast enough, the particles are directed off the race track and into the target. A cyclotron works only with charged particles, however. Another source of bullets are the neutrons already shooting about inside a nuclear reactor. The neutrons normally strike the nuclei of the fuel, making them unstable and causing the nuclei to split fission into two large fragments and two to three "free" neutrons.