MEDICAL PHYSICS TECHNIQUES

Medical physics techniques

Medical physics techniques

Draw sequences which show what happens to radioactive elements when they lose: an alpha particle; a beta particle. What happens to an atom when gamma rays are emitted?

The following image demonstrates the emission of alpha particle from a radioactive element. An alpha particle is released during an alpha decay from a radioactive element. Alpha particle consists of two protons and two neutrons and is therefore a type of helium. After an emission takes place from an element, it changes to some other element. Alpha decay normally occurs in the heaviest nucleus.

The following image demonstrates the emission of beta particle from a radioactive element. A beta particle is emitted from the element that undergoes beta decay. A beta particle is composed simply of an electron or a positron. An electron is called beta minus while a positron is called beta plus.

The following image demonstrates the emission of gamma particle from a radioactive element. During emission of gamma rays from a radioactive element, high-energy photons are emitted. The excited nucleus releases excess energy in order to drop itself into a lower energy state (Thinkquest, 2012).

A fully labelled diagram demonstrating the principles of: an X-ray tube; production of ultrasound. Use a suitable diagram to analyse what happens to an X-ray spectrum when the tube voltage is changed. Show some known X-ray peaks in your diagram. What do these peaks tell you?

Production of X-rays

X-rays are produced in a dicharge tube in which electrons are accelrated by a high voltage. These electrons on striking the metallic target emit radiations that are known as X-rays.

An X-ray tube

The energy of the x-rays increases with the increase in tube voltage. Following graph demonstrates the energy increase with the increase in tube voltage (NASA, 2007).

Production of ultrasound

Make a list of the most common radiopharmaceuticals used in medicine, describe how they are produced and briefly describe what happens when these substances enter the body.

Following are the most common radiopharmaceuticals used in medicine.

I131-Iodide, used to examine thyroid uptake.

Production

Large amounts of I131-Iodide are produced from neutral irradiation of a target made of natural tellurium in the nuclear reactor. The irradiation process of natural tellurium produces nearly whole of the I-131 as the radionuclide. Its half life is greater than hours. Furthermore, Te-130 that makes up 34% of natural tellurium absorbs a neutron and thus becomes tellurium-131, which in turn beta-decays and become I-131.

Effects on body

When I131-iodide enters the body, it causes mutation to the cells. It penetrates into the cells and can cause their death. Higher doses of this radiopharmaceutical have the tendency to kill thyroid tissues that may become cancerous.

P32-Phosphate, used in the identification of malignant tumors

Production

P-32 Phosphate is produced by the irradiation of sulfur-32 with neutrons that are moderately fast. The neutron is captured by sulfur-32 which emits a proton. As a result, its atomic number is reduced while mass number remains 32.

Effects on body

When P32-Phosphate enters the body, it can ...