Section .4Section .4: The Physics Behind the Treatment: The Physics Behind the Treatment

Lesson.9: Lesson.9: Radiation and TreatmentRadiation and Treatment

ObjectivesObjectives

Recall and describe the origins of the Recall and describe the origins of the radiation used for treatmentradiation used for treatment

Recall and describe the main medical Recall and describe the main medical uses of ionising radiation.uses of ionising radiation.

Justify the choice of radiation used for a Justify the choice of radiation used for a particular purpose.particular purpose.

Radioactive atoms behave chemically exactly like their Radioactive atoms behave chemically exactly like their non-radioactive equivalents. This means that they can be non-radioactive equivalents. This means that they can be used to watch movements of chemicals through the body. used to watch movements of chemicals through the body. Doctors use radioactive iodine to look at how well the Doctors use radioactive iodine to look at how well the kidneys are working.kidneys are working.

First the patient is injected with a First the patient is injected with a small amount of chemical small amount of chemical containing radioactive iodine. containing radioactive iodine. Most of the injection is not Most of the injection is not radioactive.radioactive.

Doctors use special radiation cameras to detect the Doctors use special radiation cameras to detect the radioactive iodine getting into the kidneys. The cameras radioactive iodine getting into the kidneys. The cameras can measure the radioactive iodine present.can measure the radioactive iodine present.

These images These images show what show what happens to the happens to the radioactive radioactive tracers. Look at tracers. Look at the way the the way the concentration concentration changes as the changes as the kidneys clear it kidneys clear it from the blood.from the blood.

QuestionsQuestions

Why don’t we use alpha radiation in tracers?Why don’t we use alpha radiation in tracers?

Why do we use radioactive materials which have Why do we use radioactive materials which have short half-lives as tracers?short half-lives as tracers?

QuestionsQuestions

Why don’t we use alpha radiation in tracers?Why don’t we use alpha radiation in tracers?

Alpha particles would not be picked up outside Alpha particles would not be picked up outside the body. They would also cause a lot of damage the body. They would also cause a lot of damage inside the body.inside the body.

Why do we use radioactive materials which have Why do we use radioactive materials which have short half-lives as tracers?short half-lives as tracers?

QuestionsQuestions

Why don’t we use alpha radiation in tracers?Why don’t we use alpha radiation in tracers?

Alpha particles would not be picked up outside Alpha particles would not be picked up outside the body. They would also cause a lot of damage the body. They would also cause a lot of damage inside the body.inside the body.

Why do we use radioactive materials which have Why do we use radioactive materials which have short half-lives as tracers?short half-lives as tracers?

So that they cause no real damage in the body.So that they cause no real damage in the body.

Learning ObjectivesLearning Objectives

Recall that nuclear radiation is used in medicine.Recall that nuclear radiation is used in medicine.

Recall that x-rays and gamma rays are electromagnetic waves.Recall that x-rays and gamma rays are electromagnetic waves.

Describe that X-rays and gamma rays:Describe that X-rays and gamma rays:• have similar wavelengths;have similar wavelengths;• are produced in different ways.are produced in different ways.

Explain that:Explain that:• gamma rays are given out from the nucleus of certain radioactive materials;gamma rays are given out from the nucleus of certain radioactive materials;• X-rays are made by firing high speed electrons at metal targets;X-rays are made by firing high speed electrons at metal targets;• X-rays are easier to control than gamma rays.X-rays are easier to control than gamma rays.

Recall that nuclear radiation can damage cells.Recall that nuclear radiation can damage cells.

Recall that the person in hospitals who takes x-rays and uses radiation is a radiographer.Recall that the person in hospitals who takes x-rays and uses radiation is a radiographer.

Recognise that gamma rays are used to treat cancer.Recognise that gamma rays are used to treat cancer.

Explain how radioactive sources are used in medicine:Explain how radioactive sources are used in medicine:1. to treat cancer:1. to treat cancer:

gamma rays focused on tumour;gamma rays focused on tumour;wide beam used;wide beam used;rotated round the patient with tumour at centre;rotated round the patient with tumour at centre;limiting damage to non-cancerous tissue.limiting damage to non-cancerous tissue.

State that radioisotopes are used as tracers in hospitals. State that radioisotopes are used as tracers in hospitals. INDUSTRY WAS COVERED INDUSTRY WAS COVERED EARLIEREARLIER

Describe that beta or gamma emitters are used as tracers in the body.Describe that beta or gamma emitters are used as tracers in the body.

Recall that only beta and gamma radiation can pass through skin.Recall that only beta and gamma radiation can pass through skin.

2. as a tracer:2. as a tracer:beta or gamma emitter;beta or gamma emitter;drunk/eaten/ingested/injected into the body;drunk/eaten/ingested/injected into the body;allowed to spread through the body;allowed to spread through the body;followed on the outside by a radiation detector.followed on the outside by a radiation detector.

Recall that nuclear radiation is used to sterilise hospital equipment.Recall that nuclear radiation is used to sterilise hospital equipment.

Complete Complete

HigherHigher‘‘Medical Uses Of Radiation’ pages 148 and 149.Medical Uses Of Radiation’ pages 148 and 149.andand ‘Non-medical uses of Radiation’ pages 150 ‘Non-medical uses of Radiation’ pages 150 and 151.and 151.

FoundationFoundation‘‘Uses of Radiation’ pages 134 and 135.Uses of Radiation’ pages 134 and 135.

Foundation MARK SCHEME