Basic Radiation Physics

Question 1

What is Particulate Radiation?

Answer 1

Consists of Tiny, fast-moving particles that have energy and mass.

Question 2

What is Particulate Radiation produced by?

Answer 2

The disintegration of radioactive elements leading to the generation of neurons and beta particles.

Question 3

What is Electromagnetic Radiation?

Answer 3

Pure energy with no mass that travels through space and matter as waves at the speed of light in stream of small “packets” of energy called photons.

Question 4

Describe the energies of “Non-ionizing” electromagnetic radiation.

Answer 4

Has energies <5eV that produce visible light microwaves and radio waves.

Question 5

Describe the energies of “Ionizing” electromagnetic radiation.

Answer 5

Has energies of >5eV volts that remove electrons from an atom and produce high energy ultraviolet radiation gamma rays, and x-rays.

Question 6

What happens when an electron traveling at high speeds strikes a target atom?

Answer 6

It will be slowed or completed stopped by the gravitational forces of that atom.

Question 7

What does the Law of Conservation of energy, say about the kinetic energy or the incoming electron, when it is traveling at a high speed to strike an atom?

Answer 7

The electron cannot be lost, and must be absorbed by the atom, or converted to another form of energy.

Question 8

About what percentage of kinetic energy will be converted into heat when an atom enters?

Answer 8

99%. The remaining will be converted into a radiating energy, known as an X-ray.

Question 9

What is needed to generate X-rays?

Answer 9

A tungsten cathode and anode encased in a Pyrex glass vacuum tube.

Question 10

What is the Cathode element used for?

Answer 10

Used to generate electrons via thermionic emission.

Question 11

What is the Anode element used for?

Answer 11

Used as the target for the accelerated electrons.

Question 12

What is a Step-Up and a Step-Down transformer used for?

Answer 12

Used to transform the regular 110V alternating current to a high voltage at the level of the tube (more than 50kV), and to a low voltage at the level of the filament (10 V).

Question 13

What is the purpose of the focusing cup?

Answer 13

It houses the cathode and helps in preventing the electrons from repelling each other away from the ligament and allows the stream of electrons from cathode to anode to be controlled.

Question 14

What is a dead man switch timer?

Answer 14

It is connected to the circuit and controls the time the electrons travel from the filament to the target.

Question 15

The higher the voltage between the cathode and the anode, the _______ the electrons will travel.

Answer 15

Faster.

Question 16

The number of electrons traveling from the cathode to the anode, is called what?

Answer 16

The tube current.

Question 17

What is the kVp and what does it stand for?

Answer 17

The maximum energy output of the X-ray tube. Also known as the kilo volt peak.

Question 18

What do filters do?

Answer 18

They absorb the low energy photons from the X-ray sprectrum.

Question 19

What is the purpose of adding a piece of aluminum to the front of the X-ray tube?

Answer 19

Additional filtration.

Question 20

If the kVp of the tube increases, what should the total filtration do?

Answer 20

Increase.

Question 21

What is the collimator made of, and what does it look like?

Answer 21

It’s a metallic barrier with an aperture in the middle, that can be circular or rectangular.

Question 22

What is the purpose of the collimator?

Answer 22

I’s used to reduce the size and change the shape of the X-ray beam. It also reduces the irradiated area in the patient.

Question 23

What does the Beam Indicating Device (BID) do?

Answer 23

It guides the direction of the X-ray beam during the exposure of radiographs. It improves and standardizes imaging, and reduces the patients risk of radiation exposure.

Question 24

How is the length of the Beam Indicating Device (BID) measured?

Answer 24

From the anode to the open end of the BID.

Question 25

What kind of wavelength does a high quality beam have?

Answer 25

Short.

Question 26

What does the kilovoltage control?

Answer 26

The quality.

Question 27

What does mAs stand for?

Answer 27

Milliampere-seconds.

Question 28

When either the amperage or the exposure time are increased, what must happen?

Answer 28

You must decrease whichever is higher, to maintain the same beam quantity.

Question 29

The intensity of a beam is affected by what two things?

Answer 29

Both the kVp and the mAs. The intensity is a product of both of these factors.