Lecture 1 - Intro to Radiology

What is the dose limit of radiation for the general public?

1 mSv/year

What is the dose limit of radiation for occupationally exposed personnel?

20 mSv/year

What is the dose limit of radiation for pregnant persons?

<5 mSv/year

What does ALARA stand for?

As low as reasonably achievable

What are the three major ways to lower radiation dose?

Time, distance, and shielding

What are the main governing bodies of radiology in Canada?

Health and Welfare Canada, Ministry of Labour, and College of Veterinarians of Ontario (CVO)

What tools can be used for hands-free techniques in radiology?

Sandbags/troughs, sedation, lead gloves

What does it mean to collimate?

Limit exposure to area of interest.

True or False: dosimeters should be store in the Xray room when not being worn

False

1 multiple choice option

What does attenuation mean?

The process by which the primary radiation is changed or absorbed as it travels through the patient

What does radiolucent mean?

Allows xray photons to pass through easily (not visible on xray)

What does radiopaque mean?

Does not allow xray photons to pass easily (visible on xray)

What is kilovoltage (kvp)?

The penetrating power of the xray beam

What are milliamperes (ma)?

Electrical current

What is the anode heel effect?

The intensity of radiation is greater on the cathode side of the xray tube

What does a conventional radiograph use?

Film cassettes

What does a digital radiograph use?

Digital plates

What are the two types of digital radiography?

Computed radiography (CR) and Direct digital radiography (DR)

What are some characteristics of xrays?

- Invisible

- Electrically neutral

- Can't be accelerated/made to change direction by a magnet/electrical field

- Travel at the speed of light in a vacuum

True or False: xrays are positively charged

False - they are electrically neutral

2 multiple choice options

True or False: xrays travel in straight lines

True

1 multiple choice option

True or False: xrays cannot be optically focused

True

1 multiple choice option

What is somatic xray damage?

Affects physical structure of the body

What is genetic xray damage?

Mutation of genes

What is carcinogenic xray damage?

Formation of cancers

What is scatter radiation?

Xrays that bounced off of the target

What happens to the weak rays of an xray?

They bounce off of the target and become scatter radiation

What happens to the strong rays of an xray?

They pass through the tissues and out of the body to create blackness on the final image

True or False: some xrays are absorbed by the patient and do not make it to the film

True

1 multiple choice option

What determines the quality of the energy of the photons in the beam?

Kilovoltage (KVP)

What will higher kilovoltage (KVP) do to xray tissue penetration?

Increase

2 multiple choice options

What happens to a film when there is over penetration?

The bones in the film turn grey

What determines the quantity of photons in the beam?

Milliamperes (MA)

What two main factors do milliamperes determine?

The density of the beam and the darkness/lightness of the entire film

When more milliamperes are applied to the cathode, what happens to the rotating anode?

It rotates faster

3 multiple choice options

What is the high-voltage transformer?

Located beneath the xray table to connect to hospital power lines

What does the xray generator do?

Sends power from the high-voltage transformer through the circuit to the xray tube

What is the xray tube?

Most important part of the xray machine; produces xrays

What do grids do in an xray machine?

Absorb scatter radiation and improve contrast

What does a collimator do?

Controls the field of view

What does a cassette do and what type of radiography is it used for (film or digital)?

Film radiography - where the film sits

What does an imaging plate do and what type of radiography is it used for (film or digital)?

Digital radiography - converts the image from the plate and sends it to the computer monitor

What do intensifying screens do?

House an active layer of phosphorus which gives off light when exposed to xrays

What material is the xray cathode commonly made of?

Tungsten

What needs to happen to the cathode in order for it to produce electrons?

It needs to be heated

3 multiple choice options

Are cathodes positively or negatively charged?

Negatively charged

Are anodes positively or negatively charged?

Positively charged

How does the size of a filament affect the size of the image produced?

Larger filaments = larger images

3 multiple choice options