Machine anatomy

What 5 things are necessary for x-ray production

1. source of electrons​

2. method of accelerating the electrons​

3. obstacle free path for the passage of high speed electrons​

4. A target which the electrons can interact, releasing x-ray energy.

5. A tube to provide a vacuum environment to prevent rapid oxidation of the elements.

Encased in a glass envelope that forms a vacuum.​

x-ray tube

what 2 sides does the x-ray tube have

Cathode and anode

purpose of the tube being cased in the metal housing

1. prevent stray radiation

2. protect the glass envelope from damage

purpose of oil in the tube

absorbs heat generated

The cathode side consists of a coiled wire filament that has what purpose

emits electrodes when heated

Filament in the cathode side is made of what metal element

tungsten (W-74)

The filament is heated by a(n):

low energy circuit

mA (milliamperage)

The amount of energy in the low energy circuit

What happens when the milliamperage is applied to the filament

1. heats up

2. released electrons

The filament is located in a concave cup called the:

focusing cup

what is focusing cup made of

molybdenum

Because of the shape of the cup, the electrons are:

• forced thru a smaller area

• directed towards the anode side more forcefully

The anode consist of what type of target made of tungsten placed on a cylinder base

beveled (15-23 degrees)

The anode is covered in copper for what purpose

conduct heat away from the target and into the oil

2 types of anodes

1. Stationary​

2. Rotating​

2 examples of stationary anode

1. dental

2. small portable x-ray units (barn/farm)

Disk shaped and rotates on an axis through the center of the tube

Rotating anode

This rotation provides:

1. cooler surface for the electron stream

2. provides a small focal spot

why do some machines not allow you to take a second exposure

The heat exceeds 3500F for a short time so you have to wait until the heat dissipates

Because of the angle (usually 20 degrees) of the anode, the x-ray beam is usually stronger on the cathode side of the film.​

Heel Effect​

how does the heel effect affect positioning the animal for x-rays

• place the thicket part of the animal toward the cathode side or the right

• place the head toward the anode side or the left

small area of the target on the anode which the electrons collide

Focal Spot​

If the focal spot was the size of a pinpoint, the x-rays would have

greater clarity

halo effect on the radiograph

penumbra

As the focal spot increases, what will happen to the quality of the radiograph

the sharpness decreases causing a halo effect

the focal spot can not be the size of a pinpoint because:

it can’t withstand that much heat

Stationary machines must have a (smaller or larger) focal spot to accommodate the high temperatures

larger

Stationary machines must have a (smaller or larger) focal spot

smaller focal spot

The exposure switch/pedal has how many stages before an x-ray is taken

2 stages

First stage

• activates the rotor

• heats the filament and transformers

Second stage

activates the exposure of radiation

Constant firing of electrons on the cathode can:

• damage the filament

• cause evaporation

When the target overheats, how does this affect the glass envelope

Metal deposits that form on the inside of the glass

deposits act as a secondary anode and skew with the tragectory of the electrons

arching

What happens when there’s a crack and air is within the glass envelope

air interacts with the electrons and decreases the x-rays produced or collides and redirects the beam

Oil leaks from the metal housing causes:

overheating and will destroy the tube

195. The focusing cup of an x-ray machine is a ​

A. Small depression where the filament is placed​

197. The filament on an x-ray tube is​

D. Tungsten coil that emits electrons when heated.​

200. Tube saturation can occur with a ​

C. Too low kVp reading​

196. The target of an x-ray machine is a/an ​

C. Area of the anode struck by electrons during an exposure​

225. With the heel effect, the x-rayy beam intensity is greater toward the​

C. Cathode​

210. The electron cloud is generated at the ​

B. Cathode​

1. When positioning an animal for radiographs, it is best to place the thicker portion of the patient toward the ______end of the tube to produce a radiograph with uniform density.​

C. Cathode​

2. A small filament produces an image of​

C. Greater detail than a large filament​

3. Which of the following is a false statement regarding portable x-ray units​

D. Have a rotating anode tube and single focal spot.​

5. X-rays are formed on the ​

A. Anode​