Lec 2 X-ray Tube

Question 1

• It is composed of a cathode and an anode.
• It is enclosed in an evacuated glass casing or tube.
• X-Rays are produced by the passing of electrons from the filament in the cathode to the target in the anode.

Answer 1

X-ray tube

Question 2

Consists of a filament and a focusing cup.

Answer 2

Cathode

Question 3

The source of the electrons within the X-Ray tube.

Answer 3

Filament.

Question 4

These filaments contain ________, which greatly increases the release of electrons from the heated wire. It is heated to a high temperature with a low-voltage source and would emit electrons the same as the temperature of the filament.

Answer 4

1% thorium

Question 5

The filament is usually made from a ___________ approximately ___ in diameter and ___ or less in length.

Answer 5

• Tungsten wire
• 2 mm (diameter)
• 1cm (length)

Question 6

The filament lies in the __________?

Answer 6

Focusing cup

Question 7

A negatively charged concave molybdenum bowl.

Answer 7

Focusing cup

Question 8

The ________ shape of the focusing cup electrostatically focuses the electrons emitted by the filament into a narrow beam directed at a small rectangular area on the anode called the _________.

Answer 8

• Parabolic
• Focal spot

Question 9

Composed of the tungsten target embedded in a copper stem.

Answer 9

Anode

Question 10

The ________ is embedded in a large block of _______ to dissipate heat and prevent it from melting.

Answer 10

Tungsten target
Copper

Question 11

Additional info:

• The purpose of the target in an x-ray tube is to convert the kinetic energy of the colliding electrons into x-ray photons.
• The conversion of the kinetic energy of the electrons into x-ray photons is an inefficient process, with more than 99% of the electron kinetic energy converted to heat.

Answer 11

Perfect :)

Question 12

The area on the target where the focusing cup directs the electrons and from which the x-rays are produced.

Answer 12

Focal spot

Question 13

TRUE OR FALSE

Size of the focal spot is integral to image quality.

Answer 13

True

Question 14

A SMALLER focal spot yields a _________ image.

Answer 14

SHARPER

Question 15

The 2 anode configurations are?

Answer 15

Stationary anode, Rotating anode

Question 16

Additional info:

A limitation to reducing focal spot size is the heat generated could cause the target to melt.

Answer 16

rawr

Question 17

This anode configuration shows a target that is placed roughly at an angle of _________ to the central x-ray beam. It is the most commonly used configuration in intraoral x-rays.

Answer 17

Stationary anode; 20 degrees

Question 18

This anode configuration shows that the tungsten target is in the form of a beveled disk that rotates during the period of x-ray production.

Answer 18

Rotating anode

Question 19

• This type of anode can be used with longer exposures and higher tube currents of 100 to 500 milliamperes (mA)
• Cephalometric X-ray, Cone Beam Computed Tomography (CBCT)

Answer 19

Rotating anode

Question 20

It is contained in the x-ray head together with the x-ray tube.

Answer 20

Power supply

Question 21

• Provide a low-voltage current to heat the x-ray tube filament.
• Generate a high potential difference to accelerate electrons from the cathode to the focal spot on the anode.

Answer 21

Power supply