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DMD 5340 Oral Imaging > Physics > Flashcards

Flashcards in Physics Deck (31):
1

What is atomic number and atomic mass?

AN= Proton #
AM= Protons and Neutrons

2

What is ionization?

Neutral atom loses electron and becomes charged and unstable.

3

What is the basics of the X-ray tube (anode, cathode, tungsten, filiment,)

Filament (tungsten wire) generates electrons at cathode (-), shoots at anode (+) (tungsten target).

4

What is the focusing cup?

Focuses electrons from filament into narrow beam directed at anode focal spot.

5

What is the anode wrapped in? Why?

Wrapped in copper to act as a heat sink.

6

Why is tungsten used?

Higher melting point, high atomic number (dense), high conductivity, low vapor pressure.

7

What is radiation?

Transmission of energy through space and matter.

8

What is particulate radiation?

Large unstable atoms breaking apart and shooting smaller particles that ionize other things.

9

What is Electromagnetic radiation (EMR)? shorter wavelength equals what kind of energy?

Movement of energy through space as a combination of electric and magnetic fields.
Shorter wavelength=higher energy.

10

How is EMR generated?

Velocity of an electrically charged particle is altered.

11

What is Bremsstrahlung radiation? 2 types?

Sudden stopping or slowing of electrons.
1. Electron directly hits atom nucleus, turns into x-ray (photon)
2. Electron flies close to nucleus, veers off course, and released x-ray photons.

12

What is characteristic radiation?

Electron hits and ejects inner electron of atom. Electrons move down to fill that shell and release x-ray (photons).

13

What is voltage? Measured in?

Force that pushed electrons. determined by potential difference between two points. Measured in kVp.

14

what is filament voltage? Want it high or low?

Foltage across the filament wire. Want it low to not burn it out and create electron cloud.

15

What is current? Measured in?

Current is # of electrons flowing. Measured in mA.

16

What is filament current? Tube current?

FC= # of electrons in filament.
TC= # of e- from anode to cathode.

17

what does the power supply do?

Generates high potential difference from cathode to anode.

18

What does a step-up transformer do? Used for?

Increases voltage from incoming power source. Used to increase V from cathode to anode.

19

Step down transformer does what? Used for?

Decreases voltage from power source. Used for filament.

20

Energy in beam is controlled by? # of photons?

E= kVp
#= kVp and mA

21

What is increasing exposure doing?

Increases exposure time increases # of photons.

22

Increase tube voltage (kvP) does what?

Increases photons and their energy level.

23

What is inherent and added filtration?

1. Inherent= materials photons encounter as they travel from focal spot to detector.
2. Added= Aliminum discs added .

24

what does the collimation do?

Limits x-ray exposure and reduces scatter.

25

What is preferred, round or rectangular collimation?

Rectangular.

26

Intesity of beam is measured how?

I1/ I2 = (D2)2/ (D1)2

27

What are apsorption and scattering interactions?

A= photons ionized atom, energy of photon absorbed.
S= photons interacts with atom, and gets ejected.

28

What is photoelectric absorption? Important for what?

Photon hits electron, knocks it out, and then ceases to exist. Most important for imaging production.

29

What is coherent scattering?

Absorbs and spits out same electron.

30

What is compton scattering?

Photon knocks out electron, photon changes direction.

31

What is beam attenuation? Penetrating value determined by what?

Beam loses intensity.
Determined by thickness of material. (reduces in half)