Introduction to Radiology

Question 1

X-Rays were discovered by

Answer 1

Wilhelm Conrad Roentegen in November 1895

Question 2

Early pioneers of X rays

Answer 2

Michael Faraday, Heinrich Giessler, Johann Hittorf, Sir WIlliam Crookes

Question 3

Dr. Otto Walkoff

Answer 3

• took first extraoral dental radiograph in December 1895
• exposure took 25 minutes
• wrapped glass photographic plate with black paper and rubber

Question 4

Dr. Edumnd Kells

Answer 4

Took first intraoral radiograph

Question 5

Dr. William Coolidge

Answer 5

• developed “hot cathode”

- made tungsten ductile and used in the filament

Question 6

Dr. William Rollins

Answer 6

• developed guidelines for protection of patients
• conducted studies on rats inducing erythema and death with x-radiation
• warned Dr. Kells of dangers of x-rays

Question 7

Radiology

Answer 7

Study or science of radiation as used in medicine and dentistry

Question 8

Radiograph

Answer 8

record image produced by x-rays on photographic film

Question 9

Film

Answer 9

Transparent material covered with photographic emulsion

Question 10

Sensors/Detectors

Answer 10

• sensors that act like film

- indirect and direct digital sensors

Question 11

Direct digital sensor

Answer 11

• solid state detector that detects remnant radiation from the patient
• interpreted by the computer as various shades of grey dependent on the radiation detected
• rement radiation is in turn dependent on the density of the tissues

Question 12

Indirect digital sensors

Answer 12

• photostimulable phospor (PSP) imaging plates which are thin and similar to x-ray film
• no wires attached
• plates produced a latent image which is then read by a laser in the computer

Question 13

Exposure

Answer 13

Act of making or exposing a radiograph. Sensor or film is exposed to x-rays

Question 14

X-Rays

Answer 14

high energy radiation produced by an x-ray tube

Question 15

How are x-rays produced?

Answer 15

• by bombarding a tungsten target (anode) with a stream of high velocity electrons
• electrons are produced at the tungsten filament (cathode) and are propelled towards the anode at a different speed dependent on the electrical potential between the cathode and anode

Question 16

Components of x-ray tube

Answer 16

• cathode
• anode
• focal spot

Question 17

Cathode

Answer 17

• filament of coiled tungsten that emits electrons when heated
• “thermionic emission” which is the boiling off of electrons
• focussing cup: negatively charged Molybdenum

Question 18

Anode

Answer 18

Tungsten target in copper stem

Question 19

Focal Spot

Answer 19

area within target where the electrons are directed. The smaller the focal spot, the better the sharpness of the image.

Question 20

What are the two types of radiation that can be produced?

Answer 20

• Bremsstrahlung

- Characteristic

Question 21

Bremsstrahlung Radiation

Answer 21

• braking radiation

- altered pathways of electrons

Question 22

Characteristic radiation

Answer 22

• characteristic of atom that it interacts with

- knocks electron out of k-shell and photon replaces it to stabilize atom

Question 23

Spectrum of photon energies

Answer 23

• characteristic around 69 and 59

- bremmsstrahlung around 35-40

Question 24

Controlling factors

Answer 24

• kV
• mA
• Time

Question 25

kV

Answer 25

- kilovoltage, controls speed of electrons from cathode to anode - kV controls the quality of the x-ray beam - higher kV= more penetrating power

Question 26

mA

Answer 26

- milliamperage, controls number of electrons and hence the quantity of radiation produced. The higher the mA the darker the radiograph.

Question 27

Time

Answer 27

1 impulse= 1/60 second

Question 28

Radiographic Density

Answer 28

- the degree of blackness on a radiograph - controlled by mA and time as expressed as Mas - is related to QUANTITY of x- radiation

Question 29

Radiographic Contrast

Answer 29

- number of shades of gray on the radiograph - controlled by kV - High contrast= short scale and less shades of grey - Low contrast= long scale and lots of shades of gray. - Higher kVp causes increased energy in beam and higher penetrability - is related to Quality of radiation

Question 30

Contrast

Answer 30

Quality

Question 31

Density

Answer 31

Quantity

Question 32

How are images formed?

Answer 32

- x-ray is emitted from the end of the cone - x-rays pass through the patient's tissues - some x-rays are arrested in the tissues- those that are relatively dense - some x-rays pass through the tissues and hit the film/sensor

Question 33

How are images formed at the film/sensor?

Answer 33

- x-rays hit the film/sensor producing varying shades of gray dependent on the amount of radiation to which the film/sensor is exposed. - a radiograph, therefore, is a black, gray, and white representation of the various densities of which the tissues are made

Question 34

Black images

Answer 34

- areas on the radiograph where tissues are less sense (sinuses and pulp chambers) - these areas have allowed the x-ray to pass through and hit the film/sensor - radiolucent

Question 35

Common radiolucencies

Answer 35

- PDL space - pulp canal - caries - sinus

Question 36

White images

Answer 36

- correspond to dense areas in patient's tissue (enamel and dentin) - These tissues stop x-rays from passing through and hitting the film/sensor (attenuation) - radiopaque

Question 37

Radiopacities

Answer 37

- Enamel - Amalgam restoration - Dentin

Question 38

Enamel and Dentin have different densities

Answer 38

- DEJ line | - Lamina Dura