Radiology Lecture

Who discovered X-rays?

Wilhelm Conrad Roentgen

What year were X-rays discovered?

1895

What does PID stand for?

position indicating device

Who applied to rule of isometry to bisecting technique?

A. Cieszynski

Who developed paralleling technique?

F.W. McCormack

Dental xrays have what wavelength and frequency?

short wavelength and high frequency

List the properties of xrays

• invisible

• travel in straight lines

• travel at the speed of light

• interact with matter, causing ionization

• can penetrate opaque tissues and structures

• can affect biological tissue

What is bremsstrahlung radiation?

when high speed electrons are stopped or slowed by the tungsten atoms of the target located inside the dental xray tube

what is characteristic radiation?

when high speed electrons collide either an orbiting K shell electron of the tungsten target

What 4 possibilities can occur when a beam of xray passes through matter?

1. no interaction

2. coherent scattering

3. photoelectric effect

4. Compton scattering

What accounts for 9% of the xrays passing through the patients tissue

no interaction

What accounts for 8% of the interactions of matter with the dental xray beam is?

coherent scattering

What percent does the photoelectric effect account for?

30%

What percent does the Compton scattering account for?

60%

What is the SI & traditional unit for Exposure?

coulombs per kg (C/kg)

roentgen (R)

What is the SI & traditional unit for Absorbed Dose?

gray (Gy)

rad

What is the SI & traditional unit for Dose Equivalent?

Sievert (Sv)

rem

What does milliampere (mA) measure?

amount of current passing through the wires of the circuit

What does kilovolt peak (kVp) measure?

speed of electrons traveling toward target on the anode, the penetrating ability of the xrays

How many impulses in a second?

60 impulses

What do you call the beam of the xray?

primary beam or useful beam

radiolucent

dark or black

radiopaque

light or white

density

darkness, blackening

contrast

shades of gray

long scale

low contrast and longer scale

a high contrast image will have few or many shades of gray?

few

What is the relationship between kVp and contrast?

inverse relationship