RAD 110 (Radiation Protection) - Test 2

Quality, penetrating power, peak kilovoltage

kVp

Higher kVp means ____

Higher kVp

What do you have to do with kVp when you have a thicker body part?

Increase

What comes out of the tube?

kEv

Quality, main factor in pt dose, the number of x-ray photons coming out of the tube

mAs

What is the radiographer job?

Select technical exposure factors, minimize dose to pt.

What happens is x-rays enters human tissue they may _____

Be absorbed, scattered, and/or pass through without interaction

What is the amount of energy per unit mass?

Absorbed dose

What happens if no x-ray photon gets absorbed into the pt?

There would only be a black image

How is a diagnostic x-ray beam produced?

When energetic electrons interacts with a positively charged target in a vacuum tube made of tungsten

Why are tungsten and tungsten phenix used as target materials?

they have high melting points and high atomic numbers

x-ray photons have a wide range of energies called

polyenergetic

Permanent Inherent Filtration is ____

filtration that is built into the x-ray tube (glass and added aluminum)

HOG

housing, oil, glass/metal

Anything that comes out of x-ray tube that goes towards the pt and IR

Primary Radiation

What is the energy of the electrons inside the x-ray tube specified in terms of?

Electrical voltage

Due to voltage acrid the tube fluctuating, it is usually characterized as?

kilovolt peak value (kVp)

An x-ray beam that passes through a pt, and does not reach the IR

Attenuation

All photons got absorbed in the tissue of pt

Absorption

Photons bounce off pt and doesn't hit IR

Scatter

What do both absorption and scatter do?

interact with pt tissue

Photons that go straight to the IR and don’t touch the pt

direct transmission

Photons go through the pt and still hit the IR (scattered or deflected)

Indirect transmission

x-ray that comes down, changes direction slightly, still hits the IR, but is not good to us (unwanted density)

Small angle scatter / fog

interaction of photons with biologic matter is ____

random

What 2 of the 5 types of interactions are important in diagnostic radiology?

Compton scattering and photoelectric absorption

No loss of energy, no interaction, very small change in direction, no impact on image, and less than 10 keV

Coherent Scattering

diagnostic radiology energy range:

23-150 kVp

Most important interaction, responsible for pt dose and contrast on image

Interaction between x-ray photon and inner shell electron (K or L), electron from outer shell drops down to inner shell and releases energy.

Photoelectric absorption

back and white in terms of contrast (finger)

High

beige and white in terms of contrast (chest an abdomen)

low

The energy that is released from outer shell electron dropping down to fill a vacancy in photoelectric absorption is called

characteristic photon

the energy of the _____ photon is less than the energy of incoming photon

Characteristic

The probability of occurrence of photoelectric absorption depends on:

Energy being strong enough and atomic number high enough

Higher the kVp the absorption is going to ____

decrease, go through without any interaction is going to increase

the greater the difference in the amount of photoelectric absorption, the ____ the contrast in the image.

greater

as absorption ____, the potential for biological damages increase.

increases

How do we get out radiation dose from?

being in the room with the pt while image is being taken and compton scattering occurs.

x-ray photon interacts with loosely bound outer shell electron ejecting it, changing direction of the photon. when this hits the IR we call it fog

compton scattering process

where in the room do you get the least amount of scatter radiation at?

right angles from the pt

What part of the room do you need to avoid the most?

The backside of the table

When energy (kVp) increases, the chances of compton interaction ______

increases

When energy (kVp) is lower, the probability of PE (photoelectric) interactions ______.

increase

What does compton scattering add to the image?

unwanted density

Compton scattering is the primary source of ______ exposure.

occupational

What are the 3 ways to control compton?

collimation, grids, compression

Occurs at 1.022 MeV (million), interacts with the nucleus, occurs in nuclear medicine

pair production

occurs at more than 10 MeV, high-energy radiation therapy treatment, interacts with nucleus, occurs in the nucleus, used in radiation therapy

Photodisintegration

x-rays were discovered

November 8, 1895 by Wilhelm Roentgen

First reports of injury from radiation

Somatic damage, redness of the skin, cancer, and blood disorders (anemia)

Used to measure radiation exposure 1900-1930

skin erythema dose

measured in the air, the amount of radiation measured above the table top

exposure (C/kg)

how energy is transferred from a beam of radiation to pt skin

Air Kerma (Gy_a)

Amount of energy given to the pt by the x-ray beam, total of air karma over the exposed area of pt surface, usually specified in units of mGy-cm²

Dose area product (DAP)

DAP Calculations

air kerma dose x irradiated surface area

If a pt receives 40 mGa to a surface area of 150 cm². what is the ____?

energy absorbed by the body, SI is Gy, traditional is RAD

Absorbed dose

The average absorbed dose in a tissue or organ

D x W_R or Sv = Gy x W_R

Equivalent Dose (EqD)

the type of radiation and the radiosensitivy of the organ irradiated

D x W_R x W_T

Effective dose (EfD)

used for radiation protection purposes, places risk associated with biologic effects on a common scale

Radiation weighting factor (W_R)

accounts for the risk to the entire organ by specific organs and tissues

Tissue weighting factor (W_T)

how much energy is deposited into the tissue

Linear Energy Transfer (LET)

When the weighting Factor increases, LET _____

increases

quantity used to describe radiation exposure of a population or group, average EfD for individual x the # of people

Collective EfD

quantity that monitors and controls human exposure ionizing radiation

Total Effective Dose Equivalent (TEDE)

Traditional: Roentgen (R)

SI: Coulombs per kilogram (C/kg)

Traditional to SI: R x .000258

SI to Traditional: C/kg / .000258

Exposure

SI: Gray (Gy_a)

No conversions

Air Kerma

SI: Gray (Gy_T)

No conversions

Tissue Kerma

Traditional: Radiation Absorbed Dose (RAD)

SI: Gray (Gy)

Traditional to SI: RAD / 100

SI to Traditional: Gy x 100

Absorbed Dose

Traditional: Radiation Equivalent Man (REM)

SI: Sievert (Sv)

Traditional to SI: REM / 100

SI to Traditional: Sv x 100

Equivalent Dose

Traditional: Radiation Equivalent Man (REM)

SI: Sievert (Sv)

Traditional to SI: REM / 100

Si to Traditional: Sv x 100

Effective Dose

Traditional: man / REM

SI: person / sievert

Traditional to SI: (man / REM) / 100

SI to Traditional: (person / sievert) / 100

Collective Effective Dose

Traditional is always _____ than SI

larger

How does peak kilovoltage (kVp) influence the x-ray beam?

It influences both the quality (penetrating power) and quantity (number of protons) in the slightest

What is the role of milliampere-seconds (mAs) in x-ray exposures?

Governs the amount of radiation produced

Why is minimizing transferred energy important in x-ray absorption in biological tissue?

to reduce the risk of biological damage

What is the purpose of filtering out low-energy x-rays in x-ray beam production?

to enhance image quality

which interaction is crucial for diagnostic radiology, causing small angle scatter and potentially degrading image quality?

photoelectric (most crucial) and compton scattering

Why is predicting the average outcome important in dealing with a large number of photons interacting with matter?

to minimize pt dose

How does photoelectric absorption impact radiographic contrast?

It enhances image contrast

What influences the probability of photoelectric absorption in specific materials?

atomic number (Z) and incident photon energy (E)

When might radiographers manually adjust technique factors, and how does raising kilovoltage peak (kVp) affect pt dose and image contrast?

To decrease pt dose, decrease image contrast

In the 1930s, what was the principle guideline for occupational radiation exposure tolerance levels?

Roentgen (R)

What was introduced as the unit to express radiation exposure in the SI system?

Coulomb per kilogram (C/kg)

Which term represents the product of the average absorbed dose and the radiation weighting factor?

Equivalent dose (EqD)

What is the primary purpose of the tissue weighting factor (W_T) in radiation protection?

To calculate effective dose (EfD)

Which dosimetric quantity attempts to describe the radiation exposure of a population from various sources?

Collective Effective Dose (ColEfD)

What is the purpose of the total Effective Dose Equivalent (TEDE)?

To account for all possible sources of radiation exposure

LET increases, bio effects ______

increase