physics 1-2 exam

ionizing radiation

radiation w/enough energy to free electrons from atoms forming ions, may cause cancer (ex. gamma, X-rays, UV).

energy capable of penetrating matter, AND eject an orbital electron from an atom's shell

natural (background)

Radiation that is contained in the environment:

-cosmic

-gases

-internal

-terrestrial

Man-made (artificial) radiation

ionizing radiation created by humans for various uses

-medical procedures

-nuclear industry

-consumer products

natural radiation and sources

-background radiation

-occur spontaneously in nature

-NOT affected by human nature

sources:

cosmic- sun/stars

gases-radon/thoron (37%)

internal - potassium 40 (5%)

terrestrial- uranium/thorium (3%)

Man-Made Radiation Sources

- computed tomography (24%)

-nuclear medicine (12%)

-interventional fluroscopy (7%)

- conventional radiography/ fluroscopy (5%)

- consumer prodcuts (2%)

-industrial (

Consumer products

-smoke detectors

-clocks/watches

-camera lens

-ceramics

-glass

-fertillzer

-exit signs

Crookes tube

by William Crookes.

glass tube filled with a small amount of gas. Electrodes (cathode/anode) in the tube allow for the passage of electricity through the gas.

-fluorsced when energized

Dr. Wilhelm Roentgen

Discovered X-rays on November 8, 1895.

"x-light"

x represents the unknown

director of physics institute

Rontgen Experiment

studying the flurescent properties of cathode rays

1.covered cathode ray tube with black cardboard

2. energized cathode ray tube

witnessed nearby piece of cardboard fluoresce (covered with barium platinocyanide)

7 weeks investigation

12 properties of x-rays

1) highly penetrating, invisible

2) electrically neutral, not affected by electric or magnetic fields

3) can be produced over a wide variety of energies and wavelengths (polyenergic/heterogenous)

4) produce secondary/scatter radiation

5) travel at the speed of light, 3x10^8 miles per second

6) travel in straight lines

7) canNOT be focused by a lens

8) cause flourosence (emission of light) of certain crystals

9) can affect photographic film

10) can ionize matter

11) release small amounts of heat when passing through matter

12) produce chemical/biological changes in matter through

Rontgens first radiograph

-first radiograph of body part

bones of his wife's hand (bertha rontgen)

-used barium platinocyanide screen

-recorded on photographic paper

early medical use

inefficient and varied x-ray output

- low kVp

-long exposure times (20-30min) could take 2 hours

indications for early medical x-ray

- Gallstones

- Bullets & Broken Bones

- Kidney Stones

Dangers of Early X-ray

-thought to be harmless

equipment was not enclosed, shielded or grounded

-skin damage, hair loss, anemia

-thought burns were caused by the heat/glow of the cathode ray tube

Thomas Edison

Invented the light bulb/ fluoroscope

-1st to document serious dangers with x-rays

-suffered radiation burns to his face and injury to his left eye during his experiments

Clarence Dally

-Thomas Edison's Assistant.

-1st documented fatailty from x-ray exposure

-death within 8 years

Dr. William Coolidge

-Developed "hot cathode" tube (coolidge tube)

-x-ray intensity/energy set separately

-intensity controlled by milliamperage (mA)

-energy controlled by kilovoltage peak (kVp)

Kilovoltage peak (kVp)

Highest voltage of x-ray tube used during an exposure

QUALITY

Milliamperage (mA)

QUANTITY of exposure

Snook apparatus

portable machine consisting of

-rotary converter

-transformer

-high-tension rectifier

connects with coolidge tube or any ordinary tube

ALARA Principle

Keep radiation exposure as low as reasonably achievable.

the 3 cardinal rules

Time, distance, shielding

time

MINImize the length of time exposed to ionizing radiation for patient, technologist

-length of exposure

-number of times the patient is exposed for a radiologic exam

-time a radiographer spends in a procedure involving fluroscopy

distance

MAXImize the distance from the source of ionzing radiation during an exposure

-inverse sqaure law

Inverse Square Law

the intensity of radiation is inversely proportional to the square of the distance from the source of radiation

-as one increases the distance from an ionzing radiation source, the intensity (quanitity) decreases

Shielding

use of radiopague materials to reduce radiation exposure to

-patient anatmoy that is not important to exam being done

-radiographers during exam

-personnel who are not able to leave exam area

most common material - lead

Protective Apparel

must be worn

must be at least 0.25 Pb

0.5 mm Pb is commonly used

reduction of occupational radiation exposure

will not exceed 1 mSv/yr

-useful beam never diercted toward operating console

-exposure cords on mobile units must be at least 2 meters long

-protective aprons

-structural lead shielding

primary barriers

Any barrier that has the potential of being struck by the primary beam

- lead 1/16 in. of lead (Pb) 7 ft. high

-perpendicular to the line of travel of the primary x-ray beam

-floor beneath the x-ray table

-wall behind upright bucky

Secondary Barriers

only be struck by scatter radiation

parallel to the line of travel or the primary x-ray beam

covers areas only exposed to scattered/leakage radiation

-wall separating the control/exam rooms

-ceiling

1/32 in Pb

factors that determine protective barrier thickness

-distance

-time of occupancy

-workload

-use (u)- % of time that x-ray beam is energized and aimed

Time Occupancy

amount of time an area is occupied by people

controlled time

-occupied by radiation

-designed to reduce exposure rate to less than 100 mrem/wk

Uncontrolled time

occupied by non-radiation personnel (general public)

-deigned as either full, partial, occasional

reduce exposure less than 10 mrem/wk

workload

radiation level activity in that area

-the more exams performed, the thicker the barrier needed

-accounts for weekly average tube current/tube

measured mA-min/wk

Collimator

Restricts the size and shape of the x-ray beam

Low kVp

high contrast

patient's tissue abosrbs ALL photons and don't reach receptor = WHITE image

High kVp

low contrast

photons pass through patient's tissue and reach receptor= DARK image

beam energy/ penterating abilty increases

Low mAs

not enough photons to record the body part on the receptor= White image

high mAs

too many photons reach receptor= Dark image

increases x-ray quantity

15% rule

A 15% increase in kVp causes a halving mAs

output intensity intensity in air

-British: Roentgen(R)- Quantify radiation intensity

-SI Metric System: coulomb/kilogram(C/kg)- Measure of the # of electrons liberated by ionization per kilogram of air

SI unit of radiation exposure

radiation absorbed dose (rad)

gray (Gy)

dose equivalent/ effective dose

radiation equivalent man (rem)

sivert (Sv)

acivity

curie (ci)

becquerel (Bq)

Coulomb per kilogram (C/kg)

measure of the # of electrons liberated by ionization per kilogram of air

Roentgen (R)

The amount of radiation that ionizes one cubic centimeter of air

Gray (Gy)

quanitity of radiation energy absorbed by tissues being irradiated

radiaton abosrbed dose (rad)

quantify the biologic effects of radiation on humans and animals

-gives measure to the amount of energy depostied by ionzing radiation

1 Gy = ___ rad

100 rad

1 rad = ___ Gy

0.01 Gy

Sievert (Sv)

addresses the different biologic effects of different types of ionizing radiation to which a radiation worker may be exposed

Radiation Equivalent Man (rem)

standard unit for occupational exposure

1 Sv = ___ rem

100 rem

1 rem= _____ Sv

0.01 Sv

Becquerel (Bq)

quantity of radioactive material

-not the effect of the radiation emitted from it

-is quantifying the # of indivdual atoms decaying per second

Curie (Ci)

traditional unit of radioactivity

kerma

kinetic energy released in matter

describes the quantity of radiation energy delivered to a given point

unit: joules/kg or Gy

air kerma

kinetic energy released per unit mass of air

1 R = air kerma

1 sv = ___ mSv

1000 mSv

1 rem = ___ mSv

10 mSv

1 rem = ___ rad

1 rad

annual dose limits

5 rem (50 mSv)

cumulative dose limit

10 mSv/ 1 rem x age (ex: 25 yo -> 250 mSv)

lens of eye dose limit

150 mSv/yr (15 rem)

skin, hands, feet dose limit

500 mSv/year (50 rem)

continous dose limit

1 mSv (0.1 rem)

2 types of personnel monitors

thermoluminescent (TLD) & optically stimulated luminscence (OSL)

OSL dosimeter

most common

consists aluminum oxide, unaffected by heat, moisture, and pressure

can measure as low as 10 uGya

can be worn for intervals up to 1 year

worn on torso

TLD dosimeter

contains lithium fluoride , has crystals, the more light= the more exposure

can measure exposure as low as 50uGya

can be worn up to 1 year

extremity TLDs

worn on fingers of dominate hand

when wearing gloves should be worn under gloves

label should be palm-side of hand

Dosimetry report

Provides radiation readings to occupational radiation workers

SL

minimal dose or dose under 20 mrem

electromagnetic theory

- has no mass

-carries energy in waves

- travels speed of light (186,000 mps or 3x10^8)

Transverse Waves

displacement is PERPENDICUALR to the direction the wave is traveling

MAGENTICE FIELD

Longitudinal Waves

displacement is PARALLEL to the direction the wave is traveling

ELECTRIC FIELD

origin of EMR

EM waves are emitted when changes in atoms occur

-electrically charged particles which are moving, generate electrical and magnetic fields that are perpendicular to each other

velocity

how FAST the wave is moving; constant

ALL EM ENERGY TRAVEL AT THE SPEED OF LIGHT IN A VACCUM

Amplitude

Height of a wave

TALLER waves carry more magnitude or more mass

intensity of the wave- controlled by mA and quantity

wavelength

length of a wave from one peak to the next peak

INVERSELY PROPORTIONAL TO ENERGY/ FREQUENCY

Frequency

# of cycles per second

DIERCTLY PROPORTIONAL TO ENERGY

INVERSELY PROPORTIONAL TO WAVELENGTH

wavelength and frequency relationship

inversely related

wavelength formula

velocity= freq x wavelength

Photon Energy

Directly proportional to frequency

controlled by Kvp

Attenuation

total # of photons

photon energy and frequency will

DECREASE

photon wavelength will

INCREASE

increase Kvp

increase energy, frequency,

decrease wavelength

decrease Kvp

increase wavelength

decrease photon energy, frequency

increase thickness in matter

decrease energy/frequency

increase wavelength

decrease thickness in matter

increase energy/frequency

decrease wavelength

quantum theory

x-ray photon is a discrete bundle of energy

quantum of EM energy

photon energy is direclty proportional to its frequency

E= hf

low to high frequency radiation

radio waves

microwaves

infrared radiation

visible light

ultraviolent

x-rays

gamma rays

radio waves

low energy

long wavelength

MRI

cannot ionize atoms

idenfited by frequncy

Microwaves

shortest wavelengths

highest frequencies

commonly used to transmit cell phone signals and heat food

do not ionize atoms

infrared light

-Sometimes used to "beam" information between electronic devices

-Does not ionize atoms

heat

visible light

represents the colors we see in the world around us

it is a tiny portion of the electromagnetic spectrum

does not ionize atoms

identifed by wavelength

Ultraviolet Light

- Has energies approaching those of x-rays and gamma rays

- Commonly used in tanning beds

- Can be harmful

- Stimulates melanin production in skin cells

- Does not ionize atoms

x rays and gamma rays are similar bc

high frequency

short wavelength

ionizing elec, radiation

Wave-Particle Duality

electrons and light can behave as both a wave and a particle