Results in ionization of atoms.
Loss of electrons
___________ must outweigh the ________ of any x-ray diagnostic study.
Two sources of ionizing radiation
natural and manmade
_____________ and __________ x-ray examinations make up the largest portion of human-made radiation exposure.
Medical and dental
Conditions necessary for x-ray production.
Source of electrons (Cathode filament)(negative) Means of accelerating electrons/high-speed motion (Voltage) Mechanism stopping electrons abruptly/deceleration (Target/Anode)(positive)
Energy of beam is expressed in __________.
Kiloelectron volts (keV)
Three possible paths an x-ray beam can undergo.
Total absorption Pass through with no energy loss Scattering/secondary interaction with loss of energy
Five types of x-ray interactions with matter.
Classic coherent scattering Photoelectric interactions Compton scattering Pair production Photodisintegration
Who does photoelectric interactions expose?
Who does compton scattering expose?
Involves very-low energy x-rays. No ionization occurs.
Classic Coherent Scattering (Thompson scattering)
What does coherent scattering do to an atom?
Atom becomes excited and emits x-ray with same energy.
Classic Coherent Scattering occurs when x-rays possess energy levels below what keV?
Occurs within the diagnostic x-ray energy range
Photoelectric effect Compton scattering
Incoming x-ray photon is completely absorbed by collision with inner-shell(k-shell) electron.
What does Photoelectric effect do to an atom?
-Electron (photoelectron) leaves atom, creating an ion pair. -Free electron eventually unites with other matter. -Secondary radiations created as a result of electron cascade from outer shells to inner shells.
In the Photoelectric effect, which electron produces an x-ray with energy high enough to impact your image?
The electron that drops in to the hole in the k-shell
Radiation interaction responsible for most hazard to patients. Why?
Photoelectric effect Because there is complete absorption in the patient
Incoming photon collides with outershell electron
What does Compton Scattering do to an atom?
-Incoming photon collides with outershell electron, creating a free Compton electron (recoil) and an ion pair. -Incoming photon loses some of its energy through collision, scatters off in a random direction (scatter angle), and undergoes other interactions until its energy is gone. -The electron vacancy is filled nearly instantly.
Reaction with matter that requires very high energy photons.
For the pair production to occur, the energy of the incoming x-ray photon must be at least:
What does Pair Production do to an atom?
-The incoming photon interacts with the force field around the nucleus then disappears. -Two particles reappear, each with equal energy (0.51 mEv). -The positron collides with a free electron and creates an annihilation reaction. -Annihilation reaction creates two photons at opposites angles to each other.
Reaction with matter that requires the energy of the photon to be extremely high.
What does Photodisintegration do to an atom?
-Incoming photon interacts with nucleus of atom, creating nuclear instability. -Nuclear fragment is given off as nucleus seeks stability
Common interaction in the nuclear industry
Measures exposure in air and is not used to express absorbed dose to individuals. A measure of ionization in air as a result of exposure to x-rays or gamma rays
Roentgen (Coulombs per Kilogram)
Measures the amount of energy absorbed in any medium, defined as 100 ergs of energy absorbed in 1 g of absorbing material
Radiation absorbed dose(rad) (Gray)
___ Gy = _____ rad
1 Gy = 100 rad
Unit of dose equivalence. Accounts for different types of radiation and their biologic effects
Radiation equivalent man (rem) (Sievert)
formula for rem
rem = rad × QF(quality factor)
Used to measure energy transferred from radiation to a material
What is KERMA?
"kinetic energy released in matter"
Measures the activity of a radioactive material (radionuclide) Used in nuclear medicine and radiation therapy
What is curie equal to?
1 Ci = 3.7 × 10^10Bq
Who regulates the Standards of Exposure?
FDA and its Center for Devices and Radiological Health (CDRH).
As Low As Reasonably Achievable
Dose equivalent for radiation workers is based on radiation received from what source?
The annual whole-body effective dose limit for the occupational worker is ____ mSv (____ rem).
50 mSv (5 rem)
Two major parts of a cell.
____% of cell content is water
Two classes of human cells.
Somatic (any cell that is not a genetic cell) Genetic (will affect future generations)
Perform all the body's functions
How many chromosomes does a somatic cell posses?
46 (23 pairs)
Reproductive cells of an organism. Very radiosensitive.
How many chromosomes does a germ cell possess?
Two theories of cellular irradiation damage exist.
Direct-hit theory Indirect-hit theory
According to the law of Bergonie and Tribondeau, cells are more radiosensitive if they are __________.
Highly mitotic Primitive in structure
Cells are most sensitive to radiation during __________.
Active division (More immature/rapidly dividing)
Results of radiation to a cell
Cellular death Delayed mitosis Altered mitotic rate
Acute radiation syndrome stages. Requires large amounts of total body exposure.
Prodromal stage Latent period Manifest stage Recovery or death
Bone marrow syndrome Gastrointestinal syndrome Central nervous system syndrome -Results in eventual death.
Cardinal rules of protection of patient.
Time (lowest possible) Distance Shielding
Three popular monitoring technologies
Pocket dosimeter Optically stimulated luminescence dosimeter(OSL) Thermoluminescent dosimeter (TLD)
Personal radiation monitor that will provide a near immediate reading of radiation exposure.
Occupational Personnel Monitoring Rules
Worn at the collar level Worn outside of lead apron Device should face forward. Pregnant radiographers may have a second device worn at waist level and under the lead apron
Monthly equivalent dose to fetus should not exceed _____mSv (____ rem)
0.5 mSv (0.05 rem)