Saia Unit 3 Flashcards
the 3 cardinal rules for xray:
time, distance, shielding
inverse square law:
I1/I2=D2^2/D1^2
primary protective barrier:
direct impact, 1/16” lead or equivelent; 7 feet high
secondary protective barrier:
scatter/leakage, 1/32” lead equivelent
xray must scatterat least:
2 times before hitting the control booth
protective tube housing enclosed by lead lined metal covering:
1/16 lead, reduces leakage
leakage from the tube housing should exceed:
100mR/hr at 1 meter
time of occupancy factor:
amount of time an area is ossupied and by whom
workload:
radiation activity level (max kvp and max mas)
Use:
the amount of time xray is “on” during the day
Lead underwear keep radiation and are used for:
brachytherapy of the prostate
mobile unit switch
should allow tech to obtain at least a distance of 6’ from patient
fluoroscopy drapes and bucky slot cover should have a minimum:
.25mm pb/eq
fluoroscopy deadman switch:
only emits radiation when constant pressure is applied
c-arm source to tabletop must not be less than:
12”
source to tabletop for fixed fluoro unit must not be less than:
15”
Total filtration of fluoroscopy equipment must be at least:
2.5mm al/eq
cumulitive timing device in fluoro creates an audible sound after:
5 minutes
lead used in fluoroscopy must be at least:
.5mm pb/eq
Fluoroscopy xray intensity at tabletop must not exceed:
10R/min
Fluoroscopy uses a high KV and low MA to
minimize dose
Fluoroscopy MA must not exceed:
5MA
Air exposure is measured in:
Traditional - Roentgen (R) ; SI - Air Kerma - grays in air (gyA)
Absorbed dose is measured in:
Traditional - RAD; SI - grays in tissue (gyT)
1 Gray is equal to:
100 Rads
Dose equivelent (tissue damage due to dose) is measured in:
Traditional - REM; SI - Seivert
RAD X QF =
REM
Activity is measured in:
Traditional - Curie; SI - Bacquerel
Roentgen (T) =
Air Kerma (SI)
RAD (T) =
Gray (SI)
REM (T) =
Sievert (SI)
Curie (T) =
Bacquerel (SI)
Quality Factor for Xray. Gamma, Beta =
1
Quality Factot for Alpha:
20
An Optically Stimulated Luminescence (OSL) Badge:
Uses Aluminum Oxide and is accurate to 1 mREM (like our badge)
A film badge uses:
Real film (old school)
A Thermoluminescent Dosimeter (TLD) badge uses:
lithium fluoroide - used in nuclear medicine
A pocket dosimeter uses:
ionization chamber, has an immediate readout, but not highly accurate
EMR - Elecrtromagnetic Energy:
Bundles of pure energy, no mass, no charge, moves at speed of light, waveform movement
Photon:
smallest quantity of any type of EMR;
AKA quanta or ray
ionizing radiation:
energy with the ability to disrupt atomic structure thereby creating ions
Energy Based:
low LET; XRAY/Gamma; bundles of pure energy; no mass/charge; travel at speed of light; waveform movement
Matter Based:
high LET; Alpha, Beta, Photon, Neutron; have matter/mass/charge; travel slower than the speed of light; straight line movement
Primary radiation:
radiation produced in xray tube, AKA useful beam
secondary radiation:
a brand new xray produced in the patient
Scatter:
re-directed primary radiation due to interraction with matter
remnant radiation:
portion of the primary beam that survives the trip through the patient
leakage radiation:
X-ray that escapes the tube housing at a point other than the tube window
off focus radiation:
X-ray produced at points of the anode other than the true/actual focal spot
Annual dose limit (Occupational) for whole body:
5 rem (50 mSv)
Annual dose limit (Occupational) for lens of eye:
15 rem (150 mSv)
Annual dose limit (Occupational) for skin/extremities:
50 rem (500 mSv)
Annual dose limit (Occupational) for whole body cumulitive:
Age x 1 rem (age x 10 mSv)
Annual dose limit (Occupational) for fetus (9 month):
0.5 rem (5 mSv)
Annual dose limit (Occupational) for fetus (1 month):
.05 rem (0.5 mSv)
Annual dose limit (Occupational) for Student less than 18 years old:
0.1 rem (1 mSv)
Annual dose limit (PUBLIC Exposure) for Infrequent Exposure:
0.5 rem (5 mSv)
Annual dose limit (PUBLIC Exposure) for Frequent Exposure:
0.1 rem (1 mSv)
3 things for xray production:
source of free electrons, acceleration of electrons (kv); Halting of accelerated electrons (Tungsten)
Photon:
smallest quantity of any type of electromagnetic energy
Amplitude:
one half the range from crest to valley
Frequency:
number wavelenths that pass a given point per second
frequency is measured in:
Hertz (Hz)
Wavelength:
the distance from one crest to the next or valley to valley
wavelength is measured in:
Meters
Velocity:
All EMR’s travel at the speed of light (c)
speed of light =
frequency x wavelength (c = f x ?) - symbolized by the figure “lambda”
Velocity is
constant
Speed of light:
3 x 10^8 m/s
xray tube consists of:
a cathode and anode encapsulated within a glass envelope and then encased in a protectuve housing
why a glass envelope?
to maintain a vacuum within
Why a vacuum?
so electrons accelarated from cathode to anode dont bump into anything AND to prevent the filament from burning
Cathode:
the negative side of the xray tube whose function is to emit electrons
Cathode consists of
a filament (tungsten), a focusing cup, and associated wiring
Thermionic Emission:
electron emission from a heated source
Electron cloud/space charge:
collection of electrons “hover” off of the filament when prep/rotor pressed
focusing cup:
cup that encases the filament, possesses a negative potential focusing electrons away from the cathode side
Anode:
positive side of the xray tube whose function is to receive the stream of high speed electrons
Anode consists of
Anode, stator, rotor, associated wiring
metallic housing:
protects the xray tube within, absorbs unusable xrays
oil-filled tube housing:
protects from unnecessary radiation, electrical risk, conducts heat away
Tungsten:
high melting point, high atomic number (74), good conductor of heat/electricity
Incident electrons:
electrons boiled off the filament accelerated toward the anode disk, possess massive kinetic energy
KE =
1/2m x V^2 (kinetic energy)
Voltage -
the force that propels electrons
KVP -
the force of electron propulsion from cathode to anode
As KVP goes up, the force ofelectron propulsion:
goes up
MA:
the number of electrons thermionically emitted from cathode filament per second
Amperage:
the number of electrons
1 Ampere:
6.3 x 10^18 electrons
MAS:
the number of electrons accelerated from cathode to anode
MAS has primary control of:
image density
Density:
overall image blackness
Bremstrahlung Interaction:
BRAKING; strength exactly equal to the amount of electron kinetic enegy lost
A vast majority of xrays created are:
Bremstrahlung
Characteristic Interaction:
COLLISION; strength equal to the difference in binding energies collision
Tungsten Binding Energies: K Shell -
69.5 KEV
Tungsten Binding Energies: L Shell -
12.1 KEV
Tungsten Binding Energies: M Shell -
2.8 KEV
Tungsten Binding Energies: N Shell -
0.6 KEV
Tungsten Binding Energies: O Shell -
0.08 KEV
Tungsten Binding Energies: P shell -
0 KEV
Classical or Coherent -
AKA Thomson or Rayleigh - SPONGE; secondary xray = primary xray
Photoelectric Interaction -
inner shell collision, characteristic cascade
Linear graph -
dose and response are proportional (straight line)
nonlinear graph -
dose and response not proportional (curved line)
threshold -
a certain dose is required before a response occurs
nonthreshold -
any exposure will cause a response
radiation protection is based upon:
nonlinear, nonthreshold
somatic effect:
damage sustained by a living organism as a result of exposure to ionizing radiation
stochastic effect:
doubt (probabilistic)
nonstochastic:
no doubt (deterministic)
fractionation:
several low dose exposures delivered over a long period of time
protraction:
single high dose exposure over a short period;
a single high dose is:
more harmful than several low doses
LET -
amount of energy transferred to tissue per unit of distance traveled in tissue
High LET:
have matter, mass, charge, straight line movement, slower than the speed of light
Low LET:
no charge, no mass, travel at speed of light, waveform movement
high LET:
Alpha (dangerous)
OER:
Oxygen Enhancement Ratio
As OER goes up, biological damage
goes up
RBE: Relative Biological Effectiveness -
biological damage produced by radiation in tissue
Quality factor for Xray, Gamma, & Beta =
1
Quality factor for Alpha =
20
Direct Action =
high LET
Indirect Action =
low LET
Single strand break -
point mutation (low LET)
Double strand break =
rupture of both DNA side rails
Mutation -
Alteration of DNA base sequence
Target theory:
master molecule within a cell; unique or key molecule, cannot be replaced
Apoptosis:
programmed cell death, occurs during interphase
Law of Bergonie and Tribondeau:
cells most sensitive to radiation injury/death include least mature/specialized, high reproduction activity, longest mitotic phase
Radiosensitive cells:
erythroblasts, lymphocytes, epithelial/endothelial tissue, oocytes, sperm, intestinal
Radioinsensitive cells:
muscle, nerve, bone, cartilage, tendons, ligaments
ARS - acute radiation syndrome:
a collection of symptoms associated with a high level of radiation to the whole body in a short period of time
4 Stages of ARS -
Prodromal stage (initial); Latent; Manifest Illness; Recovery/Death
Prodromal stage occurs:
within hours, after a whole body dose of 100 Rads ++
Latent stage occurs:
after prodromal, no symptoms, appearance of feeling better
Manifest stage:
symptoms visible, 3 types - hemaopoeitic, gastrointestinal, cerebrovascular
Hematopoeitic:
100+ Rads of whole body dose; AKA bone marrow syndrome; death in 6-8 weeks
Gastrointestinal:
600+ Rads of whole body dose; death within 3-10 days as a result of epithelial damage to GI tract
Cerebrovascular:
5000+ Rads of whole body dose; death within a couple hours-days due to increased intra cranial pressure due to damaged vessls leaking
X-ray was discovered
11/8/1895 by Roentgen
