Radiation Protection Flashcards
radiation that has the ability to make an atom a charged particle
ionizing radiation
has to have mass
doesn’t travel far
particulate radiation
what do we treat superficial with?
electrons
how do we treat deeper?
photons
energy and wavelength are ___ proportional
inversely
two major groups of radiation in rad therapy
external beam
brachytherapy
External beam:
linear accelerators/cobalt 60 machines
produce x-rays, gamma rays, and electrons
Brachytherapy sources:
137Cs, 192Ir, 125I
emit gamma rays, x-rays, alpha particles, and beta particles
example of alpha particles
helium nuclei
2 protons, 2 neutrons
alpha particles have a ___ LET
high
How do alpha particles do damage?
They have to get inside of you
how are alpha particles emitted?
from unstable nuclei
comes from nucleus
ex) radium or radon
where are beta particles edited from?
the nucleus
beta particles can be _____ or ______ charged
negative, positive
What is the rest mass of an electron?
.511 MeV
rest mass of an electron
how are beta particles best shielded?
plastic or glass
what equation is the photoelectric effect dependent on
z^3/e^3
what is the difference in x-rays and gamma rays?
gamma rays- nucleus
x-rays- orbitals
what percent of X-ray interaction is brems?
85%
what percent of x-ray interactions is characteristic?
15%
What are the sources of radiation?
- natural background
- man made
What are the natural background sources of radiation?
- cosmic: from space
- terrestrial: from ground
- internal exposure: radioactive material in body
What is an ex. of terrestrial radiation?
radon
2nd most common for lung cancer
Units for exposure
traditional: roentgen
SI: coulomb/ Kg of air
Units for absorbed dose
traditional: rad
SI: Gray
Unit for dose equivalent
** Quality Factor**
traditional: rem
SI: sievert
Unit for activity
brachytherapy
1 disintegration/sec
traditional: curie
SI: bequerel
1 roentgen= ? Coulomb/Kg of air
2.58x10^-4
quality factor of:
x-rays, gamma rays, and electrons
1
quality factor of:
thermal neutrons
5
quality factor of:
neutrons, heavy particles
20
Types of measurement devices:
- gas filled detectors
- TLD
- Film
- Pocket ionization chambers
- neutron detectors
types of gas filled detectors
-calibrated within 2%
- ionization chamber (pocket dosimeter)
- geiger muller detector (very sensitive, measures presence of radiation)
TLD
thermoluminescent dosimeter lithium fluoride, dose can be stored for days anneling process 1 hour: 400 degree C 24 hours: 80 degree C
pocket ionization chambers
immediate readout
initially expensive
for infrequently exposed
has to be charged to zero it out
neutron detectors
“rascal”
BF3 or Argon
bubble counters
OSL
optically stimulated
light in relation to dose
Al2 O3
rascal neutron detector
boriated polyethylene
above 10
our range 6-20
Regulatory Agencies:
National Council on Radiation Protection and Measurement
NCRP
set exposure levels
Regulatory Agencies:
International Commission on Radiation Protection
ICRP
set exposure levels
Regulatory Agencies:
Nuclear Regulatory Commission
NRC
isotope usage
Regulatory Agencies:
Food and Drug administration
FDA
linac license
Regulatory Agencies:
Department of Transportation
DOT
Transporting isotopes
Non stochastic effects
deterministic
threshold
stochastic
non threshold
dose response curves
linear and quadratic
probability increases with dose, not sensitivity
Somatic effects
in exposed individual
carcinogenesis
genetic effects
occurring in future children
mutagenesis
developmental effects
develop while in eutero
teratogenesis
embryologic
ALARA
as low as reasonably achievable
comparable risk
it shouldn’t be more dangerous to work in our field than any other
genetically significant dose
GSD take into account all radiation types
measurement of genetic rise to an entire population
3 major rules of radiation
- time
- distance
- shielding
In cobalt machines, exposure must be less than ____ at any point ___ m from the source
10 mR/ hour
1 m
if average radiation reads ___ then it is outside the range of reading
2 mR/ hr
What are the shielding factors?
B=pd^2/WUT
w- workload u-use factor t- occupancy factor d- distance b- transmission factor p- point of interest dose
Safety equipment
examples of quality assurance testing
- warning signs
- warning lights
- door interlocks
- visual and aural communication (should be able to see and hear pt)
- beam on monitors
- emergency off controls (if not working, go straight to circuit breaker)
- QA
Brachytherapy
- must have license from NRC
- keep a log of sources in/out
- use shielded carriers
- post patient room
- personnel monitor
- warning signs and survey
- leak tests
- HDR (High Dose Rate)
Inventory:
removing
returning
removing- take inventory
sources removed, sources remaining
returning- sources remaining, complete inventory
administrative requirements and roles
ALARA RSO- implement radiation protection program RSC- oversee the use of the material written procedure- written directive- prescription
Medical event:
recordable event
misadministration
180-200 cGy per fraction
Disposal of radioactive waste
- facility dependent
- usually separated by half life
- must decay 10 half lives
- can be in different forms
- ** All falls under NRC**
