Radiation Flashcards
Interaction of Radiation with Cellular organelles happens in a fraction of a ______________
second
Stochastic Effects
Events happen by chance
Deterministic Effects
Events sure to happen
Stochastic Effects probability
(cancer and Genetic mutation) Probability of cancer/genetic mutation increases with increasing dose, but the severity does not depend on the amount of dose.
Deterministic Effects
A Somatic effect that increases in severity with increasing absorbed doses
Deterministic Effects are shown as
cataract, skin erythema, fibrosis, and abnormal growth. ( not from diagnosis radiology. (higher the temp, worse is the burn. Longer the contact, worse is the burn)
If radiation damage to the DNA is severe enough the chromosomes can be _____________
Altered
If enough cells undergo similar changes tissues organs can be _______________
damaged
Types of Damage depends on stage of ______ ______
Cell Cycle
Different kinds of ___________ can happen from radiation damage
mutation
Mis-repaired chromosomes can lead to _____________ or slow __________ _________
lead to cell death or slow cell division
Rapid Proliferation of cells may cause ____________ _________
Malignant Development
Ionizing Radiations also affect cell division resulting in _______________
arrested mitosis and retardation of growth
As a cell repairs itself, higher total dose of radiation is needed for cell killing when radiation is delivered in fractionated manner than a single large dose
Cell Recovery
Radiation is a two edged sword:
Causes cancer, kills cancer
Rapidly dividing cells are more sensitive to radiation than
Differentiated slowly dividing cells
Stem cells are radiosensitive and mature cells are
radio-resistant
Tissues with high metabolic rate are
radiosensitive
A high proliferation rate for cells and high growth rate for tissues result in
increased radio sensitivity
Somatic Effects include responses of all types of cells except ______
germ cells of the reproductive system
Genetic effects include responses of irritated
reproductive cells
Genetic Effects are harmful when they are passed onto the
future generations
Genetic Effects are no consequence in persons who will not have
a baby
The time between radiation exposure and visible changes is __________ Period
Latent
Latent period can have a timeline of _________ or ________ latent period
Short or Long
Short term Effects of Latent Period
Minutes, Days, or Weeks
Long Term Effects of Latent Period
Years or Generation
After Latent Period, shoe changes are observed as
Temporary or Permanent
Recovery Period happens when
Recovery can happen after short term effects, cells can repair
May not be immediate clinically observable effects
Somatic Effects
There may be a time lapse before any effects are seen
Somatic Effects
Acute somatic Effects appear
Rather soon after exposure to a single massive does of radiation or after several smaller doses of radiation delivered within a relatively short period of time
Effects which appear within 60 days of exposure to radiation are classified as _________ ___________
Acute Effects
Delayed Somatic Effects may occur
anywhere from two months to as late as 20 years or more after exposure to radiation
The term latent period is usually used only in
relation to stochastic effects (malignancy)
Most Sensitive Variables in Somatic Effects
Lymphocytes, blood forming cells (bone Marrow), Germ Cells
Moderately Sensitive Somatic Effects
Skin Cells, gastrointestinal cells, oral mucosa, lens of the eye
Lease Sensitive Variables in Somatic Effects
Mature Bone Cartilage, Neurons, muscles
Total Dose:
The higher the does of radiation, the greater the severity and probability of occurrence of biological effects.
Dose Rate Dependence:
Radiation dose that would be lethal if given in a short time, such as a few hours, may result in no detectable effects if given in a small increments during a period of several years.
Dose Rate Dependence is due to the ability of
Somatic cells to repair damage caused by exposure to radiation
Tissues do not return to their original state following
Radiation damage, as there are some irreparable alterations produced
Threshold Response:
An increase in radiation dose (curve) may not produce an observable effect until the tissue has received a minimal level of exposure called the threshold dose.
Once the threshold dose has been exceeded,
Increasing dose will demonstrate exceeding observable tissue damage
A well known threshold response is
cataract and erythema of skin
Linear Response
all exposure carries a certain probability of harm and that the effects of multiple small doses are additive.
Linear Dose Response says there is no safe _________
Dose
Linear Dose Response says every exposure carries some
Risk
Absorbed Dose
Measure of how much energy radiation deposits in a unit of material
Exposure is
Measure of number of X-rays or gamma rays and the energy transferred from the beam to the molecules of air, causing ionization of air (describes the amount of radiation traveling through the air)
Air Kerma measures
the kinetic energy transferred from photons to electrons of absorber
Equivalent Dose
is used to compare the biologic effects of different types of radiation on a tissue or organ.
Equivalent Does depends on
Linear Energy Transfer
Effective Dose is used to
estimate the risk of radiation in human. Not all tissues respond identically to radiation (gun shot theory)
Helps us understand the biological risk from radiation
Effective Dose
Effective Dose Unit
Sievert
In dentistry we use microsievert
A millionth of a sievert
Radioactivity
Unit is Curie (ci)
Personal monitoring devices
stimulated with LED, intensity of visible light provides the does received by the operator, aluminum oxide crystals
Adult teeth are very resistant to the direct effect of ___________ ____________
Radiation Exposure
True or False: there is no effect on the crystalline structure of enamel, dentin, and cementum
True
Radiation Caries are caused by
individuals whose salivary glands have been damaged resulting in xerostomia. (secondary to changes in saliva)
Xerostomia is the progressive loss of
salivary secretion
Radiation effects on oral tissues: Mucosa
Mucositis starts at 3rd or 4th week, becomes red and inflamed.
Mucositis is most severe at the ________ of treatment period
end
The most important effect of ionization radiation on human mortality is judged to be
Neoplasia and leukemia
The probability of carcinogenic effect increases with
dose
Primary Protective Barrier is
a barrier of radiation-absorbing material used to reduce radiation exposure to primary or usable beam of radiation
Secondary Protective Barrier
A barrier of radiation-absorbing material used to reduce radiation to scatter and leakage radiation
Inverse Square Law
Intensity of radiation is inversely proportional to the square of the distance from the source
If operator is within the room and has no barrier then you should stand
90 to 135 degrees to the central ray, 45 degrees from the exit beam
Dose Limits are recommended by the
international commission on radiological protection
Limits are to ensure people are not exposed to unnecessary
high dose of radiation
Average dose to dental operators
0.2msv
maximum permissible occupational dose
20 msv
Maximum permissible occupational dose for a declared pregnant worker
5mvs
There is no limit for
diagnostic dose
Parallel Principle
Vertical axes of oil and objects are parallel and CR is directed at right angle to both.
Angle- Bisector Principle
Vertical axes of film and object form an angle and CR is directed at right angle to the bisector of angle between object and film
Angle Bisector Principle proper application:
Length of image and object equal, distortion present.
Improper application of angle bisector principle:
Vertical angulation too great and source moves up (image foreshortening
Image shift occlusally or incisally ( opposite to source)
Improper application of Angle Bisector Principle:
Vertical angle too small source moves down creating image elongation
Long cone is mandatory for parallel principle due to increased _ _ _
Object Film Distance
Sharpness depends on
Size of Source, OFD, SFD, SOD, Movement
Definition:
size of source and definition are inversely related (bigger the source, less is the definition)
Size of source and unsharpness are directly related (Bigger the source, more is the sharpness)
Penumbra is the
almost shadow, around the periphery of a dark shadows a light shadow is present.
Size of source and definition are inversely
related
All factors that increase magnification will decrease
Definition
meant of source of radiation
Geometric unsharpness
movement my patient and or fil
motion unsharpness
VA too great causes images to
shift down
decreasing + VA causes images to
shift up
Increasing - VA causes images to
Shift Up
Decreasing -VA causes images to
Shift Down
VA for all maxillary periapical, bitewing and occlusal radiographs is always
positive
parallel Principle: Changes in VA causes occlusal/incisal or apical image
shift
Angle-Bisector Principle: Changes in VA cause image
shift as well as elongation/forshortening
VA for nearly all mandibular PA is
Negative
The only exception is mandibular molar area where the VA may be
slightly positive +5 or 0
Increasing Horizontal Angle causes images to shift
anteriorly as well as overlapping
Decreasing horizontal angle causes images to shift
posteriorly as well as overlapping
SLOB RULE
SAME LINGUAL, OPPOSITE BUCCAL
scatter Radiation increases
Noise
Rectangular collimation reduces
scatter
Image Enhancement
Radiographic image is manipulated so that an observer can extract useful diagnostic information from
Image Restoration techniques aim at processing
corrupted images so that some diagnostic information can be retrieved
image Analysis
a technique to automatically retrieved diagnostic information from a radiographic image
Hypodontia
Few Missing teeth
Oligodontia
more than half the number missing
Adondontia
all teeth missing
Macrodonia
larger than normal
Microdontia
Smaller than average
Impacted Teeth
Teeth that can not erupt
Gemination
single tooth germ attempts to divide into two
Concrescence
union of two teeth after the are completely formed joined with cementum
Taurodontia
Molar pulp chamber bifurcates too far into the root, large pulp chamber and short root canals.
Dilaceration
Unusual angulation of roots
Dense in Dente (Dense invaginatus)
invagination of a layer of enamel and dentin into pulp (root of tooth widens)
Amelogenesis Imperfecta
Enamel is thin or absent
Dentinogenesis Imperfecta
Color of teeth brownish-blue, or opalescent crown, both dentitions affected, enamel may chip away. Teeth may wear down to alveolar process.
Osteogenesis Imperfecta
extreme probity and fragility of bones. Many fractures, deformity due to fractures, often teeth identical to dentiogenesis imperfect.
