radiation biology Flashcards
why are patients afriad of radiation
found all over in the news, from reputable sources
Ionizing radiation leads to what
Formation of free radicals
what types of effect can free radicals have
Direct effects (33%) Indirect effects (67%)
what are the direct effects of free radicals
Free radical action directly on biological moleucles
what are the indirect effects of free radicals
Radiolysis of water which then affects biological mocules
What are the possible outcomes of ionizing radiation on Cell DNA
Cell Death
Heritable mutation
Carcinogenesis
what dose is needed for Deterministic effects
Clinical symptoms appear at any dose above the threshold dose
what defines severity for deterministic effects
Proportional to dose
caused by high radiation
what does Deterministic effects leads to
Increased cell death
what dose is needed for stochastic effects
No threshold, an all or none response
greater dose increases probablitiy though
what does Stochastic effects lead to
Cell DNA injury
what is the Law of Bergonie and Tribondeau
Radiosensitivity is different for different tissues
what defines the radiosensitivity of different tissues
Amount of undifferentiated cells (undifferentiated more susseptible)
Mitotic activity (greater activity greater risk(
Length of active proliferation(greater is more likely)
also OOcytes and Lymphocytes very susseptible
what non tissue based factors for radiation injury
Age(young more susseptible)
what organs have high radiosensitivty
Lymphoid ttisues/organs Bone marrow Testes Ovaries Small intestine
What organs have fairly high radiosensitivity
Skin Cornea and lens of eyes Esophagus Stomach Rectum
what organs have moderate radiosensitivity
growing cartilage
Growing bone
Vasculature
what organas have fairly low radiosensitivity
Mature cartilage Mature bone Lungs Kidney liver Pancrease Adrenal gland Pituitary gland
what organs have low radiosensitivy
Muscle
Brain
Spinal cord
what are the modifying factors in radiation injury
Radiation source (medical and background) Dose distribution (whole body vs local) Dose rate (high rates worse) linear energy transfer (LET)
what is linear energy transfer
The rate at which the energy from photons is imparted as they travel through matter
The measure of the total energy transferred from any type of radiation to matter
Absorbed dose (rad or Gy)
what is 1 Gy
1 Gy=100 rad
A measure of how different types of radiation affect various tissues
Equivalent dose (Sv=Gy)
Calculating equivalent dose
equivalent dose= radiation weighting factor x absorbed dose
A measure of the estimate risk in hmans
Effective dose
calculating effective dose
sum of tissue weighting factor x equivalent dose
Weighting factor for Effective and Equivalent
Effect: tissue
Equivalent: radiation
what causes acute radiation syndrome
Whole body irradiation
onset of acute radiation syndome
Onset is more rapid and severe with greater dose
Managing accute raditation syndome
depends on stage
Stage of acute radiation syndrom depends on
The level of dose
dose and symtoms of prodromal acute radiation syndrom
1.5 grays Anorexia Nausea Comiting Diarrhea weakness fatigue
dose of latent acute radiation syndrom
2 gray
dose and symptoms of Hematpoietic acute radation syndrome
2-7 gray
Infections (immunosuppression
Hemorrhage (decreased clotting)
Anemia
Dose and symptoms of Gastrointestinal acute radiation syndrom
7-15 gray Dehydration Diarrhea weight loo Septicemia
dose and symptoms of acute radation syndome for Cadiovascular and CNS
50 gray Hypotension Cardiac muscle necrosis Stupor Incoordination Disorientation Convulsions
High radiation dose effects can be
Cataracts in eyes
Shortened life expectange (2 months to 2.6 years)
Impaired growth in children
what causes shortened life of high radiation dose patients
Increased heart disease
Stroke
Non-cancerous disease of digestive, respiratory, and hematopoietic systems
what does it take for radition to affect children in utero
.1 grays
what are some abnormalities in children boen after radiation exposure in utero
Microcephaly Microphthalmia Cataracts Mental impairment Small birth size and reduced growth throughout life Genital and skeletal malformations
how to differentiate radiation cancer from other cancers
Indistinguishable
how do we study radiation induced carcinogenesis
Japanese atomic bomb survivors
why did people die in two months in 1945
Burn injuries and acute radiation system
how was the study conducted to look at radiation
Systematic studies on suriviors and offspring (120,000 people) to see that they got leukemia, esophageal, salivary gland, and thyroid gland tumors
do the unexposed offspring of atomic bomb surviors have mutations
no (also true for the children of parents who have had radiotherapy)
what is the linear nonthreashold (LNT) hypothesis
Increased risk for carcinogenesis above 100,000 microGy
exposures are addative
when doing dental X-rays what are also are exposed
Red Bone Marrow Esophagus Thyroid Bone Brain Salivary glands Skin Lymph nodes muscle Oral mucosa
what is the most common oral cancers from radiotherapy
Squamous cell carcinoma (2-3%) - Tongue, floor of mouth, gingiva, lip, palate
what type of radiotherapy is found in the oral cavity
fractionated radiotherapy reaching 60-70 Gy
what can oral radiotherpay be combined with
Surgical intervention and/or chemo
when is mucositis found
2nd wek of therapy
what does Mucositis lead to
Erythematous mucosa( sloughing of irradiated tissue ans a white yellow pseudomembrane)
problems with Mucositis
Painful
Secondary infection
Difficulty consuming food
healing of mucositis
Heals within 2 months after leading to atrophic, thin, avascular tissues
why does Xerostomia occure
Parenchymal cells of salivary glands are radiosensitive leading to reduced salivary flow
what does Xerostomia lead to
Reduced buffering potential
decalcifaction of enamel
Pain/tenderness
Difficulty chewing and swolling
when does XXerostomia heal
6-12 months
how does Xerostomia heal
heals, but persistent reduced flow occures after 1 year
when does taste loss cure
Second/third week of therapy
how much does taste loss occure
Acuity decreased by a factor of 1000 to 10000
what may also lead to taste loss
Reduced salivary flow
Healing taste loss
Recovery in 60-120 days
what is trismus
Inflammation and fibrosis of musculature, usually the medial and lateral pterygoid muscles and masseter muscles
when do you get trismus
limited opening 2 months after completion of radiation therapy
how does one fix trismus
Physical therapy
why does radiation caries lead to rempant caries
due to salivary changes and direct effect on teeth
how does radiation effect on salivary gland change shit to lead to caries
Reduced saliva flow Decreased saliva pH Reduced saliva buffering increased salivary viscosity Altered bacterial flora debris accumlation
how does radiation directly effect teeth
Flake enamel
How to fix radiation caries
Good oral hygeine
Daily fluoride varnish
Restricted cariogenic foods
Restorations
what happens to children receiving radiotherapy
Incomplete formed teeth (root)
Malformed teeth
Tooth bud destrcution
Microdontia
how to fix impeded tooth development in kids
Resotorative pocedures
how much radiation does it take for Osteoradionecrosis
50-60 Gy
what does Osteoradionecrosis lead to
Reduction of blood supply, bone remodeling capacity (brittle), and mineralization
breakdown of mucosa with bone exposure
what part of the mouth is most exposed to osteoradionecrosis and why
Mandible less vasculature
what is done to fix osteoradionecrosis
Debridement
Resection
restoration
what is done to minimize the effects of osteoradionecrosis
Pre-radiotherapy clearance when possible
what are most mutations from radiation
Deletorous
what gender is more radioselective
Males
ways to reduce the effect of radiation
Low dose
Low dose rate
