1what happens at instant death of cell due to radiation
growth disrpution of form and structure (100k rad)
2what happens at reproductive death of cells due to radiation?
permantly loses ability to reproduce @ 1-100 gya
3what happens at mitotic death due to cellular radiation
radiation inhibits mitotic process
4what is mitotic delay
delay before next division due to radiation
5what is apotosis
nucleus breaks, cell breaks, then is ingested by neighboring cells
6what is main chain scission
the breakage of backbone of the long chain macomolecules
7what is cross linking
afer irradiation, spur like structures can form extending out of the main chain which attach to neighboring macomolecules
8what is point lesion
irradiation results in disruption of single chemical bond (bases are inturrupted)
9what commonly causes point lesions
low L.E.T.
10what is catabolism
the reduction of nutrient molecules for energy
11what is anabolism
production of large moecules for form and function
12what is most radiosensitive molecule?
DNA
15where is DNA located?
in the chromosomes of the cell nucleus
16what are the 3 principle effects radiation has on DNA
cell death, malignant disease, genetic disease
17of the 3 principle effects, which cannot be repaired
genetic disease
18what are the 5 ways radiation damages dna
main-chain scission with one side severed,
mainchain scission w/ both sides severed
main-chain scission and subsquent crosslinking
rung breakage causing seperation of bases
19change in or loss of a base
20which of the 5 dna damages may not be reversible
change in or loss of base
21when is chromosome dmg visible
during anaphase and metaphase
22what is aberration
when broken chromosome does not rejoin
23what is restitution
when broken chromosome rejoins (95% time)
24what is radiolysis of water
when water is irradiated it breaks into other molecular products
25how much of human body is made of water
80%
26the priniciple radiation interaction in the body is with what
water
27What happens during the first step of radiolysis of water
radiation interacts with water and initially creats an ion pair of HOH+ and e-
28After the intial interaction of radiolysis of water, what happens
HOH+ and e- can turn back into H20 or e- will find another HOH and create HOH-
29What happens to HOH+ and HOH-
They are unstable and will break apart to H+ and OH* and H* and OH-
30What is final result of radiolysis of water
formation of ion pair (H+ and OH-) and 2 free radicals (H* and OH*)
31What are free radicals
high reactive and unstable, uncharged molecules that contain a single unpaired electron on outer shell
32OH* (hydroxyl) and OH* (hydroxyl) join to produce what?
h202 (hydrogen peroxide)
33H* can join with O2 to form what?
HO2* (hydroperoxyl)
34Hydrogen peroxide can also be formed by what
2 hydroperoxyl radicals joining (HO2*+ HO2* = h2O2+O2)
35HO2 is?
hydrogen peroxyl
36H2O2 is?
hydrogen peroxide
37how do irradiation hits occur
through both indirect and direct effects
38what is direct effect
when the ionizing event occurs on target molecule (dna)
39what is indirect effect
when the ionizing event occurs on distant non-critical molecule (water) then transfers the energy to target molecule (dna)
40how do most effects of irradiation result from
indirect effects
41what is the target molecule or key molecular target
DNA
42what is Target theory
for a cell to die after radiation exposure, the target molecule must be inactivated
43when does a HIT occur
when radiation interacts with the target molecule
44what causes less hits, high or low LET
Low
45Name the two factors that can increase the probability of a hit to the target molecule?
high oxygen levels and high LET
46how are lethal effects of radiation determined
by observing cell survival not cell death
47what is single target, single hit model?
model for radiationdose relationship for simple cells, single target must be inactivated for cell to die
48what is d37
classified as a distributed dose that is sufficient to kill 63% of cell with 37% surviving
49What are low D37
radiosensitive cell
50what are High D37
radioresistant cell
51What is D0
dose necessary to reduce cell survival to 37% (mean lethal dose)
52what is DQ
ability of cell to recover from sublethal dose (threshold dose)
53what is poisson distribution
computes probability of cell death
54sublethal damage must what?
accumulate before the cell dies
55what happens to cells that survive?
grow and repopulate
56cells are able to find and repair damage at what LET
Low LET
57At what LET is mechanism not as effective
High LET
58What is cell cycle time?
the avg time from one mitosis to another
59what cycle phase is the most time variable?
G1 phase
60when can DNA snythesis be effected iff irradiation occurs
during G1 phase
61How does the radiosensitivity of human cells vary with stages of the cell cycle?
Mitosis is most radiosensitive and then G1-S phase. Late S phase is most radioresistant.
62What is the law of Bergonie and Tribondeau
Radiosensitivity of tissue varies with maturation and metabolism
63Stems cells are__? Maturation cells are__?
Radiosensitive; radioresistant
64high metabolic rate is __?
radiosensitive
65low metabolic rate is __?
radioresistant
66young tissue is more__ than older tissue
radiosensitive
67what makes a cell more radiosensitive
increased proliferation and growth rate
68What is L.E.T (linear energy transfer)
rate of which energy is transformed from ionizing radiation to soft tissue per unit length of track
69what is LET measured in?
keV/ um
70Why is LET useful
describes the quality of radiation
71What is low LET
Causes dmg through indirect action and production of free radicals (x-ray; gamma rays) Single strand breaks in DNA
72What is High LET
radiation with substantial mass and charge (alpha particles) ; Double Strand DNA breaks
73What is Relative Biologic effectiveness
capability of radiation with varying LET to produce a biologic response
74What is LET relation to RBE
as LET increases so does RBE (direct correlation)
75What is the equation for RBE
diagnostic x-rays = RBE of 1
76what is protraction and fractionation used for
allows for intracellular repair, tissue recovery and higher total doses; useful for radiation therapy
77what is protraction
dose delivered continuously but at a lower rate and over a longer period of time
78what is fractionation
dose delivered in cycles at equal portions and regular intervals
79what are the biologic factors that affect radiosensitivity
oxygen effect
age
recovery
chemical agents
81what is oxygen effect
tissues high in oxygen are more sensitive to radiation (diagnostic x-ray = 3.0 OER
82what happens when dose is large enough to kill cell before division?
interphase death
83Can cells recover from rad dmg after interphase death
no
84what is equation for recovery
interacellular repair + repopulation
85what is a radiosensitizer
increase the effects of radiation (halogenated pyrimidines)
86what is radioprotectors
decrease effect of radiation (cysteine)
87what is hormesis
possible beneficial effect of small amounts of radiation
88what does hormesis do
stimulates hormonal and immune responses and extends life span
89what is radiation dose-response relationships
the relationship between radiation dose levels and the response observed
90what is linear radiation dose- response relationship
directly proportional to dose; dose doubled = response doubles
91what is non-threshold radiation dose - response relationships
regardless of size of dose, a response is expected to be produced
92what follows linear non threshold relationships
radiation induced genetic damage and late effects
93why the linear, nonthreshold dose-response relationship is used as a model for diagnostic imaging radiation management
results can be extrapolated to estimate low dose response from high dose results
94when are threshold radiation dose- radiation relationships used
when dose is larger than 0 and the level below which there is no response
95when is sigmoid curve used
in radiation therapy to show high dose cellular response
96how many rads in 1 Gy
100 rads
97how many rads in 1dGy
10 rads
98how many rads in 1 cGy
1 rad
99how many rads in 1mGy
.1 rad
100what is REM
radiation equivalent man
101what is Sievert
SI unit of equivalent dose
1021 Sv equals how many rems
100 REM
1031 dSv = how many rem
10 rem
1041 cSv = how many rem
1 rem
1051 mSv = how many rem
.1 rem
106what are coulombs per kilo or air kerma
SI unit of ionizing radiation exposure
107how many Roentgen in 1 Gya
100 R
108how many R in 1 dGya
10 R
109how many R in 1cGya
1 R
110how many R in 1 mGya
.1 R
111what is numerical value of OER
diagnostic x-ray = OER of 3
112what is numerical value of RBE
diagnostic x-ray = RBE 1
113what is anabolism
the production of large molecules from small ones
114what is the backbone of dna made of
sugar (deoxyribose and phosphate)
115what are lipids
structural components of cell membrane/ provides energy
116what are carbohydrates
provides fuel for cell metabolism
117what are enzymes
proteins that are needed for biochemical reactions to occur
118what are hormones
proteins responsible for growth, development and regulating body functions
119what are the two major components of the cell
nucleus and cytoplasm
120where is dna located
nucleus
121what is protein synthesis
metabolic production of proteins
122what is mitochondria
known as cell engine. protein production
123what is lysomes
is suicide component of cell
124what is the most abundant atom
hydrogen
125what is endoplasmic reticulum
highway of cell, communicates nucleus and cytoplasm
126what is the most abundant molecule
h20
127what are the monosaccharides
glucose
128what do proteins function as
enzymes, hormones and antibodies
129where are hormones produced
endocrine glands
130what is the most radiation sensitive target molecule
DNA
131what does water do
delivers energy to target molecules
132where is rna located
cytoplasm
133what is catabolism
breaking down of macromolecules to smaller units
134what are antibodies
body’s defense mechanism against infection and disease
135how does water interact with other molecules
binds to make form
136how does radiation affect humans
at the atomic level
137what is important for proper metabolism
anabolism and catabolism
138what is the cell theory
all plants and animals contain cells as their basic functional unit
139what is the approximate dose of radiation required to produce measurable change in a macromolecule?
1 mRad or 10kGy
140what percentage of water makes up human structure
80%
141what is the most abundant atom
hydrogen
142what is the most abundant molecule
h20
143how does water interact with other molecules
binds to other molecules to provide form
144what does water do?
delivers energy to target molecule
145what is important for proper metabolism
anabolism and catabolism
146what is anabolism
production of large molecules from small ones such as protein synthesis
147what is catabolism
breaking down of macromolecules into simpler parts
148what is protein synthesis
metabolic production of proteins
149what are three examples of proteins
enzymes, hormones, antibodies
150what is an enzyme
protein needed for biochemical reactions
151what are hormones
needed for growth and development. regulates bonds functions and is produced by endocrine glands
152what is an antibody
bodies self defense mechanism against diseases and infection
153how much of the human body is made of protein
15%
154what are lipids
structural components of cell membrane, provides energy
155what are carbohydrates
provides fuel for cell metabolism
156what is a monosacchride
glucose
157where is dna located
nucleus
158where is rna located
cytoplasm
159what is the most radiosensitive target molecule
dna
160what is the backbone of dna made of
deoxyrose and phosphate (sugar)
161what are the two major components of the cell
nucleus and cytoplasm
162what is the endoplasmic reticulum
highway of cell. communicates nucleus to cytoplasm
163what is the mitochondria
cells engine. power house of cell. center of protein synthesis
164what are lysomes
cells suicide component. cleaners of the cell from infection or foreign bodies
165what is codon
genetic code
166what is steps of protein synthesis
codon>mRNA>endoplasmic reticulum>ribosomes> tRNA>amino acid>ribosome>protein molecule
167what are the stages of mitosis
interphase>propose>metaphase>anaphase>telophase
168what happens during the S phase of interphase
2 identical daughter dna created
169when can chromosomes be studied for radiation damage
metaphase
170what does meiosis result in
cells with 23 chromosomes each
171most tissue in the body is composed of what
muscle
172what are immature cells
stem, undifferentiated, precursor cells (more radiosensitive then mature cells)
173what determines an organs radiosensitivity
function, maturity, cell type radiosensitivty
174level of radiosensitivty of lymphatic, bone marrow and gonads
high 2-10Gy
175what are most radiosensitive tissues
gonads, lymphatic and bone marrow
176level of radiosensitivty of muscle, brain and spinal
low (over 50Gy)
177level of radiosensitivty of skin, cornea, growing bone?
intermediate (10-50Gy)
178level of sensitivity of kidney, liver, thyroid, gi tract
intermediate (10-50Gy)
179What is fluoroscopy?
real time/dynamic viewing of anatomic structures
180who invented fluoroscope
Thomas Edison in 1896
181What is the mA range of fluoroscopy?
0.5-5.0
182What is visual acuity?
the ability to see fine detail
183What is photopic vision?
daylight vision (cones)
184What is scotopic vision?
night vision (rods)
185What is the image intensifier?
Raises light level to photopic level (similar to radiograph)
186Where is visual acuity greatest at
fovea centralis
187what is visual integration
time to process image (.2 sec)
188What does the input phosphor do?
converts x-rays to light
189what does photocathode do
Converts visible light into electrons
190what does focusing lenses do?
acceleration/focusing of electrons
191What does the output phosphor do?
Convert electrons to light
192what is main advantage of image intensifier
increase image brightness
193what do electrons hit before output phosphor?
anode
194what is the correlation of number of light photons emitted to amount of xray photons exiting patient?
directly proportional
195how is input layer and output layer different
Output gets same image but minified and brighter
196what is the input layer/phosphor made of?
cesium iodide
197what is output layer/phosphor made of?
Zinc cadmium Sulfide
198what is photocathode made of?
cesium and antimony compounds
199What phosphor was used on the original fluoroscopic screen?
barium platinocyanide
200how much does 1 x-ray photon (input phosphor) equal to output phosphor?
5k-30k light photons
201What is brightness gain?
the ability of the image intensifier to increase the illumination level of the image. (5k-30k)
202what is the equation for brightness gain?
minification gain x flux gain
203What is minification gain?
The ratio of the diameter of the input phosphor (large) to diameter of the output phosphor (small)
204What is flux gain?
Ratio of the number of light photons at the output phosphor to the number of x-rays at the input phosphor
205How big is the input phosphor?
10-35 cm in diameter
206How big is the output phosphor?
2.5-5cm in diameter
207what happens when x-rays increase in input phosphor?
light intensity of output phosphor goes up
208what does viewing of fluoro image in magnification mode increase?
contrast resolution
spatial resolution
210why does magnification mode increase contrast resolution?
increase of mA
211why does magnification mode increase spatial resolution?
more of center of input phosphor
212what is vignetting
reduction in brightness at the periphery of the image
213in fluoroscopy what is the relation of x-ray output/dose to mA used
directly proportional
214what will peak/optimal kV yield?
maximum differential absorption by the tissue.
215 results in good contrast resolution.
216kVp for BE(a.c) exams
80-90
219what is most widely used tv camera
vidicon
220what is the common indirect influencing factor
room lighting
221what is ABS or ABC
maintains brightness of an image over varying thickness parts and densities by varying technique