Comprehensive Exam Flashcards
the conversion of a neutral atom to a charged entity, called an ion, by removing one or more electrons from the atom or, in some cases by adding an electron to a neutral atom
Ionization
the number of protons (Z) contained within the nucleus of an atom
atomic number
the total mass of an atom, primarily consisting of the combined mass of its protons and neutrons, with a negligible contribution from electrons
atomic mass
occurs in humans after large whole-body doses of ionizing radiation delivered over a short period (from several hours to a few days)
Acute radiation syndrome
what are the three separate dose-related syndromes or conditions that occur as part of the acute radiation syndrome?
hematopoietic syndrome
gastrointestinal syndrome
cerebrovascular syndrome
Bone marrow syndrome, occurs when people receive whole-body doses of ionizing radiation ranging from 1 to 10 Gy. Radiation exposure causes the number of red blood cells, white blood cells, and platelets in the circulating blood to decreases. Dose levels that produce this syndrome may also damage cells in other organ systems and cause the affected organ or organ system to fail. Survival time shortens as the radiation dose increases. Death may occur 6 to 8 weeks after irradiation in those who receive a whole body dose just exceeding 2 Gy
hematopoietic syndrome
Appears as a threshold dose of approx 6 Gy and peaks after a dose of 10 Gy. Without medical support to sustain life, exposed persons receiving doses of 6 to 10 Gy may die 3 to 10 days after being exposed. Even if medical assistance is provided, the exposed persons will live only a few days longer, survival time does not change with dose in this syndrome. A few hours after the dose required to cause this syndrome has been received, the prodromal, or beginning stage occurs. next is the latent period and then the manifest illness stage follows
gastrointestinal syndrome
results when the central nervous system and cardiovascular system receive doses of 50 Gy or more of ionizing radiation. A dose of this magnitude can cause death within a few hours to 2 or 3 days after exposure. After irradiation the prodromal stage begins. The latent stage only lasts up to 12 hours
cerebrovascular syndrome
What is the “concept” of radiation protection?
ALARA
What procedures could cause the radiographer to receive a dose?
fluoroscopy, surgery
what is the radiation weighting factor (quality factor) for x-rays, gamma rays, and beta particles?
1
(1 Gy = 1 Sv)
what is the radiation weighting factor for alpha particles?
20
what has the highest penetrating capability?
gamma rays
______ particles are much less penetrating. (they have large interaction cross-section or scattering probability)
alpha
______ particles will not interact as strongly with their surroundings as do alpha particles, therefore they are capable of penetrating biologic matter to a much greater depth than alpha particles, with far less ionization along their paths
beta
SI units for absorbed, equivalent, effective dose, etc.
absorbed: mGy
equivalent: mSv
effective: mSv
what is the SI unit for absorbed does?
milligray (mGy)
(amount of energy that is deposited in a material per unit mass of the material)
what is the SI unit for equivalent does?
millisievert (mSv)
(type of ionizing radiation)
what is the SI unit for effective does?
millisievert (mSv)
(measure of general harm in humans, best overall measure of the biologic effects of ionizing radiation. takes into account the amount of absorbed dose and the type of radiation)
approximates the size of the anatomical area or part to be included in the radiation field
collimator, beam limiting device
restricts the size and shape of the x-ray beam so it does not exceed the size of the selected image receptor
positive beam limitation
used to assess the overall impact of a gonadal dose on populace. defined as the equivalent dose to the reproductive organs that, if received by every human in a large population group, would be expected to bring about an identical gross genetic injury to that total population, as does the sum of the actual doses received by exposed individual members of the population
Genetically Significant Dose
How do you write Gy, cGy, mGy: Its about the decimal point
1 Gy = 100 cGy = 1000 mGy
1 cGy = 0.01 Gy
1 mGy = 0.001 Gy
what are the 4 major classes of organic compounds?
proteins, carbohydrates, lipids, nucleic acids (all contain carbon as a fundamental constituent)
compounds that do not contain carbon. these compounds found in the body occur in nature independent of living things and are made up of 3 categories
inorganic compounds
what are the 3 categories of inorganic compounds?
inorganic acids, inorganic bases, salts (electrolytes)
this radiation includes alpha particles, beta particles, neutrons, protons. all of these are subatomic particles that are ejected from the nucleus of atoms at high speeds
particulate radiation
a form of energy that travels through space as waves composed of oscillating electric and magnetic fields
wavelength (λ) = speed of light (c) / frequency (v)
or
c =λv
electromagnetic wave radiation
the amount of ionization produced in air when ionizing radiation is present
exposure (coulombs per kilogram)
- able to leave the cell nucleus
- in cytoplasm, directs the process of making proteins from amino acids
mRNA
the whole body dose of radiation that can be lethal to 50% of the exposed population within 30 days
LD 50/30
estimated to be 3.0 to 4.0 Gy without medical support
______ for humans is the most accurate measure for human survival than any shorter period
LD 50/60
What does the collimator light do?
takes a divergent beam of light and transforms it into a parallel beam, narrows a beam of particles or waves
What does the 15% rule do for patient dose?
decreases pt dose because by increasing the kVp by 15% we can decrease the mAs by a factor of 2 and still get the same quality of x-ray
What interactions cause patient dose?
any x-ray interaction that results in ionization
photoelectric effect/absorption & Compton scatter
a radiation worker’s lifetime effective dose must be limited to the individual’s age in years times ____ mSv (what is this known as?)
10
cumulative effective dose (CumEfD) limit (pertains to the whole body)
the annual effective dose limit for occupational workers is ___ mSv and ___ mSv for non-occupationally exposed individuals
50; 1
Why do we need beam filtration?
to absorb the low-energy photons because without filtration those photons would enter the patient and be almost totally absorbed in the body which significantly increase the patient dose near the surface and contributes nothing to the image
results in the absorption of most of the lower-energy photons (long wavelength or soft x-rays) from the heterogeneous beam
filtration
filtration _______ the mean energy or “quality” of the x-ray beam and is commonly referred to has “hardening” the beam
increases
Somatic cell division stages (mitosis)
prophase
metaphase
anaphase
telophase
first phase of cell division, nucleus enlarges, DNA complex coils up tightly, and chromatids becomes visible on stained microscopic slides
prophase
second phase of cell division, mitotic spindle forms between centrioles, each chromosome with two chromatids line up in the center, during this phase cell division can be stopped and visible chromosomes can be examined under a microscope, chromosome damage caused by radiation can then be evaluated
metaphase
third phase of cell division, begins with the breakdown of a protein called securing, which maintains chromosome stability by inhibiting the action of a protein called separase, whose primary function is to break down the protein complex cohesin
anaphase
fourth phase of cell division, the chromatids undergo changes in appearance by uncoiling and becoming long, loosely spiraled threads, the nuclear membrane forms anew, and two nuclei appear, the cytoplasm of the parent cell then divides into two daughter cells near its equator to separately surround each new nucleus
telophase
What causes chromosome aberrations?
when cells are exposed to radiation or carcinogens, DNA sometimes breaks, and the broken ends may rejoin in different patterns from their original arrangement
What is the average kVp range for fluoroscopy?
75 to 110 kVp
ionizing radiation from planetary and extra-planetary sources that are part of the human environment
the dose is approx 3.1 mSv
natural radiation
ionizing radiation that is __________: consumer products containing radioactive material, nuclear fuel for the generation of power, atmospheric fallout, nuclear power plants, medical radiation
man-made radiation
human made: 0.1 mSv
medical: 2.3 mSv
Who was Edison’s lab assistant? What is he doing now?
Clarence Dally, he died of radiation induced cancer in October 1904 at age 39
biologic somatic effects of ionizing radiation that can be directly related to the dose received. these reactions exhibit a threshold dose below which the response does not typically occur and above which the severity of the biologic damage increases as the dose increases
Tissue reactions
Minimum source-to-skin distance for portable/mobile radiographic units and for fixed radiographic equipment
portable: 30 cm
fixed: 15 cm
what are the occupational annual and cumulative effective and annual equivalent dose limits?
effective annual: 50 mSv
effective cumulative: 10 mSv x age in years
equivalent lens of eye annual: 150 mSv
equivalent localized areas annual: 500 mSv
Fetal monthly and entire gestation equivalent dose limits
monthly: 0.5 mSv
entire gestation: 5.0 mSv
Hierarchy of the X-ray beam from tube to image receptor (Ex. Absorbed dose)
short-term, adverse tissue reactions resulting from a dose that is significantly high enough to damage living tissues
deterministic reactions
non-threshold, randomly occurring biologic somatic changes, their chances of occurrence increase with each radiation exposure
ex: cancer, genetic alterations
stochastic reactions
the average energy deposited per unit length of track
linear energy transfer (LET)
refers to the enhancement of the therapeutic or detrimental effect of ionizing radiation due to the presence of oxygen
oxygen enhancement ratio (OER)
describes the comparative capabilities of radiation with differing LETs to produce a particular biologic reaction
relative biologic effectiveness (RBE)
extremity dosimeter, worn as a second monitor when performing fluoroscopic procedures that require the hands to be near the primary x-ray beam
thermoluminescent ring dosimeter (TLD)
most common type of device used for monitoring of occupational exposure in diagnostic imaging and radiation therapy
optically stimulated luminescence (OSL) dosimeter
a small ionization gas filled dosimeter connected to a solid state deice, with electrically erasable programmable read-only memory
personnel direct ion storage (DIS) dosimeter
an operating mode for state of the art fluoroscopic equipment in which entrance radiation levels are substantially higher than those normally employed in routine procedures
High-Level Control
the height of the lead strips divided by the distance between each strip
Grid Ratio
patient dose _________ whenever a grid is inserted
increases
high-ratio grids ______ scatter radiation more effectively than do low-ratio grids
reduce
Discarding radioisotopes
wear gloves if liquid, have personnel dosimeter, follow radiation safety rules (time, distance, shielding)
no solid encapsulated radioactive source is ever to be touched directly by hand, instead long tongs should be used
Minimum lead equivalent
0.5 mm for fluoroscopy & interventional (most commonly used)
0.25 mm is appropriate for mammo
0.5 mm for neck and thyroid shield
