ARRT STUDY GUIDE Flashcards
When was the first case of human injury from X-Ray
1895
When was Roentgen’s Paper Announcing Discovery of X - Ray?
1895
When was the first case of Cancer caused by X rays?
1902
Since when is most of our understanding of the biological effects of radiation?
World War 2
What percentage of the population’s exposure to manmade radiation is from Medical Industry?
90%
What percent of the Medical radiation exposure can be eliminated?
30%
What is the body distribution of X Ray Percentages?
Thoracic 50%
Abdomen 25%
Extremities 17%
Head and Neck, Other 8%
At what rate are X Ray exams increasing?
7%
What are primary factors and techniques that affect radiation dose?
KVP
MAS
Target to film Distance
Technique Chart
What ancillary factors affect Radiation dose?
Generator design
how are X rays produced?
Energy conversion when a fast-moving stream of electrons is suddenly decelerated in the target (anode) of an x ray tube.
What are x ray filters made of?
Aluminum
What do filters do?
absorb the less penetrating x rays before reaching the patient.
What is one of the most important things a Doctor can do while taking x rays to reduce radiation?
Collimation
What materials can cassette holders be made of?
Aluminum
Bakelite
Carbon Filber
What do Grids do?
Reduce scatter radiation
What is inside of a Cassette?
Intensifying screens
What is the purpose of an intensifying screen?
Convert the X ray beam into light to expose the films.
What is the Kilovoltage (kVp)?
Determines maximum Photon energy of the X ray beam.
What is Milliampere - Seconds (mAs)
X ray tube current time Milliamps and time
What is target to film distance?
Distance to target of x rays made of tungsten
What is the optimal target to film distance (SID/TFD)?
40 Inches
What are the Primary Factors?
KVP MA Time Distance Calipers
What is a technique chart used for?
Correlate body part measurement with Primary factors.
What is radiographic contrast largely dependent on?
the body part
what two things happen when an x ray photon interacts with matter?
it’s either absorbed or scattered
What factors affect scattered radiation?
KVP Used
Field Size
Part Thickness
Tissue Density
What are the different Generator designs?
Single Phase
Three Phase
Medium/High Frequency
Constant potential
Why are 3 phase and Med/High Frequency generators better?
High MA available for short Exposure times
High effective Kilovoltage
Near Constant Potential
What is Brems/Breaking Radiation?
Fast electrons decelerating at the target
When the Kinetic energy of electrons are transformed into electromagnetic energy the spectrum energies are?
Heterogenous
Polyenergetic
Polychromatic
When an incoming electron knocks out or displaces an orbital electron from a target atom it produces?
Charactoristic x rays
What is the x ray tube made of?
Pyrex glass
The Pyrex encloses a vacuum and contains which two major parts?
The cathode which is Negative
The anode which is positive
Where are electrons released from?
Heated tungsten filament
How many volts are used in diagnostic x ray?
50,000 to 120000
What percentage of the energy deposited in the target is converted to X rays?
1 percent, the rest is heat that gets dissipated
What lines the inside of the housing that holds the x ray tube?
Lead
Where is the useful beam emitted from the x ray tube?
The Window
What does the number of x rays depend on?
the number of electrons that flow from the filament (cathode) to the target (anode)
3 different quantities of electrons flowing per second are?
100
200
300
What is the anode angle in most x ray machines?
12 to 20 degrees
What does the size of the focal spot influence?
Resolution of the image
What causes the “Heel Effect”?
result of the Line-Focus principle that distributes radiation intensity more on the cathode side than on the anode side.
at 40 TFD, the anode end on a 14 x 17 film with receive a relative exposure of what percentage?
73%
at 40 TFD, the Cathode end on a 14 x 17 film with receive a relative exposure of what percentage?
105%
at 72 TFD, the anode end on a 14 x 17 film with receive a relative exposure of what percentage?
87%
at 72 TFD, the Cathode end on a 14 x 17 film with receive a relative exposure of what percentage?
104%
What happens to “Heel Effect” in smaller films?
Has a smaller role
Long wavelength X rays are?
Low energy
Filtration helps the beam become less Polychromatic? True or False?
True (More monochromatic)
By using added filtration the radiation dose can be reduced by what percent?
42% using 2.5 aluminum filter
What is the HVL?
Half Value Layer, thickness required to reduce x ray intensity to half
What does the inherent filtration include?
X ray tube
Tube Housing
Glass Window
Inherent filtration is equivelent to?
0.5 lead
What should be used in scoliosis x rays?
light weight leaded plastic compensating filters
To protect the breast area during scoliosis exams, what can be done.
Breast shield
exam P to A
Besides reducing radiation to the patient what else does collimation do?
improve contrast and detail
What is a shadow shield?
radio opaque substance that casts shadow over testis or ovaries.
Gonad sheilds must not be lass than ? lead equivalent?
0.5
If the gonads are within 5cm to the primary x ray beam you must?
use shields
What does a grid consist of?
Lead strips separated by radiolucent spacers
What happens to x rays that are traveling obliquely through the grid?
they are absorbed
What is the grid ratio?
Ratio between the height of the lead strips, and the interspace distance between them.
What does the grid pattern refer to?
orientation of the lead strips on their longitudinal axis.
What is a linear grid?
lead strips are parallel to each other on the longitudinal axis.
What is a focused grid?
Lead strips are angled slightly so that they focus at some distance.
What is a parallel grid?
Lead strips are parallel when veiwed in cross section.
What is the Bucky Grid?
Moving grid, more radiation, but less grid on x rays
What four conditions may result in grid cutoff?
Upside down grid
Crooked grid
Grid off center
Off focus grid
What is beneficial about grids with higher ratios?
remove scatter before it reaches the film
As a general rule Grid ratios up to 8:1 are satisfactory at tube potentials below what KVp?
90
If the Tube Potentials exceeds 90 what Grid ratio is used
10:1 , 12:1
Most grids used in practice today are?
focused grids
What grids are most x ray tables equiped with?
Linear grids
What is film sandwiched between in a cassette?
two intensifying screens
All x rays except those extremities lebow 8cm thickness are taken using ?
intensifying screens
What percentage of the x rays that hit the intensifying screens react?
30%
What percentage of the darkening of the film is produced by the intensifying screens?
95%
When using film without intensifying screens how much more x rays are needed?
20-50 times more.
What does the intesification factor mean?
speed of the screens
How much less radiation are rare earth screens?
2 - 5 times less
What are the old style screens made of?
Calcium Tungstate
What speed are medium calcium tungstate screens?
100
What exposure settings changes will result in 75% less radiation?
calcium tungstate 100 versus Rare earth 400
What is the light sensitive material in the emulsion of an x ray?
Silver Bromide Crystal
How must films be stored?
In an upright position
Which type of film should be used with Calcium Tungstate screens?
Blue - Violet
Which type of film should be used with Rare Earth screens?
Blue - Green
What type of emulsion are the screen films?
double emulsion
What do x rays produce when interacting with Phosphor substrate?
Light
Intensifying screens reduces patient radiation by how much?
95%
What are the different film speeds available?
1 - Slow Speed
2.5 - Intermediate Speed
10 - High Speed
What is (S) Speed defined as?
Reciprocal of the radiation dose in Rads required to produce density of 1.0 above base and fog
(S) = 1/R
If an intermediate film is replaced by a high speed film, the x ray exposure is?
25% as much as with Intermediate film
See diagram page (20) in syllabus
What can happen if x ray film is handled rapidly?
Static Marks
How often should a sensomatic strip be run through the x ray machines?
Once a day
If you use high Kvp then you can use lower?
MAS
What does lowering the KVP do to patient dose?
increases patient dose
If you increase KVP beyond an optimum range what happens?
long grayscale contrast
Increasing KVP can do what effect to the patient’s body?
Decrease skin radiation, but increase organ radiation.
What are some advantages to High KVP techniques?
Reduced skin radiation Shorter exposures Increased radiographic lattitude Improved control of contrast Less heat in x ray tube
What is the Tube Current?
Ma
What is the main cause of having to retake films?
wrong MAS or KVP
What do photo timers do?
measure the amount of radiation passing through the patient and sutomatically terminate the exposure.
What are some body parts that use 72” TFD?
Chest X ray, Lateral cervical
What is the inverse square law formula?
Calculating exposure difference
Where should calipers be placed?
Part where central ray enters the body
What percent of cases will require minor adjustments aside from the technique chart?
10 to 25%
There may be a difference between response of rare earth screens versus regular , what is the difference?
2:1 as it goes from 90kvp to 60kvp
In the human body what is the most important factor affecting attenuation?
Tissue density
HIgh contrast between air and soft tissues is created entirely because of what?
density differences.
Will disease processes change tissue densities?
yes
Which would need less exposure and emphysema patient or pneumonia?
Emphysema
What percent of radiation flows through the patient and is unaffected to form the image?
5 percent, remnant radiation
Tissues with less densities transmit what to the radiograph?
more rays
What are the densities of each tissues?
Water and Muscle the same
Fat 10 percent less
The primary radiation that exits the human body consists of what?
non interacting and small angle scattered photons and carries the x ray image.
What direction are secondary photons in?
scattered
What are secondary or scattered photons called
compton effect
Whats the only process that takes effect above 80 kVp?
Compton effect
What is the absorption event probability?
Photoelectric Absorption
The photoelectric absorption is dependant on what?
The atomic number
Which is the photo effect greater for high energy or low energy x rays?
low energy
What is the predominant mode of x ray interaction at higher energies?
Compton effect
What direction is the scatter radiation of Compton effect?
isotropic
What can happen is there is too much isotropic scattering? (compton effect?)
Film darkening
what percent of radiation reaching the film is scattered?
more than 50%
What 4 factors determine quantity of scatter radiation?
kVp
Part Thickness
Field Size
Tissue Denisty
Which is a more effective way to produce x rays single or 3 phase?
3 phase
What percentages are retakes for each type of personal?
2% for experienced
10% for non experienced
What percentage of retakes are due to error in exposures?
50%
What is CT
3 angles of images that are put together by computer
What generation of CT is used today?
3rd and 4th
How does the 3rd CT generation work?
Rotate-Rotate Geometry
How does 4th gen CT work?
Stationary Rotate
What type of CT has a fixed ring and only the scanners move around the patient?
Stationary rotate / 4th gen
What type of CT has less radiation and better image quality?
Neither, Both 3rd and 4th gen are the same
What is the radiation does for CT?
1 to several RADS
What type of switch is used for mobile CT?
Dead-Man
How far away from Mobile CT does the operator stand?
6 feet
What is the source to skin distance for Mobile CT
12 inches
What are the two classes of radiation biological impact?
Genetic and Somatic
What are 4 somatic changes from radiation?
Superifical Tissue
Cancer
Cateract, life shortening, infertility
Injury to fetus
What are some examples of somatic radiation measure areas?
Bone Marrow
Skin
Thyroid
What are some examples of high bone marrow dose exams?
Lumbar Spine
Retrograde Urography
Abdominal Angiography
Chest Tomography
What REM dose can stop sperm formation?
50
What is the BEIR Report?
Study about effects of radiation on ovaries
What can happen in Radiating the Ovaries?
Can cause a lasting affect on the ability to reproduce
What dosages will produce temporary Sterility?
300 for women
30 for men
What is the GSD?
Genetic Specific dose
What 3 factors is the GSD dependant on?
Future Child Expectancy
X ray examination Rate
Mean gonad does per exam
What is the definition of GSD?
Gonad Dose if received by everyone in the population would be expected to produce the same total genetic effect
What radiographs are the largest contributors to the GSD?
Lumbar
Lumbo Sacral
What effects can radiation have on a Cell
Pass through with no effect
Kill the cell
Damage te cell but can be repaired
Reult in permanent changes in the cell
The energy transferred to matter from radiation does what?
Ionizes the atoms which removes the electrons from the atoms
What is involved in the more serious effects of radio biological injury?
Nucleic acid
Small alterations in What, can cause local damage
Protein synthetic mechanism in the cytoplasm
What phenomenon is seen most presently in growing tissue exposed to radiation?
Cessation of cell division
What other cell changes can be seen with radiation exposure?
chromosome breaks clumping of chromatin formation of giant cells abnormal mitosis nuclear disintigration changes in cytoplasmic activity vacuoulization altered protoplasmic viscocity changes in membrane permeability
What is the “Latent Period”?
The time between the initial radiation exposure event and when the first clinically detectable effects occur.
When do the “short-term” or “immediate” biological effects of radiation typically occur?
Sometimes called the “early” effects, they appear in a matter of minutes, days, or weeks.
When do the “long-term” or “delayed” biological effect of radiation typically occur?
Also called the “late” effects, they appear in the following years, decades, and sometimes generations.
What is the “nonthreshold hypothesis”?
The hypothesis that any dose (of radiation), no matter how small, is considered to involve some degree of effect.
True or False: There is evidence to suggest that the genetic effects of radiation constitute a nonthreshhold phenomenon.
True. This has resulted in the conservative approach for radiation protective guides and the consideration that any radiation absorbed will exhibit a nonthreshold effect.
Despite controversy, are regulatory radiation guides based on the “threshold” or “nonthreshold” dose/effect curve?
They are based on the “nonthreshold” dose-effect relationship.
Concerning exposure, what is the total extent of effect measured by?
The total extent of effect is measured by total radiation received by the patient, the total area exposed, and nature of the organs exposed.
When the spleen or bone marrow are partially shielded how will this change the total effect?
Partially shielding these radiosensitive blood-forming organs will result in the mitigation of the total effect, especially with children.
Are rapidly dividing cells, or cells with potential for rapid division, more or less sensitive to receive damage from radiation?
They are more sensitive than cells which do not divide.
Are nondifferentiated (“primitive” or “nonspecialized”) cells more or less sensitive to radiation damage than highly specialized cells?
They are more sensitive than high specialized cells.
What is the “Law of Bergonié and Tribondeau” and when was it discovered?
In 1906 two French scientists stated their findings: “The radiosensitivity of tissue depends on the number of undifferentiated cells which the tissue contains, the degree of mitotic activity in the tissue, and the length of time the cells of the tissue stay in active proliferation.”
Is radiation-induced mitotic delay in the life cycle of a cell usually reversible?
Yes.
What are some examples of types of tissues that are more sensitive than others to radiation?
Blood forming organs (spleen and red bone marrow), gastrointestinal tissue, and a developing embryo/fetus (especially during the first trimester).
Name various types of cells in order of diminishing sensitivity to radiation damage.
- Lymphocytes
- Erythrocytes
- Epithelial
- Endothelial
- Connective tissue cells
- Bone cells
- Muscle cells
- Nerve cells
- Brain cells
What is the dose range for diagnostic radiographic examinations?
Usually between a few millirads (mrad) to a few rads.
In general, under what dosage will show no indications of injury?
25 rads or less.
Delayed radiation effects may result from what?
Previous acute, high-dose exposures or from chronic low-level exposure over a period of years or both.
Which are cause for more concern: long-term effects on people receiving low, chronic exposures or those with short-term effects brought on by high doses?
From the standpoint of public health, there is more concern for those with short-term effects from high doses. This is because of possible deleterious genetic and carcinogenic effects over an entire population.
Excepting radiation induced cataracts, are there any other unique diseases associated with the long-term effects of radiation?
No. Long term effects manifest themselves as statistical increase in incidence of certain diseases or pathology.
Observed long-term effects include:
- Somatic damage, which may result in an increased incidence of cancer, embryological effects, cataracts, and life-span shortening.
- Genetic mutations, which may be expressed many generation after the original radiation damage.
What is some historical evidence that radiation may contribute to various kinds of neoplastic disease?
- Early radiologists and dentists manifested increase in skin malignancies and leukemias.
- Radium dial painters, who ingested significant amounts of radioactive radium, have shown increased bone malignancies.
- Uranium miners have shown increased incidence of lung cancer.
- The survivors of Hiroshima and Nagasaki have increased incidence of leukemia and other neoplasms,
What are the most frequently occurring radiation-induced cancers, in descending order or susceptibility?
- Female breast
- Thyroid glands (especially in women and children)
- Hemopoetic tissue
- Lungs
- Gastrointestinal tract
- Bones
What dosage absorbed by embryo or fetus could result in spontaneous abortion?
About 50 rads.
A dose as low as what has resulted in deleterious effects on an embryo?
As little as 10 rads.
When is an embryo most radiosensitive?
The earliest stages of pregnancy, perhaps the first few weeks. This has resulted in special protocol for axamining women of childbearing capacity in case of unsuspected pregnancies.
What is a major concern for radiation and the second through sixth week of human gestation?
The production of morphological defects in the newborn.
What kind of damage to fetal tissue is more likely if radiated at later stage of pregnancy?
Functional damage concerning the central nervous system. The effects can be as subtle as alterations in learning patterns and development and may have a considerable latent period before they manifest.
What is the required dose for formation of cataracts in humans?
Probably around several hundred rads of acute dose for X-rays in the diagnostic energy range.
How does radiation cause cataracts?
By damaging the fibers which comprise the lens of the eye which are specialized to transmit light or damage to the developing immature cells which give rise to them.
Are the precursor cells of mature gametes, and gametes themselves, susceptible to nuclear damage (genetic mutations) from radiation?
Yes. If these gametes are used in conception the altered genetic information is reproduced and passed on to all of the cells of the offspring.
As a result of extensive experimentation what generalizations have been made?
- There is no indication of a threshold dose for the genetic effects of radiation.
- The degree of mutational damage which results from radiation seems to be dose-rate dependent.
Would man-made radiation simply add to the incidence of previously expressed mutations or create entirely new ones in humans?
Because mutations occur naturally as well, it is reasonable to expect that all mutations have been expressed in the past. Radiation would not cause completely new mutations.
What does “stochastic effects” mean?
It means the probability of an effect occurring, rather than its severity. It is regarded as a function of radiation dose without a threshold.
What are “Non-stochastic effects”?
It means those effects for which the severity of an effect varies with radiation dose, and for which a threshold may occur.
To limit the probability of stochastic effects the supervisor must abide by the following:
- Keep all justifiable radiation doses ALARA, economic and social factors taken into account, and
- Ascertain that no occupationally exposed individual receives more than 5 rems whole body dose equivalent in one year.
What is the percentage of reduction to a primary X-ray beam if the operator stands behind a protective barrier?
99.87%
If a patient-window with radiation attenuation equal to that required by the adjacent barrier cannot be provided what must be installed?
A mirror system.
If the operator is required to remain in the radiographic room during the exposure, he/she must:
- Stand as far as practicable from the scattered radiation source
- Wear protective apparel.
- Use personnel monitoring devices.
By what percentage is a typical scattered radiation dose reduced by if the operator is wearing protective clothing?
97%
How do hangers for protective aprons help?
- They prevent excessive local strain on the apron or coat shoulders and thus help to prevent cracking of the protective lead material.
- They make putting the apron on much easier.
When are thyroid shields generally used?
When the wearer is in close proximity to the patient during fluoroscopy or other scenarios like patient holding in radiography.
Protective gloves and thyroid shields are what lead equivalence?
.25 mm and .05 mm
Instead of holing patients during radiographic examinations what should be employed?
Mechanical holding devices, positioning aids, and similar accessories.
What contribute significantly to the radiation dose of the person holding a patient during a radiographic examination?
The scatter radiation from the patient.
True or False: Most of the reported overexposure of X-ray personnel have occurred during patient holding.
True.
Personnel monitoring equipment takes advantage of what to alert the personnel of what human senses cannot detect?
Radiation monitoring equipment measures the radiation level by measuring the ionization of matter by radiation.
When should personnel monitoring equipment be worn?
Only when on the job.
What 4 criteria should personnel monitoring devices fulfill?
- Record the exposure to ionizing radiation that has occurred.
- Measure the accumulated exposure over a specified period of time.
- Provide some indication of the type and energy of the incident radiation and the rate at which it was received.
- Provide a legally acceptable record of personnel exposure.
Since a personnel monitoring device can only detect radiation in the vicinity of the device what record should be made?
A note of the position at which it was worn should be made since the amount the person was exposed to may be many times more if it was away from the device.
Any personnel monitoring device reading is considered…
… to be a whole-body radiation dose.
Acceptable personnel monitoring devices are:
- Film badge
- Thermoluminescent dosimeter (TLD)
An addiction to a film badge or TLD these can be worn:
- Pocket changer or dosimeter
- Audible warning device
They do not provide a permanent records and are not acceptable for legal monitoring purposes on their own.
The film badge had two essential components:
- The film holder with a variety of filters.
- The packaged film that has been exposed to a known and measured amount of radiation at the supplier origin (to which a comparison will be concluded).
Films used for film badge dosimetry purposes are sensitive to exposure to doses as low as… and as high as….
As low as 10 millirad and as high as 700 rad.
What is one major disadvantage of a TLD?
One a TLD has been read it cannot be read again (the exposure information is lost). Thus is does not provide a truly permanent record of exposure.
The disadvantages in using pocket ionization chambers as personnel monitoring devices are:
- No permanent record
- Must be periodically calibrated
- Sensitive to mechanical shock
- Subjective evaluation of reading by wearer
- Limited dose range
- Possible loss of information in the event of exposure over it’s maximum range
What is an advantage of audible warning devices?
Since the film and TLD take weeks to gain exposure results it is difficult to pinpoint the cause of overexposure or determine when it occurred. Immediate warning is given with the audible warning device.
Unless specifically proven otherwise, any personnel monitoring device reading is considered to be…
… a whole-body dose. Therefore, it is sometimes advisable to wear two or more devices.
When is wearing more than one monitoring device recommended?
- When pregnant. One for the abdomen and another for extremities possibly exposed to radiation.
- When a reading is needed for on top of an apron and below it.
A “whole-body dose” for the purposes of external exposure means exposure to any of the following:
- Head
- Trunk (including male gonads)
- Arms above the elbow
- Legs above the knee
What are the annual occupation dose equivalent limits?
- Whole body (total effective dose equivalent) - 5 rem or 0.05 Sv
- Skin and extremities (shallow-dose equivalent) - 50 rem or .5 Sv
- Lens of the eye (eye dose equivalent) - 15 rem or .15 Sv
The Regulations establish what 4 types of maximum permissible dose equivalent?
- Occupational dose equivalent limits for adults (persons over 18 years of age).
- Occupational dose equivalent limits for persons under 18 years of age (may receive 10% of the adult occupational dose limits).
- Dose equivalent limits for general population.
- Radiation dose to an embryo/fetus.
What is “Occupational Dose”?
It is defined as the dose received by any individual in the course of employment, not including personal medical therapy or diagnosis.
Radiation dose limits for individual members of the public to be considered by a supervisor of X-ray operations:
- .1 rems (1 mSv) in a year, or
- .002 rem or 2 millirems in any one hour
How often are film badges and TLD badges to be changed?
Once every month.
If a reading indicate overexposure of a film badge or dosimeter assigned to an individual what does that mean and what happens?
It is considered to be presumptive evidence of exposure to the individual and must be reported to the Radiologic Health Branch.
Two classifications of personnel who must be monitored regardless of the exposure they are likely to receive:
- Persons who enter a high radiation area.
2. Persons who operate mobile X-ray equipment.
What is a “high radiation area”?
An area, accessible to individuals, in which there exists radiation levels that could result in an individual receiving a dose equivalent in excess of .1 rem in 1 hour at 30 centimeters from the radiation source or from any surface that the radiation penetrates.
What is “radiation area”?
An area, accessible to individuals, in which there exists radiation levels that could result in an individual receiving a dose equivalent in excess of .005 rem in 1 hour at 30 centimeters from the radiation source or from any surface that the radiation penetrates.
What does “exposure” mean?
It means being exposed to ionizing radiation or to radioactive material.
What if personnel monitoring is not performed in-house?
It is recommended to utilize a personnel monitoring service vendor that is certified by the National Institute of standards Technology (NIST) through the National Voluntary Laboratory Association Program (NVLAP) and/or certified by the National Sanitation Foundation Testing Laboratory as having met NSF Standard No. 16.
When is immediate notification required if an individual receives radiation?
a. When it was the total effective dose equivalent of 25 rems or more, or
b. An eye dose equivalent of 75 rems or more, or
c. a shallow-dose equivalent to the skin or extremities of 250 rads or more.
24 hour notification is required is an individual have received within 24 hours:
a. A total effective dose equivalent exceeding 5 rems, or
b. An eye dose equivalent exceeding 15 rems, or
c. A shallow-dose of equivalent to the skin or extremities exceeding 50 rems.
Requests for renewal of any certificate or permit must be filed how soon before expiration date?
30 calendar days prior.
What are the two most important quantities and corresponding unit regarding the use of radiography equipment?
a. Absorbed dose - rad (or gray - SI units)
b. Dose equivalent - rem (sievert - SI units)
Gray (Gy) is…
the SI unit of absorbed dose. One gray is equal to an absorbed dose of 1 joule/kilogram (100 rads).
A Rad is…
… the special nit of absorbed dose. One rad is equal to an absorbed dose of 1000 ergs/gram or .01 joule/kilogram (.01 gray).
A Rem is…
… the special unit of any of the quantities expressed as dose equivalent. The dose equivalent in rems is equal to the absorbed dose in grays multiplied by the quality factor (1 Sv = 100 rems).
A Seivert is…
… the SI unit of any of the quantities expressed as dose equivalent. The dose equivalent in seiverts is equal to the absorbed dose in grays multiplied by the quality factor (1 Sv = 100 rems).
A Quality factor (Q) for X-, gamma, or beta radiation is…
…1. Absorbed dose in rad is equal to 1 rem or the absorbed dose in gray is equal to 1 seivert.
What is the rad an acronym for?
Radiation Adsorbed Dose
What is more important to medical work, the amount of radiation passing through a point in air or the amount of energy absorbed by the substance at a particular point?
The energy absorbed.
What does the unit “rem” allow in correlation with a rad?
That the same absorbed dose in rads delivered by different kinds of radiation does not produce the same degree of biological effect; that some types of particulate radiation are biologically more effective than others.
What is a dose rate?
It is the radiation dose delivered per unit time. It is expressed in rems per hour.
What are the 3 basic principles, which can be used single or in combination, to reduce dose to X-radiation?
Time, distance, and shielding.
The operator exposure to scattered radiation is directly proportional to what?
The patient radiation dose.
The basic principle for “Time” for an examination?
Keep the time of the X-ray exposure as short as possible.
The basic principle for “Distance” for examinations?
Keep the distance between the source of exposure (X-ray tube, or any scattering medium such as a patient) and the exposed individual as large as practicable.
True or False: The intensity of radiation varies proportionately as the square of the distance?
False. The intensity of radiation varies inversely as the square of the distance.
What is the inverse square law?
At points distant from a common source of X-radiation, the intensities of radiation at these points vary as the square of their respective distances from the X-ray source.
By what 3 methods is energy from an X-ray lost?
- The photoelectric effect
2 Compton scattering - Pair production
What is the photoelectric effect?
A collision between a photon of a X-radiation and an orbital electron of an atom, where the electron is knocked out of its orbit and the photon loses all its energy.
What is Compton scattering?
Interaction of a photon of X-radiation with an orbital electron of the absorber atom producing a recoil electron and a photon energy which is less than that of the incident photon.
What is pair production?
Incident photon is annihilated in the vicinity of the nucleus of the absorbing atom with the subsequent production of an electron and positron pair.
As X-rays pass through an absorber, their decrease in number is governed by:
- The energy of the radiation
- The specific medium (density of the material)
- The thickness of the absorber traversed
The half-value layer (HVL) is used in what two different situations?
- Determining the quality (average penetrating ability of an X-ray beam)
- Determining the barrier thickness (amount of shielding needed to attenuate radiation to the required degree).
The quality of an X-ray beam is usually specified in terms of…
… a half-value layer (HVL).
The HVL is defined as…
… the thickness or layer of a specified material which attenuates the X-ray beam to such an extent that the exposure rate is reduced to one half. It is commonly expressed in millimeter thicknesses of aluminum,
What is “barrier thickness”?
The barrier thickness is usually expressed in terms of inches or millimeters of a specified material (usually lead) required to attenuate radiation to a specified energy (in kilovolts) to a degree where persons on the other side of that barrier will not be exposed to greater than permissible amount of radiation.
What is ‘deep- doe equivalent’?
Applied to external whole-body exposure, is the dose equivalent at a tissue depth of 1 cm (100 mg/cm^2)
The dose to an embryo/fetus shall be taken as the sum of:
- The deep-dose equivalent to the declared pregnant woman; and
- The dose to the embryo-fetus from radionuclides in the embryo/fetus and radionuclides in the declared pregnant woman.
Once a pregnancy of occupied woman becomes known, radiation dose of the embryo-fetus shall be no greater than…
… .05 rem (50 mrems) in any month (exclusing medical exposure).
In most cases of occupational exposure, the actual dose received by the embryo-fetus is less or more than received by the mother?
Less, the mother’s body absorbs some of the radiation.
What is the range of a Film Badge?
0.0 to 700 rad
What is the range of a TLD?
10 mrads to 10^5 rad
What is the range for a Pocket Ionization Chamber?
.001 to 2000 rads (theoretical); for X-ray use: 0.001 to 200 millirads
What are possible advantages for a film badge?
Inexpensive, gives estimates of integrated dose, provides permanent record, allows objective review, detects problems.
What are disadvantages for a film badge?
Moderate directional dependence, strong energy dependence for low energy X-rays, false readings produced by heat, pressure, and certain vapors.
What are advantages for a TLD?
Infinite shelf life within the useful range, small size and low directional dependence, small energy dependence, reusable, inexpensive, give estimate of integrated dose over long periods.
Since is it not possible to visually verify the amount of inherent filtration in the X-ray beam, it is necessary to measure the….
… half-value layer (HVL) of the X-ray beam.
What is “aluminum equivalent”?
The thickness of type 1100 aluminum alloy affording the same attenuation under specified conditions, as the material in question.
What is a “compliance test”?
A compliance test is performed on X-ray equipment to ensure that the X-ray unit meets the radiation safety regulations.
What is “contact therapy”?
Means irradiation of accessible lesions usually emplying a very short source-skin distance and potentials of 40-50 kV.
What is “contrast”?
In radiology, contrast is defined as the difference in density between light and dark areas on the processed film. Contrast can be measured from a characteristic or H & D curve by finding the tangent of the straight line portion of the curve.
What are “contrast agents or media”?
Low toxicity materials such as barium or iodine which possess high atomic numbers and thus decrease the transmission of X-rays. The absorption of X-rays in barium and iodine is much greater than that in bone and tissue which have much lower effective atomic numbers. The use of contrast agents in diagnostic radiology is derived from their ability to enhance the photoelectric effect.
What is a “dead-man switch”?
A switch so constructed that a circuit-closing contact can only be maintained by continuous pressure by the operator.
What is a “Diagnostic Source Assembly”?
A diagnostic source housing (X-ray tube housing) assembly with a beam limiting device attached. This assembly shall be so constructed that the leakage radiation air kerma measured at a distance of one meter from the source does not exceed 1 mGy (.1 rad) in one hour when the source is operated at its leakage technique factors.
What is a “dominant mutation”?
A genetic mutation which will probably be expressed in the offspring.
What is “distortion”?
Unequal magnification of different portions of body area being X-rayed.
What is a “personnel dosimeter’?
Devices designed to be worn or carried by an individual for the purpose of determining the dose equivalent received (e.g., film badges, pocket chambers, pocket dosimeters, ring badges, thermoluminescent dosimeters, etc.).
What is “medical exposure”?
Intentional physician prescribed exposure of an individual to radiation for diagnostic or therapeutic medical purposes.
What is a “fluoroscopy”?
A radiological examination utilizing fluorescence for observation of the transient image.
What is a “nonstochastic effect”?
Health effects, the severity of which varies with the dose and for which a threshold is believed to esit. Radiation-induced cataract formation is an example of nonstochastic effect.
What is a “phantom”?
An object used to simulate he absorption and scatter characteristics of the patient’s body for radiation measurement purposes.
What is “photometry”?
The science of the measurement and study of the quantity and intensity of radiation visible to the human eye.
What is “non-ionizing radiation”?
Electromagnetic or other radiation of insufficient energy to cause ionization of excitation of atoms with which it interacts.
What is a “sensitometer”?
An instrument used to expose film to precisely controlled steps of increasing light intensity.
What is “Source-to-Image Distance (SID)”?
The distance measured along the central ray from the center of the front of the surface of the source to the surface of the image detector.
What is “spot film”?
A radiograph taken during a fluoroscopic examination for the purpose of providing a permanent record of an area of interest or to verify the filling of a void with contrast media?
What is “Target-Film Distance (TFD)”:
The distance from the X-ray tube target (anode) to the X-ray film measured either in inches or centimeters.
What is “tomography”?
A special technique to show in detail images of structure lying in a predetermined place of tissue, while blurring or eliminating detail in images of structures in other planes.
What are “X-rays”?
Penetrating electromagnetic radiation whose wavelengths are shorter than those of visible light. For radiographic purposes, X-rays are usually produced by bombarding a metallic target with fast electrons in a vacuum.
How often are each personnel monitoring entry to be changed?
Once a month
How should Personnel monitoring entries be recorded in what form?
In rems or millirems and Dose equivalent rates in rems or millirems per hour.
How long does each recorded dose equivalent need to be kept on file?
Indefinitely
Each other record required record must be preserved for how long?
3 years
Over exposure of a film badge needs to be reported within ?
30 days
If the x ray distance from a patient is doubled then the radiation intensity is ?
1/4 the intensity.
If the distance from an x ray source is tripled then the intensity is?
1/9 the intensity
A joule is what?
unit of work equal to one newton
At what energy is the photo electric effect most important?
At low energy
An occupationally exposed Pregnant individual may not expose the fetus during the entire pregnancy to what amount of radiation?
0.5 rems (5 mSv)
In any given month how much radiation can a pregnant x ray operator get?
No more than 0.05 rem (50 memes)
If mom is exposed to radiation during pregnancy what risks are included.
Leukemia and other Cancers
What is most risky time period for pregnancy ?
First 3 months
Is there any risk of the female to be sterile or unable to child bear?
No
If an operator is pregnant the film badges should be worn where?
Pocket chamber on the abdomen and film or TLD worn at regular place.
When should you renew x ray registration?
July of every even numbered year
What is Eye dose equivalent?
Dose to the men’s taken at 0.3 centimeters.
How far should source to skin distance be?
Not less than 12 inches
How far should operator be from beam using a deadman switch?
6 feet away.
What is used to estimate the skin radiation dose?
Nomogram
How often should you check the processor sensitometer/sensitometer?
Daily
How often should you check the tank level, clean rollers, do cleanup film?
Daily
Film and chemical storage should be checked ?
Monthly
Retake rate should be checked?
Quarterly
Silver recovery should be checked?
Quarterly
Darkroom fog should be checked ?
Semiannually
How often should you check the retake rates?
Every 3 months
What QA equipment is needed?
Homogenous Phantom Coarse wire mesh contact tool Thermometer Sensitometer Densitometer
How long should written logs of x ray maintenance or repairs be kept ?
3 years
Film processor maintenance logs shall be kept for how long?
One year
Records for QV test equipment shall be kept for?
3 years
The sensomatic strips should be exposed to?
Sensitometric light only not directly to x Rays.
Processor QC programs should monitor what?
Base plus fog density
Mid-density
Density difference
Processor sensitometric evaluation
When should processor QC be done?
Beginning of each day
What is the nominal focal spot?
Manufacturers stated anode target size.
What is the Aperture?
It’s for CT, the opening in collimating that allows radiation to reach the detector.
What’s an attenuation block?
A block or stack of material with a cross section larger than the beam with a total thickness equivalent to 3.8cm of aluminum.
What is base plus fog density?
The optical density of film due to its base density plus any action of the developer on the unexposed silver halide crystals.
If you pass an unexposed film through the entire processing cycle and measuring the resultant optical density with a densitimeter it’s what?
Base plus fog density
What does the Charactoristic curve do?
Also known as H & D curve, it shows the relationship between photographic density and radiation dose.
What is a coulomb?
Unit of electric charge equal to 1 amp/second
What measures the blackening of a film?
Densitimeter.
what does the KVP determine?
Max penetrating ability of x-rays and refers to the quality
What is the linear Hypothesis?
That radiation can cause some damage
What is a Millirad?
Equal to 1/1000 of a Rad
What is a sensitometer?
produces a series of controlled exposures on a sheet of photographic material.
What is the main purpose of a filter?
to reduce the amount of low energy x rays from the patient
What is the purpose of a GRID?
remove or absorb scattered radiation that emirates from the patient before is reaches the film.
Does a grid increase radiation dose to patient?
Yes
The higher the grad ration the higher what?
Radiation to the patient
What is the intensification factor?
the speed of the screen
What technique produces less radiation to the patient?
High KVp low MAS
What temp should the processor be at?
95 Degrees
What does scatter cause?
Fog
What do faster cassette speeds do?
Lower Radiation
What does filtration remove?
Soft or low radiation beams
What color do gadalinium screens glow?
Green
Does a thicker body part produce more scatter?
Yes
What determines how wide the x ray beam is?
The anode
What should the anode angle be?
12-20 degrees
What end should be facing up?
the Anode +
What technique may give you more gray?
High KVP
When can an operator hold a patient?
only in emergency
Where is a film badge worn?
in front at waist or chest level
When wearing a lead apron were should the Film Badge be?
on the collar or on top of the apron.
What is used to monitor dose in extremities?
Finger ring dosimeters
A person gets 25 rams total dose, when is it reported?
Immediately
A person gets an eye dose of 75 teams, do you have to report it?
Yes, immediately
A persons skin gets a 250 rem dose, when do you report it?
Immediately
