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An optically stimulated luminescence dosimeter contains which of the following detectors?
- Different types of monitoring devices are available for the occupationally exposed. The film badge has photographic film; the pocket dosimeter contains an ionization chamber; TLDs use lithium fluoride crystals. OSL dosimeters are personnel radiation monitors that use aluminum oxide crystals. These crystals, once exposed to ionizing radiation and then subjected to a laser, give off luminescence proportional to the amount of radiation received
In the production of characteristic radiation at the tungsten target, the incident electron
- Ejects an inner-shell tungsten electron
- Characteristic radiation is one of two kinds of x-rays produced at the tungsten target of the x-ray tube. The incident, or incoming, high-speed electron ejects a K-shell tungsten electron. This leaves a hole in the K shell, and an L-shell electron drops down to fill the K vacancy. Because L electrons are at a higher energy level than K-shell electrons, the L-shell electron gives up the difference in binding energy in the form of a photon, a characteristic x-ray(characteristic of the K shell
Stochastic effects of radiation are those that
1. have a threshold
2. may be described as "all or nothing" effect
3. are late effects
2 and 3
Late effects of radiation can occur in cells that have survived a previous irradiation months or years earlier. These late effects, such as carcinogenesis and genetic effects, are "all-or-nothing" effects—either the organism develops cancer or it does not. Most late effects do not have a threshold dose; that is, any dose, however small, theoretically can induce an effect. Increasing that dose will increase the likelihood of the occurrence but will not affect its severity; these effects are termed stochastic. Nonstochastic effects are those that will not occur below a particular threshold dose and that increase in severity as the dose increases
The radiographer's radiation monitor report must include which of the following information?
1. Life time dose equivalent
2. Quarterly Dose Equivelent
3. Inception Date
According to state and federal law, personnel radiation monitor reports must be retained as legal documents. These documents must include such information as the user's personal data, that is, name, birth date, sex, and identification number (usually Social Security Number); type of monitor (i.e., film badge, TLD, or OSL dosimeter); radiation quality; dose equivalent (i.e., deep, eye, and shallow) for that exposure period (usually one month); quarterly accumulated dose equivalent (i.e., deep, eye, and shallow); year-to-date dose equivalent (i.e., deep, eye, and shallow); lifetime dose equivalent (i.e., deep, eye, and shallow); number of monitors received year to date; and inception date(month and year) of the dosimeter
Compared with that of the hypersthenic and sthenic body types, the gallbladder of an asthenic patient is most likely to be located
lower and more medial
he four types of body habitus describe differences in visceral shape, position, tone, and motility. One body type is hypersthenic, the very large individual with short, wide heart and lungs, high transverse stomach and gallbladder, and peripheral colon. The sthenic individual is the average, athletic, most predominant type. The hyposthenic patient is somewhat thinner and a little more frail, with organs positioned somewhat lower. The asthenic type is smaller in the extreme, with a long thorax, a very long, almost pelvic stomach, and a low medial gallbladder. The asthenic colon is medial and redundant.
If an exposure dose of 50 mR/h is delivered from a distance of 3 ft, what would be the dose delivered after 20 minutes at a distance of 5 ft from the source?
- x-ray intensity and distance formula
- i1 Density2^2
- i2 Density1^2
25x = 450
Thus, x = 18 mR/h (60 minutes) and, therefore, 6 mR in 20 minutes. Distance has a profound effect on dose received and, therefore, is one of the cardinal rules of radiation protection. As distance from the source increases, dose received decreases
To eject a K-shell electron from a tungsten atom, the incoming electron must have an energy of at least
X-ray photons are produced in two ways as high-speed electrons interact with target tungsten atoms. First, if the high-speed electron is attracted by the nucleus of a tungsten atom and changes its course, as the electron is "braked," energy is given up in the form of an x-ray photon. This is calledBremsstrahlung ("braking") radiation, and it is responsible for most of the x-ray photons produced at the conventional tungsten target. Second, a high-speed electron having an energy of at least 70 keV may eject a tungsten K-shell electron, leaving a vacancy in the shell. An electron from the next energy level, the L shell, drops down to fill the vacancy, emitting the difference in energy as a K-characteristic ray. Characteristic radiation makes up only about 15% of the primary beam.
Which of the following contributes most to occupational exposure?
In the photoelectric effect, a relatively low-energy photon uses all its energy to eject an inner-shell electron, leaving a vacancy. An electron from the shell above drops down to fill the vacancy and in so doing gives up a characteristic ray. This type of interaction is most harmful to the patient because all the photon energy is transferred to tissue. In Compton scatter, a high-energy incident photon uses some of its energy to eject an outer-shell electron. In so doing, the incident photon is deflected with reduced energy, but it usually retains most of its energy and exits the body as an energetic scattered ray. This scattered ray will either contribute to image fog or pose a radiation hazard to personnel depending on its direction of exit; thus, Compton scatter contributes the most to occupational exposure. In classic scatter, a low-energy photon interacts with an atom but causes no ionization; the incident photon disappears into the atom and then is released immediately as a photon of identical energy but with changed direction. Thompson scatter is another name for classic scatter
Biologic material is least sensitive to irradiation under which of the following conditions?
Tissue is most sensitive to radiation when it is oxygenated and least sensitive when it is devoid of oxygen. Anoxic refers to tissue without oxygen; hypoxic refers to tissue with little oxygen. Anoxic and hypoxic tumors typically are avascular (with little or no blood supply) and, therefore, more radioresistant
What is the minimum requirement for lead aprons, according to CFR 20?
.25 mm PB
Lead aprons are secondary radiation barriers and must contain at least 0.25-mm Pb equivalent, usually in the form of lead-impregnated vinyl (according to CFR 20). Many radiology departments routinely use lead aprons containing 0.5 mm Pb (the NCRP recommends 0.5-mm Pb equivalent minimum). These aprons are heavier, but they attenuate a higher percentage of scattered radiation.
Which of the following anomalies is (are) possible if an exposure dose of 40 rad (400 mGy) were delivered to a pregnant uterus in the third week of pregnancy?
1. SKeletal animaly
2. Organ Anomaly
3. Neurologic anomaly
Irradiation during pregnancy, especially in early pregnancy, must be avoided. The fetus is particularly radiosensitive during the first trimester, during much of which time pregnancy may not even be suspected. High-risk examinations include pelvis, hip, femur, lumbar spine, cystograms and urograms, and upper and lower gastrointestinal (GI) series. During the first trimester, specifically the 2nd to 10th weeks of pregnancy (i.e., during major organogenesis), if the radiation dose is sufficient, fetal anomalies can be produced. Skeletal and/or organ anomalies can appear if irradiation occurs in the early part of this time period, and neurologic anomalies can be formed in the latter part; mental retardation and childhood malignant diseases, such as cancers or leukemia, and retarded growth/development also can result from irradiation during the first trimester. Fetal irradiation during the second and third trimesters is not likely to produce anomalies but rather, with sufficient dose, some type of childhood malignant disease. Fetal irradiation during the first 2 weeks of gestation can result in embryonic resorption or spontaneous abortion. It must be emphasized, however, that the likelihood of producing fetal anomalies at doses below 20 rad is exceedingly small and that most general diagnostic examinations are likely to deliver fetal doses of less than 1 to 2 rad
Which section of the autoatic processor is associated with preservation of an xray image?
The washing part
As the exposed film enters the processor from the feed tray, it first enters the developer section (number 1), where exposed silver bromide crystals are reduced to black metallic silver. The film then enters the fixer(number 2), where the unexposed silver grains are removed from the film by the clearing agent. The film then enters the wash section (number 3), where chemicals are removed from the film to preserve the image, improving archival quality. From the wash, the film enters the dryer section
Does compton scattering occur with lowe enregy incident photons?
- Compton scatter, a fairly high-energy x-ray photon ejects an outer-shellelectron.
Exposure factors of 80 kVp and 8 mAs are used for a particular nongrid exposure. What should be the new milliampere-seconds value if an 8:1 grid is added?
- To change nongrid to grid exposure, or adjust exposure when chanigng from one grid ratio ato another, the facto for each grid ratio is:
- No grid = 1 x original mas
- 5:1 = 2 x original mas
- 6:1 = 3 x original mas
- 8:1 = 4 xo riginal mas
- 12:1 = 5 x origianl mas
- 16:1 = 6 x original mas
According to the NCRP, the pregnant radiographer's gestational dose-equivalent limit for a 1-month period is
According to the NCRP, the annual occupational whole-bodydose-equivalent limit is 50 mSv (5 rem or 5,000 mrem). The annual occupational whole-body dose-equivalent limit for students under the age of 18 years is 1 mSv (100 mrem or 0.1 rem). The annual occupational dose-equivalent limit for the lens of the eye, a particularly radiosensitive organ, is 150 mSv (15 rem). The annual occupational dose-equivalent limit for the thyroid, skin, and extremities is 500 mSv (50 rem). The total gestational dose-equivalent limit for the embryo/fetus of a pregnant radiographer is 5 mSv (500 mrem), not to exceed 0.5 mSv in 1 month.
How do you convert 4500 mrad to rad?
Divide it by 1000.
Which of the following is most likely to produce a high-quality image?
Small Image mAtrix
High Signal to Noise Ratio (SNR)
Large Pixel Size
High Signal to Noise Ratio
SNR can refer to home television images, magnetic resonance images (MRIs), ultrasound images, x-ray images, and so on. Noise interferes with visualization of image details, for example, scattered radiation fog, graininess from quantum mottle, and so no. The actual signal can be from x-rays, sound waves, and so on. The signal is desirable, the noise is not, therefore, a higher SNR produces a higher-quality image. Low SNR severely impairs contrast resolution.
Is radiographic contrast decreased when beam restriction is used?
Beam Restriction = Field size.
If you collimate more, patient hazard as well as scatter radiation decreases because theres less being irradiated.
Do grids help control the production of scatteR?
Grids have no effect on the production of scattered radiation, but they are very effective in removing scattered radiation from the beam before it strikes the IR
The term differential absorption is related to
- Beam Intensity
- Subject Contrast
Subject Contrast and Pathology
The radiographic subject, the patient, is composed of many different tissue types of varying densities (i.e., subject contrast), resulting in varying degrees of photon attenuation and absorption. This differential absorption contributes to the various shades of gray (i.e., scale of radiographic contrast) on the finished image. Normal tissue density may be significantly altered in the presence of pathology. For example, destructive bone disease can cause a dramatic decrease in tissue density. Abnormal accumulation of fluid (as in ascites) will cause a significant increase in tissue density. Muscle atrophy or highly developed muscles similarly will decrease or increase tissue density.
How is source-to-image distance (SID) related to exposure rate and radiographic density?
As SID increases, exposure rate decreases and radiographic density decreases.
According to the inverse-square law of radiation, the intensity or exposure rate of radiation from its source is inversely proportional to the square of the distance. Thus, as distance from the source of radiation increases, exposure rate decreases. Because exposure rate and radiographic density are directly proportional, if the exposure rate of a beam directed to the IR is decreased, the resulting radiographic density would be decreased proportionally.
A focal-spot size of 0.3 mm or smaller is essential for which of the following procedures?
A fractional focal spot of 0.3 mm or smaller is essential for reproducing fine detail without focal-spot blurring in magnification radiography. As the object image is magnified, so will be the associated blur unless the fractional focal spot is used. Fluoroscopic procedures probably would cause great wear on a fractional focal spot. Use of the fractional focal spot is not essential in bone radiography, although magnification of bony structures often is helpful in locating hairline fractures
Methods of reducing radiation exposure ot patients and/or personnel inlude...
1. beam restriction
3. high kvp, low mAs factors
- 1 2 and 3.
- Beam restriction is probably the single best method of protecting your patient from excessive radiation. It is also an important factor in obtaining high-quality radiographs because there will be less fog from scattered radiation.Shielding areas not included in the radiograph, especially particularly radiosensitive areas, is another effective means of reducing patient dose. If the patient is subjected to less radiation exposure, then so is the operator. Shielding, distance,and time are the three cardinal rules of radiation protection. High-kV, low-mAsexposure factors employ the use of fewer and more penetrating x-rays.
Which of the following methods can be used to reduce radiation exposure to a recently fertilized ovum?
1. Elective Booking
2. Patient Questionnaire
3. The 10 day rule
All of them
In consideration of the potential risk, female patients of childbearing age should be questioned regarding their last menstrual period (LMP) and the possibility of their being pregnant. Facilities offering radiologic services should make inquiries of their female patients regarding LMP and advise them of the risk associated with radiation exposure during pregnancy and the advisability of elective booking. The 10-day rule identifies the first 10 days following the onset of menses as the safest time to schedule elective procedures of the abdomen/pelvis. In addition to supporting the as low as reasonably achievable (ALARA) concept, many institutions also use a patient questionnaire as a guide for scheduling elective abdominal x-ray examinations on women of reproductive age. The patient completes a form that requests information concerning her LMP and the possibility of her being pregnant. In place of either or both of the preceding—or in addition to them—posters can be obtained or signs can be made that caution the patient to tell the radiologic technologist if she suspects that she might be pregnant. Most facilities will post these signs in waiting rooms, dressing rooms, and radiographic rooms.
How is entrance to skin exposure realated to source to skin distance?
ESE decreases when SSD is increased because the divergent quality of the x-ray beam increases.
Which of the two sensitometric curves shown in Figure 7–8 requires more exposure to produce a density of 2.0 on the finished radiograph?
Locate density 2.0 on the vertical axis. Follow it across to where it intersects with image 1 and then to where it intersects with image 2. At each intersection, follow the vertical line down and note the corresponding log-relative exposure. Image 1 requires an exposure of about 1.7 to record a density of 2.0, whereas image 2 requires an exposure of about 2.0 to record the same density. Image 2 is clearly the slower film. The faster film always occupies the position farthest to the left in a comparison of two or more films
When an image intensifier's magnification mode is used,
1. Output screen grain is increased
2. Resolution increases
3. Patient dose increases
All of them
During fluoroscopic procedures, as FOV decreases, magnification of the output screen image increases and contrast and resolution improve. The focal point on an image intensifier's 6-inch field/mode, is further away from the output phosphor than the focal point on the normal mode; therefore, the output image is magnified. Because less minification takes place, the image is not as bright. Exposure factors are automatically increased to compensate for the loss in brightness that occurs with smaller FOVs used in magnification mode.