Explanation:

Myelography the radiologic examination of structures within the spinal canal.Opaque contrast medium is usually used. Following injection, the contrast medium is distributed
to the vertebral region of interest by gravity; the x-ray table is angled Trendelenburg orvisualization of the cervical region and in the Fowler’s position for visualization of the thoracicand lumbar regions. While the table is Trendelenburg, care must be taken that the patient’shead be kept in acute extension to compress the cisterna magna and keep contrast mediumfrom traveling into the ventricles of the brain.

Explanation:

As the heart contracts and relaxes while functioning to pump blood from the heart, those arteries that are large and those in closest proximity to the heart will feel the effect of the heart’s forceful contractions in their walls. The arterial walls pulsate in unison with the heart’s contractions. This movement may be detected with the fingers in various parts of the body andis referred to as the pulse.

Explanation:

Superimposition of bonydetailsfrequently makes angiographic demonstration of blood
vessels less than optimal. The method used to remove these superimposed bony details iscalled subtraction. Digital subtraction can accomplish this through the use of a computer, butphotographic subtraction may also be performed using images from an angiographic series.Registration is the process of matching one series image exactly over another. A reversal image,or positive mask, is a reverse of the black and white radiographic tones.

Explanation:

Deoxygenated blood is returned by way of the inferior and superior vena cava tothe right side of the heart. The blood is emptied into the right atrium, passes through thetricuspid valve, and enters the right ventricle. It is forced through the pulmonary semilunarvalve into the pulmonary artery (by contraction of the right ventricle) and passes to the lungsfor reoxygenation. From the lungs it is collected by the pulmonary veins, which carry theoxygenated blood to the left atrium, where it travels through the mitral valve into the leftventricle. Upon contraction of the left ventricle, blood passes through the aortic valve into theaorta and to all parts of the body.

Explanation:

Generally, contrast medium is injected into the subarachnoid space between the thirdand fourth lumbar vertebrae. Because the spinal cord ends at the level of the first or secondlumbar vertebrae, this is considered to be a relatively safe injection site. The cisterna magnacan be used, but the risk of contrast entering and causing side effects increases.

Explanation:

Lower extremity venography requires an injection of contrast medium into the superficialveins of the foot. The skin on top of the patient’s foot is very sensitive and every precautionshould be taken to minimize the pain involved. Explain the procedure fully and soak the footin warm water to make the veins more accessible for injection.

Explanation:

An intervertebral disc can rupture due to trauma or degeneration. The nucleus pulposusprotrudes posteriorly through a tear in the annulus fibrosus and impinges on nerve roots andcan be demonstrated by placing positive or negative contrast media into the subarachnoidspace. Internal disc lesions can be demonstrated only by injecting contrast into the individual
discs (this procedure is termed discography). Anterior protrusion of a herniated intervertebraldisc does not impinge on the spinal cord and is not demonstrated in myelography.

Explanation:

Major branches of the common carotid arteries (internal carotids) function to supply the anterior brain, while the posterior brain is supplied by the vertebral arteries (branches of the subclavian arteries). The brachiocephalic (innominate) artery is unpaired and is one of threebranches of the aortic arch, from which the right common carotid artery is derived. The left common carotid artery comes directly off the aortic arch.

Explanation:

To increase the concentration of contrast medium in the deep veins of the leg, a Fowler’sposition is used with the table angle of approximately 45◦. Tourniquets can also be used toforce the contrast into the deep veins of the leg. Imaging may be performed with or withoutfluoroscopy and may include anteroposterior (AP), lateral, and 30◦ obliques of the lower legin internal rotation.

Explanation:

The heart wall is made up of the external epicardium, the middle myocardium, andthe internal endocardium. The pericardium is the fibroserous sac enclosing the heart and roots of the great vessels. The heart has four chambers. The two upper chambers are the atria, and the two lower chambers are the ventricles. The apex of the heart is the tip of the left ventricle.

Explanation:

The linear nonthreshold curve is used to illustrate responses such as leukemia, cancer,and genetic effects. These are also referred to as stochastic effects. Stochastic effects occurrandomly and are “all-or-nothing” type effects; that is, they do not occur with degrees ofseverity. Remember that in a nonthreshold curve there is no safe dose, that is, no dose belowwhich there will definitely be no biologic response. Theoretically, even one x-ray photon cancause a biologic response. The linear nonthreshold curve is the curve of choice to predicteffects of low level (e.g., medical and occupational) exposure to ionizing radiation

Explanation:

During the first trimester,specifically the 2nd to 8th week of pregnancy (during majororganogenesis), if the radiation dose is at least 0.2 Gy or 20 rad,fetal anomalies can beproduced. Skeletal anomalies usually appear if irradiation occurs in the early part of thistime period, and neurologic anomalies are formed in the latter part; mental retardation andchildhood malignant diseases, such as cancers or leukemia, can also result from irradiationduring the first trimester. Fetal irradiation during the second and third trimesters is not likely toproduce anomalies, but rather, with sufficient dose, some type of childhood malignant disease.Fetal irradiation during the first 2 weeks of gestation can result in spontaneous abortion.
It must be emphasized that the likelihood of producing fetal anomalies at doses below
0.2 Gy or 20 rad is exceedingly small and that most general diagnostic examinations are likelyto deliver fetal doses of less than 0.01–0.02 Gy or 1–2 rad.

Explanation:

When biologic material is irradiated, there are a number of modifying factors thatdetermine what kind and how much response will occur in the biologic material. One of these
factors is LET, which expresses the rate at which particulate or photon energy is transferredto the absorber. Because different kinds of radiation have different degrees of penetration indifferent materials, it is also a useful way of expressing the quality of the radiation.

Explanation:

LET expresses the rate at which photon or particulate energy is transferred to (absorbedby) biologic material (through ionization processes) and is dependent on radiation type andtissue absorption characteristics. RBE describes the degree of response or amount of biologicchange we can expect of the irradiated material, and is directly related to LET. As the amount oftransferred energy (LET) increases (from interactions occurring between radiation and biologicalmaterial), the amount of biologic effect or damage (RBE) will also increase; as the amount ofLET decreases, the RBE will also decrease.

Explanation:

The effects of a quantity of radiation delivered to a body is dependent on a few factors,including the amount of radiation received, the size of the irradiated area, and how the radiationis delivered in time. If the radiation is delivered in portions over a period of time, it is said tobe fractionated and has a less harmful effect than if the radiation was delivered all at once.Cells have an opportunity to repair and some recovery occurs between doses.

Explanation:

The x-ray photons produced at the tungsten target comprise a heterogeneous beam, thatis, a spectrum of photon energies. This is accounted for by the fact that the incident electronshave different energies. Also, the incident electrons travel through several layers of tungstentarget material, lose energy with each interaction, and therefore produce increasingly weakerx-ray photons. During characteristic x-ray production, vacancies may be filled in the K, L, orM

Explanation:

The tissue weighting factor (Wt) represents the relative tissue radiosensitivity of irradiatedmaterial (e.g., muscle vs. intestinal epithelium vs. bone, etc.). The radiation weightingfactor (Wr) is a number assigned to different types of ionizing radiations to better determinetheir effect on tissue (e.g., x-ray vs. alpha particles). The Wr of different ionizing radiations isdependent on the LET of that particular radiation. The following formula is used to determineeffective dose (EfD).
Effective dose (EfD) =
Radiation weighting factor (Wr) × Tissue weighting factor(Wt)×Absorbed dose

Explanation:

Frequency and wavelength areclosely associated with the relative energy of electromagneticradiations. More energetic radiations have shorter wavelengths and higher frequency;thus, they are inversely related. The relationship between frequency, wavelength, and energyis illustrated in the electromagnetic spectrum . Some radiations are energetic enoughto rearrange atoms in materials through which they pass, and can therefore be hazardous toliving tissue.

Explanation:

Electrons may undergo any one of a few types of interactions as they encounter thetarget. The emitted photons can therefore have a variety of energies and thus are termed heterogeneousor polyenergetic. It is only at extremely high energies that photon energy becomesmore homogeneous; only gamma radiation can be accurately termed homogeneous or monoenergetic.

Explanation:

Occupationally exposed individuals are concerned principally with late (i.e., longtermor delayed) effects of radiation, such as genetic effects, leukemia, cancers, and cataractogenesis,which can occur many years following initial exposure to low levels of ionizingradiation. These long-term, or delayed, effects are represented by the linear, nonthreshold,dose–response curve, with the exception of cataractogenesis, which irepresented by thelinear, threshold, dose–response curve. An acute dose of approximately 200 rad would berequired to cause radiogenic cataracts. A far greater occupational (i.e., fractionated) dose ofapproximately 1000 rad would be required to induce cataracts.

Explanation:

According to NCRP regulations, radiographic and fluoroscopic equipment must havea total Al filtration of at least 2.5 mm Al equivalent whenever the equipment is operated at70 kV or greater, to reduce excessive exposure to low-energy radiation. Collimator and beamalignment must be accurate to within 2% for manual, 4% for PBL. The SSD must not be less than12 inches for all procedures other than dental radiography. Distance is the single best protection from radiation. Excessively short SIDs/SSDs cause a significant increase in patient skin dose

Explanation:

Equipment must be properly calibrated to produce consistently predictable results;specifically, the equipment must have linearity and reproducibility. Linearity refers to consistencyin exposure with adjacent mA stations (very similar to reciprocity law) and exposure
times adjusted to produce the same mAs. Reproducibility refers to consistency in exposureoutput during repeated exposures at a particular setting. Positive beam limitation (PBL) is automatic
collimation. The two types of automatic exposure control (AEC) are the photomultiplierand ionization chamber.

Explanation:

X-rays produced at the target comprise a heterogeneous primary beam. Filtration servesto eliminate the softer, less-penetrating photons leaving an x-ray beam of higher average energy.Filtration is important in patient protection because unfiltered, low-energy photons notenergetic enough to reach the image receptor are absorbed by the body and contribute to totalpatient dose.

Explanation:

Inherent filtration is composed of materials that are a permanent part of the tubehousing; that is, the glass envelope of the x-ray tube and the oil coolant. Added filtration, usually
thin sheets of aluminum, is present to make a total of 2.5 mm Al equivalent for equipment
operated above 70 kV. Filtration is used to decrease patient dose by removing the weak x-rayshaving no value but contributing to skin dose. According to the inverse square law of radiation,exposure dose increases as distance from the source decreases, and vice versa. The effect ofthe focal spot size is principally on radiographic detail, having no effect on patient dose.

Explanation:

mAs regulates the quantity of radiation delivered to the patient. kV regulates thequality (penetration) of the radiation delivered to the patient. The higher the mAs, the greater
the patient dose. Higher energy (more penetrating) radiation—which is more likely to exit thepatient—accompanied by a lower mAs is the safest combination for the patient.

Explanation:

It is our ethical responsibility to minimize radiation dose to our patients. X-rays producedat the target comprise a heterogeneous primary beam. There are many “soft” (low-energy photons that, if not removed, would contribute to only greater patient dose. They are too weakto penetrate the patient and expose the image receptor; they just penetrate a small thicknessof tissue and are absorbed. Filters, usually made of aluminum, are used in radiography to reducepatient dose by removing this low-energy radiation, resulting in an x-ray beam of higheraverage energy. Total filtration is composed of inherent filtration plus added filtration.

Explanation:

The higher the speed of the film and screen system, the smaller the dose of radiationrequired to produce a diagnostic radiograph. As one component of the effort to reduce populationdose, rare eartphosphors are used almost exclusively today in general radiography, asthey are at least four times faster than calcium tungstat phosphors.Grids, both stationary and moving, function to remove a large percentage of scattered(primarily Compton) radiation from the remnant beam before it reaches the image receptor,
thereby improving radiographic contrast. Because scattered radiation often makes significantcontribution to the overall radiographic density, the addition of a grid (or an increase in thegrid ratio) must be accompanied by an appropriate increase in exposure factors (usually mAs)to maintain adequate density. The improvement in image quality is usually more significantthan the increased exposure to the patient
Air-gap technique functions similar to, or in place of, a grid. A distance is introducedbetween the patient and the image receptor. However, to maintain optimum recorded detailand avoid excessive magnification, the SID must be increased considerably, followed by asignificant increase in mAs.

Explanation:

Gonadal shielding should be used whenever appropriate and possible during radiographicand fluoroscopic examinations. Flat contact shields (flat sheets of flexible leaded vinyl)are useful for recumbent studies, but when the examination necessitates that oblique, lateral,or erect projections be obtained, they become less efficient. Shaped contact (contour) shieldsare best because they enclose the male reproductive organs, remaining in oblique, lateral, anderect positions—but they can be used only for male patients. Shadow shields that attach to thetube head are particularly useful for surgical sterile fields.

Explanation:

With greater beam restriction (i.e., smaller field size), less biologic material is irradiated,thereby reducing the possibility of harmful effects. If less tissue is irradiated, less scatteredradiation is produced, resulting in improved image contrast. The total filtration is not a functionof beam restriction, but rather, is a radiation protection guideline aimed at reducing patientskin dose.

Explanation:

parallel plate ionization chamber consists of a radiolucent chamber just beneaththe tabletop . As x-ray photons emerge from the patient, they enter the chamber andionize the air within. When a predetermined quantity of ionization has occurred (as determinedby the selected exposure factors), the exposure automatically terminates. In the phototimer, asmall fluorescent screen is positioned beneath the cassette . When remnant radiationemerging from the patient exits the cassette, the exposure is terminated. The manual timer
should be used as backup timer, in case the AEC fails to terminate the exposure, thus protectingthe patient from overexposure and the x-ray tube from excessive heat load. The backup timeris unrelated to filtration.

Explanation:

Explanation:

Beam restrictors function to limit size of the irradiated field. In doing so, they limit the volume of tissue irradiated (thereby decreasing the percentage of scattered radiation generated in the part) and help reduce patient dose. Because less scattered radiation is produced, less fogaffects the x-ray image thus improving contrast resolution. Beam restrictors do not affect the quality (energy) of the x-ray beam, that is, the function of kV and filtration. Beam restrictors do not absorb scattered radiation, that is, a function of grids.

Explanation:

The exposed IR is placed into the CR reader, where the PSP screen is automatically removed. The latent image appears as the PSP is scanned by a narrow high-intensity helium–neon laser, or solid-state laser, to obtain the pixel data. As the PSP is scanned in the CR reader, it releases a violet light—a process referred to as photostimulated luminescence. The luminescent light is converted to electrical energy representing the analog image. The
electrical energy is sent to an analog-to-digital converter (ADC) where it is digitized and becomes the digital image that is eventually displayed (after a short delay) on a high-resolution monitor and/or printed out by a laser printer. The digitized images can also be manipulated in postprocessing, electronically transmitted, and stored/archived.

Explanation:

The sensitometric (or Hurter and Driffield [H&D]) curve is used to illustrate the relationship
between the exposure given to the film and the resulting density. The relationshipbetween the source-to-image-receptor distance and resulting density is expressed in the inversesquare law of radiation. The effect of kV on contrast can be illustrated using a penetrometer
(aluminum step-wedge).

Explanation:

Inside the IP is the photostimulable phosphor (PSP) image storage plate. This PSP withits layer of europium-activated barium fluorohalide serves as the image receptor as it is exposedin the traditional manner and receives the latent image. The PSP can store the latent imagefor several hours; after approximately 8 hours, noticeable image fading will occur. Once the CR cassette is placed into the CR reader, the PSP screen is automatically removed. The latentimage on the PSP is changed to a manifest image as it is scanned by a narrow high intensityhelium–neon, or solid state, (monochromatic) laser to obtain the pixel data. As the PSP isscanned in the reader,it releases(polychromatic) violet light—a process referred to as photo-(or light-)stimulated luminescence.

Explanation:

Image “fading” will occur if there is delay in reading the IP/PSP. This is because after atime, trapped photo electrons are released from the “color center” and are therefore unable toparticipate in PSL. PSL intensity decreases in the interval between x-ray exposure and imagereading/processing. If the exposed PSL is not delivered to the reader/processor for 8 hours,PSL decreases by approximately 25%. Fading also increases as environmental temperatureincreases. Since PSPs are very sensitive to exposure/fogging, when unexposed IPs are unused for extended periods, they should be erased before use.

Explanation:

Using the variable kV method, a particular mAs is assigned to each body part. As partthickness increases, the kV (penetration) is also increased. The body part being imaged mustbe carefully measured and for each centimeter increase in thickness, 2 kV is added to theexposure.

Explanation:

The sensitometric curve is used to show the relationship between the exposure given
the film and the resulting film density. It can therefore be used to evaluate a particular filmemulsion’s response (speed, sensitivity) by determining how long it takes to record a particulardensity. A dose–response curve is used in radiation protection and illustrates the quantity ofdose required to produce a particular effect. The reciprocity law states that a particular mAs,regardless of the combination of mA and time, should produce the same degree of blackening.The inverse square law illustrates the relationship between distance and radiation intensity

Explanation:

In both indirect-capture flat-panel detector methods scintillation light is captured, readby a photodetector (CCD or TFT), changed to an electronic signal, and transmitted to the ADCfor digitization. In direct-capture flat-panel detector systems, x-ray energy is converted to an
electrical signal in a single layer of material such as the semiconductor a-Se. Electric chargesare applied to both surfaces of the a-Se, electron-hole pairs are created, and charges are read byTFT arrays located on the surfaces. The electrical signal is transferred to the ADC. The number
of TFTs is equal to the number of image pixels. Thus, the direct-capture system eliminates thescintillator step required in indirect DR.

Explanation:

Because pneumoperitoneum is an abnormal accumulation of air or gas in the peritonealcavity, it would require a decrease in exposure factors. Obstructed bowel usually involvesdistended, gas-filled bowel loops, again requiring a decrease in exposure factors. Withascites, there is an abnormal accumulation of fluid in the abdominal cavity, necessitating anincrease in exposure factors. Renal colic is the pain associated with the passage of renal calculi;usually no change from the normal exposure factors is required.

Explanation:

The advantages of automatic processors are quicker, more efficient operation, and consistent
results. Quicker operation is attained with increased solution temperatures. The usualtemperature of a 90-second developer is 90◦F to 95◦F. Excessively high developer temperaturecan cause chemical fog.

Explanation:

Computed radiography uses special detector plates inside cassettes to record the radiologicimage. No film is used, hence the term filmless radiography. The CR cassette is exposedjust like a conventional screen–film cassette. Upon exposure, a latent image is produced onthe photostimulable phosphor (PSP) screen, which is located inside the IP. The IP is placed inthe CR processor, and the PSP is automatically removed. A special reader scans the PSP witha narrow laser beam to obtain the pixel data, which can then be displayed on a monitor as the
radiographic image.

Explanation:

Histogram appearance can be affected by a number of things. Positioning and centeringaccuracy can have a significant effect on histogram appearance. Other factors affectinghistogram appearance include selection of the correct processing algorithm (e.g., chest vs.
femur), changes in scatter, SID, OID, and collimation. In short, anything that affects scatterand/or dose. Another factor affecting histogram appearance is delay in processing from timeof exposure. Processing delay can result in fading of the image.

Explanation:

When a film first enters the processor from the feed tray, a microswitch signals thereplenishment pump to begin sending replenisher solution into the processor. Replenishment
continues until the microswitch senses the end (edge) of the film and terminates pump action.So, as long as film is being fed into the processor, replenishment solution will be added. Thereis, therefore, more replenisher added with larger size films. There is also more replenisheradded when rectangular films are fed into the processor “the long way” because the processor is
sensing, for example, 17 inches of film rather than 14 inches of film. Film should be put through
the processor consistently according to the particular department’s preference or routine. Achange in film direction can lead to over- or underreplenishment and, hence, a change in filmdensity.

Explanation:

The radiographer can manipulate, that is, change and enhance, the digital image displayedon the monitor through postprocessing. One way to alter image contrast and/or densityis through windowing. Windowing refers to some change made to window width and/or windowlevel, i.e. a change in the LUT. Change in window width affects change in the number
of gray shades, that is, image contrast. Change in window level affects change in the image
brightness, that is, optical density. Therefore, windowing and other postprocessing mechanismspermit the radiographer to affect changes in the image and to produce “special effects” such as contrast enhancement, edge enhancement, image stitching (useful in scoliosis examinations),and image inversion, rotation, and reversal.

Explanation:

If the fixer fails to sufficiently reharden the gelatin emulsion, water will remain withinthe still-swollen emulsion. The dryer mechanism will be unable to completely rid the emulsionof wash water, and the film will emerge from the processor damp and tacky. On the otherhand, excessive hardening action may produce brittle radiographs. High air velocity usuallyencourages more complete drying. Unbalanced processing temperatures can result in blisteringof the emulsion.

Explanation:

The invisible silver halide image is composed of exposed silver grains. These are “reduced”to a visible black metallic silver image in the developer solution. The fixer solutionfunctions to remove unexposed silver halide crystals from the film.

Explanation:

All of those effects listed can result from poor storage practices. Film should be rotatedwith the oldest being used first to avoid fog from outdated film. By protecting film from chemicalfumes and from excessive temperatures, fogging of the sensitive emulsion is prevented

Explanation:

Conventional screen–film images can be scanned and digitized by a special machinecalled a film digitizer. Interpretation of digital images is made from the display monitor; thisis referred to as “soft copy display.” “Hard copies” can be made with a laser printer. A lasercamera records the displayed image by exposing a film with laser light; it can also recordseveral images on one film. The laser printer is connected for processing of the images

Explanation:

As in traditional radiography, numerous density values represent various tissue densities,for example, bone, muscle, fat, blood-filled organs, air/gas, metal, contrast media, pathologicprocesses, etc. In CR, the CR scanner recognizes these numerous values and constructsa gray-scale histogram of these values represented in the imaged part. A histogram is a graphicrepresentation defining all these values. The radiographer selects a processing algorithm byselecting the anatomical part and particular projection on the computer. The CR unit thenmatches that information with a particular Lookup Table (LUT)—a characteristic curve thatbest matches the anatomical part being imaged. Hence, histogram analysis and use of theappropriate LUT together function to produce predictable image quality in CR.

Explanation:

All other factors can be changed in the computer to manipulate the image. Geometricdetail is controlled only by source-to-image-receptor distance (SID), object-to image-receptordistance (OID), and focal spot size. These factors are fixed during the x-rayexposure.

Explanation:

When a spinning top is used to test the efficiency of a single-phase timer, the resultis a series of dots or dashes, with each dot or dash representing a pulse of radiation. With full-wave rectified current, and a possible 1/20 dots (pulses) available per second, one shouldvisualize 12 dots at 1/10 second, 24 dots at 1/5 second, 6 dots at 1/20 second, and so on.But because three-phase equipment is almost constant potential, a synchronous spinning topmust be used, and the result is a solid arc (rather than dots). The number of degrees formed bythe arc is measured and equated to a particular exposure time. A multitude of small mesh-likesquares describes a screen contact test. An aluminum step-wedge (penetrometer) may be used
to demonstrate the effect of kV on contrast (demonstrating a series of gray tones from white toblack), with a greater number of grays demonstrated at higher kV levels.

Explanation:

Bremsstrahlung (or Brems) radiation is one of the two kinds of x-rays produced at thetungsten target of the x-ray tube. The incident high-speed electron, passing through a tungsten atom, is attracted by the positively charged nucleus; therefore, it is deflected from its course with a resulting loss of energy. This energy loss is given up in the form of an x-ray photon

Explanation:

Target angle has a pronounced geometric effect on the effective, or projected, focalspot size. As target angle decreases (i.e., gets steeper or smaller), the effective (projected) focalspot becomes smaller. This is advantageous because it will improve radiographic detail withoutcreating a heat-loading crisis at the anode (as would be the case if the actual focal spot sizewere reduced to produce a similar detail improvement). There are disadvantages, however.With a smaller target angle the anode heel effect increases; photons are more noticeablyabsorbed by the “heel” of the anode, resulting in a smaller percentage of x-ray photons at theanode end of the x-ray beam and a concentration of x-ray photons at the cathode end of theimage.

Explanation:

A digital image is formed by a matrix of pixels in rows and columns. A matrix having512 pixels in each row and column is a 512×512 matrix. As in traditional radiography, spatial
resolution is measured in line pairs per mm (lp/mm). As matrix size is increased, there are moreand smaller pixels in the matrix, which means improved resolution. Fewer and larger pixelsresult in a poor resolution “pixelly” image, that is, one that you can actually see the individual pixel boxes

Explanation:

Radiographic reproducibility is an important concept in producing high-quality diagnostic films. Radiographic results should be consistent and predictable, not only in positioningaccuracy but with respect to exposure factors as well. Automatic exposure devices (phototimers and ionization chambers) automatically terminate the x-ray exposure once a predetermined quantity of x-ray has penetrated the patient, thus ensuring consistent results.

Explanation:

One advantage of computed radiography is the ability to manipulate the image after
exposure (“postprocessing”). Image manipulation postprocessing can be used for windowing,contrast and/or density modification, or image subtraction.
Windowing is a process of changing the contrast and density setting on the finished image.The window width controls the number of shades of gray in the image (contrast), while the
window level corresponds to the image density.

Explanation:

The high-voltage, or step-up, transformer functions to increase voltage to the necessarykilovoltage. It decreases the amperage to milliamperage. The amount of increase or decreasedepends on the transformer ratio, that is, the number of turns in the primary coil to the numberof turns in the secondary coil. The transformer law is as follows:

To Determine Secondary V To Determine Secondary I
Vs/Vp= Ns/ Np
I s/I p =Vp/Vs

Substituting known values,
x/220 =75000/150
150x = 16 500 000
x = 110000 V (= 110 kV)

Explanation:

The principle of self-induction is an example of the second law of electromagnetics(Lenz’s law), which states that an induced current within a conductive coil will oppose the
direction of the current that induced it. It is important to note that self-induction is a characteristicof AC only.The fact that AC constantly changes direction accounts for opposing currentsset up in the coil. Two x-ray circuit devices operate on the principle of self-induction: The
autotransformer operates on the principle of self-induction and enables the radiographer tovary the kilovoltage. The choke coil also operates on the principle of self-induction; it is a typeof variable resistor that may be used to regulate filament current. The high-voltage transformeroperates on the principle of mutual induction.

Explanation:

Transformers are used in the x-ray circuit to change the value of the supplied voltageto a value appropriate for the production of x-rays. Although the incoming voltage supply maybe 220 V, thousands of volts are required for the production of x-rays. A step-up transformerconsists of two coils, a primary and a secondary, in close proximity to each other (e.g., sideby side). As the primary coil is supplied with AC, a magnetic field rises up around the coiland proceeds to “cut” the secondary coil. Because the current supply is AC, the magneticfield is constantly expanding and contracting (rising and falling) and continuously “cutting”the secondary coil. This interaction between magnetic field and conductive coils induces acurrent in the secondary coil proportional to the number of turns in the secondary coil. Asthe number of turns in the secondary coil increases, so does the induced voltage. However,because we cannot just create energy, only change its form, the amperage in the second coilis proportionally less. For example, if the voltage in the secondary coil increased 10 times, thecurrent would decrease by a factor of 10. Therefore, in keeping with the law of conservationof energy, the product of the voltage and current in one coil must equal the product of voltageand current in the second coil.

Explanation:

A synchronous spinning top test is used to test timer accuracy or rectifier function in three-phase equipment.Because three-phase,full-wave rectified current would expose a 360 degree arc per second, a 1/20-second exposure should expose an 18-degree arc. Anything more or less indicates timer inaccuracy. If exactly one-half of the expected arc appears, one should suspect rectifier failure.

Explanation:

Sensitometry and densitometry are used in evaluation of the film processor, just onepart of a complete quality assurance (QA) program. Modulation transfer function (MTF) is usedto express spatial resolution, which is another component of the QA program. A complete QAprogram includes testing of all components of the imaging system: processors, focal spot, x-raytimers, filters, intensifying screens, beam alignment, and so on.

Explanation:

Focal spot size accuracy is directly related to the degree of geometric blur, that is, asfocal spot size increases, blur increases. Manufacturer tolerance for new focal spots is 50%and focal spot size can increase in size as the x-ray tube ages; hence, the importance of testing
new focal spots and periodic testing to monitor any focal spot changes. Focal spot size canbe measured with a pinhole camera, slit camera, or star-pattern–type resolution device. Thepinhole camera and slit camera measure the physical size of the focal spot, while the starpattern measures focal spot size as a function of resolution/geometric blur.
Perfect film–screen contact is essential to recorded detail and is evaluated with a wiremeshtest. A spinning-top test is used to evaluate timer accuracy and rectifier operation. Apenetrometer (aluminum step-wedge) is used to illustrate the effect of kV on contrast.

Explanation:

CR PSPs should be cleaned monthly. It is important that anhydrous ethanol be used forcleaning most CR PSPs. A small amount of anhydrous ethanol is placed on a lint-free cloth forcleaning and removal of any dust or other particles. Water and remnant moisture must not beused as it can cause phosphor swelling. Dust on PSPs has the same effect as dust on intensifyingscreens—a clear pinhole artifact. PSPs should also be checked for physical damage. Scratcheswill appear as clear areas on the resulting image. CR IPs should be visually checked for physicaldamage; inserting a damaged CR IP into the reader can result in mechanical failure and systemshutdown.

Explanation:

Protective lead aprons and gloves are made of lead impregnated vinyl or leather. Theyshould be checked for cracks radiographically from time to time. Otherwise, minimal care is required. Lead aprons and gloves should always be hung on appropriate hangers. Glove
supports permit air to circulate within the glove. Apron hangers provide convenient storagewithout folding. If lead aprons are folded (or just left in a heap!), cracks are more likely to form.If lead aprons or gloves become soiled, cleaning with a damp cloth and appropriate solution is all that is required. Excessive moisture should be avoided.

Explanation:

Radiographic results should be consistent and predictable not only in positioning accuracybut with respect to exposure factors and image sharpness as well. X-ray equipmentshould be calibrated periodically as part of an ongoing QA program. The quantity (mAs)and quality (kV) of the primary beam have a big impact on the quality of the finished radiograph.
The focal spot should be tested periodically to evaluate its impact on image sharpness

Explanation:

The spinning-top test is used to evaluate timer accuracy or rectifier failure.With singlephase,full-wave rectified equipment (120 pulses per second) for example, 12 dots should bevisualized when using the 1/10-second station. A few more or less indicate timer inaccuracy. If
the test demonstrated six dots, one might suspect rectifier failure.With three-phase equipmenta special synchronous spinning top (or oscilloscope) is used and a solid black arc is obtainedrather than dots. The length of this arc is measured and compared with the known correct arc.

Explanation:

Inherent filtration is that which is “built into” the construction of the x-ray tube. Beforeexiting the x-ray tube, x-ray photons must pass through the tube’s glass envelope and portwindow; the photons are filtered somewhat as they do so. This inherent filtration is usuallythe equivalent of 0.5 mm Al. Aluminum filtration placed between the x-ray tube housing andcollimator is added to contribute to the total necessary requirement of 2.5 mm Al equivalent.The collimator itself is considered part of the added filtration (1.0 mm Al equivalent) becauseof the silver surface of the mirror within. It is important to remember that as aluminum filtrationis added to the x-ray tube, the HVL increases.

Explanation:

Perfect contact between the intensifying screens and film is essential to maintain imagesharpness. Any separation between them allows diffusion of fluorescent light and subsequent
blurriness and loss of detail. Screen–film contact can be diminished if the cassette frame isdamaged and misshapen, if the front is warped, or if there is a foreign body between the
screens elevating them.

Explanation:

The accuracy of all three is important to ensure adequate patient protection. Reproducibilitymeans that repeated exposures at a given technique must provide consistentintensity. Linearity means that a given mAs, using different mA stations with appropriate exposuretime adjustments, will provide consistent intensity. Positive beam limitation (PBL) isautomatic collimation and must be accurate to 2% of the source-to-image-receptor distance(SID). Light-localized collimators must be available and must be accurate to within 2%.

Explanation:

The advantages of digital fluoroscopy (DF) over conventional fluoroscopy includehigher-speed acquisition and availability of postprocessing for image/contrast enhancement.
Although DF appears fundamentally the same as conventional fluoroscopy, DF has special
requirements: a computer, two video monitors, and an operating console that is far more complexthan the conventional console. A computer is located between the TV camera (or CCD)and the TV monitor and serves to convert the analog image to a digital image. The operatingconsole has many special function keys for patient data entry, for data acquisition, image display,and image postprocessing manipulation. Two video monitors are required—the secondmonitor is for display of the subtracted image

Explanation:

The tissue weighting factor (Wt) represents the relative tissue radio sensitivity of irradiatedmaterial (e.g., muscle vs. intestinal epithelium vs. bone, etc.). The radiation weighting factor (Wr) is a number assigned to different types of ionizing radiations in order to betterdetermine their effect on tissue (e.g., x-ray vs. alpha particles). The Wr of different ionizingradiations is dependent on the LET of that particular radiation. The following formula is usedto determine effective dose (E): Effective dose (E) = radiation weighting factor (Wr) × tissue
weighting factor (Wt) × absorbed dose

Explanation:

The PSP screen within the IP has a layer of europium-activated barium fluorohalide(BaFX:Eu2+; X = Halogen) mixed with a binder substance. This layer serves as the imagereceptor when exposed to x-rays. Just under the barium fluorohalide layer is first a reflective
layer, then the base, then an antistatic layer and finally a layer of lead foil to absorb backscatter.Over the top of the barium fluorohalide is a protective layer. When the barium fluorohalideabsorbs x-ray energy, electrons are released and they divide into two groups. One electron
group initiates immediate luminescence during the excited state of Eu2+. The other electrongroup becomes trapped within the phosphor’s halogen ions, forming a “color center.” Theseare the phosphors that ultimately form the radiographic image because when exposed to amonochromatic (often infrared) laser light source these phosphors emit polychromatic light,
termed photostimulate luminescence (PSL)

Explanation:

The abdomen is divided into quadrants: RUQ, RLQ, LUQ, and LLQ. Structures locatedin the LUQ of the average adult include the left kidney and suprarenal gland, stomach, spleen,splenic flexure, and tail of the pancreas. The ascending colon is located in the right lowerquadrant

Explanation:

Creatinine is a normal alkaline constituent of urine and blood, but increased quantitiesof creatinine are present in advanced stages of renal disease. Creatinine and BUN (blood ureanitrogen) blood chemistry levels should be checked prior to beginning an examination requiringthe use of an iodinated contrast agent. Increased levels may forecast increased possibility ofcontrast media–induced renal effects and poor visualization of the renal collecting systems.Normal creatinine range is 0.6 to 1.5 mg/100 mL. Normal BUN range is 8 to 25 mg/100

Explanation:

Adverse reactions to the intravascular administration of iodinated contrast are not uncommon,and although the risk of a life-threatening reaction is relatively rare, the radiographermust be alert to recognize and deal effectively should a serious reaction occur. Minor reactionis characterized by flushed appearance and nausea, occasionally vomiting and a few hives.Early symptoms of a possible anaphylactic reaction include constriction of the throat, possiblycaused by laryngeal edema, dysphagia (difficulty swallowing), and itching of the palms andsoles. The radiographer must maintain the patient’airway,summon the radiologist and call “code”.

Explanation:

The cervical intervertebral foramina lie 45 degrees to the midsagittal plane (and 15–20 degrees to a transverse plane) and are therefore demonstrated in the oblique position.
Intervertebral joints are well visualized in the lateral projection of all the vertebral groups.
Cervical articular facets (forming apophyseal joints) are 90 degrees to the midsagittal planeand therefore are also well demonstrated in the lateral projection

Explanation:

The effects of a quantity of radiation delivered to a body are dependent on the amountof radiation received, the size of the irradiated area, and how the radiation is delivered in time.
If the radiation is delivered in portions over a period of time, it is said to be fractionated and
has a less harmful effect than if the radiation was delivered all at once. Therefore, cells havean opportunity to repair and some recovery occurs between doses

Explanation:

Veracity is not only telling the truth, but also not practicing deception. Autonomy isthe ethical principle related to the theory that patients have the right to decide what will or willnot be done to them. Beneficence is related to the idea of doing good and being kind. Fidelityis faithfulness and loyalty

Explanation:

Somatic effects of radiation refer to those effects experienced directly by the exposedindividual such as erythema, epilation, and cataracts. Genetic effects of radiation exposure arecaused by irradiation of the reproductive cells of the exposed individual and transmitted from
one generation to the next

Explanation:

The approximately 5-foot-long large intestine (colon) functions in the formation, transport,and evacuation of feces. The colon commences at the terminus of the small intestine;
its first portion is the sac-like cecum in the RLQ, located inferior to the ileocecal valve. The ascending colon is continuous with the cecum and is located along the right side of the abdominal cavity. It bends medially and anteriorly forming the right colic (hepatic) flexure. The colon traverses the abdomen as the transverse colon and bends posteriorly and inferiorly to form the left colic (splenic) flexure. The descending colon continues down the left side of the abdominal cavity and at about the level of the pelvic brim, in the left lower quadrant (LLQ), the colon moves medially to form the S-shaped sigmoid colon. The rectum, approximately 5 inches in length, lies between the sigmoid and anal canal

Explanation:

Neither ultrasonography nor magnetic resonance imaging requires the use of ionizingradiation to produce an image. Computed axial tomography does require ionizing radiationto produce an image. Ultrasonography requires the use of high-frequency sound waves (ultrasound)to produce images of soft-tissue structures and certain blood vessels within the body.
Magnetic resonance imaging relies on the use of a very powerful magnet and specially designedcoils that send and receive radio wave signals to produce the image

Explanation:

A fistula is an abnormal tubelike passageway between organs or an organ and thesurface. Fistulas can result from abscesses, injuries, malignancies, inflammation of neighboringtissues, and from ionizing radiation exposure. A polyp is a tumor with either a pedicle(pedunculated, or having a stalk) or a broad base (sessile), commonly found in vascular organsprojecting inward from its mucosal wall. They are usually removed surgically because,although usually benign, they can become malignant.

Explanation:

A patient going into shock may exhibit pallor and weakness, a significant drop inblood pressure, and an increase in pulse rate. The patient may also experience apprehensionand restlessness, and have cool, clammy skin. A radiographer recognizing these symptomsshould call them to the physician’s attention immediately. Fever is not associated with shock

Explanation:

The production of red blood cells is called erythropoiesis. This process takes placein the bone marrow of the extremities of long bone, pelvis, ribs, sternum, and vertebrae. Redblood cells have no nucleus and a life span of approximately 120 days. After red blood cells die, they are removed from circulation by phagocytic action in the liver and spleen

Explanation:

Every radiographic examination involves an entrance skin exposure (ESE), which canbe determined fairly easily. It also involves a gonadal dose and marrow dose that, if needed, can
be calculated by the radiation physicist. If the ESE of a particular examination was calculated to
determine the equivalent whole-body dose, this is termed effective dose. For example, the ESEof a posteroanterior (PA) chest is approximately 70 mrem, while the effective dose is 10 mrem.The effective (whole-body) dose is much less because much of the body is not included in theprimary beam

Explanation:

When the body is erect,the diaphragm is more easily moved to a lower positionduring inspiration. For this reason, chest radiography is performed erect to allow maximum
lung expansion. With the body in the supine position, the abdominal viscera exert greaterpressure on the diaphragm, and it usually assumes a position 2 to 4 inches higher than when erect

Explanation:

A digital image is formed by a matrix of pixels (picture elements) in rows and columns.A matrix having 512 pixels in each row and column is a 512 × 512 matrix. The term field of
view is used to describe how much of the patient (e.g., 150-mm diameter) is included in thematrix. The matrix and/or field of view can be changed without affecting the other, but changesin either will change pixel size. As in traditional radiography, spatial resolution is measuredin line pairs per millimeter (lp/mm). As matrix size is increased, there are more and smallerpixels in the matrix, therefore improved resolution

Explanation:

With the body in the anteroposterior (AP) recumbent position, barium flows easily intothe fundus of the stomach, displacing it somewhat superiorly. The fundus, then, is filled withbarium, while the air that had been in the fundus is displaced into the gastric body, pylorus,and duodenum, illustrating them in double-contrast fashion. Air contrast delineation of thesestructures allows us to see through the stomach, to retrogastric areas and structures. Bariumfilledduodenum and pylorus is best demonstrated in the right anterior oblique (RAO) position

Explanation:

An ambulatory patient is one who is able to walk with minimal or no assistance.Outpatients as well as many inpatients are usually ambulatory. Patients who are not ambulatory are usually transported to the radiology department via stretcher

Explanation:

An ambulatory patient is one who is able to walk with minimal or no assistance. Outpatients as well as many inpatients are usually ambulatory. Patients who are not ambulatory are usually transported to the radiology department via stretcher

Explanation:

Moving the image intensifier closer to the patient during fluoroscopy reduces thedistance between the x-ray tube (source) and the image intensifier (image receptor), that is,
the SID is reduced. It follows that the distance between the part being imaged (object) and the image intensifier (image receptor) is also reduced, that is, the OID is reduced

Explanation:

The addition of a grid will help clean up the scatter radiation produced by higher kV,but it requires an mAs adjustment. According to the grid conversion factors listed below, the addition of an 8:1 grid requires that the original mAs be multiplied by a factor of 4:

No grid = 1 × original mAs
5:1 grid = 2 × original mAs
6:1 grid = 3 × original mAs
8:1 grid = 4 × original mAs
12:1 grid = 5 × original mAs
16:1 grid = 6 × original mAs

The adjustment therefore requires 32 mAs at 90 kV

Explanation:

The closer the x-ray source is to the barrier (wall), the greater the thickness necessary.Occupancy factor refers to the degree of occupancy of the room adjacent to the barrier;a stairway would require less shielding than a busy work area.Workload is important indetermining barrier thickness and refers to the number of examinations performed in the x-rayroom measured in mA-min/wk—the greater the number of examinations per week, the greaterthe barrier thickness required. Use factor is also important in determining barrier thickness,and refers to the amount of time x-rays are directed to a particular wall—the greater the amountof time, the greater the thickness required

Explanation:

Sterilization is the complete elimination of all living microorganisms and can be
accomplished by several methods. Pressurized steam, in an autoclave, is probably the mostfamiliar means of sterilization; the pressure allows higher temperatures to be achieved. Gasor chemical sterilization is used for items unable to withstand moisture and/or high temperatures.
Other methods of sterilization include dry heat, ionizing radiation, and microwaves(nonionizing radiation)

Explanation:

When examining the third through fifth fingers in the lateral position, the medial sideof the forearm (ulnar side) should be closest to the image receptor. This minimizes magnificationby achieving the shortest possible OID (object-to-image-receptor distance).The terms medial and lateral are identified while viewing the part in the anatomic position

Explanation:

The image intensifier’s input phosphor receives the remnant radiation emerging fromthe patient and converts it into a fluorescent light image. Very close to the input phosphor,separated by a thin, transparent layer, is the photocathode. The photocathode is made of aphotoemissive alloy, usually an antimony and cesium compound. The fluorescent light imagestrikes the photocathode and is converted to an electron image that is focused by theelectrostatic lenses to the output phosphor

Explanation:

Minimizing magnification through the use of increased SID (source-to-imagereceptordistance) and decreased OID (object-to-image-receptor distance) functions to improverecorded detail. Decreasing focal spot size decreases blur, thereby increasing recordeddetail. Motion, voluntary or involuntary, is most detrimental to good recorded detail. Althoughall other detail factors may be adjusted to maximize detail, if motion occurs during exposure,detail is lost. The most important ways to reduce the possibility of motion are by using theshortest possible exposure time, by careful patient instruction (for suspended respiration), andby adequate immobilization when necessary

Explanation:

Primary radiation barriers protect against direct exposure from the primary (useful) xraybeam and have much greater attenuation capability than secondary barriers, which protectonly from leakage and scattered radiation. Examples of primary barriers are the lead walls anddoors of a radiographic room, that is, any surface that could be struck by the useful beam.Primary protective barriers of typical installations generally consist of walls with 1/16-inch(1.5 mm) lead thickness and 7-feet high.
Secondary radiation includes leakage and scattered radiation. The control booth wall isa secondary barrier; therefore, the primary beam must never be directed toward it. The x-raytube housing must reduce leakage radiation to less than 100 mR/h at a distance of 1 meter fromthe housing. Lead aprons, lead gloves, portable x-ray barriers, and the like are also designedto protect the user from exposure to scattered radiation and will not protect from the primarybeam.

Explanation:

The number of heat units produced during a given exposure with single-phase equipmentis determined by multiplying mA × second × kV. Correction factors are required withthree-phase equipment. Unless the equipment manufacturer specifies otherwise, three-phase,six-pulse heat units are determined by multiplying mA × second × kV × 1.35. Three-phase, 12-pulse heat units are determined by multiplying mA × second × kV × 1.41