VET TECH PREP (DIagnostic Imaging)

Barium for an upper GI radiograph series should not be given to a patient with which of the following?

Aspiration pneumonia explanation - Patients with aspiration pneumonia or who are at risk for aspiration pneumonia should not be given oral barium for an upper GI series due to the risk of aspiration of the barium. Dehydration and renal failure are contraindications for other types of contrast such as iodide contrast agents, which are hyperosmolar and can cause osmotic diuresis and diarrhea. Barium is commonly given to animals with partial obstructions and/or diarrhea as part of their diagnostic work-up and is not contraindicated.

Which of the following correctly indicates where electrons are generated in an x-ray machine?

At the filament of the cathode explanation - The cathode flament of the x-ray machine is where electrons are generated. The kVp applied directs those electrons to the anode, where they hit a tungsten target to produce x-rays.

In order to prevent distortion on a dental radiograph when parallel technique cannot be used (impossible to position the film parallel to the long axis of the tooth), which of the following will prevent image distortion (elongation or foreshortening)?

Bisecting angle technique explanation - In most radiographs, to avoid distortion (elongation or foreshortening), the x-ray beam should be perpendicular to the long axis of the bone and the x-ray cassette. If the bones are not perpendicular to the beam, they will appear foreshortened. If the cassette is not perpendicular to the beam, the bones will appear elongated. In dental radiography, it is frequently impossible for the long axis of the tooth and the film to be parallel to each other. In this case, the bisecting angle technique may be used, where the beam is angled half-way between the angle of the long axis of the tooth and the angle of the film in order to obtain a true image that is neither elongated nor foreshortened. By angling half-way between those two angles, this technique effectively balances out the two types of distortion to obtain a true image.

Which of following typically appear hyperechoic (bright white) on ultrasound imaging?

Bone and gas explanation - Sound is strongly reflected by mineral and gas, resulting in a hyperechoic appearance of bone and gas in the gastrointestinal tract or air in lungs. Fluid such as urine in the bladder typically appears hypoechoic or anechoic (black), and most soft tissues such as spleen, liver, and kidney have varying echogenicities in between the two. In addition to a hyperechoic appearance, mineral and gas also typically create a shadow that obscures deeper structures because the sound is unable to penetrate.

What tissue is the MOST sensitive to radiation therapy?

Bone marrow explanation - Bone marrow consists of progenitor and stem cells, the most radiosensitive cells. Cells going through division are generally the most sensitive.

What are the components of a typical X-ray cassette in order from front (where X-rays enter) to back?

Cassette front, padding, intensifying screen, film, intensifying screen, padding, cassette back explanation - The intensifying screen must be next to the film and not shielded by padding in order to expose the film. Most cassettes have intensifying screens and padding on each side of the film.

Which of the following types of radiographs is helpful in confirming the presence of free air or fluid, if it is suspected based on survey films (DV, VD and lateral projections)?

Horizontal beam explanation - Standing a patient upright and taking a horizontal beam radiograph can be helpful in confirming the presence of air or fluid in a body cavity (thorax, abdomen) because this position allows fluid to settle ventrally and air to rise dorsally. The bisecting angle technique is a radiographic technique used to prevent distortion when it is not possible to place the film parallel to the structure of interest and perpendicular to the x-ray beam (common in dental radiography). A skyline view is a technique used to decrease superimposition of structures, usually in the equine carpus.

Which of these animals does not have a gall bladder?

Horse explanation - Horses do not have a gall bladder. The other species listed all do

MRI-compatible equipment might be made of which of the following metals?

Aluminum explanation - For safety purposes, whenever there is any question, no metal should be brought in or near an MRI suite. However, magnets in MRI machines attract ferrous metals which are iron, nickel, and cobalt. There are many non-ferromagnetic metals including aluminum, titanium, brass, and others. Many MRI-compatible devices are made with these. Alloys such as stainless steel may or may not contain ferromagnetic metals.

Which of the following bones is not considered a part of the axial skeleton?

Femur explanation - The axial skeleton consists of bones found on midline or attached to it. The appendicular skeleton is made up of all the bones associated with the limb.

Which bone articulates with the patella?

Femur explanation - The distal femur articulates with the patella at the level of the trochlear groove. The patella attaches to the tibial tuberosity but does not articulate with this bone. The fibula is the bone directly adjacent to the tibia. The humerus is a bone of the forelimb.

Developed radiographs that appear yellow are usually due to a problem with which of the following?

Fixer solution explanation - Yellow radiographs are usually seen when the fixer solution is low or fixation time is too short.

Nervous tissue without myelin is known as which of the following?

Grey matter explanation - Grey matter is nervous tissue that is not myelinated. White matter is myelinated. Myelin is a dielectric material that insulates and provides a sheath around the axon of a neuron. Dura mater and pia mater (along with arachnoid) are part of the meninges of the brain.

Linear artifacts on a film are usually due to which of the following?

Grid explanation - Linear artifacts can be normal gridlines or may be due to the beam not being appropriately centered on the grid. Alternatively, they may occur if the grid is otherwise out of position, upside-down, or damaged. Processing machine errors may cause streaks on the film which should not be confused with linear artifacts. Errors with the other components listed should not cause linear artifacts.

Which bone is between the scapula and radius?

Humerus explanation - The humerus lies distal to the scapula and proximal to the ulna. The tibia and central tarsal bone are bones of the hind limb.

A dog presents with weakness, depression, polyuria, polydipsia, and dilute urine. X-rays reveal a mediastinal mass. Where is the mediastinum located?

In the chest explanation - The mediastinum is the central compartment of the chest. It is located between the right and left pleura and extends from the sternum to the vertebral column. It contains all the thoracic organs except the lungs.

You pull a 6 year old film out of a folder to compare to radiographs that you took today. The old film appears to have yellow-brown staining. What is the likely cause of this?

Incomplete washing of the film explanation - Yellow-brown staining over time is the result of incomplete removal of chemicals (usually from the fixer) during the final washing step in film development. A film that is not dried completely commonly has artifacts around the edges of the film.

Which of the following is a legally acceptable method to identify a radiograph in the event that the radiograph needs to be used in court?

Lead letters with patient information are placed at the corner of the field during the radiograph exposure explanation - Legally, radiographs must be identified during or after exposure and before processing to produce the latent image.

Which of the following is NOT part of the axial skeleton?

Limbs explanation - The axial skeleton forms the core body structure. The appendicular skeleton includes the appendages, or limbs.

Which of the following components of a digital radiography unit has the biggest influence on image quality?

Monitor explanation - A PACS system consists of a server, a workstation, and a viewing monitor. The workstation receives the images and sends them for display on the monitor. The monitor is the most critical to image quality. The other components have a bigger influence on how quickly images may load. A high quality graphics card is more important for viewing movie loops of ultrasound or fluoroscopy images, which require more processing power but are inherently lower resolution.

Which of the following is the most common factor that prevents a diagnostic radiograph in a horse?

Motion explanation - Motion is a problem with any radiograph on any species. However, in horses, due to their fight or flight nature, getting them to stand still can be tricky.

What procedure requires the use of contrast (dye)?

Myelogram explanation - A myelogram involves contrast administration into the subarachnoid space so that it may be visualized on a radiograph.

A 3-year old castrated male Doberman Pinscher comes in to the emergency clinic with signs consistent with gastric dilation and volvulus (GDV). Following standard initial emergency treatment for suspected gastric dilation and volvulus, what imaging procedure would be most helpful in confirming the diagnosis?

Right lateral recumbency abdominal radiograph explanation - A typical GDV occurs with repositioning of the pylorus to the left dorsal abdomen. A right lateral radiographic image is the best perspective position for revealing a-gas filled right dorsally-displaced pylorus with a gas-filled ventral fundus separated by a soft tissue band (compartmentalized stomach). Although the features of a malpositioned stomach may be observed on the other radiographic views, they are often more difficult to interpret than that represented by the right lateral recumbency view. The severe amount of gas within the GI tract that is associated with GDV would make ultrasound exam interpretation extremely difficult at best.

You take a series of chest radiographs and notice that all of the films appear darker (more exposed) towards one side of the film. Which of the following is the most likely explanation?

The X-ray beam is usually more intense on one side of the field explanation - This phenomenon is known as the "Heel effect". X-ray distribution in diagnostic X-ray units is uneven, with the beam being most intense at the cathode side of the machine and weakest at the anode side. This effect is frequently minor but can be noticeable. It is advantageous to radiograph patients of uneven thickness (i.e. the body of a deep-chested dog) by orienting the thickest part toward the cathode side of the x-ray tube. The other choices listed could cause artifacts but should not cause such a gradient on the film.

Your practice recently purchased a portable ultrasound machine. A client calls and asks how early her mare can have an ultrasound to determine if she is pregnant. What is the very earliest that a pregnancy can be confirmed with an ultrasound in a horse?

11 days explanation - Pregnancy may be detected via ultrasound as early as 11 days after service however, most practices recommend to wait about three weeks after the mare was bred or serviced before performing ultrasound to be certain. Experienced practitioners may choose to do it closer to two weeks post breeding.

Which of the following people is not allowed to restrain a patient for a radiograph?

17-year old male veterinary assistant that is working at the clinic for the summer explanation - Individuals must be at least 18 years of age to participate in radiographic procedures. There are stricter dose limits for pregnant women, but these women are not strictly prevented from involvement in radiography. As long as the volunteer is trained and monitored appropriately, she can assist. There is no upper-limit of age restricting involvement in radiographic procedures.

Your radiograph technique chart indicates that you should use a kVp setting of 50 and mAs setting of 12.5. Which of the following would be appropriate?

250 mA, 1/20 sec explanation - mAs is a measure of the total exposure. It is the product of mA and time in seconds. Of the choices here, only 250 mA and 1/20 sec yields a product of 12.5 mAs. Generally, it is also best to maximize the mA and minimize exposure time to decrease motion artifacts.

How many days after fertilization will canine fetal skeletons first appear on a radiograph?

42 days explanation - At 42 days after fertilization, calcium is absorbed into the fetal skeletons and makes them visible on the radiograph.

An owner brings her 4-year old female Labrador Retriever to your clinic because she believes she might be pregnant. She does not remember when the dog's last heat cycle was. The dog's abdomen appears fairly distended and you take a lateral abdominal radiograph which is shown below. What would be the earliest time you would expect to be able to see fetal skeletons on abdominal radiographs in the dog?

43 days gestation explanation -The correct answer is 43 days gestation. The fetal skeleton ossifies at 42-45 days in the dog and 35-39 in the cat. In the dog, a mineralized fetus can usually be seen around 42-46 days. The scapula, humerus, and femur can be made out around 46-51 days. The ribs can be seen at 52-59 days. Teeth and toes can be seen at 58-63 days.

For a veterinary X-ray technician, what is the maximum permissible dose of radiation they can receive in one year?

50 mSv explanation - There are many units of radiation exposure and dose that are used. Old terminology used the unit of the rad for measuring dose. For radiation safety, a "quality factor" is typically multiplied by the dose to give a "dose equivalent". The rem (radiation equivalent in man) is the dose in rad multiplied by a quality factor. Accepted terminology has changed over the years, and the standard (SI) unit of dose is the Gray (Gy). There are 100 rad per 1 Gy (1 rad = 1 cGy). The Sievert is the dose in Gy multiplied by the quality factor. The maximum permissible dose for a radiation worker as described in this question is 5 rem. (5,000 mrem). This converts to 50 mSv, which is the correct answer to this question.

When taking a lateral thoracic radiograph of a dog, where should the field be centered?

5th rib and caudal border of the scapula explanation - A lateral thoracic radiograph should be taken by drawing the forelimbs forward to prevent them from overlapping the cranial thorax. The film should be centered at the 5th rib and caudal border of the scapula; the film should also be collimated to include the manubrium (as the cranial landmark) and half way between the xiphoid and the last rib (as the caudal landmark). The head and neck should be in a natural position, neither extended nor flexed, and the sternum and dorsal spinous processes should be in a plane parallel to the table, indicating that the animal is not rotated. All lung fields should be included, and the film should be taken on maximum inspiration.

When taking a radiograph of an equine limb, you take a radiograph where the portable X-ray unit source is 90 cm away from the cassette. You then move closer so that the X-ray source is now 30 cm away from the cassette. If no changes were made to the settings of the machine, what will the beam intensity be at the second radiograph relative to the first one?

9 times greater intensity at 30 cm compared to 90 cm explanation - The inverse square law states the intensity of the x-ray beam is inversely proportional to the square of the distance from the X-ray source. Therefore, the intensity is greater as the cassette is moved closer to the source. To calculate the answer, the intensity of beam 1 is (x/90)^2 and the intensity of beam 2 is (x/30)^2 where x is the number of photons produced by the x-ray machine. The math here works out as follows:(x/30)^2 / (x/90)^2 = [(x/30)/(x/90)]^2 = (90/30)^2 = (3)^2 = 9

What is a pneumocystogram?

A radiograph of the bladder taken after having had air injected into it explanation - A pneumocystogram is a radiograph of the bladder taken after insertion of a urinary catheter, draining of the urine, and injection of air (negative contrast) into the bladder via the catheter. This procedure allows the bladder wall to be visible and makes certain types of bladder stones more easily viewable.A radiograph of the bladder taken after direct injection of positive contrast is called a cystogram or a positive-contrast cystogram.A radiograph of the bladder taken after intravenous injection of positive contrast that is excreted via the kidneys is called an intravenous pyelogram (IVP) or excretory urogram.

You are training a radiology technician on methods of restraining patients using sandbags and positioning devices that will allow her to step out of the radiology suite during the radiograph exposure. The radiology technician asks you why this is necessary, since she always wears her dosimetry badge and has always been well below the established exposure limits. What important principle of radiation safety dictates that further efforts such as these should still be made to decrease radiation exposure to the radiology technician?

ALARA explanation - ALARA stands for "As low as reasonably achievable". This is the radiation safety principle that all personnel should take all reasonable efforts to minimize their radiation exposure. Even though the technician's absorbed dose is below the maximum permissible dose, it is still preferable to minimize her dose further if it is reasonably achievable. Even though doses below the maximum permissible dose are generally considered safe, there is a consensus that a lesser dose is even better and all reasonable efforts should always be taken to minimize radiation exposure.

In what anatomical location can the atlas and axis be found?

Cervical region explanation - The cervcial (neck) vertebrae C1-2 are known as the atlas and axis and articulate with each other.

Which of the following are intended to shield the user from the primary X-ray beam?

Collimator explanation - Only the collimator contains enough lead to shield the primary radiation beam. The other equipment is only intended to absorb scatter radiation. Even when wearing appropriate radiation-protective equipment, no part of the technician should ever be in the primary field of a radiograph.

You are asked to take a dorsomedial-palmarolateral oblique radiograph of a horse's fetlock with a portable x-ray unit. A cross-section of the limb is diagrammed and labeled below with the red lines representing two possible x-ray cassette placement locations. Pick the letter that corresponds to the correct cassette placement and the correct placement of the marker on the cassette.

D (lateral) explanation - This view may also be referred to as a DMPLO or simply a medial oblique. With this technique, the beam comes from 45 degrees between dorsal and medial sides of the limb and the film is placed 45 degrees between the lateral aspect and the palmar (or plantar) aspect. By convention and so that the viewer of the radiograph can determine the view easily, the marker is placed at the D position. For the DLPMO view, the marker would be placed at the B position.

The current accepted standard image format for digital radiographs is called DICOM (digital imaging and communications in medicine). DICOM files have many advantages over other types of image files. Which of the following is NOT true of DICOM images?

DICOM image files can be sent to other veterinarians or to owners and can be viewed in almost any photo viewer explanation - DICOM image files require special viewing software (i.e. eFilm or OsiriX) and cannot be opened in most photo viewing or editing software (i.e. Photoshop). This makes it difficult for the images to be altered, which maintains their integrity as a medical document. DICOM files contain information about the patient and study performed, and they can be stored, retrieved, and manipulated. Files are arranged into images, studies, and series where each study may consist of one or more series, and each series may consist of one or more images.

You are asked to take chest radiographs on a cat that has been hit by a car. You are reviewing the radiographs for technique and see that it appears the cat has intestinal contents in the chest cavity. What is this evidence of?

Diaphragmatic hernia explanation - A diaphragmatic hernia is a hole in the diaphragm. Through this hole, abdominal contents can protrude into the chest cavity. It can be helpful to hold an animal like this in an upright position to allow gravity to keep the abdominal contents out of the chest. The veterinarian should be notified immediately.

A dog in respiratory distress should not be placed in which position for radiographs?

Dorsal explanation - It is contraindicated to place an animal in respiratory distress on its back. Doing so makes it more difficult for the patient to fully expand their lungs.

A fistulogram involves taking a radiograph after a contrast agent is administered into what location?

Draining tract explanation - A draining tract, also known as a fistula, can be evaluated by injecting a contrast agent into the tract and taking a radiograph to track where the tract goes.

The radiograph cassette is usually placed on the tabletop to radiograph which of the following areas in a medium-sized dog?

Elbow explanation - Tabletop technique is usually used to image structures that are not too thick (usually <10cm thick) because there is decreased scatter, and a grid and Bucky are not needed. In this case, the elbow is the only structure on this list that is not thick enough to warrant the use of a grid and Bucky.

Which is a hinge joint connecting the humerus to the radius and ulna?

Elbow explanation - The elbow joint is a hinge joint connecting the humerus to the radius and ulna. The shoulder joint is formed by the scapula and humerus.The tarsus and stifle are joints of the hindlimb. The tarsus connects the tibia/fibula to the metatarsus (the ankle); the stifle connects the femur to the tibia/fibula (the knee).

Which of the following should be done with a dog after a myelogram to decrease the risk of procedure-related complications?

Elevate the head explanation - After a myelogram, dogs have a risk of having a seizure due to the contrast administration. The risk can be decreased by keeping the head elevated after the procedure.

What is the purpose of a Potter-Bucky diaphragm on an X-ray machine (sometimes called a "Bucky tray")?

Eliminate grid lines on the film explanation - A Potter-Bucky diaphragm is a moving grid. A grid is a series of short strips of lead that is placed over the cassette, absorbing all radiation that does not go between the strips. The strips are geometrically arranged to allow the primary radiation through but to absorb any radiation that is scattered in other directions. This results in increasing the resolution of structures on the film. However, using a grid results in the appearance of grid lines on the film unless a Potter-Bucky diaphragm is used. Using a Potter-Bucky diaphragm requires increased exposure time and/or kilovoltage.

During which of the following periods is a human embryo or fetus most sensitive to adverse effects from radiation?

First trimester explanation - The first 3 months of pregnancy are the most important in terms of radiation safety because the embryo/fetus is most sensitive at this time. This heightened sensitivity is due to the organogenesis that occurs during the first trimester.

Which of the following correctly describes the order and function of fixer and developer solutions during radiograph processing?

First, developer converts exposed silver crystals into black metallic silver and then fixer dissolves unexposed silver crystals explanation - Films go into developer first which reduces exposed silver halide into elemental metallic silver which is black. Crystals that were unexposed do not undergo this process. Fixer then coverts the unexposed crystals into a soluble form so that they dissolve away, leaving a clear image where the film was unexposed.

Which of the technical errors in radiography will result in increased film density?

Focal-film distance is too short explanation - Focal-film distance refers to the distance of the film relative to the X-ray source. As the film is moved closer to the source, density increases exponentially due to the inverse-square law. The other answer choices listed would all decrease film density.

Abdominal radiographs should be taken at which of the following times?

Full expiration explanation - Abdominal radiographs are best taken at full expiration because this is when the diaphragm is pushed cranially, which increases the amount of space in the peritoneum and minimizes the overlap of abdominal organs on the radiograph. It is usually not possible to time a radiographic exposure based on the cardiac cycle.

A thoracic radiograph should be taken at which time?

Full inspiration explanation - Thoracic radiographs should be taken at maximal inspiration to obtain the clearest image of the lung fields. When the lungs are filled with air, the air provides maximal contrast between the normal lung and pathologic processes such as fluid accumulation or the presence of a mass. It is not usually possible to time a radiographic exposure based on the cardiac cycle.

Which of the choices below is in the correct order from least-to-most radiodense (darkest-to-whitest on the film)?

Gas, fat, soft tissue and fluid, bone, metal explanation - Degree of absorption of x-rays depends on several factors, including specific gravity or density of tissue, the effective atomic number (Z) of the tissue, and the thickness of the tissue. There are 5 density shades seen on a radiograph:

The "boxing glove" shape of air in this dog's abdomen is indicative of what emergency?

Gastric dilatation and volvulus explanation - The presence of gas appears black on films, showing up on this radiograph as a stomach full of trapped air. The "boxing glove" owes it shape to the stomach twisting along its long axis.

Some x-ray machines have the option of using 2 different sized filaments at the cathode. Which of the following is an advantage of using a larger filament?

Higher exposures can be used explanation - A larger filament produces a broader electron beam with a larger focal spot. This spreads out the area of the target where heat is generated and allows higher exposures to be used. However, the wider focal spot leads to decreased image definition and increased penumbra effect, both of which are disadvantages. The penumbra effect is the blurring of margins that occurs as a result of the geometry of the x-ray beam.

Which of the following statements about ultrasound probe transducers is true?

Higher frequency probes have increased image resolution and decreased penetrating ability relative to lower frequency probes explanation - The frequency of an ultrasound probe is usually measured in MHz (megahertz). Higher frequency probes (i.e. 7.5 MHz or 10 MHz) probes have increased image resolution but sacrifice penetration. Lower frequency probes (i.e. 5 MHz) are better for imaging deeper structures or cavities but do not provide as much image resolution.

Which is a "ball and socket" type of joint?

Hip explanation - The hip joint (acetabulofemoral joint) is the ball of the head of the femur sitting in the socket (acetabulum) of the pelvis. The atlantoaxial joint is a pivot joint connecting the first and second cervical vertebrae. The stifle and elbow are hinge joints.

Choose the answer choice with three methods to INCREASE radiographic density (blackness of film).

Increase energy of X-rays; increase the number of photons; decrease distance from source to film explanation - To increase the density of the film, you must increase the number of X-ray photons reaching the film. Increasing the energy of X-rays will cause a greater percentage of photons to penetrate the patient and hit the film. Increasing the total the number of photons will also increase the number that hit the film. Decreasing the distance (moving the film closer to the source) will exponentially increase exposure to an area of film based on the inverse-square law.

Which of the following can be easily changed by a technician to increase the amount of exposure on a radiograph without affecting the amount of contrast?

Increase milliamperage explanation - The settings that affect exposure without changing contrast are milliamperage and exposure time. Increasing either will increase the exposure of the film. Changing kilovoltage changes the amount of contrast (higher kVp gives less contrast, more latitude and lower kVp gives greater contrast but less latitude). Decreasing field size will decrease the amount of scatter and may improve image quality but it will not increase exposure to the film.

Which of the following statements is true regarding radiography of the vertebrae?

Intervertebral disc spaces appear wider toward the center of the film and narrower towards the end of the film explanation - Due to divergence of the x-ray beam, intervertebral disc spaces will appear wider toward the center of the film and narrower towards the end of the film. This must be taken into account when evaluating the disc space on a vertebral film. A myelogram is useful for assessing the presence of spinal cord compression but does not improve the evaluation of intervertebral disc spaces. Intervertebral discs are much less dense than the bones unless they are abnormally mineralized.

Which of the following is true of tungsten, making it an ideal material for the filament and target of an x-ray machine?

It has a very high melting point explanation - Tungsten has a very high melting point (greater than 3,000 C). It has a high atomic number (74), making it a relatively more efficient target for producing electrons. It also has many electrons, which makes it more efficient at producing an electron cloud at the cathode (filament) via a process called thermionic emission. Despite being relatively efficient at producing x-rays, the process itself is still very inefficient, with more than 99% of the energy generated being converted to heat rather than x-rays. Therefore, the tungsten target is often embedded in copper (a good conductor of heat). Tungsten by itself is a poor heat conductor.

If a region of the film does not come into contact with developer but does run through fixer and the rest of the processing steps, what will this region look like?

It will be clear explanation - Films go into the developer first, reducing exposed silver halide into elemental metallic silver, which is black. If a region of the film does not touch the developer, there will be no black on the film even if it was exposed. The remaining crystals would be converted into a soluble form in the fixer solution, dissolving away and leaving a clear image.

An arthrogram involves contrast administration into what region?

Joint explanation - An arthrogram involves contrast administration into a joint. A myelogram involves contrast administration into the subarachnoid space. Contrast is injected into the bladder for a cystogram and ingested into the esophagus for an esophagram.

Which of the following statements is true regarding non-screen film in comparison to screen x-ray film in radiography?

Non-screen film is more sensitive to x-rays explanation - The main difference between non-screen film and screen film is that non-screen film has the image produced by x-rays themselves, whereas screen film uses light produced in an intensifying screen to generate the image. Therefore, screen film is more sensitive to light, and non-screen film is more sensitive to x-rays. The advantage of using a screen system is that much less radiation is needed to create the image but the trade-off is a loss of detail from the intensifying screen. Non-screen film is not good to use with larger animals or body parts because it requires too much exposure (and therefore a longer exposure which will have greater motion) to obtain a well exposed radiograph.

Which of the following structures in the body is most sensitive to radiation?

Ocular lens explanation - The lens of the eye is considered one of the most radiation-sensitive structures in the body. Even relatively low doses can predispose the lens to develop cataracts. The other most sensitive organs are ones with rapidly dividing cells such as the bone marrow and gonads.

If a pulmonary metastatic lesion is visible on a right lateral radiograph but not on a left lateral radiograph, where is the lesion most likely to be?

One of the left lung lobes explanation - When a patient is placed into left lateral recumbency for a left lateral radiograph, the left lung fields are compressed and do not inflate fully. This can prevent resolution of small metastatic lung lesions in the left lung lobes due to the lack of contrast with air in the left lung. The same is true of the right lung fields with a right lateral radiograph. Therefore, for evaluation of pulmonary metastasis, both a left and right lateral radiograph should be taken. In this case, a lesion that can be seen on a right lateral but not a left lateral projection is most likely in the left lung lobe because, as explained above, the lesion may be obscured on the left lateral projection due to a lack of contrast in the uninflated lung.

All of the following pieces of information legally must be present on a radiographic film EXCEPT for which of the following?

Patient breed explanation - A radiograph is part of the legal medical record. As such, it is necessary to identify the patient it was taken from, the date of the exam, and the name of the practice. It is frequently helpful to use a marker to orient the radiograph or to identify which extremity is being examined. For film radiographs, frequently patient information is imprinted by the use of special graphite-impregnated tape where the information can be written and placed on the radiograph cassette or by a light flasher system that exposes printed patient information to the film. For digital radiographs, the patient information must be entered into the computer so that it is saved along with the digital radiograph. Additional patient information such as breed can be helpful but is not required.

You are taking a lateral radiograph of the left stifle of a dog to assess for a suspected cruciate ligament injury. How should the patient and leg be oriented relative to body and film?

Patient should be in left lateral recumbency with the leg against the cassette epxlanation - Having the leg against the film instead of away from the film will provide a crisper and less distorted image. Therefore, positioning the dog in left lateral recumbency with the leg against the cassette is the best position.

Which of the following would most commonly be enlarged on chest films of a heartworm positive dog?

Pulmonary arteries explanation - Heartworm disease causes right heart enlargement and enlargement of the pulmonary arteries, which are often seen on chest radiographs in pets with heartworm disease. Right heart enlargement gives a reverse-D appearance to the heart, as seen in the x-ray below.

Which bone is adjacent to the ulna?

Radius explanation - The radius is adjacent to the ulna. The femur and tibia are bones of the hind limb.

Name one of the bones that is fractured in this radiograph. (see image)

Radius explanation - This is a radiograph of a forelimb. Notice the elbow and the carpus to help you get oriented. The humerus is the bone proximal (on the left side of the radiograph) which is connected to the scapula. The radius and ulna are the two bones fractured in this radiograph. The ulna is the smaller in diameter of the two bones.

In radiation safety, what is the difference between the "rad" and the "rem"?

Rem applies a quality factor to rad explanation - Rad and rem are both old units of types of absorbed dose that can be applied to either the patient or to personnel. More commonly, rem is used in radiation safety for personnel, and rad is used in radiation therapy in dose calculations. The difference between the two is that rad is the basic unit of absorbed dose, and rem applies a quality factor depending on the type of radiation. For x-rays, rad equals rem; but for other types of radiation such as neutrons and protons, rem may be greater than rad. Rem exposure is of greater relevance in radiation protection than rad because the biologic effects of 10 rad of neutron exposure is far greater than the biologic effects of 10 rad of x-ray exposure. The units that should be used currently are the Gray (Gy) and the Sievert (Sv) for absorbed dose and effective absorbed dose respectively, but many people still use rad and rem.

You are taking thoracic radiographs to evaluate for lung metastasis in a dog with splenic hemangiosarcoma. What radiographic views should be taken?

Right lateral, left lateral, and either a dorsoventral or ventrodorsal projection explanation - When a patient is placed into left lateral recumbency for a left lateral radiograph, the left lung fields are compressed and do not inflate fully. This can prevent resolution of small metastatic lung lesions due to the lack of contrast with air in the left lung. The same is true of the right lung fields with a right lateral radiograph. Therefore, for evaluation of pulmonary metastasis, both a left and right lateral radiograph should be taken. Either a ventrodorsal (VD) or dorsoventral (DV) view is acceptable for visualizing the lung fields in this case.

Which of the following represents the source of the most radiation exposure to a veterinary technician who is restraining a cat for a radiograph, taking the exposure, and processing the film?

Scatter from the patient area explanation - If good technique is practiced (i.e. no part of the technician is inside the primary beam), there should be no exposure to the technician from the primary beam. Most of the radiation exposure will actually come from scattered X-rays that interact with the patient's tissue and then go in another direction, potentially towards the technician. There is a much smaller amount of scatter radiation that may come off of the collimator, and no radiation should be emitted from radiograph processing equipment. The 3 important principles to minimize radiation exposure are to maximize distance from the radiation source, decrease the time of exposure to radiation whenever possible, and to use equipment to shield personnel from radiation.

What is the metallic element present on radiograph film that turns black when exposed and run through the radiograph development process?

Silver explanation - Films go into developer first which reduces exposed silver halide into elemental metallic silver which is black. Crystals that were unexposed do not undergo this process. Fixer then coverts the unexposed crystals into a soluble form so that they dissolve away, leaving a clear image where the film was unexposed.

A dorsoproximal-dorsodistal oblique radiograph of the carpus is frequently referred to as what type of radiograph?

Skyline view explanation - With a standing patient, a skyline view is taken with the carpus flexed and the x-ray cassette placed along the anterior aspect of the limb. The x-ray beam is aimed from proximally to distally and an oblique angle. This technique is used in equine radiography most frequently to view the distal radius, the proximal row of carpal bones, and the distal row of carpal bones where chip or slab fractures commonly occur, especially in racehorses. Sclerosis of the carpal bone can also be visualized here. This technique decreases the overlap of surrounding bones and structures in order to improve the ability to see lesions specifically in this area. A flexed lateral radiograph also involves flexing the carpus, but the beam is aimed from laterally and the cassette is placed medially. This technique allows the carpal bones to separate and makes the margins of the bone more clearly visible. A horizontal beam radiograph generally is used to confirm the presence of air or fluid in a body cavity (thorax, abdomen). A bisecting angle radiograph is a technique used to prevent distortion when it is not possible to place the film parallel to the structure of interest and perpendicular to the x-ray beam, commonly in dental

A double-contrast cystogram involves which of the following?

Soluble positive-contrast media and air injected directly into the bladder explanation - Double-contrast cystograms are typically performed by retrograde injection via catheter of a soluble positive-contrast agent and air.

What are the "Joints" in the skull are referred to as?

Sutures explanation - Sutures are fibrous bands of tissue that connect the bones of the skull. In neonates, the sutures are open and allow for growth of the brain and skull.

Many x-ray machines used in veterinary medicine have a 2-part exposure process. The first step involves depressing a button or pushing a pedal half-way to prepare the machine for the exposure and then a second button or fully depressing the pedal to take the exposure. What happens in the x-ray machine when the first step is started?

The anode rotates and the filament is heated explanation - To generate x-rays, the filament must be heated for a process called thermionic emission to occur, wherein a cloud of electrons forms around the filament and can be accelerated from cathode to anode for the exposure. Because a great deal of heat build-up occurs during x-ray production, most x-ray machines have a rotating anode to distribute the heat. This is done in preparation for the exposure. When the exposure button is pressed, charge in the x-ray tube accelerates the electrons, which hit the target at the anode, which emits x-rays.

When placing lateral radiographs of the stifle joint on a viewer for a veterinarian to evaluate, how should the film be oriented?

The cranial or dorsal side of the limb should be to the left and the proximal aspect should be toward the top of the viewbox explanation - It is proper to place a lateral radiograph of the stifle such that the cranial or dorsal side of the limb is to the left and the proximal aspect of the limb is toward the top of the viewbox. For a caudocranial view, the lateral side of the right limb should be to the viewer's left and the lateral side of the left limb should be to the viewer's right.

Which of the following errors in taking and processing a radiograph would result in a completely clear film?

The exposed film was put in fixer before developer explanation - In normal radiograph processing, silver halide crystals in the film that are sensitized by exposure during the x-ray are converted to black metallic silver in the developer. The remaining crystals are removed by the fixer. If a film is accidently run through the fixer first, all of the silver halide crystals will be removed, leaving a clear image. The other choices will all increase exposure of the film, making it darker.

When placing craniocaudal radiographs of the stifle joint on a viewer for a veterinarian to evaluate, how should the film be oriented?

The lateral side of the right limb should be to the viewer's left; the lateral side of the left limb should be to the viewer's right. explanation - It is proper to place a craniocaudal radiograph of the stifle such that the lateral side of the right limb is to the viewer's left and lateral side of the left limb is to the viewer's right. For a lateral radiograph, the cranial or dorsal side of the limb should be to the left and the proximal aspect should be toward the top of the viewbox.

When taking a radiograph of the radius and ulna, which of the following will occur if the x-ray beam is perpendicular to the cassette but not to the long axis of the radius and ulna?

The radius and ulna will appear foreshortened explanation - To avoid distortion (elongation or foreshortening), the x-ray beam should be perpendicular to the long axis of the bone and the x-ray cassette. If the bones are not perpendicular to the beam, they will appear foreshortened. If the cassette is not perpendicular to the beam, the bones will appear elongated. In dental radiography, it is frequently not possible for the long axis of the tooth and the film to be parallel to each other. In this case, the bisecting angle technique may be used, wherein the beam is angled half-way between the angle of the long axis of the tooth and the angle of the film in order to obtain a true image that is neither elongated nor foreshortened.

The olecranon is a structure of which bone?

Ulna explanation - The olecranon is found at the proximal portion of the ulna and forms the point of the elbow. The triceps attaches there.

When taking a radiograph of the tibia and fibula, which of the following will occur if the x-ray beam is perpendicular to the tibia and fibula but not to the x-ray cassette and film?

The tibia and fibula will appear elongated explanation - To avoid distortion (elongation or foreshortening), the x-ray beam should be perpendicular to the long axis of the bone and the x-ray cassette. If the bones are not perpendicular to the beam, they will appear foreshortened. If the cassette is not perpendicular to the beam, the bones will appear elongated. In dental radiography, it is frequently not possible for the long axis of the tooth and the film to be parallel to each other. In this case, the bisecting angle technique may be used, wherein the beam is angled half-way between the angle of the long axis of the tooth and the angle of the film in order to obtain a true image that is neither elongated nor foreshortened.

Which of the following is considered part of the plantar surface?

The underside of the hindpaw explanation - Plantar is the underside of the hindpaw. Palmar is the underside of the forepaw.

You are asked to take a DLPMO radiograph of a horse's fetlock with a portable x-ray unit. Where will the x-ray unit be and where should the film cassette be?

The x-ray beam should come from the more dorsal side of the limb, and the film will be on the more medial aspect of the limb. explanation - With a DLPMO or dorsolateral-palmaro/plantaromedial oblique, the beam comes from 45 degrees between dorsal and lateral sides of the limb, and the film is placed 45 degrees between the medial aspect and the palmar (or plantar) aspect.

Which bone is not associated with the forelimb?

Tibia explanation - The tibia is a bone of the hindlimb also known as the "shinbone". The tibia is located distal to the femur and proximal to the tarsus.

What three things help to minimize your exposure to radiation while taking radiographs, according to the U.S. Nuclear Regulatory Commission?

Time, Distance, Shielding explanation - The correct answer is Time, Distance, and Shielding (try to remember TDS). Decreasing exposure time to the x-rays, distancing yourself from the source as much as possible, and using proper shielding that includes lead (in personal protective equipment) or leaving the room during x-ray if you are not needed are all ways to minimize radiation exposure. While proper restraint and equipment are also important in minimizing exposure, they are not sufficient without the time, distance, and shielding; this question is asking specifically about the U.S. Nuclear Regulatory Commission.

Why are oblique radiographic views of certain joints typically obtained?

To decrease superimposition of structures explanation - Oblique radiographic views are typically requested in areas where there are multiple overlapping structures. The purpose of these views is to decrease superimposition of certain bones or structures so that a specific region is better isolated on the film. Typically, there is no change in the air or fluid when oblique views of a joint are obtained. Because oblique views are still usually taken across the entire joint, there is no change in the amount of scatter. Properly taken conventional radiographs of a joint should not have foreshortening or elongation artifacts.

What is the function of the screen of an X-ray cassette?

To decrease the exposure necessary to create an image on the film explanation - The screen of an X-ray cassette, sometimes called intensifying screens, are the shiny white inner surfaces of the cassette. They are made of crystals that fluoresce, emitting light, when exposed to x-rays, producing the diagnostic image.

A 7-year old Saint Bernard dog has a lesion of the left distal radius that is highly suspicious for a bone tumor (osteosarcoma). Prior to surgery, a bone scan is ordered and performed. What is the main reason for this study?

To identify possible additional bone lesions (other than the left radius lesion) that may represent bony metastases explanation - While the lungs are the most common site of metastasis of bone tumors in dogs, these tumors can also metastasize to other bony sites. Thoracic radiographs are generally sufficient to assess gross pulmonary metastasis but radiography is not typically practical for assessing all of the bones in the body. A bone scan is a nuclear medicine test that involves administration of a bone-seeking radioisotope (Technetium phosphate) that is taken up in areas of bone turnover. The test does not provide significant anatomic detail and is not confirmatory of osteosarcoma because it is not specific for cancer (osteoarthritis or osteomyelitis also are positive on bone scans). The test is used to identify additional bony sites that should be evaluated radiographically to assess for metastasis. Because this type of test is not routinely available at all practices and the overall incidence of bony metastasis is relatively low, it is usually reserved for cases where there is greater suspicion for bone metastasis. It would also be used to rule-out the presence of bone metastasis prior to performing complex or expensive limb-sparing surgeries.

What is the purpose of a grid on an x-ray table?

To prevent scatter radiation from reaching the film explanation - A grid is a series of short strips of lead that is placed over the cassette, absorbing all radiation that does not go between the strips. The strips are geometrically arranged to allow the primary radiation through but to absorb any radiation that is scattered in other directions. This results in increasing the resolution of structures on the film.

Which type of urinary stone is lucent and does not typically show up on a radiograph?

Urate explanation - Urate and Cystine are the two types of stones that do not usually show up on radiographs and require ultrasound or contrast studies to diagnose. Calcium oxalate and struvite stones are radiodense and usually visible on a radiograph. Magnesium ammonium phosphate is another name for a struvite stone.

For which of the following disorders is an intravenous pyelogram most useful in detecting?

Ureteral stones explanation - An intravenous pyelogram (IVP) is an x-ray examination of the kidneys, ureters and urinary bladder using iodinated contrast material injected intravenously and excreted via the kidneys. It is used to detect problems in the urinary tract (particularly the upper urinary tract) including kidney and ureteral stones or tumors involving the kidney, ureters, or urinary bladder. An IVP is not as useful for urethral stones because they are further down in the urinary tract; in this case, retrograde cystography would be more helpful.

A cystogram is a radiographic study performed to identify the position, shape, and lesions involving what structure?

Urinary bladder explanation - A cystogram is a radiograph of the urinary bladder region taken after injection of positive-contrast medium directly into the bladder via a urinary catheter.

During ultrasound of the bladder, a hyperechoic (white) linear structure is seen against the bladder wall that creates a black shadow obscuring all structures deep to it. What is this structure most likely?

Urolith explanation - Sound is strongly reflected by mineral and gas resulting in a hyperechoic appearance. The structure most likely to be mineralized inside the bladder is a urolith. The bladder wall should be of intermediate echogenicity as are most bladder wall tumors. The round ligament of the bladder is usually not visible sonographically but also would not create such a dramatic acoustic shadow as described in the question. Free fluid appears anechoic (black). Air inside the bladder as might be seen in emphysematous cystitis could also be echogenic and cast a shadow but this was not an answer choice.

For taking a diagnostic radiograph, which of the following techniques will reduce the amount of scatter radiation that reaches a film?

Use of a grid with a Potter-Bucky diaphragm explanation - A Potter-Bucky diaphragm is a moving grid. A grid is a series of short strips of lead that is placed over the cassette, absorbing all radiation that does not go between the strips. The strips are geometrically arranged to allow the primary radiation through but to absorb any radiation that is scattered in other directions. This results in increasing the resolution of structures on the film. However, using a grid results in the appearance of grid lines on the film unless a Potter-Bucky diaphragm is used. Scatter can also be reduced by utilizing the "air-gap" technique which involves moving the cassette and film away from the patient. This will magnify and may decrease sharpness of the film but will decrease the amount of scatter radiation reaching the film. Exposure time and the use of high-speed film or an intensifying screen do not affect the amount of scatter radiation reaching the film.

All of the following radiation protection measures are intended to decrease the dose to the technician EXCEPT which of the following?

Use of filtration at the portal of the X-ray tube explanation - Filtration of the X-ray beam is performed to eliminate low energy (soft) radiation that is part of the emitted spectrum. The soft radiation will be primarily absorbed by the patient with minimal scatter. This radiation would not contribute to the radiographic image and unnecessarily increases patient dose. Collimating the beam decreases radiation dose to the patient and the technician. Protective equipment such as lead gloves, aprons, thyroid shields, and lead glasses all decrease the radiation dose to the technician.

Which of the following principles will always improve radiographic image quality?

Use the highest milliampere (mA) setting and lowest time (s) setting possible to achieve the desired mAs explanation - The product of multiplying the milliamperage (mA) and time (s) is the mAs, which determines the degree of film exposure for a given kVp. Minimizing the time of exposure decreases motion artifact that occurs from the patient moving. It is always preferable to use the highest milliamperage and lowest time setting for this reason. Depending on the type of radiographic study and the size of the animal, a certain kVp and mAs will produce a radiograph with a corresponding amount of contrast and latitude. Maximizing contrast at the expense of latitude or vice-versa may not yield the best radiograph.

Which of the following choices most accurately describes the "heel effect" in diagnostic radiology?

X-ray beam intensity declines toward the anode side of the x-ray machine explanation - The heel effect describes how the intensity of the x-ray beam declines from the cathode side toward the anode side of the machine because of the angle of the anode. The statement about penumbra is true but is not related to the heel effect. Lower energy x-rays are preferentially absorbed by bone due to their mineral composition and the photoelectric effect.

You take and develop an abdominal radiograph of an animal, but the radiograph appears much too light (underexposed) throughout the area of the patient. You increase the exposure (mAs) and the radiograph is still much too light. The portion of the radiograph outside the body of the patient is completely black (exposed). Which of the following is the most likely problem?

X-ray energy (kVp) is too low explanation - Since part of the film is exposed correctly, you can conclude that X-rays were produced by the machine; there does not seem to be a problem with the target. Also, there are processing artifacts mentioned. The problem here appears to be that the energy of the X-rays produced is insufficient to penetrate the patient. Therefore, the patient is essentially shielding the film from exposure in that area. To fix the problem, try using a higher kVp.

Which of the following is true regarding the properties of x-rays compared to visible light?

X-rays have higher frequency and shorter wavelength explanation - The energy of a photon is directly proportional frequency and inversely proportional to wavelength. X-rays are higher energy rays than photons in the visible light spectrum, which gives them greater penetrating ability.

Which of the following components or settings influence x-ray beam quality?

kVp and filtration explanation - The "quality" of an x-ray beam refers to the energy distribution of the photons that are emitted. mAs and collimation have no effect on the energy of the emitted photons. mAs specifies the quantity of photons emitted; collimation constrains the area where the photons are emitted. The kVp is related to the peak energy of the photons emitted. Applied filtration preferentially absorbs lower-energy photons to affect beam quality.

After taking a radiograph exposure of a patient abdomen at a 40 cm focal-film distance with settings of kVp=60, mAs=2, you have to repeat the exposure using a horizontal beam technique at 80 cm focal-film distance. Assuming there is no change in the tissue penetrated and no other differences aside from the distance in radiographic technique or equipment, what settings should you use to obtain the same radiographic density?

kVp=60, mAs=8 explanation - To obtain the same radiographic density, you would not change the energy (kVp) but you would need to change the exposure to account for the difference in distance, which is based on the inverse square law. This law states that the exposure at twice the distance will be reduced to 1/4. Therefore, the mAs must be increased 4X. If there had been other equipment such as a grid on one of the views, there might also be other correction factors to take into account.