Imaging

Question 1

What is meant by the ALARA principle in radiation safety?

Answer 1

Concept of limiting exposure of radiation workers to a level As Low As Reasonably Achievable

Question 2

There are three modes of echo display in diagnostic ultrasound. A standard abdominal ultrasound would be done in which?

• A. A-Mode
• B. B-Mode
• C. M-Mode

Answer 2

B. B-Mode

Question 3

Name three radiographic signs of osteoarthritis.

Answer 3

• Joint effusion
• Widening and/or thinning of radiolucent joint space
• Enthesiophyte formation
• Increase in/remodelling of subchondral bone
• Mineralization of intraarticular and periarticular soft tissues
• Formation of subchondral cysts
• Subluxation (coxofemoral)

Question 4

What is the name of the ultrasound principle that provides information on velocity and direction of blood flow?

Answer 4

Doppler

(color or spectral [pulsed- or continuous wave])

Question 5

Which process of x-ray photon interaction with matter is the one that ultimately results in image formation?

• A. Coherent scattering
• B. Photoelectric effect
• C. Compton scattering

Answer 5

B. Photoelectric effect

Question 6

Above which measurement (cm) for body thickness should you use an anti-scatter grid in abdominal radiography?

Answer 6

10 cm

Question 7

How should the technique differ in terms of kVp and mAs between thoracic and abdominal radiographs?

Answer 7

• Abdomen: high mAs, low kVp
• Thorax: high kVp, low mAs

Question 8

In diagnostic ultrasound, which property of materials allows for an echo to be formed at the boundary of two different tissues?

Answer 8

Acoustic impedance

Question 9

What is the typical range of ultrasound frequencies used for clinical diagnostic imaging?

• A. 2 GHz - 17 GHz
• B. 2 kHz - 17 kHz
• C. 2 MHz - 17 MHz

Answer 9

C. 2 MHz - 17 MHz

Question 10

What causes reverberation artifact in diagnostic ultrasound?

Answer 10

Sound bouncing back and forth between tissue boundaries before returning to the receiver

Question 11

In reference to direction of blood flow on standard color Doppler, which color shows flow toward the probe, and which shows flow away from the probe?

Answer 11

• Blue: away
• Red: toward

(the BART rule)

Always double-check the machine.

Question 12

On abdominal ultrasound, a transverse image of bowel with a multilayered series of concentric rings is evident, with a centrally located hyperechogenicity.

What is your diagnosis?

Answer 12

Intussusception

(this is called a target or bull’s eye pattern)

The central hyperechoic material is mesenteric fat.

Question 13

What are two reasons the volume of contrast medium administered for a positive contrast gastrointestinal study is a critical factor in interpretation?

Answer 13

1. Potentially not adequately highlighting the mucosal margins of the stomach
2. Need an adequate volume bolus of contrast medium in order to stimulate normal gastric emptying and intestinal motility

i.e., a small volume of barium administered may not stimulate gastric emptying, leading to a misdiagnosis of delayed gastric emptying

Question 14

Name three radiographic signs of left-to-right shunting patent ductus arteriosus.

Answer 14

1. Segmental enlargement of the proximal descending aorta
2. Enlargement of the main pulmonary artery
3. Enlargement of the left atrium, and possibly the left auricle
4. Enlarged left ventricle
5. Enlarged pulmonary arteries and veins
6. Diffuse interstitial opacification of the lungs due to pulmonary overcirculation
7. Interstitial infiltration due to pulmonary edema

Question 15

On radiographic evaluation of the tympanic bullae, you note increased opacity or thickening of the osseous bulla. Is this consistent with otitis externa, media, or interna?

Answer 15

Otitis media

Question 16

What are the three methods of reducing radiation exposure from external radiation sources?

i.e., for the person taking radiographs

Answer 16

1. Increasing distance from the source
2. Time: reducing duration of exposure
3. Shielding: use of protective barriers

Question 17

How is a mirror image artifact created in diagnostic ultrasound?

Answer 17

The ultrasound beam reflects off a strong, smooth surface (like the diaphragm) before returning to the transducer, causing the system to display another nearby structure in duplicate, deeper than its actual location

An example is a “second” gallbladder appearing cranial to the diaphragm.

Question 18

With ultrasonography, portal veins are distinguished from hepatic veins by which feature?

Answer 18

Portal veins have hyperechoic walls

Hepatic vein walls are thin and difficult to see.

Question 19

Which radiographic views constitute a complete series for imaging the tympanic bullae in a dog or cat?

Answer 19

• Lateral
• Ventrodorsal or dorsoventral
• Open-mouth rostrocaudal
• Left rostral-right caudal oblique
• Right rostral-left caudal oblique

Question 20

What is the Morgan line?

Answer 20

It is a radiographic finding that represents the formation of enthesiophytes on the caudal aspect of the femoral neck

(medial to the trochanteric fossa)

It occurs as a result of early degenerative joint disease of the coxofemoral joint.

Question 21

What is the hallmark radiographic sign of diskospondylitis?

Answer 21

Vertebral end plate lysis and collapse of the disk space

Question 22

Sequential radiographs allow evaluation of fracture healing - especially in cases requiring surgical stabilization.

Generally, how often should such follow-up radiographs be taken?

Answer 22

Every six to eight weeks

(until healing is complete)

More frequently if increased lameness/swelling/pain on palpation or other changes in condition.

Question 23

Fill in the blank:

Based on the inverse square relationship, by decreasing the distance from the x-ray source by a factor of two, the intensity of exposure will increase by a factor of _____.

Answer 23

four

The inverse square law means that intensity decreases as the square of the distance increases.

If you cut the distance in half, the intensity goes up by 2 × 2 = 4 times. So, halving the distance quadruples the intensity.

Question 24

You are about to perform a myelogram and there are two bottles of iodinated contrast medium on the shelf: ionic (Hypaque®) and nonionic (Omnipaque®).

Which one do you choose, and why?

Answer 24

Choose nonionic iodinated contrast medium (Omnipaque®)

NEVER inject ionic iodinated contrast medium into the subarachnoid space because it causes fluid shifts into the space that are usually fatal.

Question 25

What are **two** characteristics of an **alveolar pattern** on thoracic radiographs?

Answer 25

* Air bronchograms * Silhouetting (loss of distinction between lung and surrounding soft tissue) * Alveolar opacity (uniform, homogeneous) * Lobar sign

Question 26

In **dogs**, the ultrasonographic appearance of a **gallbladder mucocele** resembles which cut fruit?

Answer 26

The kiwi fruit ## Footnote The mucocele contains echogenic, immobile bile with a striated or stellate pattern, creating a layered appearance like the cut surface of a kiwi.

Question 27

Which ultrasound **transducer** would give you better penetration for viewing **deep** **abdominal** structures in a **horse**? * A. Lower frequency (e.g., 3 MHz) * B. Higher frequency (e.g., 12 MHz)

Answer 27

A. Lower frequency ## Footnote Lower frequency for deeper structures. Increasing the frequency decreases penetration (and decreases resolution).

Question 28

With a **higher ultrasound transducer frequency**, does the image resolution increase or decrease? Why?

Answer 28

Resolution increases; high frequency sound waves improve resolution but penetrate tissues poorly because they are attenuated by tissue

Question 29

Which is more **echogenic** in health: the liver or the spleen?

Answer 29

The spleen is usually slightly more echogenic | (and has a finer, less coarse echotexture) ## Footnote Remember, from most to least echogenic: spleen, liver, kidney.

Question 30

Name two **major contraindications** for the administration of **IV contrast medium**.

Answer 30

* Dehydration * Hypersensitivity * Renal insufficiency * Heart failure

Question 31

What is the purpose of an **anti-scatter grid** in radiography?

Answer 31

Absorbs scatter radiation before it reaches the image receptor ## Footnote Improving image contrast by allowing mostly primary x-rays to form the image Especially useful for thicker body parts where scatter is more pronounced.

Question 32

What are three **radiographic signs** consistent with **intervertebral disc protrusion**?

Answer 32

1. Narrowing of the disc space 2. Narrowing of the dorsal intervertebral articular process joint space 3. A small intervertebral foramen 4. Increased opacity in the intervertebral foramen 5. Extruded, mineralized disc material within the vertebral canal ## Footnote Remember that advanced imaging (CT, MRI) is more sensitive.

Question 33

**Avoid** which **contrast medium** if performing an upper gastrointestinal positive contrast study on a patient that you suspect to have a **gastrointestinal perforation**?

Answer 33

Barium sulfate ## Footnote If leaked outside the gastrointestinal tract, barium can cause granuloma and adhesion formation. Water-soluble iodinated contrast agents (e.g., iohexol) are preferred in suspected perforation cases because they are less irritating if leakage occurs.

Question 34

In ultrasonography, what are the definition and appearance of "**acoustic enhancement**"?

Answer 34

An artifact consisting of localized increase in echogenicity deep to a structure of low attenuation ## Footnote Common examples: increased echogenicity of the liver immediately deep to the gallbladder, increased echogenicity of tissues deep to the urinary bladder.

Question 35

What are **three** of the four radiographic signs of an **aggressive bone lesion**?

Answer 35

* Cortical destruction * Bony lysis * Irregular periosteal reaction * Indistinct zone of transition from diseased to healthy bone ## Footnote Additional features sometimes considered include soft tissue swelling, pathologic fractures, or periosteal elevation.

Question 36

Name two ways to **differentiate** **mechanical ileus** and **functional** ileus radiographically.

Answer 36

1. Mechanically obstructed bowel is usually of larger diameter than functionally obstructed bowel 2. The lumen of mechanically obstructed bowel usually contains gas and fluid, functionally obstructed bowel is more gas-filled 3. Mechanical obstruction usually creates some dilated and some normal-appearing loops of bowel ("two populations of bowel"), vs. patients with functional ileus may have generalized involvement of bowel

Question 37

What causes the "**tracheal stripe sign**" on thoracic radiographs and what **disorder** does it suggest?

Answer 37

* Caused by gas outside the trachea * May represent esophageal gas, megaesophagus, aerophagia, or pneumomediastinum

Question 38

When taking **avian radiographs**, which is an appropriate method to ensure proper **positioning** and diagnostic **quality**?

Answer 38

Use appropriate sedation or general anesthesia rather than holding the bird manually ## Footnote Conscious radiographs often result in superimposed anatomy and non-diagnostic images. Avoid having handlers’ hands within the imaging field.

Question 39

A rabbit presents with anorexia and decreased fecal output. Abdominal radiographs show a markedly distended stomach containing a mottled mixture of soft-tissue and gas opacity. **What is the most likely diagnosis?** * A. Cecal impaction * B. Gastric trichobezoar * C. Intestinal foreign body * D. Gastric dilation/volvulus

Answer 39

B. Gastric trichobezoar ## Footnote Hair mixed with ingesta produces a mottled soft-tissue–gas pattern within an enlarged rabbit stomach. Use barium contrast radiography if need further confirmation.

Question 40

What radiographic finding is most consistent with **metabolic bone disease** (MBD) in **reptiles**?

Answer 40

Generalized decreased bone opacity with thin cortices +/- pathologic fractures ## Footnote Metabolic bone disease (a.k.a. secondary nutritional hyperparathyroidism) causes diffuse skeletal demineralization.

Question 41

What is a hallmark radiographic finding of **chronic laminitis** in **horses**?

Answer 41

Rotation of the distal phalanx (P3) relative to the dorsal hoof wall ## Footnote Additional findings: * Distal displacement (sinking) of P3 within the hoof capsule * Thickening of the dorsal laminar zone * Increased sole depth at the toe * Remodeling or osteolysis of the distal phalanx (a.k.a. "ski tip") * Irregular or thickened dorsal hoof wall

Question 42

You suspect a stress fracture in a horse based on history and degree of lameness, but initial radiographs appear normal. **What is the most appropriate plan?**

Answer 42

Strict stall rest (+/- external coaptation when possible) and recheck radiographs in 10-14 days ## Footnote Early stress fractures may be radiographically occult; repeat imaging may reveal the fracture line after initial bone resorption and remodeling.

Question 43

What radiographic measurement is commonly used to assess **cervical vertebral canal** narrowing in **horses** with **Wobbler syndrome**?

Answer 43

The intravertebral sagittal ratio (IVSR); a ratio of canal diameter to vertebral body height (less than ~50% suggests significant stenosis) ## Footnote Wobbler syndrome (a.k.a. cervical vertebral compressive myelopathy) causes cervical spinal cord compression, often visible as a narrowed vertebral canal. Contrast-enhanced CT or myelography provide a more definitive diagnosis.

Question 44

Name one diagnosis made on **abdominal radiographs** of adult **horses**.

Answer 44

* Enterolithiasis * Sand enteropathy ## Footnote Abdominal radiographs are mainly useful for mineralized or radiopaque material like enteroliths or sand (and rarely metallic foreign objects). Large abdominal size, superimposed intestinal loops, and gas/fecal contents obscure soft tissue details, making other disorders difficult to detect.

Question 45

What is the **gastric axis** in small animal radiography, and for what organ does it evaluate?

Answer 45

* It is the orientation of the stomach within the abdomen * Often a reflection of liver size ## Footnote On lateral radiographs, the normal gastric axis runs from the cardia dorsally/cranially to the pylorus ventrally/caudally. A more dorsally directed axis indicates hepatomegaly and a more cranioventral axis indicates microhepatica.

Question 46

Where are **x-ray photons** generated in the x-ray tube?

Answer 46

At the anode target of the x-ray tube ## Footnote X-ray photons form when high-speed electrons from the cathode strike, and abruptly stop at, the anode target.

Question 47

Which factor **controls** the energy and impact of the **x-rays**?

Answer 47

kVP determines the speed/energy of impact (and thus penetrability) of the x-rays ## Footnote mAs controls the number of x-rays (mA) and length of exposure.

Question 48

A radiograph is **too dark**. What is the best **corrective option**?

Answer 48

Decrease mAs | (decreasing kVP also decreases image density, but more affects contrast) ## Footnote Reducing mAs lowers the number of x-ray photons reaching the image receptor, decreasing image density.

Question 49

How can the **contrast** of an x-ray film be **adjusted**?

Answer 49

By changing the kVp ## Footnote kVp controls x-ray beam energy, which determines the degree of image contrast.

Question 50

What happens to x-ray beam **intensity** if the source–image distance (**SID**) is **doubled**?

Answer 50

The x-ray beam intensity decreases to one-fourth of its original strength ## Footnote X-ray intensity follows the inverse square law, decreasing with the square of the distance.

Question 51

What is **PACS**, and name one benefit of using it?

Answer 51

* PACS is "Picture Archiving and Communication System" - a digital system used to store and distribute medical images * Benefits: * Eliminates the need for film hard copies * Improves communication with other veterinarians * Prevents loss of films * Allows multiple users to view images simultaneously

Question 52

What are the **three** main methods of **radiation protection** in veterinary radiography?

Answer 52

1. Time 2. Distance 3. Shielding ## Footnote These reduce radiation exposure by minimizing exposure duration, increasing distance from the source, and using protective barriers.