VTNE Diagnostic Imaging Techniques 5 — Questions and Answers
Question 1: Which artifact on MRI appears as alternating bright and dark bands and is caused by motion during image acquisition?
- Chemical shift artifact
- Ghosting (motion artifact) (Correct answer)
- Susceptibility artifact
- Aliasing (wraparound) artifact
Correct answer: Ghosting (motion artifact)
Ghosting or motion artifact creates ghost images or banding in the phase-encode direction due to periodic motion (e.g., breathing, cardiac pulsation) during the MRI acquisition.
Question 2: A double-contrast gastrogram is performed by introducing iodinated contrast followed by air. The purpose of the air is to:
- Dilute the iodinated contrast
- Distend the stomach lumen to coat the mucosal surface with contrast (Correct answer)
- Reduce peristalsis
- Lower the risk of aspiration
Correct answer: Distend the stomach lumen to coat the mucosal surface with contrast
Air distends the stomach so that the positive contrast agent coats the mucosal folds, allowing mucosal detail and wall lesions (e.g., ulcers, masses) to be seen clearly.
Question 3: Which radiographic sign indicates free gas in the peritoneal cavity (pneumoperitoneum)?
- Serosal detail loss
- Gas opacity between the liver and diaphragm on a standing lateral or DV view (Correct answer)
- Uniform increased abdominal opacity
- Dilated fluid-filled loops of intestine
Correct answer: Gas opacity between the liver and diaphragm on a standing lateral or DV view
Free peritoneal gas rises to the highest point and is visible as a radiolucent stripe between the liver and diaphragm on a standing lateral or horizontal-beam view.
Question 4: In ultrasound physics, 'resolution' refers to the ability to distinguish two structures as separate. Which type of resolution is MOST affected by transducer frequency?
- Lateral resolution
- Temporal resolution
- Axial resolution (Correct answer)
- Contrast resolution
Correct answer: Axial resolution
Axial resolution (along the beam axis) is determined by pulse length and wavelength, both of which improve with higher transducer frequency, allowing finer discrimination along the beam path.
Question 5: A dog has a suspected portosystemic shunt. Which imaging modality provides the MOST definitive pre-surgical mapping of shunt vasculature?
- Survey abdominal radiography
- Abdominal ultrasound with Doppler
- CT angiography (Correct answer)
- Nuclear scintigraphy
Correct answer: CT angiography
CT angiography provides three-dimensional vascular mapping with high spatial resolution, allowing precise identification of shunt location, number, and anatomy critical for surgical planning.
Question 6: When performing an upper GI series with barium in cats, contrast should reach the colon within approximately:
- 15–30 minutes
- 1–2 hours
- 3–5 hours (Correct answer)
- 6–8 hours
Correct answer: 3–5 hours
In cats barium typically reaches the colon within 3–5 hours under normal GI transit; slower transit may indicate obstruction, ileus, or motility disorder.
Question 7: Which of the following is a contraindication to the use of barium sulfate as a GI contrast agent?
- Megaesophagus
- Suspected esophageal or GI perforation (Correct answer)
- Gastric foreign body
- Vomiting without suspected perforation
Correct answer: Suspected esophageal or GI perforation
Barium leaking into the mediastinum or peritoneal cavity causes severe granulomatous inflammation and is potentially fatal; water-soluble contrast is used when perforation is suspected.
VTNE Diagnostic Imaging Techniques 5
Which artifact on MRI appears as alternating bright and dark bands and is caused by motion during image acquisition?