DHA Diagnostic Imaging & Radiology 2 — Questions and Answers
Question 1: MRI is absolutely contraindicated in patients with which of the following?
- Dental implants
- Non-ferromagnetic aneurysm clips
- Older pacemakers without MR-conditional labeling (Correct answer)
- Titanium orthopedic hardware
Correct answer: Older pacemakers without MR-conditional labeling
Conventional (non-MR-conditional) pacemakers are an absolute contraindication to MRI due to risk of device malfunction, inappropriate pacing, or heat generation from radiofrequency energy.
Question 2: What does a Hounsfield Unit (HU) value of +1000 typically represent in CT imaging?
- Air
- Fat
- Soft tissue
- Cortical bone (Correct answer)
Correct answer: Cortical bone
Cortical bone has a Hounsfield Unit value of approximately +1000 HU, reflecting its high attenuation of X-rays due to calcium content.
Question 3: Ultrasound imaging is based on which physical principle?
- Electromagnetic wave absorption
- Radiofrequency resonance
- Reflection of high-frequency sound waves (Correct answer)
- Photon attenuation
Correct answer: Reflection of high-frequency sound waves
Ultrasound uses high-frequency sound waves (2–15 MHz) that are emitted and received by a transducer; echoes reflected at tissue interfaces are converted into images.
Question 4: Which chest radiograph positioning is most sensitive for detecting a small pneumothorax?
- Supine AP
- Prone PA
- Erect PA (Correct answer)
- Left lateral decubitus
Correct answer: Erect PA
An erect PA chest radiograph is most sensitive for pneumothorax because free pleural air rises to the apex when the patient is upright, creating a visible pleural line.
Question 5: Fluoroscopy is most appropriately used for which clinical application?
- Static bone density assessment
- Real-time dynamic imaging of swallowing or joint motion (Correct answer)
- Intracranial tumor detection
- Cardiac wall motion analysis
Correct answer: Real-time dynamic imaging of swallowing or joint motion
Fluoroscopy provides continuous real-time X-ray imaging, making it ideal for dynamic studies such as barium swallow, arthrography, and interventional guidance.
Question 6: A DEXA scan is the gold standard investigation for which condition?
- Liver fibrosis
- Pulmonary hypertension
- Osteoporosis and bone mineral density (Correct answer)
- Renal artery stenosis
Correct answer: Osteoporosis and bone mineral density
Dual-energy X-ray absorptiometry (DEXA) measures bone mineral density (BMD) and is the WHO-endorsed gold standard for diagnosing osteoporosis.
Question 7: Free air under the right hemidiaphragm on an erect chest X-ray most likely indicates:
- Pulmonary embolism
- Right lower lobe pneumonia
- Pneumoperitoneum (Correct answer)
- Pleural effusion
Correct answer: Pneumoperitoneum
Pneumoperitoneum (free intraperitoneal air) rises to collect under the diaphragm on an erect film, classically signaling a perforated hollow viscus requiring emergent surgery.
DHA Diagnostic Imaging & Radiology 2
MRI is absolutely contraindicated in patients with which of the following?