Diagnostic Imaging & Radiology Flashcards

MRI is absolutely contraindicated in patients with which of the following?

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.

What does a Hounsfield Unit (HU) value of +1000 typically represent in CT imaging?

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.

Ultrasound imaging is based on which physical principle?

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.

Which chest radiograph positioning is most sensitive for detecting a small pneumothorax?

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.

Fluoroscopy is most appropriately used for which clinical application?

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.

A DEXA scan is the gold standard investigation for which condition?

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.

Free air under the right hemidiaphragm on an erect chest X-ray most likely indicates:

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.