Diagnostic Imaging & Radiology Flashcards

Which nuclear medicine scan is most appropriate for detecting occult bony metastases in a cancer patient?

Answer: Tc-99m bone scan

Tc-99m methylene diphosphonate bone scintigraphy is sensitive for osteoblastic metastatic lesions and is widely used for whole-body skeletal survey.

In computed tomography, the Hounsfield Unit (HU) value for simple water is:

Answer: 0 HU

The Hounsfield scale sets water at 0 HU as the reference point, with air at -1000 HU and cortical bone at approximately +1000 HU.

Which ultrasound artifact is caused by a highly reflective structure that prevents sound from passing through, creating a dark region behind it?

Answer: Acoustic shadowing

Acoustic shadowing occurs when structures like gallstones or bones reflect nearly all the ultrasound beam, creating a shadow of no signal distal to them.

A 'Hampton's hump' on chest radiograph is associated with:

Answer: Pulmonary embolism with infarction

Hampton's hump is a pleural-based, wedge-shaped opacity caused by pulmonary infarction secondary to embolic occlusion of a pulmonary artery.

What is the recommended maximum cumulative dose of ionizing radiation considered acceptable for occupational workers per year according to international radiation protection standards?

Answer: 20 mSv/year

The ICRP recommends an effective dose limit of 20 mSv per year averaged over 5 years for occupational radiation workers.

On fluoroscopy during a barium swallow, a 'bird beak' tapering of the lower esophagus is most consistent with:

Answer: Achalasia

Achalasia causes failure of the lower esophageal sphincter to relax, producing smooth, symmetric tapering resembling a bird's beak on barium studies.

Which imaging finding on CT abdomen is most diagnostic of acute appendicitis?

Answer: Appendix diameter >6 mm with periappendiceal fat stranding

An appendiceal diameter exceeding 6 mm with surrounding inflammatory fat stranding on CT has high sensitivity and specificity for acute appendicitis.