Computed Tomography and Advanced Imaging Questions and Answers Flashcards

In CT quality control, what does the daily water phantom HU measurement test?

Answer: CT number accuracy and scanner calibration

Scanning a water phantom daily and confirming its HU value is near 0 (±5 HU) verifies CT number accuracy and proper scanner calibration.

Which reconstruction algorithm in CT produces sharper edges and is preferred for bone imaging?

Answer: Bone (sharp/high-frequency) kernel

A sharp or high-frequency reconstruction kernel enhances edge definition, making it ideal for bone and high-contrast structure imaging despite increased image noise.

What is the primary safety concern when bringing ferromagnetic objects into the MRI suite?

Answer: Projectile effect from strong magnetic field attraction

The strong static magnetic field accelerates ferromagnetic objects toward the magnet bore at high velocity, creating a dangerous projectile hazard.

In ultrasound, the term 'acoustic shadowing' describes:

Answer: Loss of signal deep to a highly reflective or absorbing structure

Acoustic shadowing occurs when a highly reflective or absorbing structure (e.g., gallstone, bone) blocks sound transmission, producing a dark shadow deep to it.

Which CT scan parameter, when increased, primarily reduces image noise?

Answer: Increasing mAs (tube current × time)

Increasing mAs increases the number of photons reaching the detector, reducing quantum mottle (image noise), but at the cost of higher patient dose.

What is the purpose of the DLP (Dose-Length Product) metric in CT?

Answer: Estimates total energy imparted to the patient over the entire scan length

DLP (CTDIvol × scan length in cm) estimates the total radiation energy delivered during a CT examination and is used to compare doses across protocols.