Computed Tomography Test Computed Tomography 5

Question 1

Which CT acquisition mode collects data continuously as the table moves through the gantry?

Accepted Answer

Helical (spiral) mode

Answer

Helical CT rotates the X-ray tube continuously while the table advances, creating a spiral data set that allows retrospective reconstruction at any slice position.

Question 2

What is the primary advantage of dual-energy CT (DECT) over single-energy CT?

Accepted Answer

Material decomposition enabling differentiation of tissues with similar HU values

Answer

DECT acquires data at two kVp settings, enabling material decomposition algorithms that distinguish substances like iodine, uric acid, and calcium that may overlap in attenuation at single energy.

Question 3

Which structure is best identified on a CT image using a bone window with a window level of approximately 300–700 HU?

Accepted Answer

Cortical bone and fracture lines

Answer

Bone windows use high window levels centered on dense cortical bone (≈400–1000 HU), which optimizes visualization of fractures, bony trabecular detail, and periosteal changes.

Question 4

A pregnant patient requires abdominal CT for suspected appendicitis. Which statement about fetal radiation risk is most accurate?

Accepted Answer

Fetal risk is negligible at typical diagnostic doses below 50 mGy, but benefits must outweigh risks

Answer

At diagnostic CT doses typically below 25 mGy, deterministic fetal effects are extremely unlikely; however, the ALARA principle still applies and clinical benefit must justify the exposure.

Question 5

What does 'multiplanar reformation' (MPR) allow in CT post-processing?

Accepted Answer

Display of axial raw data in coronal, sagittal, or oblique planes

Answer

MPR resamples the volumetric CT dataset to display images in any desired plane, allowing evaluation of anatomy that is difficult to assess on axial images alone.

Computed Tomography Test Practice Test

Computed Tomography Test Practice Test

Computed Tomography Test Computed Tomography 5