CT Image Quality and Reconstruction Flashcards
6 cards from real Computed Tomography Test practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 CT Image Quality and Reconstruction flashcards as text
In CT, spatial resolution is most commonly measured using which parameter?
Answer: Modulation Transfer Function (MTF) or line pairs per centimeter (lp/cm)
Spatial resolution in CT is quantified by the MTF or high-contrast resolution measured in line pairs per centimeter, describing the system's ability to resolve fine detail.
What is the Hounsfield Unit (HU) value of water on a CT scan?
Answer: 0 HU
Water is defined as 0 HU in the Hounsfield scale, which serves as the reference point with air at −1000 HU and dense cortical bone at +1000 HU or greater.
Which reconstruction algorithm provides the sharpest images but also the most noise in CT?
Answer: High-frequency (bone/edge) kernel
High-frequency (bone/detail) kernels sharpen edges and fine structures but amplify image noise, making them ideal for bone but not soft tissue evaluation.
What does the term 'partial volume effect' describe in CT imaging?
Answer: Averaging of attenuation from different tissues within a single voxel
Partial volume averaging occurs when a voxel contains multiple tissue types, and the assigned HU is an average of all tissues present, potentially obscuring small lesions.
In CT, increasing the field of view (FOV) while keeping matrix size constant will have what effect on voxel size?
Answer: Voxel size increases, reducing spatial resolution
Voxel size = FOV / matrix size; a larger FOV with the same matrix produces larger voxels, lowering spatial resolution.
What type of CT artifact appears as dark streaks radiating from dense metallic objects such as hip prostheses?
Answer: Beam hardening and metal streak artifact
Metal objects severely attenuate and preferentially absorb low-energy photons (beam hardening), causing dark streaks that obscure surrounding anatomy.