ARRT ARRT CT Post-Processing and Reconstruction 2 — Questions and Answers
Question 1: Minimum intensity projection (MinIP) post-processing is particularly useful for displaying which anatomical structures?
- Dense bone and calcifications
- Air-filled airways and lung parenchyma (Correct answer)
- Contrast-enhanced blood vessels
- Solid abdominal organs
Correct answer: Air-filled airways and lung parenchyma
MinIP projects the lowest attenuation voxel along each ray, making it ideal for displaying air-containing structures like the tracheobronchial tree or emphysematous lung.
Question 2: CT colonoscopy (virtual colonoscopy) relies on which post-processing technique to create a simulated fly-through view of the colon lumen?
- Maximum intensity projection
- Volume rendering with endoluminal navigation (Correct answer)
- Minimum intensity projection
- Subtraction imaging
Correct answer: Volume rendering with endoluminal navigation
Volume rendering with endoluminal navigation uses the air-distended colon as a flight path, generating a simulated colonoscopic perspective of the mucosal surface.
Question 3: What is the primary purpose of selecting a small reconstruction FOV (field of view) during CT image reconstruction?
- To reduce patient dose
- To increase the pixel size for better soft tissue contrast
- To improve spatial resolution by sampling more detail per pixel (Correct answer)
- To decrease image noise
Correct answer: To improve spatial resolution by sampling more detail per pixel
A smaller reconstruction FOV divides the imaged area into the same matrix of pixels, resulting in smaller pixel size and therefore higher spatial resolution of the region of interest.
Question 4: CT perfusion imaging requires specialized post-processing to generate which type of parametric maps?
- Hounsfield unit histograms
- Cerebral blood flow, cerebral blood volume, and mean transit time maps (Correct answer)
- Bone mineral density scores
- Standardized uptake value (SUV) maps
Correct answer: Cerebral blood flow, cerebral blood volume, and mean transit time maps
CT perfusion post-processing applies deconvolution or maximum slope models to time-attenuation curves to produce quantitative maps of CBF, CBV, and MTT.
Question 5: In CT angiography post-processing, bone subtraction is performed primarily to:
- Remove iodine signal from vessels
- Eliminate overlying bone to improve visualization of adjacent vessels (Correct answer)
- Reduce noise in the image
- Correct for beam hardening
Correct answer: Eliminate overlying bone to improve visualization of adjacent vessels
Bone subtraction algorithms register and subtract non-contrast images from contrast-enhanced images, removing osseous structures that would otherwise obscure adjacent vessels.
Question 6: Which statement best describes an isotropic voxel in CT imaging?
- A voxel with equal dimensions in x, y, and z axes (Correct answer)
- A voxel that contains only one tissue type
- A voxel reconstructed using iterative algorithms
- A voxel with maximum attenuation value
Correct answer: A voxel with equal dimensions in x, y, and z axes
Isotropic voxels have equal measurements in all three spatial dimensions, enabling high-quality MPR and 3D reconstructions in any plane without stair-step degradation.
ARRT ARRT CT Post-Processing and Reconstruction 2
Minimum intensity projection (MinIP) post-processing is particularly useful for displaying which anatomical structures?