CAMRT Computed Tomography and Advanced Imaging Questions and Answers 2 — Questions and Answers
Question 1: In MRI, the term 'T1-weighted image' refers to a sequence that highlights contrast based on:
- Spin-spin relaxation time differences between tissues
- Spin-lattice (longitudinal) relaxation time differences between tissues (Correct answer)
- Proton density only
- Diffusion of water molecules
Correct answer: Spin-lattice (longitudinal) relaxation time differences between tissues
T1 weighting uses the longitudinal (spin-lattice) relaxation time (T1) to differentiate tissues; fat appears bright and fluid appears dark on T1 images.
Question 2: Which contrast agent is most commonly used for MRI enhancement?
- Iodinated contrast (e.g., iohexol)
- Gadolinium-based contrast agent (GBCA) (Correct answer)
- Barium sulfate
- Ferromagnetic iron particles only
Correct answer: Gadolinium-based contrast agent (GBCA)
Gadolinium-based contrast agents (GBCAs) shorten T1 relaxation time, causing enhanced tissues to appear brighter on T1-weighted MRI sequences.
Question 3: A patient with a pacemaker presents for an MRI examination. What is the most appropriate action?
- Proceed with MRI using a lower field strength scanner
- Consult the ordering physician and check if the pacemaker is MR-conditional before proceeding (Correct answer)
- Perform the MRI immediately as modern pacemakers are always safe
- Refuse the exam without any consultation
Correct answer: Consult the ordering physician and check if the pacemaker is MR-conditional before proceeding
MR technologists must verify the pacemaker model, determine if it is MR-conditional, and consult the ordering physician and MRI physicist before proceeding.
Question 4: In nuclear medicine, which radionuclide is most commonly used for bone scans?
- Iodine-131 (I-131)
- Technetium-99m (Tc-99m) (Correct answer)
- Thallium-201 (Tl-201)
- Gallium-67 (Ga-67)
Correct answer: Technetium-99m (Tc-99m)
Tc-99m labeled phosphonates (e.g., MDP) are the standard radiopharmaceuticals for bone scintigraphy due to their favorable physical properties and affinity for bone.
Question 5: What does the term 'slice thickness' affect in CT image quality?
- Only image noise
- Z-axis resolution and partial volume averaging (Correct answer)
- Only contrast resolution
- Scan time only
Correct answer: Z-axis resolution and partial volume averaging
Thinner slices improve z-axis (longitudinal) spatial resolution and reduce partial volume averaging, but increase image noise.
Question 6: Which fluoroscopic technique reduces patient dose by pulsing the x-ray beam rather than continuous fluoroscopy?
- High-dose-rate fluoroscopy
- Pulsed progressive fluoroscopy (Correct answer)
- Last-image-hold (LIH) only
- Digital subtraction angiography
Correct answer: Pulsed progressive fluoroscopy
Pulsed progressive fluoroscopy delivers x-ray pulses at lower frame rates, significantly reducing patient and staff dose compared to continuous fluoroscopy.
CAMRT Computed Tomography and Advanced Imaging Questions and Answers 2
In MRI, the term 'T1-weighted image' refers to a sequence that highlights contrast based on: