CBET Diagnostic Imaging Equipment 5 — Questions and Answers
Question 1: What is the function of the Bucky grid in radiographic imaging?
- Focus the X-ray beam onto the detector
- Move the grid during exposure to blur grid lines while absorbing scatter (Correct answer)
- Amplify the X-ray signal at the detector
- Provide filtration to remove low-energy photons
Correct answer: Move the grid during exposure to blur grid lines while absorbing scatter
The Bucky mechanism oscillates the grid during exposure so its lead strips do not appear as artifacts on the image while still absorbing scattered radiation.
Question 2: In nuclear medicine, the term 'half-life' as applied to a radiopharmaceutical refers to:
- Time for 50% of injected activity to be excreted by the kidneys
- Time for radioactive decay to reduce activity to half its initial value (Correct answer)
- Duration of the imaging window after injection
- Time required to synthesize the radiopharmaceutical
Correct answer: Time for radioactive decay to reduce activity to half its initial value
Physical half-life is the time required for half the radioactive atoms in a sample to undergo decay, reducing activity by 50%.
Question 3: A DICOM workstation cannot retrieve images from the PACS server. After confirming network connectivity, the BMET should verify:
- Monitor calibration with a photometer
- AE Title, IP address, and port configuration for both nodes (Correct answer)
- JPEG compression level settings
- Hard disk RAID redundancy status
Correct answer: AE Title, IP address, and port configuration for both nodes
DICOM communication requires matching Application Entity (AE) Titles, correct IP addresses, and open TCP ports between devices.
Question 4: Which MRI safety zone requires strict ferromagnetic screening of all personnel and equipment?
- Zone I
- Zone II
- Zone III
- Zone IV (Correct answer)
Correct answer: Zone IV
Zone IV is the MRI scanner room itself, where the static magnetic field is always present, requiring the strictest screening.
Question 5: On a mammography unit, the automatic exposure control (AEC) sensor is placed:
- Between the X-ray tube and the breast
- Behind the image receptor, in the beam exit path (Correct answer)
- Inside the compression paddle
- Adjacent to the collimator assembly
Correct answer: Behind the image receptor, in the beam exit path
The mammography AEC detector is positioned behind (distal to) the image receptor so it samples the transmitted beam to terminate exposure at the correct dose.
Question 6: During ultrasound transducer acceptance testing, a BMET uses a tissue-equivalent phantom to assess:
- Electrical leakage current of the transducer cable
- Dead elements, sensitivity uniformity, and depth penetration (Correct answer)
- Maximum output voltage of the pulser circuit
- Doppler shift accuracy only
Correct answer: Dead elements, sensitivity uniformity, and depth penetration
Tissue-equivalent phantoms with wire targets and grayscale layers allow evaluation of element function, sensitivity uniformity, axial/lateral resolution, and penetration depth.
Question 7: The half-value layer (HVL) of an X-ray beam is used to characterize:
- The focal spot size of the X-ray tube
- The beam quality (effective energy) based on its penetrating ability (Correct answer)
- The patient entrance dose for a standard projection
- The maximum kVp achievable by the generator
Correct answer: The beam quality (effective energy) based on its penetrating ability
HVL is the thickness of a specified material that reduces beam intensity by 50%, indicating the beam's effective penetrating energy.
CBET Diagnostic Imaging Equipment 5
What is the function of the Bucky grid in radiographic imaging?