FR FieldReady Academy
Certified Radiology Equipment Specialist CRES

Certified Radiology Equipment Specialist CRES Practice Test: 20 Free Questions with Answers

Twenty questions in the exam's domain weights, each with its answer and the reason. The full course has 300 explained questions plus generated math items, scored tests in the real exam's format, and lessons built from what you miss.

  1. A service manual for a radiographic table tells you to level the detector to the midcoronal plane. Which division of the body does that plane describe?

    1. Vertically into equal left and right halves
    2. Vertically into front and back parts
    3. Horizontally into upper and lower parts
    4. Along the long axis of a limb
    Show the answer

    Answer: B. Coronal planes divide the body vertically into anterior and posterior parts, and the midcoronal plane runs through the middle of that split. Sagittal divides left from right and transverse divides upper from lower.

    From the lesson Body Organization, Planes, Habitus, and Positional Terminology.

  2. A technologist reports feeling a tingle from a cassette holder on a table. Which current level does a just-perceptible tingle correspond to, and what should you do?

    1. About 10 mA, and the device may stay in use until the next PM
    2. About 1 mA, and the device comes out of service for testing
    3. About 100 mA, and the room is evacuated
    4. About 5 A, and the breaker should be replaced
    Show the answer

    Answer: B. The threshold of perception is about 1 mA. A tingle is proof of a real leakage path, so the device leaves service for ground and leakage testing; 5 mA is the accepted harmless maximum, 10 to 20 mA is let-go, and 100 to 300 mA is the fibrillation range.

    From the lesson Electrical and Mechanical Safety in the Imaging Suite, Patient Transfer and Moving.

  3. A visiting physicist reports a cumulative reading of 2 rem for a staff member. What is that in millisieverts?

    1. 2 mSv
    2. 200 mSv
    3. 20 mSv
    4. 0.2 mSv
    Show the answer

    Answer: C. 1 Sv equals 100 rem, so 1 rem is 10 mSv and 2 rem is 20 mSv. The same factor of 100 links the gray and the rad: 1 Gy equals 100 rad.

    From the lesson How Radiation Harms: Ionization, Dose Quantities and Units, Occupational and Public Limits.

  4. Measuring a low-voltage rail in a generator cabinet, you find 24 V across an 8 ohm load resistor. What current is flowing?

    1. 0.33 A
    2. 32 A
    3. 3 A
    4. 192 A
    Show the answer

    Answer: C. Ohm's law gives I = V / R = 24 / 8 = 3 A, and the power in that resistor is P = V x I = 24 x 3 = 72 W. Rearranging the same law three ways covers most circuit arithmetic on the exam.

    From the lesson Voltage, Current, Resistance, and Power: Ohm's Law, Series and Parallel.

  5. Tracing a filter stage on a generator board, how do a capacitor and an inductor differ in what they pass?

    1. Both pass direct current freely
    2. Both block alternating current
    3. A capacitor blocks alternating current and passes direct current, while an inductor passes any change in current without opposing it
    4. A capacitor passes alternating current and blocks direct current, while an inductor opposes a change in current
    Show the answer

    Answer: D. A capacitor stores charge, so it passes alternating current and blocks direct current, and it smooths rectified voltage. An inductor opposes a change in current, which is what makes chokes, stator windings, and transformer windings behave as they do.

    From the lesson Components in a Circuit: Passive, Active, Rectifiers, and Reading the Schematic.

  6. A trainee asks why a hand technique at 60 kVp produces no characteristic radiation from a tungsten target. What is the correct answer?

    1. Characteristic radiation needs a rotating anode and this exposure used the stationary mode
    2. Characteristic radiation only appears above the tungsten K-shell energy of about 69.5 keV
    3. Added filtration removes all characteristic photons below 70 kVp
    4. Characteristic radiation is produced only at the small focal spot
    Show the answer

    Answer: B. A characteristic photon carries the difference between two binding energies, and only tungsten K-shell transitions near 69.5 keV are diagnostically useful. Below that tube potential the electrons cannot remove a K-shell electron, so the beam is all bremsstrahlung.

    From the lesson X-ray Production: Cathode, Anode, Focal Spot, Bremsstrahlung and Characteristic Radiation.

  7. A single-phase room is used for a lumbar series at 80 kVp and 100 mAs. How much thermal loading does that one exposure put on the anode?

    1. 800 HU
    2. 11,200 HU
    3. 8,000 HU
    4. 80,000 HU
    Show the answer

    Answer: C. On single-phase equipment heat units are kVp x mA x s, which is kVp x mAs: 80 x 100 = 8,000 HU. At about 1.4 J per heat unit that is roughly 11 kJ dumped into a focal track a few millimeters wide.

    From the lesson The Tube: Housing, Rotating Anode, Line-Focus Principle, Dual Focus, Heat Units, Cooling, Failure.

  8. A service manual states that the tube potential on a generator never falls below about 86 percent of peak. Which waveform is described?

    1. Single-phase full wave
    2. High frequency
    3. Three-phase twelve pulse
    4. Three-phase six pulse, with about 14 percent ripple
    Show the answer

    Answer: D. Six-pulse three-phase power has about 14 percent ripple, so the voltage stays near 86 percent of peak or above. Twelve pulse is about 4 percent ripple and stays above about 96 percent, and high frequency is about 1 percent.

    From the lesson Generators: kVp, mA, Time, mAs, Rectification and Waveform, High-Voltage Transformers, Timers.

  9. During a quality control check you place lead over the selected exposure control chamber and fire. Where must the exposure stop?

    1. At 6 s or 600 mAs, whichever comes first
    2. At 2 s or 200 mAs
    3. At the minimum response time
    4. When the anode reaches its rated heat
    Show the answer

    Answer: A. Starving the chamber forces the system onto its backup, which must end the exposure at 6 s or 600 mAs, whichever comes first. That test proves the patient and the tube are protected when the automatic control fails to terminate.

    From the lesson Automatic Exposure Control, Technique Charts, and the Exposure Factors.

  10. Checking collimator accuracy with the tube set 100 cm from the receptor, how far may the light field edge differ from the radiation field edge?

    1. 5 cm
    2. 2 cm
    3. 1 mm
    4. 10 cm
    Show the answer

    Answer: B. The light field must agree with the radiation field within 2 percent of the source-to-image distance, which is 2 cm at 100 cm. Automatic collimation and the distance indicator are held to the same 2 percent.

    From the lesson Collimation, Filtration, Grids, and Air Gap: Controlling the Beam and Scatter.

  11. A technologist reports that room 2 is "not working" and walks away. What is your FIRST step?

    1. Order the most commonly failed board for that generator
    2. Get the symptom in the operator's words with the room, the exam, and the step where it happens, then reproduce it
    3. Open the generator cabinet and measure the internal supplies
    4. Take the room out of service until the vendor can attend
    Show the answer

    Answer: B. Not working is not a symptom. The method starts by recovering what was actually seen, with the exam, the step, and how often, and then reproducing it yourself, because a fault you cannot reproduce is still only a report.

    From the lesson The Method: Symptom, History, Isolate, Verify; Device Error Versus Use Error.

  12. Three calls arrive at once: a cosmetic panel on a scanner, a radiographic room whose measured kVp is 18 percent off while it is still imaging patients, and a chest stand with a drifting detent. Which comes FIRST?

    1. The cosmetic panel, because it is quick
    2. The drifting detent, because a stand that will not hold position affects every exam in the room
    3. The kVp fault, because the room is outside tolerance and still in use
    4. All three on the same visit, in arrival order
    Show the answer

    Answer: C. Measured kVp must sit within 10 percent of the indicated value. A system outside its limits and still imaging patients comes out of service first; convenience and workflow items are logged and scheduled.

    From the lesson Prioritizing Imaging Repairs by Risk, Downtime, and Regulatory Exposure.

  13. You need the sequence of events that happens inside a generator during an exposure. Which part of the service manual carries it?

    1. The parts list and exploded views
    2. The specification tables
    3. The installation requirements
    4. The theory of operation
    Show the answer

    Answer: D. Theory of operation is where the block diagram and the exposure sequence live, which is what you need to decide where to look. Adjustments, error codes, parts, and tolerances each sit in their own section.

    From the lesson Using the Resources: Schematics, Service Manuals, Diagnostic Software, and Error Logs.

  14. A radiographic room makes no exposure and the console displays no error code at all. What is the MOST likely cause?

    1. An open contact somewhere in the interlock chain
    2. A failed high-voltage transformer
    3. A defective flat-panel detector
    4. A tube that has exceeded its anode heat limit and is waiting to cool
    Show the answer

    Answer: A. No exposure with no code points at the series interlock string: door, emergency stop, rotor ready, receptor parked and size selected, collimator or tray switch, and the exposure switch itself. Thermal and high-voltage faults announce themselves with a code.

    From the lesson Power and Generator Faults: No Exposure, Interlocks, High-Voltage Failures, Tube Arcing.

  15. Images from one table Bucky show fine parallel lines across the whole field. What is the MOST likely cause?

    1. A stale detector gain calibration
    2. A grid that is not moving during the exposure
    3. Patient motion during an exposure time that ran too long
    4. An incomplete erase of the imaging plate
    Show the answer

    Answer: B. Grid lines appear when a reciprocating grid stands still, so the strips are recorded instead of being blurred out. Check the Bucky drive, its motor, and the switch that starts it before suspecting the receptor.

    From the lesson Tube and Image Quality Faults: Heat, Focal-Spot Blur, Artifacts, Grid Errors, Motion.

  16. A new console works perfectly with the other devices in its own room but cannot reach anything elsewhere in the hospital. Which setting should you check FIRST?

    1. The port number used by the archive
    2. The subnet mask only
    3. The name server entries
    4. The default gateway
    Show the answer

    Answer: D. The gateway is the exit to other networks, so a wrong gateway leaves a device able to talk to its own subnet and nothing beyond it. Users describe that as the whole network being down from one console.

    From the lesson Networking Fundamentals for the Imaging Network: IP, Subnets, Switches, VLANs.

  17. A scanner needs a 10 Gbps link to the archive over a copper run of about 80 m. Which cable and connector fit?

    1. Cat 6A with an RJ45 connector
    2. Cat 5e with an RJ45 connector
    3. Coaxial cable with a screw connector
    4. Single-mode fiber with an optical connector
    Show the answer

    Answer: A. Cat 5e supports 1 Gbps and Cat 6A supports 10 Gbps, both on RJ45 connectors with a 100 m channel limit that includes the patch cords at each end. Fiber is for distance beyond that and for runs near heavy electrical noise.

    From the lesson Wired and Wireless Hardware: Cabling, NICs, Access Points, Cable Tracers.

  18. An archive's storage array reports that it is degraded after a drive failure, and the department is still working normally. How should you treat it?

    1. As a completed self-repair, since the array is still serving data
    2. As a failure already in progress whose margin is gone, needing urgent replacement
    3. As a backup copy that can now be relied on
    4. As a performance problem to be scheduled with the next upgrade, since the array rebuilds itself from parity
    Show the answer

    Answer: B. A RAID set survives a drive and warns you, but a degraded array has lost its safety margin and a second failure takes it. It is also not a backup: an array deleted, encrypted, or destroyed takes every copy inside it.

    From the lesson Computer Hardware and Software for Imaging Systems: Workstations, Storage, Backups, Virtualization.

  19. The local disk on one radiographic room fills every week and studies have to be cleared by hand. Which archive function should you check?

    1. Prefetching of prior studies
    2. The hanging protocols on the reading stations
    3. Storage commitment from the archive
    4. The routing rules to the subspecialty readers
    Show the answer

    Answer: C. Storage commitment is the archive confirming it has taken permanent responsibility for a study, which is what makes clearing the local copy safe. When commitment fails quietly, nothing can be cleared automatically and local disks fill.

    From the lesson PACS: The Archive, Workstations, and the Image Lifecycle.

  20. Two imaging nodes must negotiate an association before anything moves. Which four items have to agree?

    1. Address, subnet mask, gateway, and name server
    2. Compression ratio, matrix size, bit depth, and transfer rate
    3. Patient name, accession number, study date, and modality
    4. AE title, host address, port, and supported SOP classes
    Show the answer

    Answer: D. Three of those four are typed by a human during installation, which is why a single mistyped character is the most common reason a new room cannot send. Ports are commonly 104 or 11112, and the titles are case sensitive.

    From the lesson DICOM: Objects, Services, Modality Worklist, and DICOM Echo.