ACI CRES Certified Radiology Equipment Specialist

Which structure within an X-ray tube is responsible for producing electrons via thermionic emission?

• AThe tungsten filament at the cathode
• BThe rotating anode disc
• CThe glass or metal vacuum envelope
• DThe copper stem of the anode assembly

In diagnostic radiography, what does increasing the kVp setting primarily affect?

• AThe quantity of X-ray photons produced
• BThe quality (penetrating ability) of the X-ray beam
• CThe focal spot size on the anode
• DThe exposure time duration

Which imaging modality relies on the piezoelectric effect to generate and receive sound waves?

• AComputed tomography (CT)
• BMagnetic resonance imaging (MRI)
• CDiagnostic ultrasound
• DDigital radiography (DR)

Iodinated contrast media used in CT examinations primarily enhance image contrast by which mechanism?

• AEmitting fluorescent light when struck by X-rays
• BIncreasing the atomic number of tissues, thereby increasing X-ray attenuation
• CReducing patient motion artifacts during scanning
• DIncreasing the signal-to-noise ratio of the detector

In MRI, the Larmor frequency of hydrogen protons is directly proportional to which factor?

• AThe radiofrequency coil diameter
• BThe main magnetic field strength (B0)
• CThe patient's body mass index
• DThe gradient coil slew rate

A chest X-ray shows the heart shadow occupying more than 50% of the thoracic diameter. Which anatomical condition does this most likely indicate?

• APneumothorax
• BCardiomegaly
• CPleural effusion
• DPulmonary embolism

Which physiological effect is of greatest concern when a patient with a ferromagnetic implant enters the MRI scan room?

• AThermal burns from radiofrequency heating
• BProjectile effect and implant displacement from the static magnetic field
• CPeripheral nerve stimulation from gradient switching
• DAcoustic noise-induced hearing damage

What is the maximum permissible whole-body occupational radiation dose limit per year for a radiation worker in the United States?

• A1 mSv (100 mrem)
• B5 mSv (500 mrem)
• C50 mSv (5,000 mrem)
• D100 mSv (10,000 mrem)

Which type of personal radiation monitoring device provides an immediate, real-time dose reading?

• AFilm badge dosimeter
• BOptically stimulated luminescence (OSL) dosimeter
• CElectronic personal dosimeter (EPD)
• DThermoluminescent dosimeter (TLD)

According to NFPA 99, what is the maximum allowable leakage current from a patient-applied medical device?

• A10 microamperes (μA)
• B50 microamperes (μA)
• C100 microamperes (μA)
• D500 microamperes (μA)

What is the primary purpose of the lead apron worn by staff during fluoroscopy procedures?

• ATo reduce scattered radiation exposure to the operator
• BTo improve image quality by reducing scatter reaching the detector
• CTo shield the X-ray tube from overheating
• DTo comply with fire safety codes in the fluoroscopy suite

Under FDA/CDRH regulations, which class of medical device recall indicates the highest risk of serious adverse health consequences or death?

• AClass I recall
• BClass II recall
• CClass III recall
• DMarket withdrawal

A CRES technician discovers a frayed power cord on a portable X-ray unit. What is the correct immediate action?

• AApply electrical tape to the frayed area and continue use
• BRemove the equipment from service, tag it as unsafe, and initiate a repair work order
• CNotify the radiology department and allow limited use until repair parts arrive
• DReduce the workload on the unit to prevent further damage

What is the recommended minimum frequency for performing electrical safety inspections on patient-care medical equipment in a hospital?

• AEvery 6 months
• BAnnually
• CEvery 2 years
• DOnly after a reported incident

During infection control procedures, which level of disinfection is required for ultrasound transducers used in transvaginal or transrectal examinations?

• ALow-level disinfection
• BIntermediate-level disinfection
• CHigh-level disinfection
• DSterilization

According to Ohm's Law, if a circuit has a voltage of 120V and a resistance of 60 ohms, what is the current?

• A0.5 A
• B2 A
• C60 A
• D7,200 A

In an AC circuit, what is the phase relationship between voltage and current in a purely capacitive load?

• AVoltage and current are in phase
• BCurrent leads voltage by 90 degrees
• CCurrent lags voltage by 90 degrees
• DCurrent leads voltage by 180 degrees

What is the primary function of a full-wave bridge rectifier in an X-ray generator?

• ATo step up the voltage from the autotransformer
• BTo convert AC to pulsating DC for the X-ray tube
• CTo regulate the filament heating current
• DTo store energy for rapid exposure sequences

A transformer has a primary winding of 200 turns and a secondary winding of 1,000 turns. If the primary voltage is 220V, what is the secondary voltage?

• A44V
• B220V
• C1,100V
• D5,000V

Which electronic component stores energy in an electric field and blocks DC while allowing AC to pass?

• AResistor
• BInductor
• CCapacitor
• DDiode

What is the total resistance of three resistors (10Ω, 20Ω, and 30Ω) connected in parallel?

• A5.45Ω
• B10Ω
• C20Ω
• D60Ω

In a digital logic circuit, what is the output of an AND gate when both inputs are HIGH (1)?

• ALOW (0)
• BHIGH (1)
• CIndeterminate
• DFloating

What type of power supply regulation maintains a constant output voltage despite variations in input voltage or load current?

• AUnregulated power supply
• BLinear regulated power supply
• CIsolation transformer only
• DAutotransformer only

A bipolar junction transistor (BJT) in an X-ray generator control circuit is operating in saturation mode. What does this indicate?

• AThe transistor is completely off and blocking current
• BThe transistor is acting as a fully on switch with minimal voltage drop
• CThe transistor is operating in its linear amplification region
• DThe transistor has failed and must be replaced

What component in an X-ray generator uses a thyristor (SCR) to precisely control exposure timing?

• AThe filament transformer
• BThe high-voltage transformer
• CThe exposure timer/switching circuit
• DThe line voltage compensator

In a high-frequency X-ray generator, what advantage does the inverter circuit provide over conventional single-phase or three-phase designs?

• AIt eliminates the need for a high-voltage transformer entirely
• BIt produces a nearly constant (ripple-free) DC output for more consistent X-ray production
• CIt allows the X-ray tube to operate without a rectifier circuit
• DIt reduces the tube current (mA) needed for any given exposure

What is the primary purpose of the rotating anode in a diagnostic X-ray tube?

• ATo focus the electron beam to a smaller focal spot
• BTo distribute heat over a larger area, allowing higher tube loadings
• CTo filter out low-energy X-ray photons
• DTo increase the speed of electron travel from cathode to anode

During preventive maintenance on a CT scanner, the CTDI (Computed Tomography Dose Index) measurement is found to be 25% higher than the manufacturer's baseline specification. What is the most appropriate action?

• AContinue using the scanner since CTDI varies naturally
• BRecalibrate the X-ray tube output and detector system, then re-measure
• CIncrease the filtration to compensate for the higher dose
• DReplace the X-ray tube immediately

In CT imaging, what do Hounsfield units (HU) measure?

• AThe radiation dose delivered to the patient
• BThe relative linear attenuation coefficient of tissue compared to water
• CThe spatial resolution of the reconstructed image
• DThe rotational speed of the gantry

What is the primary safety concern associated with the quench of a superconducting MRI magnet?

• ALoss of image data stored in the system computer
• BRapid boil-off of liquid helium causing oxygen displacement in the scan room
• CPermanent demagnetization requiring replacement of the magnet
• DElectrical shock from the gradient coil power supply

Which component in an MRI system is responsible for spatial localization of the signal?

• AThe main superconducting magnet (B0)
• BThe radiofrequency (RF) transmit coil
• CThe gradient coils
• DThe shim coils

During a mammography unit quality control check, the measured half-value layer (HVL) is below the minimum required value. What does this indicate?

• AThe X-ray beam is too heavily filtered and needs less filtration
• BThe X-ray beam contains too many low-energy photons, increasing patient skin dose
• CThe compression paddle is applying too much force
• DThe automatic exposure control (AEC) is overexposing images

What is the primary advantage of a flat-panel digital detector over a computed radiography (CR) cassette system?

• ALower initial purchase cost
• BHigher detective quantum efficiency (DQE) and faster image acquisition
• CGreater portability between different X-ray rooms
• DNo need for quality control testing

During preventive maintenance on a fluoroscopy system, the measured entrance skin dose rate exceeds the regulatory limit of 88 mGy/min (10 R/min) for standard fluoroscopy. What is the required action?

• ADocument the finding and schedule repair during the next planned downtime
• BImmediately remove the system from clinical use until the dose rate is corrected
• CReduce the default fluoroscopy kVp to compensate
• DInform the radiologist to use shorter fluoroscopy times

What is the function of the automatic brightness control (ABC) system in a fluoroscopy unit?

• ATo adjust room lighting during procedures
• BTo maintain a consistent image brightness by automatically adjusting kVp, mA, or pulse wi…
• CTo control the C-arm positioning during surgery
• DTo regulate the amount of contrast media injected

A portable X-ray unit uses a rechargeable battery-powered capacitor discharge generator. What is the main limitation of this design?

• AIt cannot produce diagnostic-quality images
• BThe output voltage drops during the exposure as the capacitor discharges
• CIt requires a three-phase power connection
• DIt is heavier than conventional generator units

During preventive maintenance on an ultrasound system, the CRES technician performs a tissue-mimicking phantom scan. The measured axial resolution is significantly worse than the manufacturer's specification. Which component is the most likely cause?

• AThe DICOM network interface card
• BThe transducer's piezoelectric element array
• CThe monitor display calibration
• DThe system's battery backup unit

What is the primary purpose of the collimator on a diagnostic X-ray tube housing?

• ATo filter out low-energy photons from the beam
• BTo restrict the X-ray beam to the area of clinical interest, reducing patient dose and sc…
• CTo cool the X-ray tube during operation
• DTo measure the radiation output for quality control

A C-arm fluoroscopy unit displays an error indicating that the anode heat capacity has reached 80%. What should the CRES technician advise?

• AImmediately replace the X-ray tube
• BAllow the tube to cool before continuing, and check the anode cooling system if this recu…
• CIncrease the mA to complete the procedure faster
• DDisable the heat warning and continue the procedure

What is the purpose of the Dose Length Product (DLP) in CT scanning?

• ATo measure the spatial resolution of the CT image
• BTo estimate the total radiation dose delivered to the patient for the entire scan series
• CTo calculate the optimal contrast injection rate
• DTo determine the X-ray tube heat loading

A CT scanner's detector calibration (air calibration) should be performed in which situation?

• AOnly during annual preventive maintenance
• BAfter X-ray tube replacement, detector module replacement, or when ring artifacts appear
• CBefore every patient scan
• DOnly when the manufacturer issues a software update

What is the Specific Absorption Rate (SAR) in MRI, and why is it monitored?

• AThe rate of magnetic field decay; monitored to maintain image quality
• BThe rate of RF energy absorption by tissue; monitored to prevent patient heating
• CThe rate of helium boil-off; monitored to predict quench events
• DThe rate of gradient switching; monitored to prevent peripheral nerve stimulation

A mammography system uses a molybdenum (Mo) anode with a molybdenum filter. For which breast type is this target/filter combination most appropriate?

• AVery thick, dense breasts
• BAverage thickness, non-dense breasts
• CBreast implant views
• DAll breast types equally

What is the standard preventive maintenance interval recommended by most manufacturers for diagnostic X-ray tube housing leakage radiation testing?

• AMonthly
• BQuarterly
• CAnnually
• DEvery 5 years

Which calibration tool is used to verify the accuracy of a CT scanner's Hounsfield unit measurements?

• AA wire-mesh resolution phantom
• BA multi-material CT calibration phantom (e.g., ACR CT phantom)
• CA chest X-ray anthropomorphic phantom
• DAn ultrasound tissue-mimicking phantom

A CRES technician is troubleshooting a digital radiography (DR) system that produces images with a consistent vertical line artifact. What is the most probable cause?

• AA faulty X-ray tube filament
• BA defective column of detector elements (dead pixel column) on the flat-panel detector
• CIncorrect SID (source-to-image distance) setting
• DLow developer temperature in the film processor

A CT scanner produces ring artifacts in every scan. Which troubleshooting step should the CRES technician perform first?

• AReplace the X-ray tube
• BPerform a detector air calibration (gain calibration)
• CReplace the slip ring assembly
• DUpdate the reconstruction software