ARRT Radiographic Equipment Flashcards

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Questions and Answers

What are the components of a fixed radiographic unit?

Designed for diagnostic radiographic work only (correct)

Permit tilting of the table

Produces high frequency output

Operates on rechargeable batteries

Which of the following best describes mobile (portable) radiographic units?

Fixed and cannot be moved

Do not permit tilting of the table

Operate on rechargeable batteries (correct)

Designed for diagnostic radiographic work only

What is the primary purpose of a dedicated chest radiographic unit?

Designed specifically to perform radiographic chest x-rays.

What is the function of the operating console in a radiographic unit?

Controls for selecting kVp, mA, exposure time & AEC. Signup and view all the answers

What is the purpose of the glass envelope in a radiographic unit?

Protects internal components of the tube & maintains a vacuum. Signup and view all the answers

What is the atomic number of tungsten?

74 Signup and view all the answers

What material is used for the stationary anode in X-ray tubes?

Rhenium-alloyed tungsten. Signup and view all the answers

What material is the rotating anode typically made of?

Molybdenum. Signup and view all the answers

Induction motor consists of the _____________

stator, windings & motor. Signup and view all the answers

Induction motor operates the ________ which spins the anode.

rotor. Signup and view all the answers

An induction motor obtains the electric current in the rotor by _ from the magnetic field of the stator winding.

electromagnetic induction. Signup and view all the answers

Where is the induction motor located?

Outside the vacuum envelope. Signup and view all the answers

Where is the rotor located in the induction motor?

Inside the stator and inside the envelope, attached to the anode disk. Signup and view all the answers

What is the high-speed rotation range of the rotor?

10,000 - 12,000 rpm. Signup and view all the answers

What is the maximum allowable leakage radiation at 1 meter?

100mR/hr. Signup and view all the answers

X-rays are produced _____________ (equal intensity in all directions).

isotropically. Signup and view all the answers

What is the role of insulating oil in a radiographic unit?

Assists in cooling and contributes to inherent filtration. Signup and view all the answers

What does Automatic Exposure Control (AEC) do?

Reproduces a desired amount of exposure to the IR of selected body parts. Signup and view all the answers

The single function of an AEC is to eliminate the need for the radiographer to set an _.

exposure time. Signup and view all the answers

Back-up times for AEC should be set at _______ of the anticipated manual exposure time.

150%. Signup and view all the answers

What protects the patient from excessive radiation exposure due to AEC malfunctions?

Backup timer. Signup and view all the answers

Proper use of the density controls is accomplished when the configuration of the ______________________ cannot be adapted.

ionization chamber cells. Signup and view all the answers

Minimum response time in the region of __________.

0.001 sec. Signup and view all the answers

MA should be _________ to permit longer AEC time.

decreased. Signup and view all the answers

What type of controls require the use of a technique chart?

Manual exposure controls. Signup and view all the answers

What is the purpose of bottom shutters in collimators?

Reduce penumbra along the periphery. Signup and view all the answers

What do upper shutters in collimators reduce?

Off-focus (stem) radiation. Signup and view all the answers

What automatically collimates to IR size?

Positive Beam Limitation (PBL). Signup and view all the answers

Collimator results in some filtration of the beam =

1 mm of aluminum. Signup and view all the answers

What is the simplest of all beam-restricting devices?

Aperture Diaphragm. Signup and view all the answers

Study Notes

Components of Radiographic Units

Fixed Units: Do not allow table tilting and are specifically designed for diagnostic radiographic work.
Mobile Units: Operate on rechargeable batteries and utilize generators to produce high-frequency output.
Dedicated Chest Units: Specifically designed for performing radiographic chest x-rays.

Operating Console

Controls enable selection of kVp, mA, exposure time, and AEC (Automatic Exposure Control).
Includes indicators for tube energization (e.g., bell, beeper, tube current meter).
Features a power switch to turn off the unit.

Glass Envelope

Made of leaded pyrex glass, characterized by a high melting point.
Protects internal tube components and maintains a vacuum.
Contains a window port where x-rays are directed.

Tungsten Properties

Tungsten's atomic number is 74, making it a key material in radiography.
Stationary Anode: Constructed from rhenium-alloyed tungsten to provide greater elasticity under heat expansion.
Rotating Anode: Made of molybdenum, providing weight reduction benefits.

Induction Motor Components

Consists of a stator with windings and a rotor to drive the anode.
The rotor spins the anode for increased surface area, enhancing heat capacity and tube efficiency.
Operates through electromagnetic induction, utilizing the stator's magnetic field.

Rotor and Speed

The rotor is located inside the stator and the vacuum envelope, attached to the anode disk.
Electromagnetic fields cause the rotor to spin at a high speed of 10,000 - 12,000 rpm.

Radiation Safety

Leakage radiation limit is 100 mR/hr at 1 meter, ensuring patient safety.
X-rays are produced isotropically, meaning they have equal intensity in all directions.

Insulating Oil

Helps with cooling and is located outside the glass envelope.
Contributes to inherent filtration of x-rays.

Automatic Exposure Control (AEC)

AEC is designed to ensure a consistent exposure to the IR, compensating for patient variations.
The primary function of AEC is to eliminate manual exposure time settings by the radiographer.
Backup time for AEC should not exceed 150% of the expected manual exposure time.
Includes a backup timer to prevent excessive radiation exposure during AEC malfunctions.

Exposure Time Management

Proper use of density controls is essential when ionization chamber cells cannot be adapted for positioning.
The minimum response time for AEC is approximately 0.001 seconds.
Reducing mA allows for a longer AEC time during exposure.

Manual Exposure Controls

Require a technique chart and involve determining exposure factors based on part size or thickness.
AEC feature is inactivated under manual controls.

Collimator and Beam Restriction

Bottom Shutters: Reduce penumbra along the periphery of the x-ray beam.
Upper Shutters: Reduce off-focus (stem) radiation.
Positive Beam Limitation (PBL): Automatically collimate the beam to match IR size.
Provides some filtration of the x-ray beam, equating to 1 mm of aluminum.

Diaphragm and Cones

Aperture Diaphragm: A flat lead sheet with a central opening, attached to the x-ray tube port; the simplest beam-restricting device.

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Description

Test your knowledge on the components of radiographic units with these flashcards tailored for the ARRT exam. Each card features essential definitions and characteristics to help you understand different types of equipment used in diagnostic radiography.