CHAPTER 3 EQUIPMENT OPERATION AND QUALITY CONTROL EXAMINATION REVIEW FOR RADIOGRAPHY

ARRT Certification Exam: Equipment Operation and Quality Control Twenty-two questions (11% of the examination) Three primary sections Principles of Radiation Physics Imaging Equipment Quality Control of Imaging Equipment and Accessories

Principles of Radiation Physics: X-ray Production Primary requirements Source of free electrons Cathode (− charge) Heated filament Focusing of electrons Focusing cup Acceleration of electrons Applied kVp Deceleration of electrons Rotating tungsten anode (+ charge)

Principles of Radiation Physics: X-ray Production—(cont.) The x-ray tube produces x-rays due to the conversion of high-speed electrons (kinetic energy) into electromagnetic energy (x-ray photons, heat, and light). X-ray tube efficiency: 1% x-ray production 99% of energy produced: heat Two primary atomic interactions occur in the x-ray tube Bremsstrahlung (85% of radiation produced) Characteristic (15% of radiation produced)

Bremsstrahlung Radiation Projectile electron loses kinetic energy (KE) as it interacts with the nuclear field of a target atom. Deceleration occurs due to a change in direction of the projectile electron. Lost KE converted to x-ray photons Produces varying energy levels and wavelengths of x-ray photons

Characteristic Radiation Projectile electron ionizes a k-shell electron of a target atom. Opening in K-orbit replaced by an outer shell electron (transition) Characteristic radiation photon released Produces fixed energy x-ray photons In a tungsten target, no characteristic radiation will be produced under 69 kVp.

Fundamental Properties of Electromagnetic Radiation and X-ray Photons Descriptive or controlling factors Frequency Wavelength Velocity Energy Inverse square law

Characteristics of the X-ray Beam Descriptive or controlling factors Quality Voltage Quantity Current Filtration Target material Voltage waveforms/generators

Primary versus Remnant (Exit) Radiation Primary radiation Primary beam Leakage radiation Remnant or exit radiation

Imaging Equipment: Operating Console Power: (on/off) kVp control Provides E for beam penetration mA control Controls quantity or intensity of x-ray beam Timer Used in conjunction with mA to control the intensity of x-ray beam

Imaging Equipment: Automatic Exposure Control Components Ion chambers or sensors Density controls −2 to +2 Backup timer

Imaging Equipment: Circuit Components X-ray tube Produces x-rays Transformers Controls and varies voltage Incoming current: 60 Hertz AC Each peak = one pulse Rectifers Converts AC to DC Generators Single phase Three phase

Imaging Equipment: Accessory Devices Beam restriction devices Adjustable collimator Aperture diaphragm Cones and cylinders Grids Stationary Reciprocating (Bucky device)

Dedicated X-ray Equipment Chest: freestanding system for upright imaging Often incorporates Automatic vertical tracking Automatic collimation Tomography: focuses on a single plane Tube and IR move synchronously around a fulcrum

Fluoroscopic Equipment Used for real-time imaging Conventional and digital systems available Fixed or mobile (C- arm) systems Components X-ray tube Image intensifier Automatic brightness control Display screen/monitor Recording device(s)

Digital Imaging Filmless equipment Two types Computed radiography (CR) Digital radiography (DR)

Digital Imaging: Computed Radiography (CR) Components and image acquisition Reusable imaging plate Photostimulable phosphor (PSP) Stores latent image Laser reader Stimulates phosphor to release light photons Monitor Displays image Fluorescent light Erases PSP

Digital Imaging: Digital Radiography (DR) Components and image acquisition (two types) Direct panel DR (amorphous selenium) Converts x-ray photons directly to an electric signal, sent to a computer Indirect panel DR (amorphous silicon) Converts x-ray photons to light to an electric signal, sent to a computer

Quality Control (QC) of Equipment and Accessory Devices Beam restriction devices QC tests X-ray/light field alignment: ±2% of SID Central ray alignment Shielding QC tests (aprons, gloves, and gonadal shields) Visual inspection for tears or cracks Fluoroscopy check for holes or cracks

Digital Imaging Quality Control: Artifacts Types/causes Debris/dust Scratches Incomplete erasure Ghost images Fog Software

Digital Imaging: Monitor Quality Control Checked monthly or quarterly SMPTE (Society of Motion Picture and Television Engineers) test pattern Tests monitor for Sharpness Distortion Luminance