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CHAPTER 3 EQUIPMENT OPERATION AND QUALITY CONTROL EXAMINATION REVIEW FOR RADIOGRAPHY Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Principles of Radiation Physics: X-ray Production • Primary requirements – Source of free electrons • Cathode (− charge) • Heated filament – Focusing of electrons – Acceleration of electrons • Applied kVp – Deceleration of electrons • Rotating tungsten anode (+ charge) • Focusing cup Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins 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) Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins 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. Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Fundamental Properties of Electromagnetic Radiation and X-ray Photons • Descriptive or controlling factors – Frequency – Wavelength – Velocity – Energy – Inverse square law Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Characteristics of the X-ray Beam • Descriptive or controlling factors – Quality • Voltage – Quantity • Current – Filtration – Target material – Voltage waveforms/generators Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Primary versus Remnant (Exit) Radiation • Primary radiation • Primary beam • Leakage radiation • Remnant or exit radiation Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Imaging Equipment: Automatic Exposure Control • Components – Ion chambers or sensors – Density controls • −2 to +2 – Backup timer Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Imaging Equipment: Circuit Components • X-ray tube – Produces x-rays • Transformers – Controls and varies voltage • Incoming current: 60 Hertz AC • Rectifers – Converts AC to DC • Generators – Single phase – Three phase – Each peak = one pulse Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Imaging Equipment: Accessory Devices • Beam restriction devices – Adjustable collimator • Grids – Stationary – Reciprocating (Bucky device) – Aperture diaphragm – Cones and cylinders Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Dedicated X-ray Equipment • Chest: freestanding system for upright imaging • Often incorporates – Automatic vertical tracking • Tomography: focuses on a single plane • Tube and IR move synchronously around a fulcrum – Automatic collimation Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Fluoroscopic Equipment • Used for real-time imaging • Components – X-ray tube • Conventional and digital systems available – Image intensifier • Fixed or mobile (Carm) systems – Display screen/monitor – Automatic brightness control – Recording device(s) Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Digital Imaging • Filmless equipment • Two types – Computed radiography (CR) – Digital radiography (DR) Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins Digital Imaging Quality Control: Artifacts • Types/causes – Debris/dust – Scratches – Incomplete erasure – Ghost images – Fog – Software Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins 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 Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins