RT4MIDTERM REVIWER.pdf

RT4IMEQMA - MIDTERM MARY FAITH BAUTISTA, RRT 3 PRINCIPAL PARTS OF X-RAY IMAGING SYSTEM B. Floor-to-Ceiling support - has one single column with...

RT4IMEQMA - MIDTERM MARY FAITH BAUTISTA, RRT 3 PRINCIPAL PARTS OF X-RAY IMAGING SYSTEM B. Floor-to-Ceiling support - has one single column with rollers attached to each end, one on the ceiling 1. Operating Console/ Control Console mounted rail and other on the floor mounted. - also known as the low voltage section. C. Floor mount system - alternative for the column - allows the radtech to control the x-ray tube current and mount. voltage. D. Fluoroscopy - mounted underneath the radiographic Control console basic controls : table. Energize during fluoroscopy where the image a. On and off switch b. mAs selection c. kVp selection tower is locked into place. d. voltmeter e. exposure switch E. C- Arm - X ray tube are mounted on a support 2. High Voltage Generator - responsible for converting low shaped like C. Used as portable fluoroscopy units or in voltage from electric power company into a kilovoltage peak special procedures unit. waveform. F. Portable or Mobile machines - used to perform 3. X-ray tube - creates x-ray photons from electric energy radiography on patients that cannot be easily supplied by the x-ray generator. transported to the radiology department. - 30 to 50 cm long and 20 cm in diameter.  Quantity - refers to the number of x-rays or intensity of 2. Protective Housing - provide mechanical support to the the xray beam. x-ray tube, protects the x-ray tube from rough handling, - controlled by mAs ( directly proportional) guards the radtech against electric shock. - expressed in the unit of mR (milliRoentgen/ Roentgen). - reduces the amount of leakage radiation to less than 100 mR/hr at 1 meter.  Quality - refers to the penetrability of the x-ray beam. - controlled by kVp. Protective housing contains oil for : - expressed in kilovolt peak or HVL (half value layer). Electric insulator and thermal cushion  Autransformer - Varies or controls the voltage to 100-200V. 3. Glass Envelope - maintains a vacuum or empty space inside the x-ray tube.  Major or minor kVp - represents two separate series of - made up of Pyrex Glass. connection on the autotransformer. - located on the secondary side of AT. 2 INTERNAL STRUCTURES OF X-RAY TUBE  Line Compensator - design to supply a precise voltage. 1. Cathode - negative side of the x-ray tube. - located on the primary side of AT. - side where the electrons are released.  Pre-reading Voltmeter - allows the voltage to be 2 PARTS OF CATHODE monitored before the expoosure. A. Filament - releases electrons 3 PRINCIPAL PARTS OF HIGH VOLTAGE GENERATOR - made up of Thoriated tungsten. Usually about 2mm in diameter and 1 to 2 cm long. 1. High Voltage Transformer - design to provide high voltage to the x-ray tube; Step -up transformer. B. Focusing Cup - a metal cup where the filament is - controlled by kVp embedded. - Turns ratio : between 500:1 - 1000:1 2. Anode - positive side of the x-ray tube. 2. Filament Transformer - in-charged for increasing the current and intensity for the filament to be heated; Materials commonly used for anode : GraCoMo Step-down transformer. Graphite, Copper and Molybdenum - controlled by mAs. Copper is the most common of all 3 3. Rectifier - converts alternating current to direct current. 3 EXTERNAL STRUCTURES OF X-RAY TUBE 2 PARTS OF ANODE 1. Supporting Structure (6) A. Focal Spot - actual source of radiation. A. Ceiling support - consist of 2 sets of rails mounted to  Effective Focal Spot - focal spot that is projected to the ceiling directly over the radiographic table. patient and imaging receptor.  Small Focal Spot - used when better spatial resolution is required. (ranges from 0.1 mm - 0.5 mm) - This reviewer is for RT4IMEQMA students only - REFERENCE BOOK :RADTECH INTERGRALS  RT4IMEQMA - MIDTERM MARY FAITH BAUTISTA, RRT  Large Focal Spot - used when technical factors that 5 TYPES OF X-RAY TIMERS produce high heat are required. (ranges from 0.4 mm - to 1.2 mm) - Works under clock system MECHANICAL TIMERS - Used in portable and dental units B. Target - area of anode struck by the electrons or - Precision device radiation. SYNCHRONOUS - 1/17 msec, exposure time - made up of allow of tungsten and rhenium. TIMERS - Cannot be used for rapid serial exposure - Most complicated, accurate, Properties of a Tungsten as a target material : sophisticated  High atomic number - 74 ELECTRONIC TIMERS - Can be used for rapid serial  Thermal Conductivity - efficient in heat dissipation. exposure  High melting point - 3410 degree Celsius melting point. - product of mA and time - determines the number of x-rays 2 TYPES OF ANODE mAs TIMERS emitted - terminates the exposure when A. Stationary/Stator Anode - used in units that does the desired mAs is attained not require high tube and high power. - Device that measures the - commonly used in dental and portable units. AUTOMATIC quantity of radiation reaching EXPOSURE CONTROL / the image receptor. B. Rotating/Rotor Anode - used in producing high PHOTOTIMER - Terminates the exposure when intensity x-ray beams in a short time such as general the desired density is attained. x-rays. - speed rotation of anode ; 3400 rpm  Voltage Ripple - Another way to characterized voltage waveform.- Variation in peak voltage waveform Anode functions : Eletrical conductor, mechanical support for the  Single Phase Power = 100% voltage ripple target, thermal dissipator.  3 Phase, 6 pulse power = 13% voltage ripple  3 Phase, 12 pulse power = 4% voltage ripple  Thermionic Emission - the process of emission of  High Frequency Generator = less than 1% voltage electrons when the filament is heated. ripple  2200 -degree Celsius - melting point / temp. of the Main Advantage : the less the voltage ripples the greater filament. radiation quantity and quality.  Space Charge Effect - the phenomenon wherein electrons emitted by the cathode stays in front of the 3 TYPES OF RECTIFICATION filament. 1. Half-Wave Rectification  Direct Current, at 220 V - required by the c-ray machine - voltage is not allowed to swing negatively to operate. during the negative half of its cycle. - Contains at least 1-2 diodes.  Projectile Electrons - electrons traveling form cathode - 1⁄2 of AC waveform to anode constitute the x-ray tube current. - 60 pulse/second Tungsten vaporization with internal deposition 2. Self-Rectified - most common cause of tube failure. - X-ray tube serves as the vacuum tube rectifier. - Waveform is same as half-wave rectification.  kVp (kiloVolt peak) - energy that determines the 3. Full-Wave Rectification penetrating ability of the x-ray beam. - Contains at least 2- 4 diodes. kVp = patient body/part thickness (in cm) x 2 + machine - 120 pulses/second constant Main advantage : exposure time for any given technique is  mA (milliAmpere) - measures the intensity of the x-ray cut in half. beam and the number of x-ray photons. mAs = milliAmpere x time (in seconds) - This reviewer is for RT4IMEQMA students only - REFERENCE BOOK :RADTECH INTERGRALS  RT4IMEQMA - MIDTERM MARY FAITH BAUTISTA, RRT  Diodes - electronic device that contains 2 electrodes. C. 3 Phase, 12 Pulse Power - Its allows the current to flow on one direction. - it severely restricts current from flowing in the Heat Unit (HU) = (1. 41) kVp x mAs opposite direction. 3. House Cooling Chart - similar to anode cooling chart and is used in precisely All diode rectifiers has vacuum tubes called Valved the same way but for the housing of the tube. Tubes. Then, valved tubes has been replaced by SOLID STATE RECTIFIERS  Solid State Rectifier - smaller rectifiers, more reliable and have a longer life. - Selenium was the first material used. - Silicon is now the most common material.  Single Phase Power - Results in pulsating x-ray beam. - Cause by the alternate swing in voltage from 0 to maximum potential 120 times / second.  Three Phase Power - More efficient way to produce x-ray than single phase power. - Multiple voltage waveform are superimposed on one another. There can be either : A. 6 pulses per one sixtieth of a second B. 12 pulses per one sixtieth of a second POWER RATING FORMULA: A. 3 Phase Power & High Frequency Generator Power Rating (kW) = milliAmpere (mA) x kiloVolts (kV) 1000 B. Single Phase Power Power Rating = (0.7) milliAmpere (mA) x kiloVolts (kV) 1000 3 TYPES OF RATING CHARTS 1. Radiographic Rating Chart - it conveys which radiographic techniques are safe and which techniques are unsafe for x-ray tube operation. - most important chart. 2. Anode Cooling Chart - shows time required for heated anode to cool. - thermal energy is measured in heat units (HUs) or Joules (J) (in x-ray application only). - 350,000 maximum heat unit capacity. HEAT UNIT FORMULA A. Single Phase Power Heat Unit (HU) = kVp x mAs B. 3 Phase, 6 Pulse Power Heat Unit (HU) = (1. 35) kVp x mAs - This reviewer is for RT4IMEQMA students only - REFERENCE BOOK :RADTECH INTERGRALS