Nt1310 Final Exam
1. List the components of the x-ray generating system and the primary functions of each. a. Line compensator- measures the voltage provided to the x-ray imaging system and adjust that voltage to precisely 220 V. input voltage can vary up to 5%. b. Autotransformer- is designed to supply precise voltage to the primary side of high voltage transformer and to the filament circuit. c. kVp controls- by selecting the major or minor kVp controls, a more precise kilovolt peak is provided. kVp major changes secondary side connection on autotransformer to 10-20 turns. kVp minor changes secondary side connection on autotransformer to 1-2 turns. The kVp meter connected to the output terminals of the autotransformer reads voltage not kV. The pre-reading meter voltage is also monitored continuously.
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d.
mA controls- mA is the number of electrons crossing from cathode to anode (tube current). It is determined by the filament temperature. Filament temperature is controlled by the filament current. As the temperature increases, thermionic emission increases. The tube current is controlled by the filament circuit which the connection on the autotransformer provides voltage to the filament circuit. The mA selector is a resistor bank or rheostat (variable resistor). This transformer increases or decreases voltage. e. Filament Transformer- a step down transformer that is located between mA selector and filament. It increases the current to heat the filament and decrease voltage. The mA selector provides precise current to the step down transformer. f. Exposure timers- a timer circuit on the primary side of high voltage transformers. There are 4 types that are controlled by the technologist the mechanical; synchronous- timed off of # of cycles; electric- can do less than 1/60 s; mAs- on secondary side of high voltage transformer. There is one that is automatic, the AEC (phototimer) which selects the
mAs. g. High voltage generator- has three main parts: high-voltage transformer, filament transformer, and rectifiers. It is usually immersed in oil to prevent electric shock and dissipate heat. h. High voltage transformer- a step up transformer that steps up voltage to kilovoltage. It only functions on AC not DC. i. Rectifiers- converts AC to DC. It requires DC so the electrons can accelerate from cathode to anode only. The rectifier is an electronic device that allows the electrons to flow in 1 direction. It is usually accomplished with diodes.
2. List the components of the main circuitry and what this circuitry mainly adjusts. a. Line compensator b. Autotransformer c. kVp controls d. High voltage transformers e. Rectifiers f. Tube
This circuit mainly modifies incoming voltage to produce x-rays. 3. List the components of the filament circuitry and what this circuitry mainly adjusts. a. Line compensator b. Autotransformer c. mAs selector d. Filament transformer e. Filament
This circuit produces thermionic emission at the filament on the cathode side. 4. Describe the electron target interactions.
Electrons that are in motion make up the tube current. There are two types of electron target interactions: Heat production and x-ray production. X-ray production is either characteristic or bremsstrahlung. Heat and characteristic x-rays results from projectile electrons interacting with the target atom electrons. Bremsstrahlung x-ray results from projectile electron interacting with target atom’s nuclear field.
Heat is the most common electron target interaction is over 99% of projectile kinetic energy is converted to heat. The constant excitation and return of outer-shell electrons are responsible for most of the heat generated in the anodes of x-ray tubes.
Characteristic x-ray depends on target material. It is an ionizing event that results when electron target interaction is violent enough to ionize an atom by removing an inner shell electron. Projectile electron from filament knocks out inner shell electron of target atom -> atom is ionized -> outer shell electron fills void -> produces x-ray photon with energy=difference in binding energies. Projectile electron can still have subsequent reactions until it loses kinetic energy.
Bremsstrahlung x-ray is the most common x-ray produced. It is a nonionizing event where a projectile electron can lose its kinetic energy if it interacts with the nuclear field of a target atom. The kinetic energy of the projectile electron is converted into electromagnetic energy. Projectile electron is influenced by the nuclear field -> electron slows and turns -> lost kinetic energy that is converted into x-ray. A projectile electron loses its energy by being slowed by force of attraction. It can lose some, all, or nearly none of its energy. If electron loses no energy, it didn’t interact. It also can keep interacting until it loses kinetic energy.
5. List the factors that affect quantity and describe how affects it. a. mAs- directly proportional. Double the mAs=double quantity. b. kVp- quantity varies rapidly as kVp changes. Quantity is proportional to kVp2. Theoretically increasing kVp by 40% will double intensity. Clinically increasing kVp by 15% will double OD. c. Distance-quantity varies inversely with the square of the distance. The square law states that as SID increases then mAs needs to be increased by SID2 to maintain OD. d. Filtration- reduces quantity because it absorbs the low energy photons it also reduces image contrast because of beam hardening. Beam hardening increases the number of high energy x-rays in the beam by removing the lower energy nonpenetrating x-rays
6. List the factors that affect quality and describe how affects it. a. kVp- as kVp increases, quality increases. It increases the penetrability of the beam. b. Filtration- quality increases the penetrability of the beam because filtration removes low energy x-rays
7. List the x-ray interaction with matter starting with lowest to highest.
Coherent -> Compton -> Photoelectric -> Pair Production -> Photodisintegration
d.
mA controls- mA is the number of electrons crossing from cathode to anode (tube current). It is determined by the filament temperature. Filament temperature is controlled by the filament current. As the temperature increases, thermionic emission increases. The tube current is controlled by the filament circuit which the connection on the autotransformer provides voltage to the filament circuit. The mA selector is a resistor bank or rheostat (variable resistor). This transformer increases or decreases voltage. e. Filament Transformer- a step down transformer that is located between mA selector and filament. It increases the current to heat the filament and decrease voltage. The mA selector provides precise current to the step down transformer. f. Exposure timers- a timer circuit on the primary side of high voltage transformers. There are 4 types that are controlled by the technologist the mechanical; synchronous- timed off of # of cycles; electric- can do less than 1/60 s; mAs- on secondary side of high voltage transformer. There is one that is automatic, the AEC (phototimer) which selects the
mAs. g. High voltage generator- has three main parts: high-voltage transformer, filament transformer, and rectifiers. It is usually immersed in oil to prevent electric shock and dissipate heat. h. High voltage transformer- a step up transformer that steps up voltage to kilovoltage. It only functions on AC not DC. i. Rectifiers- converts AC to DC. It requires DC so the electrons can accelerate from cathode to anode only. The rectifier is an electronic device that allows the electrons to flow in 1 direction. It is usually accomplished with diodes.
2. List the components of the main circuitry and what this circuitry mainly adjusts. a. Line compensator b. Autotransformer c. kVp controls d. High voltage transformers e. Rectifiers f. Tube
This circuit mainly modifies incoming voltage to produce x-rays. 3. List the components of the filament circuitry and what this circuitry mainly adjusts. a. Line compensator b. Autotransformer c. mAs selector d. Filament transformer e. Filament
This circuit produces thermionic emission at the filament on the cathode side. 4. Describe the electron target interactions.
Electrons that are in motion make up the tube current. There are two types of electron target interactions: Heat production and x-ray production. X-ray production is either characteristic or bremsstrahlung. Heat and characteristic x-rays results from projectile electrons interacting with the target atom electrons. Bremsstrahlung x-ray results from projectile electron interacting with target atom’s nuclear field.
Heat is the most common electron target interaction is over 99% of projectile kinetic energy is converted to heat. The constant excitation and return of outer-shell electrons are responsible for most of the heat generated in the anodes of x-ray tubes.
Characteristic x-ray depends on target material. It is an ionizing event that results when electron target interaction is violent enough to ionize an atom by removing an inner shell electron. Projectile electron from filament knocks out inner shell electron of target atom -> atom is ionized -> outer shell electron fills void -> produces x-ray photon with energy=difference in binding energies. Projectile electron can still have subsequent reactions until it loses kinetic energy.
Bremsstrahlung x-ray is the most common x-ray produced. It is a nonionizing event where a projectile electron can lose its kinetic energy if it interacts with the nuclear field of a target atom. The kinetic energy of the projectile electron is converted into electromagnetic energy. Projectile electron is influenced by the nuclear field -> electron slows and turns -> lost kinetic energy that is converted into x-ray. A projectile electron loses its energy by being slowed by force of attraction. It can lose some, all, or nearly none of its energy. If electron loses no energy, it didn’t interact. It also can keep interacting until it loses kinetic energy.
5. List the factors that affect quantity and describe how affects it. a. mAs- directly proportional. Double the mAs=double quantity. b. kVp- quantity varies rapidly as kVp changes. Quantity is proportional to kVp2. Theoretically increasing kVp by 40% will double intensity. Clinically increasing kVp by 15% will double OD. c. Distance-quantity varies inversely with the square of the distance. The square law states that as SID increases then mAs needs to be increased by SID2 to maintain OD. d. Filtration- reduces quantity because it absorbs the low energy photons it also reduces image contrast because of beam hardening. Beam hardening increases the number of high energy x-rays in the beam by removing the lower energy nonpenetrating x-rays
6. List the factors that affect quality and describe how affects it. a. kVp- as kVp increases, quality increases. It increases the penetrability of the beam. b. Filtration- quality increases the penetrability of the beam because filtration removes low energy x-rays
7. List the x-ray interaction with matter starting with lowest to highest.
Coherent -> Compton -> Photoelectric -> Pair Production -> Photodisintegration