CH 6 Xray Equipment 1313 physics

What are the 2 types of x-ray equipment?

diagnostic and therapeutic

What are the ranges for diagnostic (mA, seconds, kVp)?

- 10-1200mA

- 0.001-10 seconds

- 25-150 kVp

For fixed a tilting model tables, what's the ranges? (3)

-90/15

-90/45

-90/90

- trendelenburg tilt

Upright receptor units support and contain what?

- supports image receptor in a vertical orientation

- contain a Bucky assembly and may include AEC

What is the line current for USA?

60 cycle

What is the line current worldwide?

50 cycle

What is the line current for a 3 phase?

440-480V

Which type of power is the most inefficient in x-ray production?

Single-phase power- b/c touches zero

This type of power is most popular and widely available

Three-phase power (High Frequency)

Describes the flow that changes direction periodically

Alternating current (AC)

Is the unidirectional flow of electric charge

Direct current (DC)

Nearly all x-ray equipment operates on?

210-220 V

What is root mean square (rms)?

Refers to the most common mathematical method of defining the effective voltage or current of an AC wave

Which phase produces 100% ripple?

Single phase

Full wave-rectification is?

The most efficient, x-ray production occurs during this portion of the voltage waveform

multi-phase power

What is the most efficient type of electrical power?

Changes AC to DC

What does a rectifier do?

Main power switch:

an on-off switch for the unit connected to the facility's power supply

Line compensator:

device usually wired to the autotransformer that automatically adjusts the power supplied to the x-ray machine to 220 volts

Circuit breakers:

Protect against shirt circuits and electric shock

Autotransformer:

an adjustable transformer controlled by the kilovolt peak (kVp) selector on the operating console

Step up transformer:

increases voltage and decreases current

Timer circuit (exposure timer):

- located in this section because it is easier to control (turn on and off) a low voltage than a very high one.

- timer circuit variations include the synchronous timer and the electronic timer

What is a synchronous timer?

Drives a shaft of 60 revolution a minute

What is an electronic timer?

Most accurate, allows for intervals as small as 1 millisecond

Autotransformer:

- requires AC to operate: to induce voltage, generates magnetic flux, inducing electricity

- turns ratio determines how much voltage is stepped up

- voltage is being induced in the secondary coil which has more wires than the primary coil

mA meter:

a device placed in the secondary circuit that monitors x-ray tube current

Rheostat/ variable resistor/ mA selector

An adjustable resistor controlled by the mA selector on the operating console

Exposure timer: AEC

Works with the rheostat; together; they determine the quantity of electrons boiled off of the filament & available for x—ray production

Step-down transformer:

used in the filament circuit to increase the current by reducing the voltage that is applied to the filament

filament step-down transformer

Responsible for changing the amps to milliamps

Focal spot selector:

Controls spatial resolution/ recorded detail, and influenced by filament

Exposure switch/ Deadman Switch:

- closes circuit, located behind control window on generator console.

- located behind control window on generator console

Single-phase generator

This generator is least efficient and produced the highest patient dose

Full wave rectified:

- 2 pulses per Hz

- 120 pulses per second

- 100% voltage ripple

Full wave rectified with 6 diodes:

-6 pulses per Hz

-360 pulses per second

-Voltage ripple 13-25 percent (little more efficient)

Full wave rectified with 12 diodes:

- 12 pulses per Hz

- 720 pulses per second

- Voltage ripple 4-10 percent

High frequency generators: AC & DC power converters and inverters

- convert 60 cycle to kilohertz (kHz)

- full-wave rectified can produce 12-13 kHz waveform

- voltage ripple 1%

- most popular am common type of generator!!

- most efficient x-ray production!!!

(IMPORTANT)

What is used to rate generator output?

power rating (VA0.7=W

Falling load generators:

- the mA starts at the highest possible setting and "falls" throughout the exposure

Electronic timers

Which timer is most sophisticated?

Milliampere-second (mAs) timers

This timer is based upon a predetermined mAs value

AEC (Automatic Exposure Controls) also knows as phototimer or Automatic Exposure Devices

These timers terminate exposure based upon a predetermined exposure value and uses an ionization chamber?

Modern minimum reaction time

- 0.001 seconds

- 1/1000

What are ionization chambers used for?

For trunk, chest, abdomen, spine.

-radiolucent at correct kVp's

-typically have 3 detector positions

Backup time circuit

This should be set at 150% of anticipated manual technique

What is the maximum exposure per U.S public law?

600 mAs

-exposures >50 kVp