physics ch 5 part 2 Flashcards Preview

spring 2015 > physics ch 5 part 2 > Flashcards

Flashcards in physics ch 5 part 2 Deck (21)
Loading flashcards...
0

What does the cathode provide

The source of electrons needed for xray production

1

Be able to describe the cathode

Made up of the filaments and the focusing cup and is connected to two different parts of the xray circuit

2

What is a dual focus tube

General purpose tubes have two filaments represented by the large and small focal spot options on the operating console

3

Be able to describe a filament

A coil of wire usually 7-15mm long and 1-2mm wide. They are usually made of tungsten with 1% - 2% thorium added

4

Know what the filament affects on an image

Recorded detail

5

Know what thermionic emission is

Boiling off electrons

6

Describe the focusing cup

Made of nickel and surrounded each filament on its back and sides leaving the front open and facing the anode target

7

Know what determines how well the cathode focuses the electrons on the target

The size, shape, and charge of the focusing cup as well as how the filaments are designed and placed

8

Know what happens when the exposure switch is first pressed

Some of the electricity is diverted to the induction motor of the X-ray tube to bring the rotor up to speed

9

Know what the second phase of operation initiates

The xray production process

10

Know the three things needed to produce X-rays

1. Large potential difference to give kinetic energy to the filament electrons (kVp setting)
2. A vehicle on which kinetic energy can ride (quantity of electron provided by mAs)
3. A place for interaction (the target of the anode)

11

Know the major causes of tube failure

Frequent use of very high or maximum exposure factors, use of lower but very long exposure factors, overloading the filament(prolonged excessive heating caused by prepping the rotor unnecessarily or arching from the filament)

12

Know the built in methods of the tube that help dissipate heat

Oil bath and cooling fans, rotating anodes, heat-tolerant materials, radiational cooling of anode

13

Know the three processes of heat transfer within the X-ray tube

◾️conduction of heat by heat tolerant materials
◾️radiation of heat energy from the anode to the oil bath
◾️convection of heat into the Room by the cooling fans

14

Know how much of the actual xray production is actually converted into heat

99%

15

Know what the cooling charts were used for

To determine cooling time needed before continued operation or to prevent exceeding maximum heat loads

16

Know what the cooling charts are currently used for

Quality control tools to determine If protective circuits are functioning properly

17

Know the 3 technical factors plotted on a tube rating chart

◾️kVp
◾️milliamperage
◾️exposure times

18

Define heats units

A measure of the amount of heat stored in a particular device

19

Know what anode cooling charts are used for

To determine the time it takes for the anode to cool based on the factors given

20

Know the 3 guidelines and procedures used for extending tube life

⚫️the warmup steps specific to the unit should be followed completely and routinely
⚫️do not prep rotor excessively
⚫️do not routinely use extremes of exposure factors