physics ch 5 part 2

Question 0

Be able to describe the cathode

Answer 0

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

Question 1

What does the cathode provide

Answer 1

The source of electrons needed for xray production

Question 2

What is a dual focus tube

Answer 2

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

Question 3

Be able to describe a filament

Answer 3

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

Question 4

Know what the filament affects on an image

Answer 4

Recorded detail

Question 5

Know what thermionic emission is

Answer 5

Boiling off electrons

Question 6

Describe the focusing cup

Answer 6

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

Question 7

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

Answer 7

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

Question 8

Know what happens when the exposure switch is first pressed

Answer 8

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

Question 9

Know what the second phase of operation initiates

Answer 9

The xray production process

Question 10

Know the three things needed to produce X-rays

Answer 10

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)

Question 11

Know the major causes of tube failure

Answer 11

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)

Question 12

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

Answer 12

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

Question 13

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

Answer 13

◾️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

Question 14

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

Answer 14

99%

Question 15

Know what the cooling charts were used for

Answer 15

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

Question 16

Know what the cooling charts are currently used for

Answer 16

Quality control tools to determine If protective circuits are functioning properly

Question 17

Know the 3 technical factors plotted on a tube rating chart

Answer 17

◾️kVp
◾️milliamperage
◾️exposure times

Question 18

Define heats units

Answer 18

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

Question 19

Know what anode cooling charts are used for

Answer 19

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

Question 20

Know the 3 guidelines and procedures used for extending tube life

Answer 20

⚫️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