priciples of imaging: charts

the amount of heat given off is expressed in...

heat units (HU)

number of HU produced depends on the...

type of generator and the exposure factors used

alternating current

alternating betwee positive and negative flow

xray generator wave forms

single phase recified current

3 phase 6 pulse wave form

3 phase 12 pulse current

high frequency wave form

(ordered in low frequency to high)

each type of generator produces...

different voltage wave form

ripple

fluctuation in voltage output

the higher the frequency the higher the ripple

tube heat load capacity

-every tube has a specific heat load capacity

-amount of heat tube can withstand w/o damage tube components

heat is produced according to:

technical factors selected

-kVp, mA, time

-focal spot size selected

small focal spot typically not used above

200 mA

generator type

-more powerful generator produces xrays more efficent

-also creates more heat units (typically 1.4 times more)

generator factor indicates ______

heat production

the more _______ the generator, the _____ the heat units produced within the tube during xray production

efficient

higher

equation for heat unit

HU= kVp x mA x time x generator factor

single phase unit

1

three phase 6 pulse

1.35

three phase 12 pulse

1.41

high frequency

1.45

3 types of rating charts

tube rating chart

anode cooling chart

housing cooling charts

tube rating chart

-determine technical factors that can be used without overloading tube

-any combinations of facotrrs at or under the curve is safe

tube chart

y axis

x axis

curved lines

kVp

time (sec)

mA

find intersection of kVp and time on graph

technical factors

miliamperage, kilovoltage, time

(most important things we set on control panel)

housing cooling charts (dont really focus on)

similar to anode cooling chart

anode will reach heat limits before housing

kVp on graphs is usually between

30-150 kVp

cooling anode chart

calculates the time it takes for the anode to cool from a given exposure or time it will take to cool off enough to make another exposure

anode cooling chart

y axis

x axis

curved line

total heat capacity

time (mins)

starting point HU to end time of complete cooling

equation/ calculating cooling chart

kVp x mA x time x general factor

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