CHAPTER 6 THE X-RAY BEAMSPECIFIC OBJECTIVES NOTED IN THIS

POWER POINT BEGIN ON PAGE 110-117.

• 1) Synchronous-min time is 1/60. Increase in equal multiples

• 2) Electronic-most accurate/controlled by microprocessor

• Where are 1 and 2 located in the circuit?• mAs time and falling load generator-let’s

discuss this!• AEC

Four timers

• WHAT IS THE PURPOSE OF AN AEC?

• HOW DO YOU USE THEM WHEN POSITIONING?

• CHAMBERS VS. PHOTOMULTIPLIERS

• Can they produce the same density of radiograph for any size patient?

AEC

• Waits for a charge• Sequence

– X-ray– Patient– Ion chamber– IR

• Collects a charge via light

• Sequence– X-ray – Patient– Special cassette– photodiode

Ion chamber vs photomultiplier or photodiode

• What do you remember?High Voltage Transformer

• Unrectified

• Half wave rectified

• Fully rectified

RECTIFICATION

• Single

• Three phase

• Three phase/6 pulse

• Three phase/12 pulse

• High Frequency• How do these phases

impact technique??

• 100%

• 13 or 14%

• 3 or 4%

• Less than 1%

Phases Voltage Ripplepage 30 Fauber figure 2-12

• UNIT OF MEASUREMENT OF POWER IS WATTS• AMPS MEASURES THE QUANTITY OR QUALITY?• Volts measures the ________________________ • Amps=current• Volts = potential

• Try this problem: If your kitchen is on a 25 amp circuit breaker and 110 volts is the available voltage what is the maximum watts this circuit can handle?

• ON TO CHAPTER SEVEN!!

POWER RATING

• REVIEW THE PROTECTIVE HOUSING• Let’s dissect the cathode• What happens at the cathode?• Focusing cup

– Imbedded in cathode– Two (page 15 in fauber, figure 2-1)– Confines the electron beam

• Grid controlled tubes• Allows for tube to be turned off and on

quickly• Space charge and space charge effect

– High mAs and low kVp can be space charge limited..why?

CHAPTER SEVEN

• Three functions of the anode -What do you know already about the anode

• The target

• What does the rotor do?

• Note: please skip induction motors at this time

The Anode

• Focal spot and target angle (Fauber pg 16 figure 2-2)

• The smaller focal spot– More concentration of heat– Better detail– Usually located in the smaller angle

• Large focal spot– Less concentration of heat– Less detail– Larger angle– Page 25 Fauber, figure 2-10

Focal spot, line focus principle and anode heel effect

• Effective focal spot size is always smaller than the actual focal spot size

• Fauber-pg 34 figure 2-13 and pg 35 figure 2-14

Line Focus Principle

• Bushong pg 130, pg 7-20• The heel effect is more or less with a

greater angle?• Which side has greatest intensity?• Off Focus radiation

Anode Heel effect

• Tube rating charts• Heat units• Anode cooling charts

How is heat dissipated in the tube?