CHAPTER 6 THE X-RAY BEAM
SPECIFIC OBJECTIVES NOTED IN THIS POWER
POINT BEGIN ON PAGE 110-117.
Four timers
• 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
AEC
• 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?
Ion chamber
• Waits for a charge
• Sequence
–
–
–
–
X-ray
Patient
Ion chamber
IR
vs photomultiplier or
photodiode
• Collects a charge via
light
• Sequence
–
–
–
–
X-ray
Patient
Special cassette
photodiode
High Voltage Transformer
• What do you remember?
RECTIFICATION
• Unrectified
• Half wave rectified
• Fully rectified
Phases
Voltage Ripple
page 30 Fauber figure 2-12
• Single
• 100%
• Three phase
• Three phase/6 pulse
• 13 or 14%
• Three phase/12 pulse
• 3 or 4%
• High Frequency
• How do these phases
impact technique??
• Less than 1%
POWER RATING
•
•
•
•
•
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!!
CHAPTER SEVEN
•
•
•
•
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?
The Anode
• 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
Focal spot, line focus principle and anode heel
effect
• 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
Line Focus Principle
• 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
Anode Heel effect
•
•
•
•
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
How is heat dissipated in the tube?
• Tube rating charts
• Heat units
• Anode cooling charts
0
