Chapter 2 From Notes Flashcards
The filament is made of
coiled tungsten wire
Focusing Cup is made of
Molybdenum or Nickle
Anode is made of
(90%) Tungsten, (10%) Rhenium, embedded with Molybdenum and Graphite
In order to help xrays exit tube the anode is
beveled/angled
Why is Tungsten efficient at producing xrays?
High melting point
Atomic number 74
In Mammography what comprises 97% of the target
Molybdenum
Another purpose of anode is to ________________ away from tube so tube is not damaged
Dissipate Heat
The physical area that is bombarded by electrons during x-ray production
AFS
Actual Focal Spot
Tube housing is lined with ______ for additional shielding from leakage
Lead
The 1% x-ray beam is comprised of
Brehms and Characteristic
Brems above 70kVp
85-90% of primary beam
Brems below 70kVp
100% of beam
Projectile electrons interact with electrons from K or inner shell of atoms on anode
Production of Characteristic Radiation
Is Characteristic radiation produced below 70kV?
N0
above 70kV the amount of the primary beam that is characteristic is
10-15%
X-ray energy measured in
kiloelectron volts or kEv
The xray beam is heterogeneous or polyenergetic
emission spectrum
Positive pressure switch in fluro
Deadman’s Switch
Filament current operates at _______amps & about _______volts
3-5amps and about 6-12volts
Frequency and wavelength are _________ proportional
Inversely
Electron cloud in front of filament
Space charge
Tendency of space charge to not allowed more electrons to be boiled off. Focusing cup forces __________ to stay together.
Space Charge Effect
Flow of electrons from cathode to anode displays on mA meter when exposure takes place
Tube Current
Controls patients dose.
mA
Controls grey scale
kV
Long scale, low contrast, more colors, decreased patient dose, wide latitude, increased scatter
High kV
Increases volts and decreases amps to produce kilovoltage
Step-up transformer
The types of transformers
- Single phase
- Three phase
- High frequency
Decreased ripple effect=
Increased efficiency
“More fifty shades of grey”=
Great penetration
Used to measure tube current or number of electrons flowing per unit time between cathode and anode
Milliamperage
Density=
receptor exposure
Determines length of time that x-ray tube produces x-rays
Exposure time
Exposure time X mA=
mAs
Measured directly under anode targer
EFS
Effective Focal Spot
Large FS can withstand heat produced by large exposures
100 mAs
Small FS gives what?
Better image quality/Detail
The SMALLER the anode angle, the smaller the _______________
EFS
Effective Focal Spot
**The PROJECTED of EFS is ____________ than the AFS
SMALLER
Too high of an mAs with too small of a FS.
Affects detail and spatial resolution
BLOOMING
XRays are stronger on which side of tube?
Cathode
Put thickest part of anatomy at what side of tube?
Cathode
FAT-CAT
Three things to enhance Anode Heel Effect
- Steep/small anode angle
- Short SID
- Long IR
Filtering removes what kind of wavelengths?
Maximum
Inherent=
Glass envelope
Oil
Mirror
