Term
| external structure of the xray tube |
|
Definition
support structure
protective housing
enclosure |
|
|
Term
| three types of suppport systems |
|
Definition
ceiling support system
floor to ceiling support
c- arm support |
|
|
Term
|
Definition
most common
two sets of perpendicular ceiling mounted rails |
|
|
Term
|
Definition
most commonly used in angiointerventional systems
ceiling mounted and flexible
also l arm and u arm |
|
|
Term
|
Definition
| must not exceed 100 mr/hr at 1 m per federal standards |
|
|
Term
|
Definition
10 in x 6 in x 2 in
increases efficiency
prevents collision of high speed electrons with gas molecules
prevents oxidation of filament |
|
|
Term
|
Definition
for mammography
uses special metallic beryllium window to avoid attenuating low energy photons |
|
|
Term
|
Definition
composed of photons not produced at the focal spot
causes ghosting of structures
can contribute as much as 25-30% of total primary beam
lower energy |
|
|
Term
|
Definition
part of cathode that emits electrons resulting in a tube current
interchangable with cathode
made of thoriated tungsten, rhenium or molybdenum
.1-.2 mm in diameter, coil is 1-2 mm wide and 7-15 mm long |
|
|
Term
|
Definition
metal shroud negatively charged surrounding filament that condenses the electron beams to a small area in anode
usually made of molybdenum or nickel |
|
|
Term
|
Definition
| electron cloud near filament |
|
|
Term
|
Definition
| region of anode struck by electrons emmitted in the filament |
|
|
Term
|
Definition
double filament
differ in size, producing focal spots two different sizes
a low voltage high filament current is applied, about 10 volts and 3-5 amps |
|
|
Term
|
Definition
| stationary coil windings located in the protective housing, but OUTSIDE the glass envelope |
|
|
Term
|
Definition
effective target area
focal spot projected onto patient and IR
much smaller than actual focal spot |
|
|
Term
|
Definition
also called ACTUAL focal spot
region of anode where electrons interact to produce xrays
as seen from cathode end |
|
|
Term
|
Definition
absorption of xrays in heel of target resulting in reduced xray intensity
smaller the angle, the larger the heel effect |
|
|
Term
|
Definition
design in xray tube targets to allow a large area for heating while maintaining a small focal spot
by angling the target towards the film/patient, the projected area is smaller and sharper than the target area |
|
|
Term
|
Definition
target consists of tungsten-alloy metal embedded in a copper anode
called focus or focal spot |
|
|
Term
|
Definition
a graphite disc with tungsten alloyed with rhenium focal track at its periphery
molybdenum and graphite layered underneath tungsten
driven by induction motor |
|
|
Term
|
Definition
allows anode to rotate inside glass envelope with no mechanical connection to the outside
works on electromagnetic induction, similar to that for a transformer and on Lenzs law |
|
|
Term
| parts of an induction motor |
|
Definition
1. stator assembly (located outside glass envelope)
2. rotor assembly
3. anode stemp/ neck |
|
|
Term
|
Definition
| 3000-3600 rpm for single phase units |
|
|
Term
|
Definition
| used to obtain fire radiographic definition |
|
|
Term
|
Definition
| can handle heavier loading in shorter exposure time |
|
|
Term
|
Definition
located on beveled face of anode
allows for high tube mA/ higher tube ratings
special tubes can tolerate current as high as 1000 mA for very short exposures operating on 3 phase current |
|
|
Term
|
Definition
| target area= Length x width |
|
|
Term
|
Definition
| target area= length x 2xpixr |
|
|
Term
|
Definition
degree of beveling=target/anode angle
steeper angle= diminished EFS and FS |
|
|
Term
|
Definition
| xray tubes have EFS of .3mm-3.0mm and target angles of 7-18 degrees |
|
|
Term
|
Definition
| greatest along the anode side of beam |
|
|
Term
| advantages of heel effect |
|
Definition
when shooting chests, cathode towards feet
in abdominal, cathode towards head
also applicable in lat t spine, AP femur, and RAO sternum |
|
|
