2. Bucky slot cover
During fluoroscopy the Bucky tray is
moved to the end of the table
This leaves an opening in the side of the
table about 5cm
Approximately at what level is the bucky?
3. Bucky slot cover
• The opening should
automatically be
covered with at least
0.25 mm Pb equiv..
5. The Control Console
• The control console is
device that allows the
technologist to set
technical factors (mAs
& kVp) and to make
an exposure.
• Only a legally
licensed individual is
authorized to
energize the console.
6. Control Panel
• All the electric circuits connecting the meters
and controls are at low voltage to minimize the
possibility of shock.
7. Operating Console
Controls:
Line Compensation, kVp, mA and time
Quantity = # of x-rays
Milliroentges (mR) or (mR/mAs)
Quality = the pentrability
Kilovolts peak (kVp)
8. Operating Console has
meters to measure
kVp, mA, & exposure time
Modern units only display mAs
Units with ACE’s will have a separate
meter for mAs
10. AEC
Automatic Exposure Control
Uses an ionization chamber
Technologist sets kVp, mA, back-up
time & sensors
Exposure terminates the IR has proper
OD
Patient positioning must be absolutely
accurate
12. APR
Anatomically Programmed Radiography
(Ch 15)
Radiologic Technologist selects on the
console a picture or a written
description of the anatomic part to be
imaged and the patient body habitus
A computer selects the appropriate
kVp and mAs.
13. APR
The whole process uses an AEC
Precise patient positioning over the
phototiming sensor is critical
20. Line Compensation
Most imaging systems are designed to operate
on 220 V. (some 110 V or 440 V)
However power from the wall is not always
accurate continuously
21. Line Compensation
Wired to the autotransformer is the line
compensator
Designed to maintain the accurate
voltage required for consistent production
of high-quality images
Today’s line compensators are automatic
and are not displayed on the control panel
23. Autotransformer
The power for the x-ray imaging system
is delivered first to the autotransformer
The autotransformer works on the
principle of electromagnetic induction
It has one winding and one core
There are a number of connections along
its length
24. Autotransformer
• A’s = primary
connections &
power into the
transformer
• Other connections
allow for variations
of voltages
25. Autotransformer
Is designed to step up voltage to about
twice the input voltage value
The increase in voltage is directly related
to the number of turns
27. X-ray tube current or
Filament circuit
A separate circuit crossing from cathode
to anode
Measured in milliampers (mA)
What determines how many x-rays are
created?
28. X-ray tube current or
Filament circuit
# of e- is determined by the temperature
of the filament. The hotter the filament
the more e-
Are their any limiting factors to thermionic
emission?
33. Exposure Timers
The timer circuit is separate from the other
main circuits of the imaging system
It is a mechanical or electronic device
whose action is to “make” and “break” the
high voltage across the x-ray tube
This is done on the primary side of the high
voltage transformer.
34. mAs Timers
Monitors the product of mA and exposure
time
Terminates the exposure when the
desired mAs value is reached
Located on the secondary side of the
high-voltage transformer since actual
tube current must be monitored
35. mAs Timers
Designed to proved the highest mA for
the shortest exposure
Modern X-ray machines have falling-load
generator
Automatically adjusts to the highest mA at
the shortest exposure time possible
36. AEC Control
AEC measure the quantity of radiation
reaching the IR
Automatically terminates when the IR has
received enough radiation for desired OD
Two types are common
37. Flat, parallel plate
ionization chamber
Located between the patient and the IR
Made radiolucent
Ionization w/in the chamber creates a
charge; calibrated to produce a given OD
on the IR
38. Photomultiplier (Photodiode)
detector assembly
Located behind the IR
Contains a fluorescent screen and a
photomultiplier
The photomultiplier detects the light from
the fluorescent screen until the desired
OD on the IR is reached terminating the
exposure
39.
40. AEC’s
Upon instillation must be calibrated by
the service engineer
Technologists selects the desired OD
which then sets the mA & kVp
41. AEC’s
A back up timer usually automatically set
to prevent over exposure if the AEC fails
Should be set to 1.5 times the expected
exposure time Why?
When the ionization chamber or
photodiode reaches the preset level, a
signal is returned to the operating
console to terminate the exposure
42. High-Voltage Generator
Responsible for increasing the output
voltage from the autotransformer to the
kVp necessary for x-ray production
3 parts: High-voltage transformer (step-
up), filament transformer (step-down) and
rectifiers
43. High voltage transformer
Or step up transformer
Connected to the Major and Minor kVp
selector
Increases the volts from the
autotransformer to kilovolts
45. Voltage Rectification
Converts AC to DC current
During the negative cycle current can
only flow from anode to cathode
E- must travel cathode to anode – DC
current keeps e- traveling in the correct
direction, cathode to anode
Attracted to the positive anode
49. High-Voltage Generation – converts
220 volts of AC to kilovolts of DC
The generator is a FIXED component of
the imaging system, not under the
control of the technologist
Three basic types: single phase, three
phase, and high frequency
The generator affects the quality and
quantity of photons produced
