the completion of the elapsed preset time. Re-initiation
of the fluoroscopic exposure without resetting the timer
shall restart the audible warning (Reference #l).
Older.
non-certified units and some certified units may termi-
nate the exposure as an alternate to the audible warning.
The operation
of the timer
should be checked.
and audible warning
One should verify that the timer
activates the signal (or shuts off the-radiation) at the
termination of the preset time. Since this
timer may be
used to measure the total fluoroscopic exposure time per
case,
the radiologic physicist should verify the elapsed
exposure time accuracy
of the timer (exposure
time vs
indicated time), if exposure time is indicated.
II-4. Lead Protective Devices
Three types of lead protective devices are unique to
fluoroscopic equipment.
A lead drape hanging from the
fluoroscopic tower or other image intensifier support
intercepts scatter radiation from-the patient.
It should
be in good condition.
The operator should be able to
move it so it can be positioned between the operator and
patient at all times. A lead drape normally is not found
in special procedure rooms because its presence might
violate sterile fields on the surface of the patient.
The shield of the slot for the cassette holder is a
second type of protective device; it intercepts leakage
radiation from under table x-ray
tubes.
The Bucky slot
shield may consist of folding steel arms, a hinged steel
door, and/or a lead or steel erectable panel. Verify
that it is operating properly.
One or more of these
designs may be found on the 'same unit.
The table-end shield is a third type of protective
device which intercepts leakage radiation. While newer
fluoroscopic tables have end shields, some older units
may not because they
are modified radiographic
tables.
The table end shields may simply be the steel covers of
the table skirt panels.
II-5. Minimum Source to Skin Distance (SSD)
A minimum allowed Source
focal spot to
to Skin Distance (SSD,
skin
distance) has been
established
(Reference #l) within Federal
Standards to minimize
entrance skin exposure during fluoroscopic examinations.
The minimum SSDs are:
(a) Stationary fluoroscopes - 38 cm (15")
(b) Mobile fluoroscopes - 30 cm (12")
"Stationary"
means any fixed installation..
Thus, the 38
cm minimum SSD applies to remote control over-table x-ray
tube fluoroscopic systems with or without tomographic
23
Manymanuals.com
Manymanuals.de
Manymanuals.fr
Manymanuals.it
Manymanuals.pl
Manymanuals.cz
Manymanuals.es
Manymanuals-pt.com
Comentários a estes Manuais