6 Automatic exposure modes
86500-IMG rev 3
GE Healthcare
51
6.4
A
UTOMATIC
COMPRESSION
RELEASE
(A
UTO
R
EL
)
Automatic Compression Release is the default setting on Diamond and
will release the compression paddle after each exposure or in the event of
a power failure. You must decide whether or not you wish your Diamond
to release compression automatically after compression. The automatic
release is automatically switched off when Delta 32 or biopsy paddles are
inserted. If a power failure occurs while ‘Auto Rel’ is switched off, the C-
Arm remains compressed and compression paddle will not auto-release.
The Auto Release can be manually switched off and on with a function key
below Auto Rel text on Control Panel LCD-screen.
Fig 6.4.
The control panel screen with Auto Rel-text
6.5
A
UTO
P
OINT
AEC
DETECTORS
Diamond incorporates automatically or manually selectable detectors.
Diamond’s software control system can automatically determine the
most appropriate AEC detector location for you at each exposure,
depending upon the individual breast being examined. Each detector can
also be selected manually by the user by simply pressing the relevant
membrane button on the Detector Location Display that represents each
detector. The semicircle and oval graphics printed on the Diamond’s
compression paddle indicate the size and location of each detector.
Testing the AEC
1
Expose at 28 kV and 40mm acrylic
2
Develop the film
3
Measure the O.D.
6.6
S
ELECTION
OF
M
A
S
VALUE
During the exposure, the highest possible mA is automatically selected
(within the range described in the mAs selection table) and this enables
the minimum exposure time to be used. The AEC system terminates the
exposure when the correct amount of radiation has reached the film. The
exposure time range is from 0.02 sec. to 5 sec. when using the large focus
(Bucky or cassette tunnel exposures), and from 0.04 sec. to 10 sec. when
using the small focus (magnification exposures).
In manual exposure mode, the kV range is 20-39kV. In AEC mode the
range for Bucky is 23-35kV and for the magnification tunnel 25-35 kV. In
specimen mode, the kV range is 15-39kV.
Lowering mA for small breasts (from sw 1.02.1 and up)
When small breasts are examined, the O.D. may end up being too high.
This may happen if exposure time saturates (exposure time shorter than
0.05s cannot be achieved with AEC), but the tube current can be lowered
to 50%. Lower mA values can be used with Buckies and AEC mode only. If
you want to use low mA mode for low thicknesses, have your Service
Technician adjust preheat values for low mA for large focus (LF) and set
FOR
TRAINING
PURPOSES
ONLY!
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