MTR 221 ACS - MTR 221 ACS DHHS
MANUALE ISTRUZIONI / INSTRUCTION MANUAL
C
ALIBRATION
36
Model R 221 ACS - R 221 ACS DHHS
MTR
2
21
ACS
-
MTR
2
21
AC
S DHH
S - Cali
bration
• For required values is referred to the System Reference Manual. However, the values L1 +
L2 and W1 + W2 shall NEVER exceed 2 cm (representing 2% of the SID).
• Note the measured values in Chart below.
• Repeat preceding steps with small focus selected.
Collimator to Focal Spot Alignment (Primary Shutter Cut-Off)
Inspect the four images of the four collimator shutters which form the edges of the x-ray field.
A definitely indistinct edge indicates that the primary shutter, close to the focal spot, is the one
forming the line, rather than the outermost shutter.
To correct the condition, use the four mounting/centering adjustment screws to shift the
collimator in the direction of the indistinct line. Repeat the test film exposure after making the
adjustment.
L
IGHT
F
IELD
TO
X-
RAY
F
IELD
A
LIGNMENT
Misalignment of the light field/ X-ray field in either the X (cross table) or Y (long table) direction
must not exceed 2% of the SID. In this case, it would be less than 20 mm (0.80"). If the test film
shows that the light field (shadows of the copper strips) matches the X-ray field (shadow of the
collimator shutters) to within the diameter of one strips and, if the diameter is less than 20 mm
(0.80"), then alignment complies with the regulations.
Greater precision than this is possible. Recommended maximum deviation is one fourth. It is
important the greatest degree of congruency possible is achieved.
If misalignment is detected in both X and Y directions, check the spacing from the focal spot to
the collimator mounting surface is 80 mm (3.14") +/- 1 mm. If spacing needs to be adjusted,
repeat the test film exposure after the adjustment.
If the source flange distance (
SFD
) is correct, but adjustment is still necessary proceed as
follows:
SID = 100 cm (40")
2.0% x 100 cm (40") =
LARGE L1+L2
FOCUS W1+W2
=..........+..........=..........
=..........+..........=..........
=
≤
2.0% SID
=
≤
2.0% SID
SMALL L1+L2
FOCUS W1+W2
=..........+..........=..........
=..........+..........=..........
=
≤
2.0% SID
=
≤
2.0% SID
N
OTE
T
HE
HEEL
EFFECT
WILL
CAUSE
THE
FIELD
TOWARD
THE
CATHODE
TO
BE
SLIGHTLY
LESS
SHARP
THAN
ON
THE
OTHER
THREE
SIDES
.
THIS
IS
NORMAL
AND
CANNOT
BE
CORRECTED
BY
ADJUSTMENT
.
IN
ADDITION
,
AN
X
-
RAY
TUBE
OF
12°
OR
LESS
TARGET
ANGLE
WILL
PRODUCE
AN
ASYMMETRICALLY
SHAPED
FIELD
WHEN
A
LARGE
FIELD
SIZE
IS
USED
AT
SHORT
SID
,
BECAUSE
OF
ANODE
CUT
-
OFF
EFFECT
.
THIS
IS
NORMAL
AND
MAY
NOT
BE
CORRECTED
BY
ADJUSTMENT
.
