DIAMENTOR E2
Calibration
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D651.131.00/05 en
7 Calibration
Electrical Calibration
The DIAMENTOR E2 is electrically calibrated in the
factory. You can verify the calibration as described
in section 5.2. If the electrical calibration values are
outside the admissible range, the device should be
returned to PTW-Freiburg for repair, as the electri-
cal calibration cannot be corrected on site.
Radiological Calibration
The chamber calibration can be verified on site (see
below) or in the PTW calibration laboratory. We
recommend to have the system calibrated annually
or every 2 years in our calibration laboratory of
PTW-Freiburg.
Some Basic Facts On Chamber Calibration
(PTW-Freiburg Calibration Laboratory)
−
For verification of the chamber calibration fac-
tor only the ionization chamber (without the
measuring system) needs to be returned to the
factory.
−
The ionization chambers calibrated in the PTW
calibration laboratories can be used with over-
couch and undercouch tubes.
−
In order to take into account the different ab-
sorption conditions of overcouch and under-
couch tubes, an additional absorber equivalent
to 0.35 mm AI is placed between the X-ray
tube and the ionization chamber during the
factory calibration. Therefore the measure-
ment error of overcouch tube installations
where there is no absorber between chamber
and patient is up to - 9 %. In conjunction with
undercouch tubes the absorption of the patient
couch situated between the patient and the
chamber is equivalent to 0.5 to 0.7 mm AI,
which results in a measurement error of up to
+ 5 %.
−
The chamber calibration factors are noted
down on the calibration certificate.
−
Enter the new chamber calibration factors as
described in section 4.5. For this, multiply the
chamber calibration factor K
G
by a correction
factor of
1.10 for over-couch tubes
and of
0.95 for under-couch tubes
.
Verifying the Chamber Calibration in Conjunc-
tion with the X-Ray System
Specially trained staff will be able to perform the
chamber calibration on site.
The required accesso-
ries/tools are:
−
1 diagnostic dosemeter (e.g., PTW-DIADOS,
PTW-DALi, PTW-NOMEX or PTW-UNIDOS)
−
1 X-ray film, 13 cm x 18 cm (for radiography)
−
1 measurement phantom (for fluoroscopy)
−
1 adapter for DIADOS detector (part no.
T20002), (for fluoroscopy)
Check the electrical calibration as described in sec-
tion 5.1.
Radiography
−
Make adjustments for a field size of approx.
10 cm x 10 cm and mark the area on the pa-
tient couch.
−
Place the X-ray film on the patient couch and
make a radiograph (70 kV and 40 mAs).
−
Develop the film (only briefly to obtain sharp
edges) and measure the exact size of the field
(noting down the result A).
−
Place the detector of the diagnostic dosemeter
in the center of the area marked on the patient
couch. Make a radiograph (70 kV and 40 mAs).
