CPI Canada Inc.
Interfacing and Programming
3C
Use and disclosure is subject to the restrictions on the title page of this CPI document.
CMP 200
®
X-Ray Generator Service Manual Ch # 901476-04 Rev. C
Page 3C-77
3C.11.3 DAP Calibration Procedure (Cont)
Use these steps to calibrate the DAP meter(s) in the generator.
Step
Action
1.
Set up the dosimeter as per figure 3C-20. The probe should be centered relative to the central ray from the X-ray tube, and
sufficiently far off the tabletop to minimize scatter radiation.
Do not use any absorber during this procedure
.
2.
Open the collimator such that the field size at the location of the probe is approximately 12 cm X 12 cm. Ensure that the
probe is fully irradiated.
3. Enter the
DAP SETUP
menu.
4.
Set the generator to 70 kV, 100 mA, 20 ms.
5. Press
DAP
to access the RESET / TEST /PRINT menu, then press
RESET
to reset the DAP display to zero. The DAP will
reset to zero, then the generator will return to the
DAP SETUP
menu.
6.
Make an X-ray exposure and note the dose per the dosimeter. Record the mR or mGy value in a copy of table 3C-4.
Convert the mR value to mGy, if necessary.
7.
Note the DAP value as displayed on the console, and record the value in a copy of table 3C-4.
8.
Replace the dosimeter with an X-ray cassette and film if available. The film plane must be at the same location as the
dosimeter was in step 8.
If using an image sensor such as an I.I., or flat panel, or other non-film image sensor, the image pickup plane must be at the
same location as the dosimeter was in step 8.
THE IMPORTANCE OF THIS STEP CANNOT BE OVERSTATED: THE IRRADIATED AREA MEASUREMENT MUST BE
MADE AT A POINT THAT IS THE SAME DISTANCE FROM THE X-RAY SOURCE AS THE DOSE WAS MEASURED
AT.
9.
Ensure that the collimator field at the measurement plane is smaller than the active area of the image pick-up device (film,
I.I., or other). Refer to figure 3C-21.
Do not readjust the collimator from the setting that was used in step 8.
10.
Make another exposure using the same settings as in step 6.
11.
Develop the film (if used).
12.
Measure the irradiated image area. For film, measure the length and width of the exposed area, and record the results in
table 3C-4. Refer to figure 3C-21.
If using a digital imaging system, some systems have a cursor available that allows measurement of the length and width of
the area in question. If the digital imaging system does not allow image size measurement, it is suggested that an X-ray
opaque item of known dimensions be placed at the image plane. (A collimator test tool would be useful in this application).
The length and width of the irradiated area can then be extrapolated by comparison to the size of the reference object.
Record the length and width of the irradiated area at the measurement plane in table 3C-4.
13.
Calculate the irradiated image area, in cm
2
. Use the length and width recorded in table 3C-4.
14.
Calculate the dose-area product by multiplying the area from table 3C-4 X the dose in mGy from table 3C-4. Record the
resulting value at step 3 in table 3C-4.
