52 Chapter 5 Acquiring Images
7. Move the X-ray generator tube head to the patient and align it with the tooth of the patient and the
imaging plate.
8. Select the X-ray exposure time according to the region of interest and the patient type. Follow the user
instructions of your X-ray generator. The following tables provide guidelines for exposure times for an
X-ray generator at 70 kV and 7mA. Add your values for the exposure time in seconds in the column on
the right.
Table 4 Exposure times
Parameter DC-emitter, 7mA, tube length 20 cm DC-emitter, 7mA, tube length 30 cm
recommended exposure time (s) recommended exposure time (s)
Upper jaw 60kV 70kV 60kV 70kV
incisors 0.1 0.08 0.2 0.16
pre-molars 0.125 0.1 0.25 0.2
molars 0.16 0.125 0.32 0.25
Lower jaw 60kV 70kV 60kV 70kV
incisors 0.1 0.08 0.2 0.16
pre-molars 0.125 0.1 0.25 0.2
molars 0.125 0.1 0.25 0.2
Bitewing 0.16 0.125 0.32 0.25
Important: Make sure that the tube head is not shaking.
Important: These are suggested exposure times and need to be adjusted
for your specific X-ray generator. For dark images, reduce the exposure
time and for grainy images, increase the exposure time.
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