Figure 1-4.Control panel for wall mounted X-ray machine.
tube 1. The depressed button and a lamp on the selected
tube head will glow.
3. Select the kilovoltage. Adjust the kilovoltage
(kV) until the desired kilovolt peak (kVp) is registered
on the kilovolt meter. The kVp setting will vary,
depending on the patient's bonesize and density;
specific settings will be given later in this chapter.
NOTE: Some X-ray machines shut off
automatically if the setting exceeds 90 kVp. Refer to
the manufacturer's instructions for resetting
4. Set the exposure time. Check the X-ray film
manufacturers recommended time setting for the type
of film being used, the kVp and mA settings, and the
film focal distance (FFD). The time settings may be in
fractions of a second or impulses. An impulse equals
1/60 of a second. To protect the patient from needless
exposure to radiation, use the minimum exposure time
necessary to produce the desired results.
5. Check to see that the machine is emitting
X-rays. Place an unexposed packet of X-ray film on the
seat of the dental chair. Put a penny on top of the film
packet and position the tube head. The tube head
cylinder should be pointed down, 6 inches above and
centered on the penny. When the tube head is correctly
positioned, prepare to make the exposure.
WARNING: You must be behind a lead-lined
shield or at least 6 feet from the tube head when making
6. Make the exposure by depressing the exposure
button located on the control panel. Exposure start is
delayed approximately 1/2 second. If the machine is
working correctly, you will hear a click and the tone
signal, and the "X-ray" lamp on the control panel will
glow. This indicates that an exposure is being made. Do
not release the exposure switch until the selected
exposure time is completed.
7. After making the exposure, process the X-ray
film. If the processed film shows a light area where the
penny was, the X-ray machine is working properly.
Processing techniques will be discussed later in this
MACHINE OPERATION (WITH
Once the X-ray machine's operational readiness
check has been completed, it is a simple matter to
prepare it to take radiographs on a patient. Set the mA
selector, the tube head selector (if necessary), the kVp
selector, and the exposure time. Before you make the
exposure, position the patient, the film packet, and the
tube head cylinder. These patient positioning
procedures are discussed later.
SECURING THE X-RAY MACHINE
At the end of each work day, deactivate the off
switch and secure the machine (e.g., the tube head
extension arm should be completely folded to
minimize the weight of the tube head on the arm and
wall mounting plate).