SECURING THE X-RAY MACHINE

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 procedures. 4. Set the exposure time. Check the X-ray film manufacturer’s 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 the exposure. 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 chapter. MACHINE OPERATION (WITH A PATIENT) 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). 1-5