Case study
To help you understand the practical use of altering exposure variables on a dental x-ray machine, consider the following patients with these characteristics:
• A 9-year-old female, height 4' 8'' and weight 85 pounds, who has been assessed for bitewing radiographs to determine the evidence of caries.
• A 21-year-old male college football player, height 6' 1'', 280 pounds, who has been assessed for periapical radiographs of suspected impacted third molars.
• A 58-year-old female, diagnosed with Bell’s palsy with slight head and neck tremors, who has been assessed for a full mouth series for the evaluation of periodontal disease.
1. Would you select an increased or decreased amount of radiation to produce diagnostic quality radiographic images for each of these patients?
2. Which of these three exposure variables—milliamperage, kilovoltage, or time—control(s) the amount of radiation produced?
3. Which exposure variable would be the best choice to alter to increase or decrease the amount of radiation produced for each of these patients?
4. Would you select an increased or decreased penetrating ability of the x-ray beam to produce diagnostic quality radiographic images for each of these patients?
5. Which of the three exposure variables—milliamperage, kilovoltage, or time—control(s) the penetrating ability of the x-ray beam?
6. Which exposure variable would be the best choice to alter to increase or decrease the penetrating ability of the x-ray beam?
7. Suppose that you wanted to decrease the amount of time of the exposure, as may be needed when patient movement is anticipated (as in the case of patient 3), but still wanted to produce enough radiation to achieve a diagnostic qualityradiographic image. Which variable—milliamperage or kilovoltage—would you adjust? Would you increase or decrease this variable? Think of other characteristics patients may present with that would require you to adjust these x-ray machine variables. Keep in mind that increasing one factor may necessitate decreasing an opposing factor. Discuss the rationale for your choices.