National Board Dental Hygiene Examination (NBDHE) Dental Hygienist Practice Test

Which component of the x-ray tubehead is responsible for collimation?

1. Aluminum filter

2. Focusing cup

3. PID

4. Target

The correct answer is: PID

The component of the x-ray tubehead responsible for collimation is the position-indicating device (PID). The PID is designed to shape and restrict the beam of x-rays that emanates from the tubehead, thus reducing the exposure area and improving the quality of the radiographic image. By narrowing the beam, the PID helps limit the patient's radiation exposure and enhances the focus of the image by reducing scatter radiation. Collimation is crucial in dental radiography because it helps to comply with the principle of keeping unnecessary exposure to a minimum while obtaining the diagnostic information required. The size and shape of the x-ray beam can significantly impact the quality of the images captured, making the PID a key component in effective x-ray production. The aluminum filter serves a different purpose by removing low-energy, longer wavelength x-rays from the beam, which helps to enhance the quality of the image and protect patient safety. The focusing cup is involved in directing the electrons toward the target and has no role in beam shaping or collimation. The target is where the electrons collide to produce x-rays and also does not participate in collimation. Thus, the PID's specific design and function make it the correct answer for collimation.