Which of the following is true about the photoelectric effect?

Question

Question

Answer 1

Correct Answer: It is responsible for image contrast

Rationale:

The photoelectric effect is a phenomenon where photons are absorbed by matter, resulting in the ejection of electrons from the material. This effect is crucial in the context of medical imaging, particularly in X-ray imaging.
The photoelectric effect is responsible for the image contrast in X-ray imaging. The varying degrees of absorption in different tissues (such as bone and soft tissue) create the contrast seen on the X-ray images, which is essential for diagnostic purposes.
The degree of photoelectric absorption depends on the atomic number (Z) of the tissue and the energy of the incoming X-ray photons. Higher atomic number tissues (like bone) absorb more X-rays, leading to higher contrast on the radiograph.

Explanation of Other Options:

It increases at higher X-ray energies

Rationale: This statement is incorrect. The probability of the photoelectric effect actually decreases with increasing photon energy. At higher X-ray energies, Compton scattering becomes more dominant compared to the photoelectric effect.

It reduces radiation dose

Rationale: The photoelectric effect itself does not reduce radiation dose. Instead, it involves the absorption of X-ray photons, which contributes to the patient's radiation dose. Proper imaging techniques and protocols are used to manage and minimize radiation exposure.

It occurs only in diagnostic ultrasound

Rationale: This statement is incorrect. The photoelectric effect does not occur in diagnostic ultrasound. Ultrasound imaging relies on the reflection of sound waves, not the interaction of photons with matter. The photoelectric effect is specific to X-ray and other photon-based imaging modalities.

Conclusion:

The photoelectric effect is fundamental to the creation of image contrast in X-ray imaging, which is essential for distinguishing different tissues and making accurate diagnoses. Understanding the role of the photoelectric effect helps in optimizing imaging techniques and improving diagnostic accuracy.