What does the Entrance Dose (ESD) measure?

• A. The radiation dose absorbed by the skin
• B. The effective dose of radiation
• C. The dose of radiation from environmental exposure
• D. The cumulative radiation exposure over a lifetime

Answer: (A)

The Entrance Dose (Effective Dose to Skin, or ESD) specifically measures the amount of radiation absorbed by the skin at the point of entry of the x-ray beam. This measurement is particularly important in diagnostic radiology and bone densitometry, as it indicates the potential for skin damage due to ionizing radiation. It quantifies the initial exposure before any scattering or absorption by tissues deeper than the skin occurs.

Understanding the significance of ESD helps in monitoring patient safety and ensuring that radiation exposure is kept as low as reasonably achievable (ALARA principle). It serves as a critical metric for evaluating the safety of diagnostic procedures and contributes to the assessment and management of patient radiation dose during imaging.

In contrast, effective dose refers to the risk of exposure to ionizing radiation across different tissues in the body and is not limited to just skin absorption. Environmental exposure and cumulative lifetime exposure measures are broader assessments of an individual's radiation exposure from various sources, not specific to a single imaging procedure.