What is the SI unit for exposure corresponding to the traditional roentgen?

The SI unit for exposure that corresponds to the traditional roentgen is the coulomb per kilogram (C/kg). The roentgen is a measure of the amount of ionization produced in air by X-rays or gamma rays and is related to the charge of ion pairs generated. In the SI system, this is defined as coulombs of charge per kilogram of air. The conversion specifics state that 1 roentgen is approximately equal to 2.58 x 10^-4 C/kg.

This measurement is crucial in radiation therapy and radiological practices because it allows for the quantification of radiation exposure in a standardized way, which is essential for patient safety and effective treatment planning. Understanding exposure in terms of coulombs per kilogram is particularly important for calculating dose and ensuring accurate delivery of radiation to target areas while minimizing exposure to healthy tissues.

In contrast, the other choices represent different concepts within radiation measurement: joule per kilogram relates to absorbed dose, gray is a unit for absorbed dose, and sievert measures the biological effect of radiation, factoring in the type of radiation and the tissue affected, which are not directly equivalent to exposure.