What the heck is a sievert? What happened to roentgens?
Sieverts is a measure of biological effect. This varies with the isotope and with the body part involved. Typically an average is made for the overall effect on a body, but the isotope should be taken into account for the measurement to mean anything.
You mean they don't call them Rems or Rads?
Sievert replaced rem’s. Roentgen’s are still around for educational purposes.
1 sievert = 100 rems