Any quantification, which has been normalized, adjusted or derived by a mathematical process or computation, of the corpuscular or electromagnetic radiations emitted consequent to nuclear disintegration of a radioactive isotope which is replacing a stable chemical element in a compound that has been introduced into lymphocytes (small agranulocytic leukocytes that originate from fetal stem cells and develop in the bone marrow) rendering them able to be followed or tracked through the body.