21901
Here , the difference between c ( t ) measured per volume ( as in images ) or per weight ( as indicated by the unit MBq/kg above ) is ignored assuming that in case of soft tissues the mass density is approximately 1 kg/L .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 None