Compute the blood volume within the body of horse:

Problem:

A 0.6 cm³ solution containing 7.5 µCi /cm³ of ⁵⁹Fe was injected into the blood stream of a horse After equilibration, 1.0 cm³ of blood was taken out and it gave 13239 counts in 3 min. compute the blood volume within the body of horse.

Answer:

      7.5 µCi /cm³   = 7.5×10^-6×3.7×10¹⁰ counts/s = 27.75×10⁴ cps

Total activity added to the blood = 0.6×27.75×10⁴ = 166.5×10⁴ dps

Activity of blood taken out = 13239/3×60 = 73.55 cps

Allow the volume of blood in the body of horse be X cm³

As the amount of solution added to the horse body is insignificant compared to the large blood volume, it is not essential to use the Eq. (11.2). Instead, we can assume the constancy of total activity because of long half life of radiotracer that is 44.5d

73.55 X = 166.5×10⁴  or X = 2.26×10⁴ cm³ = 22.6 dm³

Ans Horse body contains 22.6 dm³ of blood