Nuclear medicine liver function tests for pregnant women and children 1. Breath tests with 14C-methacetin and 13C-methacetin

Stable isotopes, such as ¹³C, should be substituted for the long-lived radionuclide ¹⁴C in the ¹⁴C breath test when doing liver function tests in children and pregnant women. For comparison ¹³C, ¹⁵N-methacetin and ¹⁴C-methacetin were synthesized as suitable diagnostic agents. Methods are described for the measurement of ¹⁴C and ¹³C in the breath. After oral administration of labelled methacetin to healthy subjects and patients with liver diseases a good correspondence between ¹³C- and ¹⁴C-measurements in the same subject on the one hand, and a good discrimination between controls and patients on the other hand were shown. Findings with regard to ¹⁴C measurements in urine are discussed supporting the supposed advantage of ¹³C-methacetin over ¹⁴C-methacetin application.