Measurement of Thoron in the Breath

Abstract

A method of measuring the thoron content of the breath of patients who have been injected with colloidal thorium dioxide as a radiological contrast medium, is described. The levels are sufficiently high for the decay of the thoron to be observed using only four litres of breath, being in the range 250 to 2000 μμc per litre, and they can be used to estimate the volumes of colloid injected many years previously. It is also shown that not more than about 10% of the thoron produced in the liver and spleen (the organs containing the major part of the thorium) is exhaled.