Quantification of P-32 removed during leukapheresis by bremsstrahlung counting

The activity of P-32 removed during leukapheresis of a patient previously administered P-32 for therapy of chronic myelogenous leukemia (CML) was determined. The bremsstrahlung produced by P-32 beta rays in the pheresis bags allowed the quantitation of radioactivity by well counting in a sodium iodide detector and by a gamma camera. Bremsstrahlung counting demonstrated that leukapheresis removes such a small amount of radioactivity that the therapeutic effect of a previously administered P-32 dose was still valid. Bremsstrahlung counting offers advantages to a Nuclear Medicine Department over the conventional use of a liquid scintillation counter to detect P-32 beta rays in that it is simpler and more readily available.