Bolus Injections of Measured Amounts of Radioactivity

Abstract

Many time-based radionuclide techniques, such as glomerular filtration rate measurement (GFR), require prompt intravenous delivery of an accurately measured tracer bolus with minimal residual tracer retention at the injection site. The quality assurance aspects of two antecubital vein, quantitative injection techniques were investigated. A flush bolus technique using a tuberculin syringe piggybacked onto a 10-ml saline flush was compared to a single blood pressure cuff injection technique. Scintillation camera data for each technique were compared for bolus duration in the abdominal aorta and for residual activity at the injection site at 5 min. Bolus times were measured as the FWHM of the gamma variate fit to the abdominal aortic regional time-activity curves. The mean FWHM was 8.3 ± 2.2 sec for the flush bolus (n = 19), and 11.4 ± 3.7 sec for the cuff technique (n = 23) (mean ± 1 s.d.). Relatively little focal activity was seen in the antecubital injection site following the flush bolus: marked residual activity was seen following the blood pressure cuff injections. The injection site/arm background ratios averaged 1.3 for the flush bolus and 30.1 for the cuff technique (n = 20). Although both methods allowed accurate in vitro determination of administered radioactivity, only the tuberculin syringe flush bolus technique was acceptable for time-based quantitation because of its superior in vivo characteristics.