Scintigraphic investigations of the lymphatic system: the influence of injected volume and quantity of labeled colloidal tracer.

Abstract

Volumes injected for lymphoscintigraphic investigations are highly variable, and the quantity of labeled colloids injected is usually not reported. The aim of the present study was to evaluate whether and how volume and quantity quantitatively affect lymphoscintigraphic results. Each of 9 healthy volunteers (4 men and 5 women; mean age, 21 y; range, 19-26 y) participated in 4 lymphoscintigraphic investigations using the same protocol, in which the volume injected was 0.2 or 1.0 mL and the quantity injected was 0.02 or 0.2 mg. Subcutaneous injections of (99m)Tc-labeled human serum albumin nanosized colloids were placed in the first interdigital space of each foot. Activity at the injection sites and in the inguinoiliac nodes after a standardized sequence of rest, exercise, and normal-activity periods was measured and analyzed as a function of volume and quantity. The highest extraction rate was observed for a quantity of 0.2 mg and a volume of 0.2 mL. This extraction rate was significantly higher than the rates obtained for a quantity of 0.2 mg and a volume of 1.0 mL or for a quantity of 0.02 mg and a volume of 0.2 mL, neither of which differed from the extraction rate for a quantity of 0.02 mg and a volume of 1.0 mL. Activity in inguinoiliac nodes was significantly higher for a quantity of 0.2 mg than for a quantity of 0.02 mg, irrespective of volume. With quantity remaining constant, volume did not influence the activity in inguinoiliac nodes. Both volume and quantity influence the results of lymphoscintigraphic investigations with regard to the quantities extracted from injection sites and the accumulations in nodal regions. Therefore, volume and quantity should be standardized when quantitative parameters are used for diagnostic purposes.