Evaluation of technetium-99m red blood cell labeling efficiency in adults receiving chemotherapy and the clinical impact on pediatric oncology patients.

OBJECTIVE Technetium-99m-labeled RBCs are used to evaluate ventricular function and are the preferred method for monitoring the cardiac function of patients receiving chemotherapy. Optimal imaging quality is critical for monitoring small but important changes in ventricular function. The labeling efficiency of three products from two manufacturers and images from 30 patients (21 men, 9 women; age 60.3 +/- 11.9 yr) referred for clinical radionuclide ventriculograms before chemotherapy were evaluated to determine the best labeling technique. METHODS Patients received RBCs labeled in one of three ways. Two pyrophosphate methods used a modified in vitro method and the manufacturer's instructions were used for the in vitro method. Imaging was performed and, upon completion (42.1 +/- 9.6 min), blood samples were drawn, separated and counted to determine labeling efficiency. RESULTS The labeling efficiencies were: (a) 88.1% +/- 4.2% and (b) 88.4% +/- 4.8% for the two modified in vitro methods; and (c) 95.3% +/- 1.7% for the in vitro method. The difference between the methods was statistically significant (p = 0.019). Twenty pediatric oncology patients (6.4 +/- 5.2 yr) received in vitro labeled RBCs through their Hickman catheters. All 20 pediatric studies were of high quality. CONCLUSION In vitro labeling demonstrated a higher labeling efficiency than the modified in vitro methods. In vitro labeling also yielded high-quality images when the labeled RBCs were injected through existing chronic in-dwelling catheters.