Combining dose and injection volume for good performance of a specific radiopharmaceutical for sentinel node detection.

INTRODUCTION: The aim of this work was to quantify the effects of injection volume at different technetium-99m specific radiotracer doses on its lymphatic movement in animal model. PROCEDURES: Effects of injection volume (50, 100 µl) at different doses (0.05, 0.135, 0.22 nmol) on popliteal node (PN) detection were studied in rats. The radiotracer under study was (99m)Technetium-cysteine-mannose-dextran conjugate (30 kDa). RESULTS: At 0.05 nmol dose, higher PN uptake was observed at 50 µl injection volume (2.6 fold increase). Conversely, at 0.135 nmol dose, an increase of radiotracer retention in PN was achieved at 100 µl volume, 78% higher than 50 µl. However, at 0.22 nmol dose, the injection volume changes did not influence on the PN uptake. Considering as suitable radiotracer performance: high PN uptake and extraction, better combinations were 0.05 nmol/50 µl, 0.135 nmol/100 µl, 0.22/50 µl. CONCLUSION: Suitable performances could be reached by proper combinations of dose, injection volume and concentration for a specific radiotracer used in sentinel lymph node detection.

Influence of colloid particle profile on sentinel lymph node uptake.

INTRODUCTION: Particle size of colloids employed for sentinel lymph node (LN) detection is not well studied. This investigation aimed to correlate particle size and distribution of different products with LN uptake. METHODS: All agents (colloidal tin, dextran, phytate and colloidal rhenium sulfide) were labeled with (99m)Tc according to manufacturer's instructions. Sizing of particles was carried out on electron micrographs using Image Tool for Windows (Version 2.0). Biodistribution studies in main excretion organs as well as in popliteal LN were performed in male Wistar rats [30 and 90 min post injection (p.i.)]. The injected dose was 0.1 ml (37 MBq) in the footpad of the left posterior limb. Dynamic images (0-15 min p.i.) as well as static ones (30 and 90 min) were acquired in gamma camera. RESULTS: Popliteal LN was clearly reached by all products. Nevertheless, particle size remarkably influenced node uptake. Colloidal rhenium sulfide, with the smallest diameter (5.1 x 10(-3)+/-3.9 x 10(-3) microm), permitted the best result [2.72+/-0.64 percent injected dose (%ID) at 90 min]. Phytate displayed small particles (<15 microm) with favorable uptake (1.02+/-0.14%ID). Dextran (21.4+/-12.8 microm) and colloidal tin (39.0+/-8.3 microm) were less effective (0.55+/-0.14 and 0.06+/-0.03%ID respectively). Particle distribution also tended to influence results. When asymmetric, it was associated with biphasic uptake which increased over time; conversely, symmetric distribution (colloidal tin) was consistent with a constant pattern. CONCLUSION: The results are suggesting that particle size and symmetry may interfere with LN radiopharmaceutical uptake.