Particle sizes of colloids to be used in sentinel lymph node radiolocalization

Objectives To investigate particle size distribution and possible effects of colloid concentration and time after its preparation on the particle sizes of albumin nanocolloid (Nanocoll), rhenium sulfide nanocolloid (Nanocis) and tin colloid (Hepatate). Methods All three kits were prepared according to the manufacturers' instructions using the following volumes of decayed Tc-99m generator eluate: 1.5 ml, 3.5 ml and 5.0 ml (albumin nanocolloid); 1.0 ml, 2.0 ml and 3.0 ml (rhenium sulfide nanocolloid); 3.0 ml, 5.0 ml and 9.0 ml (tin colloid). The particle sizes were determined by photon correlation spectroscopy inmediately after preparation, then at 30 min, 1 h, 2 h, 3 h and 4 h (all three kits) and at 6 h (Nanocoll and Hepatate). Each measurement was performed in three different preparations. Results The particle sizes of the three colloids did not change significantly after preparation throughout their period of validity. For Nanocoll, 95% of the particles were between 3 and 16 nm, approximately (mean around 8 nm). Small (<= 1 nm) but significant variations on the mean diameter were found depending on the volume of pertechnetate used in the preparation. For Nanocis, 95% of the particles were between 8 and 68 nm, approximately (mean around 23-25 nm). In this kit, there were no significant differences among colloidal suspensions prepared with different volumes of pertechnetate. For Hepatate, 95% of the particles were between 33 and 255 nm, approximately (mean, around 72-90 nm). The upper limit and the mean size increase with the volume of eluate used were from 190 nm and 73 nm (3 ml) to 255 nm and 85 nm (9 ml). Conclusions The particle sizes of Nanocoll, Nanocis and Hepatate are very stable throughout their period of validity. For Nanocoll, 95% of particles have a diameter < 16 nm, with a mean diameter around 8 nm. There are small (<= 1 nm) but significant variations on the mean diameter depending on the volume of pertechnetate used in its preparation. For Nanocis, 95% of particles have a diameter < 70 nm, with a mean around 24 nm, and are independent of the volume of pertechnetate used in their preparation. For Hepatate, the upper size limit for 95% of particles is between 190 and 255 nm, with a mean between 72 and 88 nm, depending on the volume of pertechnetate used in its preparation. This tin colloid could be a good candidate for evaluating clinical suitability in sentinel node localization.