Approximate Ranges of Particle Size Estimated for Various Radiocolloids
| Agent | Estimate | Median (nm) | |
|---|---|---|---|
| Concordant (nm) | Other (nm) | ||
| 99mTc-dextran | 2–4 | 2 | |
| 198Au-colloid | 9–15 | 4–20/30 | 5–15 |
| 99mTc-antimony trisulfide | 3–12/30 | 15–25 | 17–22 |
| 99mTc-sulfur colloid (prefiltered)* | 5/15–50 | 5–25 | <30 |
| 99mTc-HSA nanocolloid† | 4–100 | 5–80 | |
| 99mTc-stannous fluoride | 50–600 | ||
| 99mTc-rhenium sulfide | 50–200/400 | 40–2,200 | 440 |
| 99mTc-stannous phytate | 200–1,000 | ||
| 99mTc-HSA microcolloid‡ | 200–2,000/3,000 | <1,000 | |
| 99mTc-sulfur colloid (unfiltered)§ | 15/50–>5,000 | 100/200–1,000 | 100–600 |
| 99mTc-sulfur colloid (modified protocol)¶ | <30–>10,000 | ||
| 99mTc-sulfur colloid (filtered)∥ | 50–100 | 50–200 | <40 |
↵* Commercial preparation microfiltered before freeze-drying and radiolabeling (Lymphoscint; Nycomed-Amersham-Sorin, Sorin, Italy).
↵† About 80% of particles < 40–50 nm, 95% < 80 nm, 4% between 80 and 100 nm, and 1% > 100 nm.
↵‡ About 90% of particles < 1,000 nm.
↵§ About 15%–20% of particles < 100 nm, 70%–80% between 100 and 600 nm, and 2%–4% between 700 and 5,000 nm (minor fraction > 5,000 nm).
↵¶ Reduced heating, with 72-h ingrowth of 99mTc: about 47% of particles < 30 nm, 1% between 50 and 80 nm, 5% between 80 and 200 nm, 21% between 200 and 400 nm, 16% between 400 and 800 nm, 5% between 800 and 2,000 nm, 1% between 2,000 and 5,000 nm, and 5% > 10,000 nm.
↵∥ Depending on pore size used for microfiltration after radiolabeling.
Particle sizes are derived from manufacturers or other sources (11,87,95–98). For comparison scale, molecular size of HSA is approximately 7.2 × 10−6 nm.