Microspheres: materials and preparation

Microspheres: materials and preparation

The ideal properties for radiolabeled microspheres or particles for intra-arterial
therapy are summarised in Table 1. Müller and Rossier [8] first described the use of
particles radiolabeled with gold-198 (198Au), which were used in the treatment of lung
cancer. Early studies used angular fragments that were made by crushing the bulk
material and sieving the particles to grade in the desired diameter [9]. The first plastic
microspheres were labeled with 90Y and showed an unpredictable and catastrophic
leaching of yttrium, which brought them into question [10]. This problem was solved
later by the use of glass beads. As well as these glass beads, resin-based and other
polymeric microspheres are currently being used. An overview is given in Table 2.


Table 1. Ideal properties of radiolabeled microspheres for intra-arterial therapy [7]
1. High mechanical stability to resist breakdown and passage through the capillary
network
2. High chemical stability to resist elution of radioactive label, macrophage
removal, or radiolysis
3. Uniform size
4. Unit density to prevent settling or streaming
5. Relative ease of label
6. Radionuclide label with high-energy beta particle, low photofraction,
and intermediate (days) half-life