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. Author manuscript; available in PMC: 2009 Aug 2.
Published in final edited form as: J Nucl Med. 2009 May 14;50(6):999–1007. doi: 10.2967/jnumed.108.059576

TABLE 2.

Requirements for T2 Agents in MRI: Number of Particles Required Scales Inversely with Relaxivity of Carrier Particle

Diameter of particle containing iron oxide (nm) [Iron] in tissue (μM) if 1 particle per (100 μm)3 voxel No. of particles per cell to achieve 5 μM iron to produce ΔR2 ~ 2 in (100 μm)3 voxel
10 30 × 10−6 166 every cell
100 30 × 10−3 1 every 6 cells
1,000 30 1 every 6,000 cells