Selected Operational Parameters, Advantages, and Disadvantages of Modalities Used in Molecular Imaging
| Modality | Probes | Spatial resolution (mm) | Sensitivity (mol/L) | Advantages | Disadvantages |
|---|---|---|---|---|---|
| PET | Positron emitters (18F, 15O, 13N, 11C, 64Cu, 76Br) | 1–2 | 10−11−10−12 | Superior sensitivity; tracer chemically identical to parent compound; established attenuation correction algorithms | Short–half-life tracers; expensive equipment; requirement for on-site cyclotron; advanced radiochemistry |
| SPECT | Photon emitters (201Tl, 99mTc, 111In, 125I) | 0.5–2 | 10−10−10−11 | Superior sensitivity; multiple-isotope imaging; emission proportional to concentration of probe | Exposure to ionizing radiation; accuracy limited by attenuation of low-energy photons |
| Ultrasound | Microbubbles | 0.05–0.5 | To be determined | Widely available; relatively inexpensive; no ionizing radiation | Limited penetration depth; lack of molecular probes |
| CT | Iodinated contrast agents | 0.05–0.2 | 10−3−10−5 | Absorption proportional to concentration of contrast agent; superior spatial resolution | Exposure to ionizing radiation; contrast agent nephrotoxicity; low sensitivity |
| MRI | Gadolinium chelates, iron oxides | 0.02–0.1 | 10−3−10−5 | No ionizing radiation; superior spatial resolution; available instrumentation | Low sensitivity; susceptibility to motion artifacts; lack of molecular probes |