Table 1.

Modalities for Clinical Molecular Imaging

Imaging Modality	Advantages	Disadvantages
Fluorescence Imaging	High sensitivity for ligand detection. Easiest to combine with interventional procedures.	Poor depth penetration makes imaging of some body parts inaccessible
- Microscopic/confocal	Extremely high spatial resolution allows visualization of subtle anatomic abnormalities	Very limited depth penetration, difficult to examine large surface areas
- Macroscopic	High spatial resolution, quantitative, and ability to screen entire colon	Limited depth penetration best suited for mucosal or submucosal targets
- Tomographic	Specialized equipment can evaluate entire human organs (such as breast) 12	Low spatial resolution. Multiple tissue interfaces preclude routine imaging of human colon
Positron Emission Tomography (PET) / Single Photon Emission Computed Tomography (SPECT)	Very high sensitivity for ligand detection, hundreds of agents already tested in people, and many agents approved for human use. Can be used to evaluate metastatic lesions.	Radiation dose somewhat decreases utility in low risk screening applications. Low spatial resolution.
Magnetic Resonance Imaging (MRI)	High spatial resolution and intrinsic simultaneous anatomic correlation	Low sensitivity for ligand detection
Ultrasound	Inexpensive and easy to combine with interventional techniques	Very difficult to image extra-vascular molecular targets
Computed Tomography (CT)	Very high spatial resolution can provide anatomic map for multi-modal imaging applications	Very poor sensitivity for ligand detection