Table 1 Summary of imaging modalities advantages, disadvantages, and potential applications

Autofluorescence

Real-time imaging;

no fluorophore needed;

wide FOV

Shallow DOF; low specificity; high cost

Superficial tumor monitoring; pre-neoplastic evaluation; surgical margin assessment

Near-infrared fluorescent imaging

Real-time imaging; deep DOF; high signal-to-noise

Need of imaging device; dye administration time

Surgical guidance; real-time monitoring and modulation of EBRT dose

Nonspecific Fluorescent Contrast Agents

Low dye toxicity; rapid hepatic clearance of dye

Contraindicated with contrast allergy; low signal-to-noise; no intracellular dye accumulation

Staging; guidance of radiotherapy planning; imaging for treatment delivery

Targeted Contrast Agents

Use Ig-based therapies as ligand; deep DOF via NIRF imaging

Require external fluorophore; few agents currently available

Diagnosis; staging

Radiofrequency Spectroscopy

No fluorophore needed; real-time imaging; handheld devices now exist

Limited FOV; shallow DOF

Residual disease detection; improved diagnostic imaging in solid tumors

Raman Spectroscopy

Real-time imaging; determine tissue response to radiation

Shallow DOF; low signal-to-noise; thermally damage samples

Measuring treatment response; post-op residual disease detection

Elastic Scattering Spectroscopy

Handheld devices; no fluorophore needed; rapid image acquisition; strong optical signal

Signal interference; variable DOF

Radiation damage detection; radiotherapy response monitoring

High-frequency Ultrasound

Sub-millimeter resolution; no fluorophore needed; approved devices

No ionizing radiation; variable sensitivity and specificity; complex image analysis algorithms

Superficial tumor assessment; reduce morbidity of prostate radiotherapy

Contrast-enhanced ultrasound

Real-time, continuous imaging; compatible with targeted contrast agents; widely-available; inexpensive; relatively safe

Shallow DOF; short half-life of contrast; potential for microvascular collapse

Primary/ metastasis characterization; ablation guidance

Optical Coherence Tomography

Cellular-level resolution; real-time imaging; handheld; no fluorophore needed; automated image analysis

Shallow DOF; narrow FOV

Renal mass identification; prostate cancer margin assessment

Optoacoustic Imaging

Real-time imaging; high resolution; enhanced by contrast agents

Historically shallow DOF but now improved

Staging; post-op planning for residual disease

Confocal Microscopy

Micron-level resolution; real-time imaging; no fluorophore needed; enhanced with fluorophores; automated image analysis; digital staining

Shallow DOF; narrow FOV; high device cost; user training necessary for manual interpretation

Detection and planning of cutaneous tumors and soft-tissue sarcomas