Table 2.
Comparison of the features of IR/Raman imaging with those of the other main modalities used in research and clinics. These features depend on the experimental configuration [2,66]. PET: Positron Emission Tomography, SPECT: Single-Photon Emission-Computed Tomography, SERS: Surface-Enhanced Raman Scattering, SORS: Spatially Offset Raman Spectroscopy and NIRF: Near Infrared Fluorescence.
| Imaging Modality | Spatial Resolution | Temporal Resolution | Penetration Depth | Sensitivity |
|---|---|---|---|---|
| IR | 2.5–6 μm | s/min | 10 μm–1 mm | 10−4–10−5 M |
| Raman | 0.5–1 μm 20–100 nm (SERS) |
s/min | 200–300 μm 20–100 μm (SERS) ~1 mm (SORS) |
10−6–10−7 M 10−12–10−15 M (SERS) |
| MRI | 25–100 μm (preclinical) ~1 mm (clinical) |
s/h | unlimited | 10−3–10−5 M |
| Luminescence | 2 to 3 mm 1–10 μm (NIRF) |
s/min | <2 cm | 10−9–10−12 M |
| Intravital microscopy | 100–300 nm | ms/s | ~1 mm | 10−15–10−17 M |
| Resonance energy transfer | 2 to 3 mm | s | <2 cm | 10−6–10−10 M |
| Optical coherence tomography (OTC) | 1 μm | s | ~2 to 3 mm | 10−10–10−11 M |
| Photoacoustic imaging (PAI/PAT) | 5 μm–1 mm (depth-dependent) |
s/min | <6 cm | 10−9–10−11 M |
| Ultrasound imaging (US) | 10–100 μm (at ~mm depth); 1 to 2 cm (at ~cm depth) |
s/min | 1 cm | 10−6–10−9 M |
| γ-imaging | 1–10 mm | min | unlimited | 10−10–10−11 M |
| PET | <1 mm (preclinical), ~5 mm (clinical) |
s/min | unlimited | 10−11–10−12 M |
| SPECT | 0.5–2 mm (preclinical), 8–10 mm (clinical) |
min | unlimited | 10−10–10−11 M |
| Computed tomography (CT) | 25–200 μm (preclinical), 0.5–1 mm (clinical) |
s/min | unlimited | 10−3 M |