FIGURE 1.

Properties of various whole-body imaging modalities. Imaging modalities are ordered according to the electromagnetic spectrum they exploit for imaging (top, high energy; bottom, low energy). Routinely achievable spatial resolution (left end) and fields of view (right end) are shown in red. Where bars are blue, they overlap red bars and indicate the same parameters but achievable with instruments used routinely in the clinic. Imaging depth is shown in black alongside next to sensitivity ranges. Instrument cost estimations are classified as ($) < 125,000 $, ($$) 125-300,000 $ and ($$$) > 300,000 $. ^#Generated by positron annihilation (511keV). *Contrast agents sometimes used to obtain different anatomical/functional information. **In “emission mode” comparable to other fluorescence modalities (∼nM). ***Fluorophore detection can suffer from photobleaching by excitation light. ****Highly dependent on contrast agent. ^& Dual isotope PET is feasible but not routinely in use; it requires two tracers, one with a positron emitter (e.g. ¹⁸F and ⁸⁹Zr) and the other with a positron-gamma emitter (e.g. ¹²⁴I, ⁷⁶Br, and ⁸⁶Y), and is based on recent reconstruction algorithms to differentiate the two isotopes based on the prompt-gamma emission (Andreyev and Celler, 2011; Cal-Gonzalez et al., 2015; Lage et al., 2015). ^&⁣&Multichannel MRI imaging has been shown to be feasible (Zabow et al., 2008). PET, positron emission tomography; SPECT, single photon emission computed tomography; CT, computed tomography; BLI, bioluminescence imaging; FLI, fluorescent lifetime imaging; FRI, fluorescent reflectance imaging; FMT, fluorescence molecular tomography; OCT, optical coherence tomography; OPT, optical projection tomography; PAT, photoacoustic tomography; MSOT, multispectral optoacoustic tomography; RSOM, raster-scan optoacoustic mesoscopy; MRI, magnetic resonance imaging; US, ultrasound.