Molecular imaging in inflammatory bowel disease

Abbreviations

CAC

colitis-associated cancer

CD

Crohn’s disease

CLE

confocal laser endomicroscopy

CT

computed tomography

FITC

fluorescein isothiocyanate

IBD

inflammatory bowel disease

SSA

sessile serrated adenoma

SPECT

single-photon emission computed tomography

TNF

tumor necrosis factor

VDZ

vedolizumab

Introduction

Molecular imaging is based on the principle of utilizing fluorescently labeled probes with high specificity toward defined molecular targets and their subsequent detection and visualization with endoscopic devices ( Table 21.2 ), thereby enabling visualization of single molecules or receptors . Generally speaking, different type of probes can be utilized for molecular imaging such as antibodies, enzymes, affibodies, lectins, or peptides, all of which have certain advantages and disadvantages, as summarized in Table 21.1 . The ideal probe for molecular imaging should exhibit high affinity toward the molecular target, rapid binding kinetics with sufficient tissue penetration, and at the same time low immunogenicity.

Table 21.1

Characteristics of various probes used for molecular imaging.

Source: Adapted from Atreya R, Goetz M. Molecular imaging in gastroenterology. Nat Rev Gastroenterol Hepatol 2013;10:704–12; Sturm MB, Wang TD. Emerging optical methods for surveillance of Barrett’s oesophagus. Gut 2015;64:1816–23 .

	Antibodies	Peptides	Enzymes	Affibodies	Lectins
Advantages	High specificity High affinity Clinically approved	High affinity Low toxicity Low costs Good tissue penetration	High specificity High stability High signal-to-background ratio	High specificity High affinity Small size	High specificity pH stability Low costs Low toxicity
Disadvantages	Immunogenicity High costs Low tissue penetration	Unknown binding site Formulation is complex	High costs Complex formulation	Complex formulation	Large size

Table 21.2

Endoscopic devices used for molecular imaging.

Wide-field detection devices	Autofluorescence imaging
	Multimodal colonoscope CF-Y0012 (Olympus)	Collection of wide-field images of white light, fluorescence, and reflectance
	Fiber-optic colonoscope FC-38 LV (Pentax)	Collection of wide-field images from probes labeled with Cy5
Narrow field of view devices	Probe-based CLE (Mauna Kea, France)
	Endoscope-based CLE (Pentax Medical, discontinued)
	Handheld confocal endomicroscopy probe (FIVE 1, Optiscan, Australia)

CLE , confocal laser endomicroscopy.

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