Biomedical Imaging: Principles, Technologies, Clinical Aspects, Contrast Agents, Limitations and Future Trends in Nanomedicines

Dual Imaging Gold Nanoplatforms for Targeted Radiotheranostics

“…It often makes use of the paramagnetic properties of Gd 3+ based Contrast Agents (GBCAs) to enhance image contrast, due to their reduction of water proton relaxation times of selected tissues. MRI provides anatomical images inside the human body with high spatial resolution, although with relatively low sensitivity [12][13][14][15][16]. The Solomon-Bloembergen-Morgan (SBM) theory predicts that very high relaxivities, of the order of magnitude 100 mM −1 •s −1 at magnetic fields relevant for clinical imaging, are attainable by Gd 3+ chelates displaying simultaneous optimization of the main parameters that govern relaxivity: Rotational correlation times (τ R ), water exchange rate constant (k ex ), and electron spin relaxation parameters (τ v and ∆ 2 ) [12,[17][18][19].…”

Engineering Intelligent Nanosystems for Enhanced Medical Imaging

“…[42,43] MRI is one of the most used modalities, as it is safe, offers high spatial resolution and high contrast in soft tissues, as well as no depth limit. [1] Alternatively, X-ray CT offers high-resolution imaging without depth limits by measuring the attenuation of an electromagnetic beam through a sample or body. The beam source and detector spin around the body so that images are taken at every angle, which can be computed into 2D and 3D images.…”

“…The technique is very cost-effective and offers fast image acquisition and processing, but the ionizing radiation may cause long-term genetic damage, and soft-matter tissue contrasts are suboptimal. [1] Distribution of radiotracers (chemical entities labeled with a radionuclide) can be observed using PET or SPECT. In PET, positrons emitted after spontaneous radioactive decay annihilate with an electron, resulting in the formation of two photons travelling in diametrically opposite directions.…”

“…Interestingly, gadolinium in free form has well-known toxic effects, and is therefore only used in chelated formulations. [1,14] Here, the investigators claim that degradation-induced Gd 3þ release induces a therapeutic cytotoxic effect in situ. [60] Finally, Huynh et al reported the in situ conversion of microbubbles (2-8 μm) into nanoparticles (5-500 nm) using low-frequency US.…”

Development and characterization of aptamer-conjugated imaging tools for diagnostic applications

“…Since their development, magnetic resonance imaging (MRI) and CT imaging have revolutionized the field of medical imaging and are among the most well-established technologies in the field. 54,55 To allow for better delineation of anatomical structures, and differentiation between normal and pathological tissues, contrast materials are utilized in both. Gadolinium (Gd(III)) can be characterized as the most widespread MRI contrast entity and is administered as part of stable chelates with multi-dentate ligands, such as diethylenetriaminepentaacetic acid (DTPA) (Magnevist), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) (Dotarem) and others (see section 2.6.4.1 for more details).…”