Nanomaterials for Medical Imaging …
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is commercially available at even primary health centers at a lower cost, the disease
diagnosis in developing countries would be effective. This would also reduce the
failure rate and fasten the clinical trials by improved results of the preclinical studies.
Incorporating nanomaterials in preclinical studies would help in determining the
dynamics and the fate of drugs. Nanoparticles delivered in the tumor-targeted region
can eventually improve the sensitivity of the CT system for personalized diagnosis.
The performance of different materials (Bi, Ta, Au, Yb, Eu, and Iodine) has no standard protocol to evaluate its performance in CT imaging. Also, these nanoparticles
used in preclinical imaging with different concentrations. Also, a thorough examination of these materials on compatibility aspects is needed for a clinical translation.
Since most of the materials are of high atomic number, their metabolism, degradation, and excretion have to be studied extensively. The cost of the new contrast agents
should be addressed because it requires a high concentration for better imaging [49].
Even though the attention towards the nanoparticle for CT imaging is less when
compared to MR and optical imaging, considerable research interest in developing
hybrid nanoparticles would help combine the advantage of each modality.
7 Nanomaterials for MRI Imaging
Analogous with CT, information obtained from Magnetic resonance imaging (MRI)
provides structural information with more detailed features in the tissues [142].
Images are acquired by magnetic behavioral changes of tissues when placed in a
large magnetic field. A magnetic field is generated exposed to the protons or atoms
in the tissues that align with a magnetic dipole. When a radio frequency (RF) signal
is a resonance with Larmor frequency of the protons, then they relax to its normal
state for a short duration of time known as T1 and T2 relaxation [3]. Magnetic relaxation of protons in tissues produces a RF signal that varies with the tissue type and
density. For more details about the relaxation properties of MRI, readers can refer
to this article [3, 143]. The complete mechanism of longitudinal and transverse (T1
and T2) relaxation of MRI concerning on/off RF signals.
MRI is a non-invasive technique that generates 3D images of tissues. Unlike CT,
MRI does not involve any type of hazardous radiation, and it is entirely safe for
repeated measurements [144]. Clinical MRI is not suitable for small animal imaging
and is associated with many problems and limitations [145]. Clinical MRI has a large
bore, less magnetic field up to 2 T) produces a low signal to noise ratio. Therefore, a
particular type of MRI requires a high magnetic field up to 10 T is required to study the
developmental biology of animals is called micro-MRI [146]. Micro-MRI produces
high-resolution anatomical, molecular and functional imaging for drug discovery
applications. The main disadvantages of micro-MRI are expensive due to uniform
high magnetic field generation. Animal models have to be anesthetized for detection, localization, volume of tumors, and blood flow characteristics. Also, time taken
to acquire MRI images takes longer compared to micro-CT [147]. Another major
361
is commercially available at even primary health centers at a lower cost, the disease
diagnosis in developing countries would be effective. This would also reduce the
failure rate and fasten the clinical trials by improved results of the preclinical studies.
Incorporating nanomaterials in preclinical studies would help in determining the
dynamics and the fate of drugs. Nanoparticles delivered in the tumor-targeted region
can eventually improve the sensitivity of the CT system for personalized diagnosis.
The performance of different materials (Bi, Ta, Au, Yb, Eu, and Iodine) has no standard protocol to evaluate its performance in CT imaging. Also, these nanoparticles
used in preclinical imaging with different concentrations. Also, a thorough examination of these materials on compatibility aspects is needed for a clinical translation.
Since most of the materials are of high atomic number, their metabolism, degradation, and excretion have to be studied extensively. The cost of the new contrast agents
should be addressed because it requires a high concentration for better imaging [49].
Even though the attention towards the nanoparticle for CT imaging is less when
compared to MR and optical imaging, considerable research interest in developing
hybrid nanoparticles would help combine the advantage of each modality.
7 Nanomaterials for MRI Imaging
Analogous with CT, information obtained from Magnetic resonance imaging (MRI)
provides structural information with more detailed features in the tissues [142].
Images are acquired by magnetic behavioral changes of tissues when placed in a
large magnetic field. A magnetic field is generated exposed to the protons or atoms
in the tissues that align with a magnetic dipole. When a radio frequency (RF) signal
is a resonance with Larmor frequency of the protons, then they relax to its normal
state for a short duration of time known as T1 and T2 relaxation [3]. Magnetic relaxation of protons in tissues produces a RF signal that varies with the tissue type and
density. For more details about the relaxation properties of MRI, readers can refer
to this article [3, 143]. The complete mechanism of longitudinal and transverse (T1
and T2) relaxation of MRI concerning on/off RF signals.
MRI is a non-invasive technique that generates 3D images of tissues. Unlike CT,
MRI does not involve any type of hazardous radiation, and it is entirely safe for
repeated measurements [144]. Clinical MRI is not suitable for small animal imaging
and is associated with many problems and limitations [145]. Clinical MRI has a large
bore, less magnetic field up to 2 T) produces a low signal to noise ratio. Therefore, a
particular type of MRI requires a high magnetic field up to 10 T is required to study the
developmental biology of animals is called micro-MRI [146]. Micro-MRI produces
high-resolution anatomical, molecular and functional imaging for drug discovery
applications. The main disadvantages of micro-MRI are expensive due to uniform
high magnetic field generation. Animal models have to be anesthetized for detection, localization, volume of tumors, and blood flow characteristics. Also, time taken
to acquire MRI images takes longer compared to micro-CT [147]. Another major