Nanomaterials for Medical Imaging …
375
Tremel and his colleagues showed the interaction of MONPs with Superoxide
Dismutase possesses enhanced MR signals when radicals of oxygen converted into
hydrogen peroxide [243]. The higher relaxivity in both T 1 and T 2 times enhanced
the contrast with simultaneous treatment modulates oxidative stress that helps in the
progression of tumor growth. A combination of anatomical models and molecular
imaging helps to understand and characterize for effective therapy and diagnosis.
Multimodal imaging with targeted MONPs was developed by Zhan et al. studied the
tumor vasculature using MRI and PET. They incorporated Cu-64 PET tracer linked
MONPs functionalized with a monoclonal antibody (TRC105). In vivo distribution
studies were performed using PET/MRI carried out in xenografted glioma tumor
model. A 20 mg/kg of nanomaterials were injected through intravenous injection
and observed positive contrast and consistent with PET imaging [244]. Composites
of manganese-based MR contrast agents were developed as multimodal imaging and
therapeutic effects. For instance, Manganese ferrite [245–247], MnO combined with
Au and SiO2 [248], manganese silica [249], manganese carbonate [250].
8 Nanomaterials for Ultrasound Imaging
Ultrasound (US) imaging is another versatile non-invasive imaging system that uses
high frequency (2–200 MHz) sound waves to differentiate tissues. Ultrasound uses
non-ionizing radiations when compared to other X-ray CT, and they are ubiquitous
works on principles of refraction by tissue components having a different acoustic
impedance. US is commonly used to understand the development of fetuses, breast,
neck, and blood flow studies [251]. Recent trends in US have improvised the imaging
quality changed from B mode to 3D and later into 4D (concerning time). Artifacts
such as tissue harmonic aberration, reduction of aberration, ghost effects in tissues.
But the significant concerns associated with US are quality of image compared to CT
or MRI, and absorption by bone limits the depth of penetration [3]. Contrast-enhanced
ultrasonic agents such as air bubbles or gas loaded particles are required to overcome
the above limitations. The first gas-filled contrast agents were developed Unger et al.
with a size range between 7 and 8 microns made of di-palmitoyl phosphatidyl choline
(DPPC) [252]. The problems associated with these microbubbles are large size, cell
penetration is difficult, traps at alveolar ducts, and restricted to cardiac imaging
[253]. Nanosized particles loaded with gas molecules are called nanobubbles with
a size between 100 and 1000 nm. Further developments in the nano-sized contrast
agents such as liposomes, nanobubbles, nanodroplets less than 1-micron particles
[254]. Several types of gases used in US contrast agents such as perfluorocarbons
or sulphur hexafluoride (SF 6 ), oxygen, and hydrogen [34]. These nanobubbles are
being more efficient reflectors when ultrasound is excited over the particles. These
nanobubbles are effectively used as in vivo imaging and accumulate in the tissues
via the EPR effect.
375
Tremel and his colleagues showed the interaction of MONPs with Superoxide
Dismutase possesses enhanced MR signals when radicals of oxygen converted into
hydrogen peroxide [243]. The higher relaxivity in both T 1 and T 2 times enhanced
the contrast with simultaneous treatment modulates oxidative stress that helps in the
progression of tumor growth. A combination of anatomical models and molecular
imaging helps to understand and characterize for effective therapy and diagnosis.
Multimodal imaging with targeted MONPs was developed by Zhan et al. studied the
tumor vasculature using MRI and PET. They incorporated Cu-64 PET tracer linked
MONPs functionalized with a monoclonal antibody (TRC105). In vivo distribution
studies were performed using PET/MRI carried out in xenografted glioma tumor
model. A 20 mg/kg of nanomaterials were injected through intravenous injection
and observed positive contrast and consistent with PET imaging [244]. Composites
of manganese-based MR contrast agents were developed as multimodal imaging and
therapeutic effects. For instance, Manganese ferrite [245–247], MnO combined with
Au and SiO2 [248], manganese silica [249], manganese carbonate [250].
8 Nanomaterials for Ultrasound Imaging
Ultrasound (US) imaging is another versatile non-invasive imaging system that uses
high frequency (2–200 MHz) sound waves to differentiate tissues. Ultrasound uses
non-ionizing radiations when compared to other X-ray CT, and they are ubiquitous
works on principles of refraction by tissue components having a different acoustic
impedance. US is commonly used to understand the development of fetuses, breast,
neck, and blood flow studies [251]. Recent trends in US have improvised the imaging
quality changed from B mode to 3D and later into 4D (concerning time). Artifacts
such as tissue harmonic aberration, reduction of aberration, ghost effects in tissues.
But the significant concerns associated with US are quality of image compared to CT
or MRI, and absorption by bone limits the depth of penetration [3]. Contrast-enhanced
ultrasonic agents such as air bubbles or gas loaded particles are required to overcome
the above limitations. The first gas-filled contrast agents were developed Unger et al.
with a size range between 7 and 8 microns made of di-palmitoyl phosphatidyl choline
(DPPC) [252]. The problems associated with these microbubbles are large size, cell
penetration is difficult, traps at alveolar ducts, and restricted to cardiac imaging
[253]. Nanosized particles loaded with gas molecules are called nanobubbles with
a size between 100 and 1000 nm. Further developments in the nano-sized contrast
agents such as liposomes, nanobubbles, nanodroplets less than 1-micron particles
[254]. Several types of gases used in US contrast agents such as perfluorocarbons
or sulphur hexafluoride (SF 6 ), oxygen, and hydrogen [34]. These nanobubbles are
being more efficient reflectors when ultrasound is excited over the particles. These
nanobubbles are effectively used as in vivo imaging and accumulate in the tissues
via the EPR effect.