Nanomaterials for Medical Imaging …
343
This book chapter covers the significant aspects and design principles of various
types of nanoparticles (NPs) specific to pre-clinical imaging techniques. Sections of
this chapter are well organized that explain the nanomaterials in research as well
as in the drug development process. Also, the chapter provides a multidisciplinary
approach for students, industries, the scientific community, and healthcare professions to enhance the knowledge on understanding the bond between nanoprobes and
pre-clinical imaging.
4 Nanomaterials for CT Imaging
After the discovery of X-rays in 1895 by W.C Roentgen, medical imaging has evolved
drastically for non-invasive clinical diagnosis. X-rays are used to determine the location of implants, bone deformities, dental issues, calcifications, arthritis, and determine small objects swallowed by infants [46]. X-rays radiographic projections (2D
images) are currently used to visualize anatomical structures of bone in a post and
pre-surgical treatment. Compared to other imaging systems, X-rays have been used
as an initial screening for several diseases due to their low cost, high resolution,
less toxic to tissues, and scans at short duration [47]. Medical image processing
techniques in radiographic X-ray images convert 2D images to 3D that help physicians for precise diagnosis of disease. Computed tomography (CT), a collection of
2D images are acquired by rotating source and detector from the different axis and
post-processing these images to visualize in 3D.
Further advancements in image processing tools provide high-resolution images
with fewer artifacts [48]. Readers can get a more detailed review of the principles of
X-ray CT reconstruction is provided in [49]. Contrast agents like Iodine and bismuth
are used to understand the structural modification in the tissues. These exogenous
contrast materials help in improving the resolution and sensitivity of the diseased
location. Figure 5 shows the family of different contrast agents used in preclinical
X-ray CT imaging [50].
5 Conventional CT Contrast for In Vivo Imaging
Clinically, used iodinated contrast agents (1,3,5-triiodo benzene) are injected intravenously, typically for enhancing X-ray CT images. These iodinated contrast agents
are also used in fluoroscopy, angiography, and sometimes in plain radiography. Iodine
is commonly used as a contrast medium for CT because its K-edge (33.2 keV) lies
in the average diagnostic energy. There are two types of iodinated contrast agents,
namely, ionic and non–ionic based on water solubility. Iodinated contrast agents have
several disadvantages, (i) molecular weight of Iodine is less thereby clears rapidly
through kidneys; (ii) high concentration of Iodine is required for better signals but
shows toxicity (iii) Iodinated contrast agents cannot be targeted to a particular region
343
This book chapter covers the significant aspects and design principles of various
types of nanoparticles (NPs) specific to pre-clinical imaging techniques. Sections of
this chapter are well organized that explain the nanomaterials in research as well
as in the drug development process. Also, the chapter provides a multidisciplinary
approach for students, industries, the scientific community, and healthcare professions to enhance the knowledge on understanding the bond between nanoprobes and
pre-clinical imaging.
4 Nanomaterials for CT Imaging
After the discovery of X-rays in 1895 by W.C Roentgen, medical imaging has evolved
drastically for non-invasive clinical diagnosis. X-rays are used to determine the location of implants, bone deformities, dental issues, calcifications, arthritis, and determine small objects swallowed by infants [46]. X-rays radiographic projections (2D
images) are currently used to visualize anatomical structures of bone in a post and
pre-surgical treatment. Compared to other imaging systems, X-rays have been used
as an initial screening for several diseases due to their low cost, high resolution,
less toxic to tissues, and scans at short duration [47]. Medical image processing
techniques in radiographic X-ray images convert 2D images to 3D that help physicians for precise diagnosis of disease. Computed tomography (CT), a collection of
2D images are acquired by rotating source and detector from the different axis and
post-processing these images to visualize in 3D.
Further advancements in image processing tools provide high-resolution images
with fewer artifacts [48]. Readers can get a more detailed review of the principles of
X-ray CT reconstruction is provided in [49]. Contrast agents like Iodine and bismuth
are used to understand the structural modification in the tissues. These exogenous
contrast materials help in improving the resolution and sensitivity of the diseased
location. Figure 5 shows the family of different contrast agents used in preclinical
X-ray CT imaging [50].
5 Conventional CT Contrast for In Vivo Imaging
Clinically, used iodinated contrast agents (1,3,5-triiodo benzene) are injected intravenously, typically for enhancing X-ray CT images. These iodinated contrast agents
are also used in fluoroscopy, angiography, and sometimes in plain radiography. Iodine
is commonly used as a contrast medium for CT because its K-edge (33.2 keV) lies
in the average diagnostic energy. There are two types of iodinated contrast agents,
namely, ionic and non–ionic based on water solubility. Iodinated contrast agents have
several disadvantages, (i) molecular weight of Iodine is less thereby clears rapidly
through kidneys; (ii) high concentration of Iodine is required for better signals but
shows toxicity (iii) Iodinated contrast agents cannot be targeted to a particular region