Mini Review Open Access Journal of Nanomedicine & Nanotechnology J o u r na l o f N a n o m e d i c i n e & N a n o t e c h n o l o g y ISSN: 2157-7439 Khosroshahi, J Nanomed Nanotechnol 2018, 9:1 DOI: 10.4172/2157-7439.1000485 J Nanomed Nanotechnol, an open access journal ISSN: 2157-7439 Volume 9 • Issue 1 • 1000485 Biomedical Imaging: Contrast Agents and Multifunctionality Mohammad E Khosroshahi* MIS-Electronics, Nanobiophotonics and Biomedical Research Lab., Richmond Hill, Canada *Corresponding author: Mohammad E Khosroshahi, MIS-Electronics, Nanobiophotonics and Biomedical Research Lab., Richmond Hill, Canada, Tel: 14169781287; E-mail: Khosrom@mie.utoronto.ca Received: February 09, 2017; Accepted: February 21, 2018; Published: February 23, 2018 Citation: Khosroshahi ME (2018) Biomedical Imaging: Contrast Agents and Multifunctionality. J Nanomed Nanotechnol 9: 485. doi: 10.4172/2157- 7439.1000485 Copyright: © 2018 Khosroshahi ME. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Bioimaging Bioimaging is one of the major streamlines of comprehensive cancer care in both diagnosis and research with signifcant advantages of real time monitoring, minimal or no invasive action, and operational over relatively wide ranges of time and size scales involved in biological and pathological processes. Bioimaging plays a great role in diferent stages of cancer management: Prediction, screening, biopsy for detection, staging, prognosis, therapy planning, therapy guidance and therapy response [1-5]. Biomarkers identifed from the genome and proteome can be selectively targeted and chemical binding can improve their imaging signal. Various pharmaceutical therapies that have been developed for cancer are classifed as cytotoxic, antihormonal, immunotherapeutic and molecular targeted. Imaging can help the molecular targeted therapies to control their efectiveness and include: signal transduction, angiogenesis, cell cycle inhibitors, apoptosis inducers and epigenetic modulators [6]. Te molecular imaging is a combined functional and structural imaging modality, which efectively can be used to achieve the health beneft from understanding the spatial mapping at the whole-body level and molecular processes within cells and tissues [7]. Various targeted agents for cancer markers are for example: epidermal growth factor receptor (EGFR), α v β 3 integrin, vascular endothelial growth factor (VEGF), carcinoembryonic antigen (CEA) and folate receptors (FR). Clearly, the development of minimally invasive targeted therapy and drug delivery should be based on the guided imaging system. Most clinical imaging systems are based on the interaction of electromagnetic radiation with body tissues and fuids except ultrasound which is based on the refection, scattering and the frequency shifs of acoustic waves (i.e., Doppler efect). Ultrasound also has the capability of imaging tissue elasticity, thus can be employed in diferential diagnosis of breast cancer, prostate cancer, and liver fbrosis because cancer tissues are less elastic than normal tissue and ultrasound elastography [8,9]. High frequency electromagnetic radiation such as γ-rays, X-rays or UV light is ionizing, which can cause mutation hence leading to cancer. In contrast, non-ionizing radiation imaging systems including IR spectroscopy, microwave imaging spectroscopy, photoacoustic and thermoacoustic imaging which are readily used for imaging poses no such danger. Imaging systems has one common point; they vary in physical properties including sensitivity, temporal and spatial resolution. In addition, the imaging systems produce images that have diferences in contrast. Te diferences in contrast can be due to changes in physical properties caused by the endogenous nature of the tissue e.g.: radiation absorption, refection, transmission, magnetic relaxivity, magnetic susceptibility, oxygenation, spectral distribution, electrical impedance, mechanical elasticity, etc. or exogenous mechanisms e.g.: radiation absorption, refection, emission, magnetic relaxivity, magnetic susceptibility, isotope spectra, fuorescence, perfusion, hypoxia, etc. Finally, it is believed that the sensitivity and specifcity of diagnostic systems can be improved by combining the systems as one system known as multimodal system. Multimodal Strategies No single imaging system can provide all the required information in biomedical imaging technology. As mentioned above each imaging modality has its own advantages and limitations in terms of sensitivity, resolution, accuracy and quantitative capabilities. Te major problem which is ofen faced with single-modality imaging is the inability to assure the conformance of diagnosis, which is very important factor in determining the treatment. Te problem is solved by multimodal imaging system where a combination of techniques with complementary strengths ofer unique benefts which are not met by individual methods. Terefore, utilizing such complementary imaging modes will greatly improve the diagnosis and treatment reliance and render extra comfort to both physicians and patients. Multimodal imaging techniques can be obtained in two diferent approaches (i) combining the diferent imaging instruments into one unit, (ii) to develop multimodal imaging agents. Examples of combined imaging systems • PET-CT • MRI-Optical • MRI-CT • MRI-PET • MRI-PET-NIRF • MRI/SPECT • MRI-PA-Raman • SPECT-CT • PA-US • PA-OCT • PA-Fluorescence • PA-US-Agents. Examples of multimodal imaging agents Although every individual imaging modality system has its particular contrast agents, multimodal imaging systems also require its customized multimodal contrast agents. Some examples are as follows: Iron oxide-Gold nanoparticles (SPION-Au): has been used in MRI-PAI dual mode imaging [10] where they showed the defned structural characteristics and physical properties of this agent not only