Current Medical Imaging - Volume 8, Issue 4, 2012

With the current advances in genomics and proteomics, cardiovascular molecular imaging techniques such as PET and SPECT, in combination with other cardiac molecular imaging techniques, will identify new markers of disease activity and will play a central role in screening of patients, diagnosis, prognosis and patient management. The complexity of the development process of vulnerable atherosclerotic plaques provides an excellent example of the need for combined molecular imaging. Predicting outcome by molecular imaging of atherosclerotic plaques should offer new paradigms for the management of coronary artery disease. In cardiac neurotransmission, molecular imaging can offer insights and provide better understanding of pathophysiologic mechanisms and help to improve patient management, in particular in patients with heart failure or at risk of arrhythmias. A recent important advance in the area of cardiovascular molecular imaging is reporter gene imaging. The concept has been validated in animal models, where reporter genes are only expressed by living stem cells, offering a means to track stem cell survival. Reporter genes are passed on to daughter cells, making assessment of cell proliferation possible. Reporter gene imaging can be applied to a variety of stem cells or therapeutic genes of interest in stem cell or gene based therapy in cardiovascular medicine.

Novel nanoparticles, including various gold nanostructures with intrinsic optical properties can be tuned to have strong absorption in the near-infrared region. These nanoparticles have been shown to be useful for a variety of potential applications in biomedicine, including cancer molecular imaging, photothermal ablation therapy, and controlled drug delivery. In this article, we provide an up-to-date review of these nanoparticles integrating both diagnostic and therapeutic functions, and their applications in image-guided cancer therapy.

In vivo cell tracking has been enabled by molecular imaging technology and, recently, monitoring cell fate changes has become possible in small animals. Stem cells and induced pluripotent stem cells (iPSCs) can differentiate in vivo after implantation, and lineage commitment of these cells can be successfully imaged using cell-specific promoterdriven reporter genes. For this purpose, imaging sensitivity has been significantly enhanced by engineering luciferase or adopting molecular amplification techniques. After transplantation of stem cells within a polymer scaffold, the fate changes of cells into neuronal lineages were monitored long enough to recognize possible adoption within endogenous microenvironment. Multiplexing and optimizing the imaging method to trace fate changes of transplanted stem cells can now be implemented broadly in vivo in small animals and possibly in humans.

Coronary artery disease is the major cause of death in developed countries. PET myocardial perfusion image has become more important in the diagnosis and risk stratification for coronary artery disease patients. The available evidence supported that PET is the “gold standard” for detecting myocardial perfusion, comparing to other noninvasive assessment techniques. Its ability to quantify absolute myocardial blood flow and evaluate left ventricle function from rest to stress provides an extra value in multi-vessel disease and prognosis. As the development of scanners, software, novel radiotracers, hybrid imaging technique and the emerging clinical evidence, the clinical application of PET will be further enhanced in the near future. This review summarized clinical application of PET myocardial perfusion imaging and its new developments.

Molecular imaging technologies have undergone explosive growth during the past two decades, providing noninvasive and quantitative imaging of biological and biochemical processes within intact living subject. Conventional anatomical imaging techniques such as X-ray computed tomography (XCT) or magnetic resonance imaging (MRI) can offer detailed anatomical structures but are weak in providing physiological information. Primary functional imaging modalities including radionuclide imaging and optical imaging are able to offer high-sensitive molecular information but suffer from poor spatial resolution. Improvements in overall imaging performance can be achieved by combining the strengths of different imaging modalities. These combinations, such as radionuclide/XCT, radionuclide/MRI, optical/XCT, optical/MRI, and optical/radionuclide, are expected to have a significant impact on disease detection, treatment planning, and drug development. Here, the review summarizes the recent developments in multi-modality molecular imaging, and highlights their applications in preclinical and clinical researches.

Peripheral benzodiazepine receptor (PBR) has been implicated in the regulation of various cellular processes, including regulation of steroidogenesis,immunomodulation, porphyrin transport, heme synthesis, cell apoptosis and proliferation. Also, PBR expression levels were shown to be increased in a variety of cancers indicating its important role in cancer development.The investigation and biological evaluation of specific potent radioligands for positron emission tomography PET (Positron emission tomography) studies of PBRs are of great value as they have been associated with a variety of disease processes such as cancer, autoimmune diseases, viral infection, neurodegeneration,stress, and brain injury. More than twenty years have seen the development of radiolabelled quinoline derivaties (3-isoquinolinecarboxamide and quinoline-2-carboxamides) and some of these novel probes have been evaluated for the PET imaging of PBR. This mini review is aiming to provide a brief overview on the research on this kind of imiging probe.

One of the most costly steps in drug development is the identification of a genuinely druggable compound for human beings, from pre-clinical animal model research. In order to overcome this problem, the importance of screening compounds with desirable distributions and metabolism in human bodies, using a microdosing technique, is increasingly apparent. In addition, screening compounds with high ligand efficiency is crucial to identify druggable compounds at an early stage of the research, and structure-based drug development is the most powerful tool for this strategy. Thus, the combined utilization of structural biology/structural genomics and molecular imaging technology will be critically important for drug discovery research in the near future. This review focuses on current topics of structural genomics, including protein synthesis systems and structural analyses, toward rational drug development in collaboration with molecular imaging.

Music is one of the oldest experimental study subjects in psychology. Functional neurological techniques, including functional magnetic resonance imaging (MRI), positron emission tomography (PET), electroencephalography and magnetoencephalography, are powerful methods of investigation of neural structure and functional correlates of music processing in humans. Herein, we offer a conceptual review of music and methodological guide to illustrate the value of PET as a valuable method of investigating a multitude of complex cognitive functions related to music and the neural mechanisms of these functions with an emphasis on perception of components of musical processing, the emotions induced by music, and the factors that may influence the results of activated brain regions described by literatures in studies of musical neural basis imaged using PET.

Validation is now considered as a mandatory step in any development of new medical image processing methods, systems, or components. It allows studying performances and adequacy with clinical applications, and comparison with similar solutions. Being able to correctly answer these three issues requires proper design, performance, and report of validation studies and results. This could be made easier by 1) the use of standardized solutions and 2) the explicit formalization and description of validation study components when designing and reporting such studies. In this paper, we will identify the major components involved in a validation study of a medical image processing (MIP) method, embedded or not in a wider clinical system. Emphasis will be given on the study conditions, and especially on the validation data sets. Main freely available validation data sets usable for MIP validation will be listed and shortly described. Finally, we will outline the need for validating the validation study itself and explain the two main aspects it includes.

Diffusion tensor imaging (DTI) is an effective technology for the study of the internal structure of the brain non-invasively. At present, this technology is widely applied to clinical diagnosis and can reflect a series of pathological changes in the microstructure due to changes in nerve fibers. This article first explains the basic principles of DTI and some parameters like fractional anisotropy (FA) and relative anisotropy (RA). It then reviews several clinical applications of DTI from three perspectives, namely the clinical applications of anisotropy indices, fibers tracking, and DTI combined with other neuroimaging methods. Through the studies of the changes in the parameters of DTI and the contrast among a series of white matter fiber images, researchers can obtain important information about the changes in the structure of tissues, which can in turn be applied in clinic, and also include the value of DTI in the work-up of diseases as a tool in the differentiation of normal tissues and diseased tissues. This article also reviews the clinical application of fiber tracking and DTI combined with functional magnetic resonance imaging (fMRI), electroencephalogram (EEG), and mangnetoencephalography (MEG), and others. Moreover, this article summarizes the advantages of DTI over traditional imaging technology like magnetic resonance imaging (MRI) and diffusion weighted imaging (DWI). Some prospect applications of the DTI as well as unsolved problems are also briefly reviewed.