Abstracts


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In vivo cellular imaging for translational medical research
Arbab A.S., Janic B., Haller J., Pawelczyk E., Liu W., Frank J.A

Personalized treatment using stem, modified or genetically engineered, cells is becoming a reality in the field of medicine, in which allogenic or autologous cells can be used for treatment and possibly for early diagnosis of diseases. Hematopoietic, stromal and organ specific stem cells are under evaluation for cell-based therapies for cardiac, neurological, autoimmune and other disorders. Cytotoxic or genetically altered T-cells are under clinical trial for the treatment of hematopoietic or other malignant diseases. Before using stem cells in clinical trials, translational research in experimental animal models are essential, with a critical emphasis on developing noninvasive methods for tracking the temporal and spatial homing of these cells to target tissues. Moreover, it is necessary to determine the transplanted cells, engraftment efficiency and functional capability. Various in vivo imaging modalities are in use to track the movement and incorporation of administered cells. Tagging cells with reporter genes, fluorescent dyes or different contrast agents transforms them into cellular probes or imaging agents. Recent reports have shown that magnetically labeled cells can be used as cellular magnetic resonance imaging (MRI) probes, demonstrating the cell trafficking to target tissues. In this review, we will discuss the methods to transform cells into probes for in vivo imaging, along with their advantages and disadvantages as well as the future clinical applicability of cellular imaging method and corresponding imaging modality. Â^© 2009 Bentham Science Publishers Ltd.


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Metabolite quantification in tumours by magnetic resonance spectroscopy: Objectives, results and perspectives
Canese R., Iorio E., Ricci A., Pisanu M.E., Giannini M., Podo F

Magnetic resonance spectroscopy (MRS) allows non invasive detection of tissue metabolism. Absolute or relative quantification of metabolites and chemical compounds detected by 1H and 31P MRS can today be performed in a number of pathological tissues including different types of cancer lesions, consequently improving accuracy in disease diagnosis and prognosis. Methods allowing quantification of tumour metabolites under in vivo MR spectral profiles have been progressively developed in the past and are now entering the clinical routine. Several methods of quantification have been proposed and validated in healthy tissues in a number of single- and multi-centre studies. Most of these approaches are not always directly applicable to cancer lesions because of their inherent heterogeneity or variability in water content, thus peak area ratios can, in some cases, represent better indicators of disease progression and response to therapy. An additional important limitation may derive from the excessive duration of some MRS measurement protocols, which would be added to a routine clinical MRI examination in the same session. We propose a critical overview of the principal methods currently applied for the quantification of metabolites and chemical compounds, mostly detected by 1H MRS in tumours. Â^© 2009 Bentham Science Publishers Ltd.


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Spatiotemporal modulation of central neural pathway underlying acupuncture action: A systematic review
Bai L., Qin W., Liang J., Tian J., Liu Y

Acupuncture, an ancient therapeutic technique, is currently gaining popularity as an important modality of alternative and complementary medicine in the West world. Concurrently, scientific interests in exploring whether acupuncture is therapeutically effective are raised alongside those about the means by which it may operate. Modern neuroimaging techniques such as functional magnetic resonance imaging, positron emission tomography, electroencephalography, and magnetoencephalography provide a means to safely monitor brain activity in humans. In this review, we have summarized evidence derived from the neuroimaging studies and tried to elucidate the neurophysiological correlates of acupuncture. Previous investigations on the neural responses to acupuncture mainly focus on its acute effects and explore the correlation between the specific acupoints and cortical activations only in the spatial domain. However, abundant clinical reports and psychophysical analysis suggest the kinetics of acupuncture is longer acting as a function of time. Consequentially, an accurate interpretation of acupuncture actions depends on how effectively we can characterize the nature of temporal variations underlying neural activities, rather than simply detect the occurrence of such changes. This emerging picture indicates that both designing paradigms and statistical models involved in acupuncture studies should be applied with great care. Â^©2009 Bentham Science Publishers Ltd.


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Overview of X-ray scatter in Cone-beam computed tomography and its correction methods
Niu T., Zhu L

X-ray cone-beam computed tomography (CBCT) is widely used nowadays, mainly for its large volume coverage and hardware compatibility with open-gantry x-ray imaging systems. As the size of x-ray illumination increases, an inevitable and adverse effect is the boost of scatter contamination on the x-ray images, which becomes one of the fundamental limitations of CBCT imaging. The large scatter signals in CBCT cause severe streaking and cupping artifacts in the CT images and greatly hamper the applications of CBCT due to its degraded image quality as compared to that of the conventional x-ray CT scanner. Research on scatter correction has gained heated attention in recent years. In this review, we first analyze the magnitudes of scatter in CBCT and its resultant errors in the reconstructed images. The existing CBCT scatter correction methods are then summarized in several categories: pre-processing methods, and post-processing methods including measurement-based, software-based, hardware-based decomposition and hybrid methods. An important issue related to the post-processing methods, the noise increase in the scatter corrected images, is also discussed. Although numerous scatter correction methods have been proposed in the literature, each approach has its own strengths and drawbacks and an optimal and standard method is still elusive. This review provides a comprehensive summary of the current research on scatter correction, and suggests future directions from the authors' perspective. Â^© 2010 Bentham Science Publishers Ltd.


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Prior image constrained compressed sensing (PICCS) and applications in X-ray computed tomography
Chen G.-H., Tang J., Nett B., Qi Z., Leng S., Szczykutowicz T

A new image reconstruction algorithm, prior image constrained compressed sensing (PICCS), will be reviewed in this paper. PICCS enables accurate image reconstruction with high contrast-to-noise ratio from undersampled projection data sets. Several clinically relevant applications are reviewed to demonstrate how the new algorithm can be utilized to: reduce radiation dose, provide high quality four dimensional cone beam CT images used for image guided radiation therapy, achieve high temporal resolution cardiac cone beam CT for image guided cardiac interventions, enable perfusion measurements with micro CT and significantly improve temporal resolution in diagnostic multi-detector cardiac CT. The computational speed concerns for this iterative algorithm are also discussed and a method to accelerate the reconstruction using commercially available graphic cards is presented. Future research directions using the PICCS algorithm are also briefly discussed. Â^© 2010 Bentham Science Publishers Ltd.


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Positron emission tomography imaging of tumor hypoxia
Fang S., Tian M., Zhang H

Hypoxia, a condition of insufficient O2 to support metabolism, occurs when tumor outgrows its vascular supply. As the tumor cells gradually become hypoxic, they adapt by up-regulating the production of numerous proteins that promote their survival and metastatic spread. These changes result in patients with hypoxic tumors invariably experience poor outcome to treatment. Accordingly, the development of assays for the detection of hypoxia in patients in order to predict outcome and identify patients with a worse prognosis and/or patients that would benefit from appropriate treatments is of potential interest to researchers and clinicians. A variety of invasive and noninvasive approaches have been developed to detect tumor oxygenation. These approaches including oxygen-sensitive electrodes and hypoxia marker techniques using various labels that can be detected by different methods such as autoradiography, immunohistochemistry, nuclear medicine imaging and magnetic resonance imaging. In this review, we will discuss the non-invasive, potentially providing a quantitative and high resolution three-dimensional molecular imaging modality with positron emission tomography which is available to measure tumor hypoxia. Â^©2010 Bentham Science Publishers Ltd.


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Directing minimal invasive image guided therapy of hepatic colorectal cancer metastases - Imaging strategies for patient evaluation, therapy planning, therapy monitoring, and follow-up
Schnapauff D., Grieser C., Denecke T

In contrast to surgical therapy and cytostatic therapy, locally ablative treatment of colorectal liver metastases is still lacking of large controlled trials to definitely prove its benefit on patient survival. Despite this, many different modalities have been developed for minimal invasive locoregional treatment, such as thermotherapy (radiofrequency ablation, laser induced thermotherapy) or brachytherapy (interstitial brachytherapy, transarterial radioembolization). As all of these modalities are performed under imaging guidance, success and risk strongly depends on the imaging strategy chosen for patient evaluation, treatment monitoring, and follow-up. There are not yet comprehensive guidelines on the use of locally ablative therapies, and, even more so, the use of diagnostic imaging largely depends on individual experiences and policies. Beyond oncological routines, the planning and monitoring of locally ablative treatment pose specific demands on the available imaging procedures. Many innovative applications of ultrasound, CT, MRI, PET and SPECT help to fulfill these requirements. Algorithms are needed for pretherapeutic decision making regarding the appropriate treatment strategy, as well as for posttherapeutic follow-up to confirm local control and to rule out new disease. This review summarizes current opinions to the use of diagnostic imaging in the scope of different image guided therapy modalities. Important, partly unpublished data for comprehensive pre- and posttherapeutic imaging algorithms is worked up. It also outlines challenges and possible solutions for improved guidance and monitoring of minimal invasive locoregional cancer treatment. Â^© 2009 Bentham Science Publishers Ltd.


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Mitochondrial encephalomyopathies in children. Part I: Conventional MR imaging findings
Munoz A., Mateos F., Simon R., Martin-Hernandez E., Camacho A., Ferrando P., Arenas J., Martin M.A

Background and Purpose: Mitochondrial encephalomyopathies (ME) may promote many brain abnormalities that can be detected with advanced neuroradiologic tools. The aim of this first of two reports is to evaluate if there are representative neuroradiological patterns of the most common ME disorders affecting children. Methods: Non-selected longitudinal study in 55 patients over 15 years. All of them underwent one or more MR imaging studies. Five different patterns of imaging involvement were proposed: 1-Myelinization delay and atrophy, 2-Gray nuclei involvement, 3-Leukodystrophyc pattern, 4-Menke's pattern, and 5-Others. Results: Leigh's disease (LD): 19 (34.5%), Alper's disease (AD):12 (22.18%), Kearns-Sayre syndrome (KSS): 3 (5.4%); Menkes and Menkes-like diseases and variants: 4 (9%), others: 17 (30.9%). On imaging grounds, there were statistical association between the main syndromes and the patterns proposed. Conclusion: MRI imaging shows non-specific features in about one third of the patients, whereas the other two third are associated with some few characteristic neuroradiologic-phenotypes proposed. Although these findings are not pathognomonic they provide a guide in imaging approach for children suspected of ME. Â^© 2009 Bentham Science Publishers Ltd.


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Shift of focus region (SFR) in heated tissues by high intensity focused ultrasound (HIFU)
Zu W.Q., Ye S., Fei X., Zhu Z., Jiang W., Yang Y., Xiao L

In high intensity focused ultrasound (HIFU) experiments it is found that the center of the heated region is always deviated from the geometrical focus point of transducers. This phenomenon is called the shift of the focus region (SFR). To achieve optimal result in HIFU treatment, the focused region should be adjusted to compensate the shift. In this paper, a quantitative method to measure SFR is proposed and applied to the experiments for porcine tissues in vitro by the authors. In the experiments it is observed that the maximum SFR which are towards to the HIFU transducer can exceed 1 cm. Â^©2009 Bentham Science Publishers Ltd.