Publications by authors named "Silun Wang"

36 Publications

Hippocampal and Amygdalar Morphological Abnormalities in Alzheimer's Disease Based on Three Chinese MRI Datasets.

Curr Alzheimer Res 2020 ;17(13):1221-1231

Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, China.

Background: Early detection of Alzheimer's disease (AD) and its early stage, the mild cognitive impairment (MCI), has important scientific, clinical and social significance. Magnetic resonance imaging (MRI) based statistical shape analysis provides an opportunity to detect regional structural abnormalities of brain structures caused by AD and MCI.

Objective: In this work, we aimed to employ a well-established statistical shape analysis pipeline, in the framework of large deformation diffeomorphic metric mapping, to identify and quantify the regional shape abnormalities of the bilateral hippocampus and amygdala at different prodromal stages of AD, using three Chinese MRI datasets collected from different domestic hospitals.

Methods: We analyzed the region-specific shape abnormalities at different stages of the neuropathology of AD by comparing the localized shape characteristics of the bilateral hippocampi and amygdalas between healthy controls and two disease groups (MCI and AD). In addition to group comparison analyses, we also investigated the association between the shape characteristics and the Mini Mental State Examination (MMSE) of each structure of interest in the disease group (MCI and AD combined) as well as the discriminative power of different morphometric biomarkers.

Results: We found the strongest disease pathology (regional atrophy) at the subiculum and CA1 subregions of the hippocampus and the basolateral, basomedial as well as centromedial subregions of the amygdala. Furthermore, the shape characteristics of the hippocampal and amygdalar subregions exhibiting the strongest AD related atrophy were found to have the most significant positive associations with the MMSE. Employing the shape deformation marker of the hippocampus or the amygdala for automated MCI or AD detection yielded a significant accuracy boost over the corresponding volume measurement.

Conclusion: Our results suggested that the amygdalar and hippocampal morphometrics, especially those of shape morphometrics, can be used as auxiliary indicators for monitoring the disease status of an AD patient.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2174/1567205018666210218150223DOI Listing
January 2020

Deep-Learning-Based Segmentation and Localization of White Matter Hyperintensities on Magnetic Resonance Images.

Interdiscip Sci 2020 Dec 2;12(4):438-446. Epub 2020 Nov 2.

YIWEI Medical Technology Co., Ltd, Room 1001, MAI KE LONG Building, Nanshan, ShenZhen, 518000, China.

White matter magnetic resonance hyperintensities of presumed vascular origin, which could be widely observed in elderly people, and has significant importance in multiple neurological studies. Quantitative measurement usually relies heavily on manual or semi-automatic delineation and intuitive localization, which is time-consuming and observer-dependent. Current automatic quantification methods focus mainly on the segmentation, but the spatial distribution of lesions plays a vital role in clinical diagnosis. In this study, we implemented four segmentation algorithms and compared the performances quantitatively and qualitatively on two open-access datasets. The location-specific analysis was conducted sequentially on 213 clinical patients with cerebral ischemia and lacune. The experimental results suggest that our deep-learning-based model has the potential to be integrated into the clinical workflow.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s12539-020-00398-0DOI Listing
December 2020

Revealing hemodynamic heterogeneity of gliomas based on signal profile features of dynamic susceptibility contrast-enhanced MRI.

Neuroimage Clin 2019 22;23:101864. Epub 2019 May 22.

Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, United States of America. Electronic address:

Dynamic susceptibility contrast enhanced magnetic resonance imaging (DSC MRI) is widely used for studying blood perfusion in brain tumors. While the time-dependent change of MRI signals related to the concentration of the tracer is used to derive the hemodynamic parameters such as regional blood volume and flow into tumors, the tissue-specific information associated with variations in profiles of signal time course is often overlooked. We report a new approach of combining model free independent component analysis (ICA) identification of specific signal profiles of DSC MRI time course data and extraction of the features from those time course profiles to interrogate time course data followed by calculating the region specific blood volume based on selected individual time courses. Based on the retrospective analysis of DSC MRI data from 38 patients with pathology confirmed low (n = 18) and high (n = 20) grade gliomas, the results reveal the spatially defined intra-tumoral hemodynamic heterogeneity of brain tumors based on features of time course profiles. The hemodynamic heterogeneity as measured by the number of independent components of time course data is associated with the tumor grade. Using 8 selected signal profile features, machine-learning trained algorithm, e.g., logistic regression, was able to differentiate pathology confirmed low intra-tumoral and high grade gliomas with an accuracy of 86.7%. Furthermore, the new method can potentially extract more tumor physiological information from DSC MRI comparing to the traditional model-based analysis and morphological analysis of tumor heterogeneity, thus may improve the characterizations of gliomas for better diagnosis and treatment decisions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.nicl.2019.101864DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6558214PMC
June 2020

Traumatic Brain Injury Results in Dynamic Brain Structure Changes Leading to Acute and Chronic Motor Function Deficits in a Pediatric Piglet Model.

J Neurotrauma 2019 10 17;36(20):2930-2942. Epub 2019 Jun 17.

Regenerative Bioscience Center, University of Georgia, Athens, Georgia.

Traumatic brain injury (TBI) is a leading cause of death and disability in children. Pediatric TBI patients often suffer from crippling cognitive, emotional, and motor function deficits that have negative lifelong effects. The objective of this study was to longitudinally assess TBI pathophysiology using multi-parametric magnetic resonance imaging (MRI), gait analysis, and histological approaches in a pediatric piglet model. TBI was produced by controlled cortical impact in Landrace piglets. MRI data, including from proton magnetic resonance spectroscopy (MRS), were collected 24 hours and 12 weeks post-TBI, and gait analysis was performed at multiple time-points over 12 weeks post-TBI. A subset of animals was sacrificed 24 hours, 1 week, 4 weeks, and 12 weeks post-TBI for histological analysis. MRI results demonstrated that TBI led to a significant brain lesion and midline shift as well as microscopic tissue damage with altered brain diffusivity, decreased white matter integrity, and reduced cerebral blood flow. MRS showed a range of neurochemical changes after TBI. Histological analysis revealed neuronal loss, astrogliosis/astrocytosis, and microglia activation. Further, gait analysis showed transient impairments in cadence, cycle time, % stance, step length, and stride length, as well as long-term impairments in weight distribution after TBI. Taken together, this study illustrates the distinct time course of TBI pathoanatomic and functional responses up to 12 weeks post-TBI in a piglet TBI model. The study of TBI injury and recovery mechanisms, as well as the testing of therapeutics in this translational model, are likely to be more predictive of human responses and clinical outcomes compared to traditional small animal models.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1089/neu.2018.6303DOI Listing
October 2019

Metabolite Profile of Alzheimer's Disease in the Frontal Cortex as Analyzed by HRMAS H NMR.

Front Aging Neurosci 2018 9;10:424. Epub 2019 Jan 9.

Graduate School, Medical College of Nanchang University, Nanchang, China.

Investigation on neurochemical changes in the frontal cortex in individuals with Alzheimer's disease (AD) and different Apolipoprotein E (APOE) genotypes, using solid-state high-resolution NMR analysis, may lead to a better understanding of the neurochemistry associated with AD as well as new AD-specific metabolite biomarkers that might potentially improve the clinical diagnosis of AD. Intact tissue samples of the frontal cortex were obtained from 11 patients and 11 age-matched non-demented controls. Metabolite profiles in all samples were analyzed , using solid-state high-resolution magic angle spinning (HRMAS) 600 MHz H nuclear magnetic resonance (NMR). A logistic regression analysis was used to rank metabolites based on their level of contribution in differentiating the AD patient tissues and the controls, and different AD-associated APOE genotypes (APOE ε4 vs. APOE ε3). Tissue samples from the AD patients showed significantly lower NAA/Cr ( = 0.011), Ace/Cr ( = 0.027), GABA/Cr ( = 0.005), Asp/Cr ( < 0.0001), mI/Cr ( < 0.0001), and Tau/Cr ( = 0.021), and higher PCho/Cr ( < 0.0001), GPCho/Cr ( < 0.0001), and α&β-Glc/Cr ( < 0.0001) than the controls did. Specifically, a newly observed resonance at 3.71 ppm, referred to as α&β-Glc, was observed in 90.9% of the AD samples (10/11). Samples with APOE ε4 also exhibited higher PCho/Cr ( = 0.0002), GPCho/Cr ( = 0.0001), α&β-Glc/Cr ( < 0.0001), and lower Asp/Cr ( = 0.004) and GABA/Cr ( = 0.04) than the samples with APOE ε3 did. In the logistic regression analysis, PCho, GPCho, ASP, and α&β-Glc were found to be the most relevant metabolites for differentiating the AD patient tissues and the controls, and different APOE genotypes. HRMAS H NMR with high spectral resolution and sensitivity offers a powerful tool to gain quantitative information on AD associated neurochemical changes. There are important neurochemical differences in the frontal cortex between the AD patient tissues and the controls, and between those with different APOE genotypes. The resonance (α&β-Glc) found at 3.71 ppm in the AD patient tissues may be further investigated for its potential in the diagnosis and monitoring of AD.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fnagi.2018.00424DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6333733PMC
January 2019

Evaluation of neuregulin-1's neuroprotection against ischemic injury in rats using diffusion tensor imaging.

Magn Reson Imaging 2018 11 21;53:63-70. Epub 2018 Jul 21.

Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road NE, Atlanta, GA 30329, USA; Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA. Electronic address:

Stroke is a devastating neurovascular disorder that results in damage to neurons and white matter tracts. It has been previously demonstrated that neuregulin-1 (NRG-1) protects neurons from ischemic injury following stroke. Here, diffusion tensor imaging (DTI) was utilized to characterize the effects of NRG-1 treatment on cererbral infarction and integrity of white matter after ischemic insult using a permanent middle celebral artery occlusion (pMCAo) rat model. In the present study, sixteen Sprague-Dawley rats underwent pMCAo surgery and received either a single intra-arterial bolus (20 μg/kg) dose of NRG-1 or saline immediately prior to pMCAo. MRI including T2-weighted imaging and DTI was performed in the first 3 h post stroke, and repeated 48 h later. It is found that the stroke infarction was significantly reduced in the NRG-1 treated group. Also, NRG-1 prevented the reduction of fractional anisotropy (FA) in white matter tracts of fornix and corpus callosum (CC), indicating its protection of CC and fornix white matter bundles from ischemia insult. As a conclusion, the present DTI results demonstrate that NRG-1 has significantly neuroprotective effects in both cerebral cortex and white matter including corpus callosum and fornix during acute stroke. In particular, NRG-1 is more effective on stroke lesion with mild ischemia. As CC and fornix white matter bundles play critical roles in transcallosal connectivity and hippocampal projections respectively in the central nervous system, the findings could provide complementary information for better understanding the biological mechanism of NRG-1's neuroprotection in ischemic tissues and neurobehavioral effects.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.mri.2018.07.002DOI Listing
November 2018

Progressive Assessment of Ischemic Injury to White Matter Using Diffusion Tensor Imaging: A Preliminary Study of a Macaque Model of Stroke.

Open Neuroimag J 2018 30;12:30-41. Epub 2018 Mar 30.

Yerkes National Primate Research Center, Emory University, Atlanta, Georgia 30329.

Background: Previous Diffusion Tensor Imaging (DTI) studies have demonstrated the temporal evolution of stroke injury in grey matter and white matter can be characterized by DTI indices. However, it still remains not fully understood how the DTI indices of white matter are altered progressively during the hyperacute (first 6 hours) and acute stage of stroke (≤ 1 week). In the present study, DTI was employed to characterize the temporal evolution of infarction and white matter injury after stroke insult using a macaque model with permanent ischemic occlusion.

Methods And Materials: Permanent middle cerebral artery (MCA) occlusion was induced in rhesus monkeys (n=4, 10-21 years old). The brain lesion was examined longitudinally with DTI during the hyperacute phase (2-6 hours, n=4), 48 hours (n=4) and 96 hours (n=3) post-occlusion.

Results: Cortical infarction was seen in all animals. The Mean Diffusivity (MD) in lesion regions decreased substantially at the first time point (2 hours post stroke) (35%, p <0.05, compared to the contralateral side) and became pseudo-normalized at 96 hours. In contrast, evident FA reduction was seen at 48 hours (39%, p <0.10) post-stroke. MD reduction in white matter bundles of the lesion area was much less than that in the grey matter during the hyper-acute phase but significant change was observed 4 hours (4.2%, p < 0.05) post stroke . Also, MD pseudonormalisation was seen at 96 hours post stroke. There was a significant correlation between the temporal changes of MD in white matter bundles and those in whole lesion areas during the entire study period. Meanwhile, no obvious fractional anisotropy (FA) changes were seen during the hyper-acute phase in either the entire infarct region or white matter bundles. Significant FA alteration was observed in entire lesion areas and injured white matter bundles 48 and 96 hours post stroke. The stroke lesion in grey matter and white matter was validated by pathological findings.

Conclusion: The temporal evolution of ischemic injury to the grey matter and white matter from 2 to 96 hours after stroke onset was characterized using a macaque model and DTI. Progressive MD changes in white matter bundles are seen from hyperacute phase to acute phase after permanent MCA occlusion and temporally correlated with the MD changes in entire infarction regions. MD reduction in white matter bundles is mild in comparison with that in the grey matter but significant and progressive, indicating it may be useful to detect early white matter degeneration after stroke.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2174/1874440001812010030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5897992PMC
March 2018

Application of Image Processing Techniques in Molecular Imaging of Cancer.

Contrast Media Mol Imaging 2017 13;2017:2758749. Epub 2017 Nov 13.

Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, USA.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1155/2017/2758749DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5702919PMC
October 2018

Longitudinal MRI evaluation of neuroprotective effects of pharmacologically induced hypothermia in experimental ischemic stroke.

Magn Reson Imaging 2017 07 2;40:24-30. Epub 2017 Apr 2.

Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, United States; Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, United States. Electronic address:

Pharmacologically induced hypothermia (PIH) shows promising neuroprotective effects after stroke insult. However, the dynamic evolution of stroke infarct during the hypothermic therapy has not been understood very well. In the present study, MRI was utilized to longitudinally characterize the infarct evolution in a mouse model of ischemic stroke treated by PIH using the neurotensin agonist HPI201. Adult male C57BL/6 mice underwent permanent occlusion of the right middle cerebra artery (MCA). Each animal received a vehicle or HPI201 intraperitoneal injection. The temporal changes of stroke lesion were examined using T2-weighted imaging and diffusion-weighted imaging (DWI) in the acute phase (1-3h) and 24h post stroke. Significantly reduced infarct and edema volumes were observed in PIH treated stroke mice, in agreement with TTC staining findings. Also, the TUNEL staining results indicated apoptotic cells were widely distributed among the ischemic cortex in control group but limited in PIH treated mice. Dramatically reduced growth rate of infarction was seen in PIH treated stroke mice. These results demonstrate HPI201 has strong neuroprotection effects during acute stroke. In particular, MRI with the numerical modelling of temporal infarct evolution could provide a unique means to examine and predict the dynamic response of the PIH treatment on infarct evolution.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.mri.2017.03.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5541904PMC
July 2017

Amyloid-Related Imaging Abnormalities in an Aged Squirrel Monkey with Cerebral Amyloid Angiopathy.

J Alzheimers Dis 2017 ;57(2):519-530

Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA.

Amyloid-related imaging abnormalities (ARIA) in magnetic resonance imaging scans have emerged as indicators of potentially serious side effects in clinical trials of therapeutics for Alzheimer's disease. These anomalies include an edematous type (ARIA-E) that appears as hyperintense (bright) regions by T2-weighted MRI, and a type characterized by the deposition of hemosiderin (ARIA-H) that elicits a hypointense signal, especially in T2* susceptibility weighted images. ARIA in general has been linked to the presence of amyloid-β (Aβ)-type cerebral amyloid angiopathy, an accumulation of misfolded Aβ protein in the vascular wall that impairs the integrity of brain blood vessels. However, the pathobiology of ARIA remains poorly understood, in part due to the absence of an animal model of the disorder that would enable a contemporaneous analysis of tissue integrity in the affected region. Here we describe both ARIA-E and ARIA-H in an aged squirrel monkey (Saimiri sciureus), a nonhuman primate model of naturally occurring cerebral amyloid angiopathy. Histopathologic examination of the anomalous region revealed reactive astrocytosis and microgliosis, infiltration of systemic inflammatory/immune cells, damage to axons and myelin, and hemosiderin deposition. The disruption of axons in particular suggests that ARIA-E could have functional consequences for affected regions. The squirrel monkey model can be useful for studying the pathogenesis and long-term effects of ARIA, and for testing the safety and efficacy of emerging therapies for Alzheimer's disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3233/JAD-160981DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5624788PMC
February 2018

Genetic engineered molecular imaging probes for applications in cell therapy: emphasis on MRI approach.

Am J Nucl Med Mol Imaging 2016 22;6(5):234-261. Epub 2016 Sep 22.

Department of Human Genetics, Emory University School of MedicineAtlanta, GA, USA; Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research CenterAtlanta, GA, USA.

Recent advances in stem cell-based regenerative medicine, cell replacement therapy, and genome editing technologies (i.e. CRISPR-Cas 9) have sparked great interest in cell monitoring. Molecular imaging promises a unique approach to noninvasively monitor cellular and molecular phenomena, including cell survival, migration, proliferation, and even differentiation at the whole organismal level. Several imaging modalities and strategies have been explored for monitoring cell grafts . We begin this review with an introduction describing the progress in stem cell technology, with a perspective toward cell replacement therapy. The importance of molecular imaging in reporting and assessing the status of cell grafts and their relation to the local microenvironment is highlighted since the current knowledge gap is one of the major obstacles in clinical translation of stem cell therapy. Based on currently available imaging techniques, we provide a brief discussion on the pros and cons of each imaging modality used for monitoring cell grafts with particular emphasis on magnetic resonance imaging (MRI) and the reporter gene approach. Finally, we conclude with a comprehensive discussion of future directions of applying molecular imaging in regenerative medicine to emphasize further the importance of correlating cell graft conditions and clinical outcomes to advance regenerative medicine.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5069277PMC
September 2016

Determining Cardiac Fiber Orientation Using FSL and Registered Ultrasound/DTI volumes.

Proc SPIE Int Soc Opt Eng 2016 Feb 1;9790. Epub 2016 Apr 1.

Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA; Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA.

Accurate extraction of cardiac fiber orientation from diffusion tensor imaging is important for determining heart structure and function. However, the acquisition of magnetic resonance (MR) diffusion tensor images is costly and time consuming. By comparison, cardiac ultrasound imaging is rapid and relatively inexpensive, but it lacks the capability to directly measure fiber orientations. In order to create a detailed heart model from ultrasound data, a three-dimensional (3D) diffusion tensor imaging (DTI) with known fiber orientations can be registered to an ultrasound volume through a geometric mask. After registration, the cardiac orientations from the template DTI can be mapped to the heart using a deformable transformation field. This process depends heavily on accurate fiber orientation extraction from the DTI. In this study, we use the FMRIB Software Library (FSL) to determine cardiac fiber orientations in diffusion weighted images. For the registration between ultrasound and MRI volumes, we achieved an average Dice similarity coefficient (DSC) of 81.6±2.1%. For the estimation of fiber orientations from the proposed method, we achieved an acute angle error (AAE) of 22.7±3.1° as compared to the direct measurements from DTI. This work provides a new approach to generate cardiac fiber orientation that may be used for many cardiac applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1117/12.2217296DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5029420PMC
February 2016

Register cardiac fiber orientations from 3D DTI volume to 2D ultrasound image of rat hearts.

Proc SPIE Int Soc Opt Eng 2015 Mar;9415

Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA; Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA.

Two-dimensional (2D) ultrasound or echocardiography is one of the most widely used examinations for the diagnosis of cardiac diseases. However, it only supplies the geometric and structural information of the myocardium. In order to supply more detailed microstructure information of the myocardium, this paper proposes a registration method to map cardiac fiber orientations from three-dimensional (3D) magnetic resonance diffusion tensor imaging (MR-DTI) volume to the 2D ultrasound image. It utilizes a 2D/3D intensity based registration procedure including rigid, log-demons, and affine transformations to search the best similar slice from the template volume. After registration, the cardiac fiber orientations are mapped to the 2D ultrasound image via fiber relocations and reorientations. This method was validated by six images of rat hearts . The evaluation results indicated that the final Dice similarity coefficient (DSC) achieved more than 90% after geometric registrations; and the inclination angle errors (IAE) between the mapped fiber orientations and the gold standards were less than 15 degree. This method may provide a practical tool for cardiologists to examine cardiac fiber orientations on ultrasound images and have the potential to supply additional information for diagnosis of cardiac diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1117/12.2082317DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4737950PMC
March 2015

3D imaging of rat hearts by high frequency ultrasound and its application in myofiber orientation wrapping.

Proc SPIE Int Soc Opt Eng 2015;9419

Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA ; Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA.

Cardiac ultrasound plays an important role in the imaging of hearts in basic cardiovascular research and clinical examinations. 3D ultrasound imaging can provide the geometry or motion information of the heart. Especially, the wrapping of cardiac fiber orientations to the ultrasound volume could supply useful information on the stress distributions and electric action spreading. However, how to acquire 3D ultrasound volumes of the heart of small animals for cardiac fiber wrapping is still a challenging problem. In this study, we provide an approach to acquire 3D ultrasound volumes of the rat hearts . The comparison between both and geometries indicated 90.1% Dice similarity. In this preliminary study, the evaluations of the cardiac fiber orientation wrapping errors were 24.7° for the acute angle error and were 22.4° for the inclination angle error. This 3D ultrasound imaging and fiber orientation estimation technique have potential applications in cardiac imaging.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1117/12.2082326DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4581442PMC
January 2015

Simulating cardiac ultrasound image based on MR diffusion tensor imaging.

Med Phys 2015 Sep;42(9):5144-56

Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia 30329; Department of Mathematics and Computer Science, Emory University, Atlanta, Georgia 30329; and Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, Georgia 30329.

Purpose: Cardiac ultrasound simulation can have important applications in the design of ultrasound systems, understanding the interaction effect between ultrasound and tissue and setting the ground truth for validating quantification methods. Current ultrasound simulation methods fail to simulate the myocardial intensity anisotropies. New simulation methods are needed in order to simulate realistic ultrasound images of the heart.

Methods: The proposed cardiac ultrasound image simulation method is based on diffusion tensor imaging (DTI) data of the heart. The method utilizes both the cardiac geometry and the fiber orientation information to simulate the anisotropic intensities in B-mode ultrasound images. Before the simulation procedure, the geometry and fiber orientations of the heart are obtained from high-resolution structural MRI and DTI data, respectively. The simulation includes two important steps. First, the backscatter coefficients of the point scatterers inside the myocardium are processed according to the fiber orientations using an anisotropic model. Second, the cardiac ultrasound images are simulated with anisotropic myocardial intensities. The proposed method was also compared with two other nonanisotropic intensity methods using 50 B-mode ultrasound image volumes of five different rat hearts. The simulated images were also compared with the ultrasound images of a diseased rat heart in vivo. A new segmental evaluation method is proposed to validate the simulation results. The average relative errors (AREs) of five parameters, i.e., mean intensity, Rayleigh distribution parameter σ, and first, second, and third quartiles, were utilized as the evaluation metrics. The simulated images were quantitatively compared with real ultrasound images in both ex vivo and in vivo experiments.

Results: The proposed ultrasound image simulation method can realistically simulate cardiac ultrasound images of the heart using high-resolution MR-DTI data. The AREs of their proposed method are 19% for the mean intensity, 17.7% for the scale parameter of Rayleigh distribution, 36.8% for the first quartile of the image intensities, 25.2% for the second quartile, and 19.9% for the third quartile. In contrast, the errors of the other two methods are generally five times more than those of their proposed method.

Conclusions: The proposed simulation method uses MR-DTI data and realistically generates cardiac ultrasound images with anisotropic intensities inside the myocardium. The ultrasound simulation method could provide a tool for many potential research and clinical applications in cardiac ultrasound imaging.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1118/1.4927788DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4537486PMC
September 2015

Spatio-temporal assessment of the neuroprotective effects of neuregulin-1 on ischemic stroke lesions using MRI.

J Neurol Sci 2015 Oct 27;357(1-2):28-34. Epub 2015 Jun 27.

Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road NE, Atlanta, GA 30329, USA; Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA. Electronic address:

The neuroprotective effects of neuregulin-1 (NRG-1) on stroke lesions were assessed longitudinally in rats with middle cerebral artery occlusion (MCAo) using MRI. Sprague-Dawley rats (n=16, 250±20g) underwent permanent MCAo surgery with cerebral blood flow (CBF) monitored by laser doppler flowmetry at ipsilateral side of bregma for 20min post-occlusion. A single 50μl bolus dose of NRG-1 or vehicle was administered into the left internal carotid artery immediately prior to MCAo. The expansion of the ischemic lesion into the cortex was attenuated by NRG-1 over a 48-hour (h) time span as measured by diffusion weighted imaging (DWI). The final infarct volumes of NRG-1 treated rats were significantly smaller than those of the vehicle treated rats at 48h (264.8±192.1 vs. 533.4±175.5mm(3), p<0.05). The NRG-1 treated rats were further subdivided into 2 subgroups according to their CBF reduction during stroke surgery: mild ischemia (<70% CBF reduction) or severe ischemia (>70% CBF reduction). In particular, ischemic infarction was not usually observed in the cortex of NRG-1 treated rats with mild ischemia at 3 and 48h post-occlusion. Histological results validated the imaging findings and demonstrated that NRG-1 treated rats had fewer injured neurons in peri-infarct areas 48h post-ischemia. In summary, the neuroprotective effect of NRG-1 in the pMCAo stroke model was demonstrated by prevention of ischemic lesion expansion, reduced infarct volume and protection of neurons from ischemic damage.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jns.2015.06.055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6691739PMC
October 2015

Temporal evolution of ischemic lesions in nonhuman primates: a diffusion and perfusion MRI study.

PLoS One 2015 6;10(2):e0117290. Epub 2015 Feb 6.

Yerkes National Primate Research Center, Emory University, Atlanta, Georgia 30329, United States of America; Department of Psychiatry and Behavioral Sciences, School of Medicine, Emory University, Atlanta, Georgia 30322, United States of America.

Background And Purpose: Diffusion-weighted imaging (DWI) and perfusion MRI were used to examine the spatiotemporal evolution of stroke lesions in adult macaques with ischemic occlusion.

Methods: Permanent MCA occlusion was induced with silk sutures through an interventional approach via the femoral artery in adult rhesus monkeys (n = 8, 10-21 years old). The stroke lesions were examined with high-resolution DWI and perfusion MRI, and T2-weighted imaging (T2W) on a clinical 3T scanner at 1-6, 48, and 96 hours post occlusion and validated with H&E staining.

Results: The stroke infarct evolved via a natural logarithmic pattern with the mean infarct growth rate = 1.38 ± 1.32 ml per logarithmic time scale (hours) (n = 7) in the hyperacute phase (1-6 hours). The mean infarct volume after 6 hours post occlusion was 3.6±2.8 ml (n = 7, by DWI) and increased to 3.9±2.9 ml (n = 5, by T2W) after 48 hours, and to 4.7±2.2ml (n = 3, by T2W) after 96 hours post occlusion. The infarct volumes predicted by the natural logarithmic function were correlated significantly with the T2W-derived lesion volumes (n = 5, r = 0.92, p = 0.01) at 48 hours post occlusion. The final infarct volumes derived from T2W were correlated significantly with those from H&E staining (r = 0.999, p < 0.0001, n = 4). In addition, the diffusion-perfusion mismatch was visible generally at 6 hours but nearly diminished at 48 hours post occlusion.

Conclusion: The infarct evolution follows a natural logarithmic pattern in the hyperacute phase of stroke. The logarithmic pattern of evolution could last up to 48 hours after stroke onset and may be used to predict the infarct volume growth during the acute phase of ischemic stroke. The nonhuman primate model, MRI protocols, and post data processing strategy may provide an excellent platform for characterizing the evolution of acute stroke lesion in mechanistic studies and therapeutic interventions of stroke disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0117290PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4319749PMC
March 2015

Mapping Cardiac Fiber Orientations from High-Resolution DTI to High-Frequency 3D Ultrasound.

Proc SPIE Int Soc Opt Eng 2014 Mar;9036:90361O

Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA ; Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA.

The orientation of cardiac fibers affects the anatomical, mechanical, and electrophysiological properties of the heart. Although echocardiography is the most common imaging modality in clinical cardiac examination, it can only provide the cardiac geometry or motion information without cardiac fiber orientations. If the patient's cardiac fiber orientations can be mapped to his/her echocardiography images in clinical examinations, it may provide quantitative measures for diagnosis, personalized modeling, and image-guided cardiac therapies. Therefore, this project addresses the feasibility of mapping personalized cardiac fiber orientations to three-dimensional (3D) ultrasound image volumes. First, the geometry of the heart extracted from the MRI is translated to 3D ultrasound by rigid and deformable registration. Deformation fields between both geometries from MRI and ultrasound are obtained after registration. Three different deformable registration methods were utilized for the MRI-ultrasound registration. Finally, the cardiac fiber orientations imaged by DTI are mapped to ultrasound volumes based on the extracted deformation fields. Moreover, this study also demonstrated the ability to simulate electricity activations during the cardiac resynchronization therapy (CRT) process. The proposed method has been validated in two rat hearts and three canine hearts. After MRI/ultrasound image registration, the Dice similarity scores were more than 90% and the corresponding target errors were less than 0.25 mm. This proposed approach can provide cardiac fiber orientations to ultrasound images and can have a variety of potential applications in cardiac imaging.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1117/12.2043821DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4201058PMC
March 2014

Quantitative multiparametric MRI assessment of glioma response to radiotherapy in a rat model.

Neuro Oncol 2014 Jun 22;16(6):856-67. Epub 2013 Dec 22.

Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland (X.H., M.W., Y.F., B.M., S.W., J.Z.); Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China (X.H., L.L.); Department of Radiation Oncology, Johns Hopkins University, Baltimore, Maryland (K.D., J.W.); Department of Neurology, Kennedy Krieger Institute, Baltimore, Maryland (B.L., J.L.); Department of Neurosurgery, Johns Hopkins University, Baltimore, Maryland (B.T., A.M.); Department of Neurology, Johns Hopkins University, Baltimore, Maryland (J.L.); F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland (J.Z.).

Background: The inability of structural MRI to accurately measure tumor response to therapy complicates care management for patients with gliomas. The purpose of this study was to assess the potential of several noninvasive functional and molecular MRI biomarkers for the assessment of glioma response to radiotherapy.

Methods: Fourteen U87 tumor-bearing rats were irradiated using a small-animal radiation research platform (40 or 20 Gy), and 6 rats were used as controls. MRI was performed on a 4.7 T animal scanner, preradiation treatment, as well as at 3, 6, 9, and 14 days postradiation. Image features of the tumors, as well as tumor volumes and animal survival, were quantitatively compared.

Results: Structural MRI showed that all irradiated tumors still grew in size during the initial days postradiation. The apparent diffusion coefficient (ADC) values of tumors increased significantly postradiation (40 and 20 Gy), except at day 3 postradiation, compared with preradiation. The tumor blood flow decreased significantly postradiation (40 and 20 Gy), but the relative blood flow (tumor vs contralateral) did not show a significant change at most time points postradiation. The amide proton transfer weighted (APTw) signals of the tumor decreased significantly at all time points postradiation (40 Gy), and also at day 9 postradiation (20 Gy). The blood flow and APTw maps demonstrated tumor features that were similar to those seen on gadolinium-enhanced T1-weighted images.

Conclusions: Tumor ADC, blood flow, and APTw were all useful imaging biomarkers by which to predict glioma response to radiotherapy. The APTw signal was most promising for early response assessment in this model.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/neuonc/not245DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4022217PMC
June 2014

Radiation induced brain injury: assessment of white matter tracts in a pre-clinical animal model using diffusion tensor MR imaging.

J Neurooncol 2013 Mar 20;112(1):9-15. Epub 2013 Jan 20.

Department of Diagnostic Radiology, The University of Hong Kong, Room 406, Block K, Queen Mary Hospital, 102 Pokfulam Road, Hong Kong, Hong Kong.

We aim to study radiation induced white matter injury in a pre-clinical model using Diffusion tensor MR imaging (DTI). Nineteen 12-week old Sprague-Dawley rats were irradiated to the right hemisphere using a linear accelerator. The dose distribution map was coregistered to the DTI map to generate the actual radiation dose to each white matter tract. Rats underwent longitudinal DTI scans at five time points from 4 to 48 weeks post-radiation with histological evaluations. Fractional anisotropy (FA) of the external capsule, fornix, cerebral peduncle, anterior commissure, optic tract and optic nerve was evaluated. Radiation dose was highest at the ipsilateral external capsule and fornix (29.4 ± 1.3 and 29.8 ± 1.1 Gy, respectively). Optic nerve received 50 % dose to the external capsule and other white matter tracts received 80 % dose. Significantly lower FA was firstly found in the ipsilateral external capsule at 4 weeks post-radiation and in the ipsilateral fornix at 40 weeks post-radiation compared to the contralateral side. Significantly lower FA was found in contralateral optic nerve compared to ipsilateral optic nerve at 48 weeks post-radiation despite ipsilateral optic nerves receiving higher radiation dose than contralateral optic nerve (p = 0.021). No differences were found in other white matter regions until 48 weeks. Histology indicated demyelination, axonal degeneration and coagulative necrosis in all injured white matter. DTI can serve as a promising tool for assessment of radiation induced white matter injury and regional radiosensitivity of white matter tracts.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11060-012-1031-0DOI Listing
March 2013

Combined use of 18F-FDG PET/CT, DW-MRI, and DCE-MRI in treatment response for preoperative chemoradiation therapy in locally invasive rectal cancers.

Clin Nucl Med 2013 May;38(5):e226-9

Department of Diagnostic Radiology, The University of Hong Kong, Queen Mary Hospital, Hong Kong, China.

We investigated if 18F-FDG PET/CT, DW-MRI, and DCE-MRI are able to predict preoperative chemoradiation therapy (CRT) response in patients with T3-4 rectal adenocarcinomas. MRI and PET/CT scans were performed within 1 week, at baseline, early midtreatment (2 weeks of CRT), and posttreatment (6 weeks after completing CRT). Responders (n = 4) and nonresponders (n = 4) were defined according to tumor regression grade by histology. Only SUVmax (P = 0.030) at early midtreatment could significantly differentiate between responders and nonresponders, suggesting that 18F-FDG PET/CT may be effective to predict early treatment response compared with DW-MRI and DCE-MRI in T3-4 rectal cancer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/RLU.0b013e318266ce52DOI Listing
May 2013

Diffusion tensor magnetic resonance imaging of rat glioma models: a correlation study of MR imaging and histology.

J Comput Assist Tomogr 2012 Nov-Dec;36(6):739-44

Division of MR Research, Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.

Introduction: Diffusion tensor magnetic resonance (MR) imaging (DTI) can be used to characterize the microstructures of ordered biological tissues. This study was designed to assess histological features of gliomas and surrounding brain tissues in rats using DTI.

Methods: Three types of tumors, a 9L gliosarcoma (n = 8), a F98 glioma (n = 5), and a human glioblastoma xenograft (GBM22; n = 8) were incubated in rat brains and underwent conventional MRI and DTI scanning using a 4.7-T animal MRI system. Fractional anisotropy (FA), isotropic apparent diffusion coefficient, parallel diffusivity (λ//), and perpendicular diffusivity (λ⊥), as well as histological features within several regions of interest were analyzed.

Results: All tumor masses consisted of low-FA central zones (tumor center) and high-FA peripheral regions (tumor rim). Histological examination revealed the existence of highly coherent tumor organizations (circular for 9L and F98 or radial for GBM22) in the tumor rims. There were higher apparent diffusion coefficient, λ⊥, and λ// in the peritumoral edema compared to the contralateral gray matter. There were significantly lower FA and higher λ⊥ in the ipsilateral white matter than in the contralateral white matter for the GBM22 tumor, whereas there were no differences for the 9L and F98 tumors. Histologic examination showed GBM22 tumor infiltration into the ipsilateral damaged white matter.

Conclusions: Quantitative analysis of DTI indices provides useful information for assessing tumor microstructure and tumor cell invasion into the adjacent gray matter and white matter.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/RCT.0b013e3182685436DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3513798PMC
February 2013

Growth properties of SF188/V+ human glioma in rats in vivo observed by magnetic resonance imaging.

J Neurooncol 2012 Dec 27;110(3):315-23. Epub 2012 Sep 27.

Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, MD, USA.

SF188/V+ is a highly vascular human glioma model that is based on transfection of vascular endothelial growth factor (VEGF) cDNA into SF188/V- cells. This study aims to assess its growth and vascularity properties in vivo in a rat model. Thirty-two adult rats were inoculated with SF188/V+ tumor cells, and, for comparison, five were inoculated with SF188/V- tumor cells. Several conventional magnetic resonance imaging (MRI) sequences were acquired, and several quantitative structural (T(2) and T(1)), functional [isotropic apparent diffusion coefficient (ADC) and blood flow], and molecular [protein and peptide-based amide proton transfer (APT)] MRI parameters were mapped on a 4.7 T animal scanner. In rats inoculated with SF188/V+ tumor cells, conventional T(2)-weighted images showed a highly heterogeneous tumor mass, and post-contrast T(1)-weighted images showed a heterogeneous, strong enhancement of the mass. There were moderate increases in T(2), T(1), and ADC, and large increases in blood flow and APT in the tumor, compared to contralateral brain tissue. Microscopic examination revealed prominent vascularity and hemorrhage in the VEGF-secreting xenografts as compared to controls, and immunohistochemical staining confirmed increased expression of VEGF in tumor xenografts. Our results indicate that the SF188/V+ glioma model exhibits some MRI and histopathology features that closely resemble human glioblastoma.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11060-012-0974-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3500409PMC
December 2012

Assessment of MRI parameters as imaging biomarkers for radiation necrosis in the rat brain.

Int J Radiat Oncol Biol Phys 2012 Jul 5;83(3):e431-6. Epub 2012 Apr 5.

Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.

Purpose: Radiation necrosis is a major complication of radiation therapy. We explore the features of radiation-induced brain necrosis in the rat, using multiple MRI approaches, including T(1), T(2), apparent diffusion constant (ADC), cerebral blood flow (CBF), magnetization transfer ratio (MTR), and amide proton transfer (APT) of endogenous mobile proteins and peptides.

Methods And Materials: Adult rats (Fischer 344; n = 15) were irradiated with a single, well-collimated X-ray beam (40 Gy; 10 × 10 mm(2)) in the left brain hemisphere. MRI was acquired on a 4.7-T animal scanner at ~25 weeks' postradiation. The MRI signals of necrotic cores and perinecrotic regions were assessed with a one-way analysis of variance. Histological evaluation was accomplished with hematoxylin and eosin staining.

Results: ADC and CBF MRI could separate perinecrotic and contralateral normal brain tissue (p < 0.01 and < 0.05, respectively), whereas T(1), T(2), MTR, and APT could not. MRI signal intensities were significantly lower in the necrotic core than in normal brain for CBF (p < 0.001) and APT (p < 0.01) and insignificantly higher or lower for T(1), T(2), MTR, and ADC. Histological results demonstrated coagulative necrosis within the necrotic core and reactive astrogliosis and vascular damage within the perinecrotic region.

Conclusion: ADC and CBF are promising imaging biomarkers for identifying perinecrotic regions, whereas CBF and APT are promising for identifying necrotic cores.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijrobp.2011.12.087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3361588PMC
July 2012

Evaluation of radiation necrosis and malignant glioma in rat models using diffusion tensor MR imaging.

J Neurooncol 2012 Mar 27;107(1):51-60. Epub 2011 Sep 27.

Department of Radiology, Johns Hopkins University School of Medicine, 600 N. Wolfe Street, 336 Park Building, Baltimore, MD 21287, USA.

Standard MRI cannot distinguish between radiation necrosis and tumor progression; however, this distinction is critical in the assessment of tumor response to therapy. In this study, one delayed radiation necrosis model (dose, 40 Gy; radiation field, 10 × 10 mm(2); n = 13) and two orthotopic glioma models in rats (9L gliosarcoma, n =8; human glioma xenografts, n = 5) were compared using multiple diffusion tensor imaging (DTI) indices. A visible isotropic apparent diffusion coefficient (ADC) pattern was observed in the lesion due to radiation necrosis, which consisted of a hypointense central zone and a hyperintense peripheral zone. There were significantly lower ADC, parallel diffusivity, and perpendicular diffusivity in the necrotic central zone than in the peripheral zone (all P < 0.001). When radiation-induced necrosis was compared with viable tumor, radiation necrosis had significantly lower ADC than 9L gliosarcoma and human glioma xenografts (both P < 0.01) in the central zone, and significantly lower fractional anisotropy than 9L gliosarcoma (P = 0.005) and human glioma xenografts (P = 0.012) in the peripheral zone. Histological analysis revealed parenchymal coagulative necrosis in the central zone, and damaged vessels and reactive astrogliosis in the peripheral zone. These data suggest that qualitative and quantitative analysis of the DTI maps can provide useful information by which to distinguish between radiation necrosis and viable glioma.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11060-011-0719-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3268835PMC
March 2012

Relationship between cardiac valvular and arterial calcification in patients with rheumatoid arthritis and systemic lupus erythematosus.

J Rheumatol 2011 Apr 1;38(4):621-7. Epub 2011 Feb 1.

Cardiology Division, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong.

Objective: Cardiac valvular calcification has been linked with systemic atherosclerosis in the general population. The prevalence and relationship with arterial calcification in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) is unknown. We investigated the prevalence of valvular calcification in patients with RA and SLE and its relationship with arterial atherosclerotic calcification.

Methods: We compared aortic valve calcification (AVC), mitral valve calcification (MVC), and systemic vascular bed calcification using multidetector computed tomography in 110 patients (mean age 46.5 ± 9.4 yrs, 97 women) with RA (n = 58) or SLE (n = 52) and 60 age and sex-matched healthy controls.

Results: Patients with RA and SLE, combined, had significantly higher prevalence of AVC (21.8% vs 3.3% in controls; p < 0.01), MVC (19.1% vs 0% in controls; p < 0.01), and arterial calcification in different vascular beds (all p < 0.05). AVC was not associated with any specific clinical characteristics, but MVC was associated with older age, hypertension, C-reactive protein level, and duration of disease. The presence of MVC was independently associated with coronary calcification and calcification in any vascular bed upon adjustment with clinical measures.

Conclusion: Our study demonstrated that cardiac valvular calcification is more prevalent in patients with RA and SLE compared with healthy controls. The presence of MVC, but not AVC, independently predicted the occurrence of premature atherosclerosis with arterial calcification in patients with RA and SLE.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3899/jrheum.100844DOI Listing
April 2011

Dynamic contrast-enhanced MRI of primary rectal cancer: quantitative correlation with positron emission tomography/computed tomography.

J Magn Reson Imaging 2011 Feb;33(2):340-7

Department of Diagnostic Radiology, The University of Hong Kong, Queen Mary Hospital, Hong Kong.

Purpose: To assess the correlations between parameters measured on dynamic contrast-enhanced magnetic resonance imaging and 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in rectal cancer.

Materials And Methods: To assess the correlations between parameters measured on dynamic contrast-enhanced MRI and FDG-PET in rectal cancer.

Results: Significant correlations were only demonstrated between k(ep) and SUVmax (r = 0.587, P = 0.001), and k(ep) and SUVmean (r = 0.562, P = 0.002). No significant differences were found in imaging parameters between well, moderately and poorly differentiated adenocarcinoma groups. However, there was a trend that higher imaging values were found in poorly differentiated adenocarcinomas.

Conclusion: Positive correlations were found between k(ep) and SUV values in primary rectal adenocarcinomas suggesting an association between angiogenesis and metabolic activity and further reflecting that angiogenic activity in washout phase is better associated with tumor metabolism than the uptake phase.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jmri.22405DOI Listing
February 2011

Differentiation between glioma and radiation necrosis using molecular magnetic resonance imaging of endogenous proteins and peptides.

Nat Med 2011 Jan 19;17(1):130-4. Epub 2010 Dec 19.

Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.

It remains difficult to distinguish tumor recurrence from radiation necrosis after brain tumor therapy. Here we show that these lesions can be distinguished using the amide proton transfer (APT) magnetic resonance imaging (MRI) signals of endogenous cellular proteins and peptides as an imaging biomarker. When comparing two models of orthotopic glioma (SF188/V+ glioma and 9L gliosarcoma) with a model of radiation necrosis in rats, we could clearly differentiate viable glioma (hyperintense) from radiation necrosis (hypointense to isointense) by APT MRI. When we irradiated rats with U87MG gliomas, the APT signals in the irradiated tumors had decreased substantially by 3 d and 6 d after radiation. The amide protons that can be detected by APT provide a unique and noninvasive MRI biomarker for distinguishing viable malignancy from radiation necrosis and predicting tumor response to therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nm.2268DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3058561PMC
January 2011

Quantitative assessment of diffusion-weighted MR imaging in patients with primary rectal cancer: correlation with FDG-PET/CT.

Mol Imaging Biol 2011 Oct 25;13(5):1020-8. Epub 2010 Sep 25.

Department of Diagnostic Radiology, The University of Hong Kong, Hong Kong, China.

Purpose: The aim of the study was to assess correlations between parameters on diffusion-weighted imaging and 2-deoxy-2-[(18)F]fluoro-D-glucose-positron emission tomography/computed tomography (FDG-PET/CT) in rectal cancer.

Procedures: Thirty-three consecutive patients with pathologically confirmed rectal adenocarcinoma were included in this study. Apparent diffusion coefficient (ADC) maps were generated to calculate ADC(mean) (average ADC), ADC(min) (lowest ADC), tumor volume, and total diffusivity index (TDI). PET/CT exams were performed within 1 week of magnetic resonance imaging. Standardized uptake values (SUVs) were normalized to the injected FDG dose and body weight. SUV(max) (maximum SUV), SUV(mean) (average SUV), tumor volume, and total lesion glycolysis (TLG) were calculated using a 50% threshold.

Results: Significant negative correlations were found between ADC(min) and SUV(max) (r = -0.450, p = 0.009), and between ADC(mean) and SUV(mean) (r = -0.402, p = 0.020). A significant positive correlation was found between TDI and TLG (r = 0.634, p < 0.001).

Conclusion: The significant negative correlations between ADC and SUV suggest an association between tumor cellularity and metabolic activity in primary rectal adenocarcinoma.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11307-010-0433-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3179585PMC
October 2011

MR imaging of high-grade brain tumors using endogenous protein and peptide-based contrast.

Neuroimage 2010 Jun 24;51(2):616-22. Epub 2010 Feb 24.

Department of Radiology, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong, China.

Amide proton transfer (APT) imaging is a novel MRI technique, in which the amide protons of endogenous proteins and peptides are irradiated to accomplish indirect detection using the bulk water signal. In this paper, the APT approach was added to a standard brain MRI protocol at 3T, and twelve patients with high-grade gliomas confirmed by histopathology were scanned. It is shown that all tumors, including one with minor gadolinium enhancement, showed heterogeneous hyperintensity on the APT images. The average APT signal intensities of the viable tumor cores were significantly higher than those of peritumoral edema and normal-appearing white matter (P<0.001). The average APT signal intensities were significantly lower in the necrotic regions than in the viable tumor cores (P=0.004). The APT signal intensities of the cystic cavities were similar to those of the viable tumor cores (P>0.2). The initial results show that APT imaging at the protein and peptide level may enhance non-invasive identification of tissue heterogeneity in high-grade brain tumors.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuroimage.2010.02.050DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2856810PMC
June 2010