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MR Imaging (mr + imaging)
Terms modified by MR Imaging Selected AbstractsBifunctional Gd2O3/C Nanoshells for MR Imaging and NIR Therapeutic ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 2 2009Chih-Chia Huang Abstract This paper reports dual function Gd2O3/C nanoshells for application in MR contrast images and NIR-triggered killing cancer cells. The nanoshells are prepared using biological gelatin particles as core templates through a two-step thermal treatment. The surfaces of the nanoshells can be readily modified by poly(styrene-alt-maleic acid) (PSMA) polymer to improve their water-dispersible properties and increase their biocompatibility. The Gd2O3/C nanoshells show brightened images of kidney cortex and liver in mice, whereas the Gd2O3/C@PSMA nanoshells show a darkened liver signal. The biodistribution is measured as a function of time and shows that the nanoshells circulate in the vessels and are cleared out gradually from organs. The graphite carbon coated on the Gd2O3 nanoshells displays absorbance in the near-IR (NIR) region. A large extinction coefficient is obtained, indicating the potential of the nanoshells as photothermal agents. The Gd2O3/C@PSMA nanoshells conjugated with anti-epithermal growth factor receptor antibodies are used for targeting and destroying A549 lung cancer cells by means of NIR-triggered killing capability. Both laser power density and material dose dependence are investigated to evaluate photothermolysis in cancer cells. [source] In Vivo Determination of Bone Structure in Postmenopausal Women: A Comparison of HR-pQCT and High-Field MR Imaging,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2008Galateia J Kazakia PhD Abstract Bone structural measures obtained by two noninvasive imaging tools,3T MRI and HR-pQCT,were compared. Significant but moderate correlations and 2- to 4-fold discrepancies in parameter values were detected, suggesting that differences in acquisition and analysis must be considered when interpreting data from these imaging modalities. Introduction: High-field MRI and high resolution (HR)-pQCT are currently being used in longitudinal bone structure studies. Substantial differences in acquisition and analysis between these modalities may influence the quantitative data produced and could potentially influence clinical decisions based on their results. Our goal was to compare trabecular and cortical bone structural measures obtained in vivo by 3T MRI and HR-pQCT. Materials and Methods: Postmenopausal osteopenic women (n = 52) were recruited for this study. HR-pQCT imaging of the radius and tibia was performed using the XtremeCT scanner, with a voxel size of 82 × 82 × 82 ,m3. MR imaging was performed on a 3T Signa scanner using SSFP imaging sequences, with a pixel size of 156 × 156 ,m2 and slice thickness of 500 ,m. Structure parameters were calculated using standard HR-pQCT and MRI analysis techniques. Relationships between measures derived from HR-pQCT, MRI, and DXA were studied. Results: Significant correlations between HR-pQCT and MRI parameters were found (p < 0.0001) and were strongest for Tb.N (r2 = 0.52), Ct.Th (r2 = 0.59), and site-specific Tb.Sp (r2 = 0.54,0.60). MRI and HR-pQCT provided statistically different values of structure parameters (p < 0.0001), with BV/TV and Tb.Th exhibiting the largest discrepancies (MR/HR-pQCT = 3,4). Although differences in the Tb.N values were statistically significant, the mean differences were on the order of our reproducibility measurements. Systematic differences between MRI and HR-pQCT analysis procedures leading to discrepancies in cortical thickness values were observed, with MRI values consistently higher. Minimal correlations were found between MRI or HR-pQCT parameters and DXA BMD or T-score, except between HR-pQCT measures at the radius and the ultradistal radius T-scores, where moderate correlations were found (r2 = 0.19,0.58). Conclusions: This study provides unique insight into two emerging noninvasive tools for bone structure evaluation. Our findings highlight the significant influence of analysis technique on results of in vivo assessment and underscore the importance of accounting for these differences when interpreting results from these modalities. [source] Follow-up of Probably Benign Lesions (BI-RADS 3 category) in Breast MR ImagingTHE BREAST JOURNAL, Issue 3 2010Elke Hauth MD Abstract:, The purpose of our study was to determine the frequency of BI-RADS 3 lesions in breast MR imaging in a clinical patient population and their frequency of malignancy in follow-up breast MR imaging. In 44/698 (6.3%) patients with breast MR imaging, 56 lesions were categorized to BI-RADS 3. These lesions were all not palpable and not detectable at conventional mammography or ultrasound. In follow-up, lesions were score in complete resolved (CRL), partial resolved (PRL), stable lesions (SL), and progressive lesions (PL). Initial signal enhancement of lesions was coded by color intensity (bright for high, medium for medium, dark for low), the postinitial signal enhancement by color hue (blue for increase, green for plateau, red for wash-out). In first follow-up breast MR imaging 23/56 (41%) lesions were PRL, 14/56 (25%) lesions were CRL, 14/56 (25%) lesions remained SL. In one of five PL lesions, histopathology revealed a malignant tumor. In initial breast MR imaging, CRL showed significant fewer high pixels (p = 0.002), medium pixels (p = 0.006) significant more low pixels (p = 0.005) and significant more increase pixels (p = 0.037) than PRL. In a clinical patient population the frequency of malignancy of BI-RADS 3 lesions in breast MR imaging and their frequency of malignancy are similar to that in conventional mammography. In initial breast MR imaging, complete resolved lesions showed less suspicious contrast kinetics than other lesions. In follow-up, the increase of lesion size should warrant histopathological diagnosis. [source] Proposing magnetic nanoparticle hyperthermia in low-field MRICONCEPTS IN MAGNETIC RESONANCE, Issue 1 2010Pádraig Cantillon-Murphy Abstract This work examines feasibility, practical advantages, and disadvantages of a combined MRI/magnetic particle hyperthermia (MPH) system for cancerous tumor treatment in low perfusion tissue. Although combined MRI/hyperthermia systems have been proposed and constructed, the current proposal differs because the hyperthermia system would be specifically designed to interact with the magnetic nanoparticles injected at the tumor site. The proposal exploits the physical similarities between the magnetic nanoparticles currently employed for MPH and those used as superparamagnetic iron oxide (SPIO) contrast agents in MR imaging. The proposal involves the addition of a rotating magnetic field RF hyperthermia source perpendicular to the MRI B0 field which operates in a similar manner to the MRI RF excitation field, B1, but at significantly higher frequency and field strength such that the magnetic nanoparticles are forced to rotate in its presence. This rotation is the source of increases in temperature which are of therapeutic benefit in cancer therapy. For rotating magnetic fields with amplitudes much smaller than B0, the nanoparticles' suspension magnetization rapidly saturates with increasing B0. Therefore, the proposal is best suited to low-field MRI systems when magnetic saturation is incomplete. In addition, careful design of the RF hyperthermia source is required to ensure no physical or RF interference with the B1 field used for MRI excitation. Notwithstanding these caveats, the authors have shown that localized steady-state temperature rises in small spherical tumors of up to 10°C are conceivable with careful selection of the nanoparticle radius and concentration, RF hyperthermia field amplitude and frequency. © 2010 Wiley Periodicals, Inc. Concepts Magn Reson Part A 36A: 36,47, 2010. [source] Effect of slice angle on inhomogeneity artifact and its correction in slice-selective MR imagingCONCEPTS IN MAGNETIC RESONANCE, Issue 4 2009Kwan-Jin Jung Abstract The inhomogeneity of a local magnetic field causes an image artifact of geometric distortion and intensity abnormality because of the slice offset and readout shift in slice-selective MR imaging. It has been found that this artifact can be corrected by the projection of the slice offset onto the readout axis at a certain oblique slice angle. The slice angle for the artifact correction is determined by the amplitude of slice selection and readout gradients, and is independent of the magnetic field inhomogeneity and the main magnetic field direction. In addition, the existing view-angle tilting technique is found to be valid only for the slice orientation orthogonal to the object axis. The slice angle effect on the inhomogeneity artifact was confirmed experimentally through phantom and volunteer's head imaging for both regular and view-angle tilted spin echo sequences at 3 T. © 2009 Wiley Periodicals, Inc.Concepts Magn Reson Part A 34A: 238,248, 2009. [source] Dynamic study of cerebral bioenergetics and brain function using in vivo multinuclear MRS approachesCONCEPTS IN MAGNETIC RESONANCE, Issue 2 2005Wei Chen Abstract One of the greatest merits of nuclear magnetic resonance (NMR) methodology used in biomedical research and clinical settings is its capability of measuring various physiological parameters in vivo. Besides MR imaging (MRI), which has been routinely applied to obtain vital information in living organs at normal and diseased states, in vivo MR spectroscopy (MRS) provides an invaluable tool for determining metabolites, chemical reaction rates, bioenergetics, and their dynamic changes in the human and animals noninvasively. These MRS capabilities are further enhanced at high/ultrahigh magnetic fields because of significant gain in NMR detection sensitivity and improvement in the spectral resolution. Recent progress has shown that in vivo MRS holds great promise in many biomedical research areas,in particular, brain research. This article provides a broad review of (i) in vivo multinuclear MRS approaches, (ii) advanced MRS methodologies, and (iii) MRS applications for determining cerebral metabolism as well as bioenergetics at resting brain state and their dynamic changes in response to brain activation. © 2005 Wiley Periodicals, Inc. Concepts Magn Reson Part A 27A: 84-121, 2005 [source] Perfusion MR imaging with pulsed arterial spin-labeling: Basic principles and applications in functional brain imagingCONCEPTS IN MAGNETIC RESONANCE, Issue 5 2002Yihong Yang Abstract Basic principles of the arterial spin-labeling perfusion MRI are described, with focus on a brain perfusion model with pulsed labeling. A multislice perfusion imaging sequence with adiabatic inversion and spiral scanning is illustrated as an example. The mechanism of the perfusion measurement, the quantification of cerebral blood flow, and the suppression of potential artifacts are discussed. Applications of the perfusion imaging in brain activation studies, including simultaneous detection of blood flow and blood oxygenation, are demonstrated. Important issues associated with the applications such as sensitivity, quantification, and temporal resolution are discussed. © 2002 Wiley Periodicals, Inc. Concepts Magn Reson 14: 347,357, 2002 [source] MR imaging for the longevity of mesenchymal stem cells labeled with poly- L -lysine,Resovist complexesCONTRAST MEDIA & MOLECULAR IMAGING, Issue 2 2010Gang Liu Abstract Superparamagnetic iron oxide (SPIO) nanoparticles are emerging as ideal probes for noninvasive cell tracking. In this study, poly- L -lysine (PLL) was mixed with Resovist to form the PLL,Resovist complexes and the control of the complexes formed by PLL and Resovist and their subsequent properties was easily achievable. MSCs could be safely and efficiently labeled for MR imaging using PLL,Resovist complexes (w/w 0.01:1) and the labeled MSCs could be detected to have definite decreased signal intensity on T2 -weight imaging until 20 days with standard 1.5,T MR equipment. This study describes a simple protocol to label MSCs using PLL,Resovist complexes and the results presented in our study can provide a basis for the application of PLL,Resovist complexes cell labeling. Copyright © 2010 John Wiley & Sons, Ltd. [source] CMR2009: 3.03: Oral manganese-based contrast agent CMC-001 for liver MR imaging in patients with hepatic metastases: initial experience of a phase II trialCONTRAST MEDIA & MOLECULAR IMAGING, Issue 6 2009M. Rief No abstract is available for this article. [source] Erratum: MR imaging in assessing cardiovascular interventions and myocardial injuryCONTRAST MEDIA & MOLECULAR IMAGING, Issue 2 2007Alexis Jacquier Contrast Media and Molecular Imaging, MR imaging in assessing cardiovascular interventions and myocardial injury, Alexis Jacquier, Charles B. Higgins and Maythem Saeed, published in CMMI 2:1, DOI: 10.1002/cmmi122, pp1,15. Contract/Grant Sponsor information relating to Dr. A. Jacquier was absent from the published article. It should be noted that Dr. A. Jacquier was supported by the Société Française de Radiologie, Paris, as a research fellow. [source] MR imaging in assessing cardiovascular interventions and myocardial injuryCONTRAST MEDIA & MOLECULAR IMAGING, Issue 1 2007Alexis Jacquier Abstract Performing an MR-guided endovascular intervention requires (1) real-time tracking and guidance of catheters/guide wires to the target, (2) high-resolution images of the target and its surroundings in order to define the extent of the target, (3) performing a therapeutic procedure (delivery of stent or injection of gene or cells) and (4) evaluating the outcome of the therapeutic procedure. The combination of X-ray and MR imaging (XMR) in a single suite was designed for new interventional procedures. MR contrast media can be used to delineate myocardial infarcts and microvascular obstruction, thereby defining the target for local delivery of therapeutic agents under MR-guidance. Iron particles, or gadolinium- or dysprosium-chelates are mixed with the soluble injectates or stem cells in order to track intramyocardial delivery and distribution. Preliminary results show that genes encoded for vascular endothelial and fibroblast growth factor and cells are effective in promoting angiogenesis, arteriogenesis, perfusion and LV function. Angiogenic growth factors, genes and cells administered under MR-guided minimally invasive catheter-based procedures will open up new avenues in treating end-stage ischemic heart disease. The optimum dose of the therapeutic agents, delivery devices and real-time imaging techniques to guide the delivery are currently the subject of ongoing research. The aim of this review is to (1) provide an updated review of experiences using MR imaging to guide transcatheter therapy, (2) address the potential of cardiovascular magnetic resonance (MR) imaging and MR contrast media in assessing myocardial injury at a molecular level and labeling cells and (3) illustrate the applicability of the non-invasive MR imaging in the field of angiogenic therapies through recent clinical and experimental publications. Copyright © 2007 John Wiley & Sons, Ltd. [source] CMR 2005: 4.05: Ultra-small supraparamagnetic iron oxide-enhanced MR imaging of antigen-induced arthritis: a comparative study between SH U 555 C, ferumoxtran-10 and ferumoxytolCONTRAST MEDIA & MOLECULAR IMAGING, Issue 2 2006G.H. Simon [source] Insights into the acute cerebral metabolic changes associated with childhood diabetesDIABETIC MEDICINE, Issue 5 2005F. J. Cameron Abstract Aims Type 1 diabetes is a prevalent chronic disease in childhood with the commonest single cause of death being cerebral oedema in the context of diabetic ketoacidosis (DKA). The nature of the alterations in cerebral metabolism that may result in vulnerability to neuronal injury remains unknown. The aim of this study was to analyse the magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) brain data from eight children with diabetes following acute presentation with hyperglycaemia with or without ketoacidosis, to determine the nature and timing of any alterations in cerebral structure and metabolism. Methods This study used MRI and MRS to investigate regional cerebral abnormalities in a small series of diabetic patients with and without DKA. Changes were compared with the clinical and biochemical features of the patients studied. Results Our small series of patients all demonstrated abnormal signal changes in the frontal region on fluid attenuated inversion recovery (FLAIR) MR imaging, suggestive of oedema, and spectroscopic abnormalities of increased taurine, myoinositol and glucose levels. The MR abnormalities varied in severity but did not correlate with any clinical or biochemical parameters. Conclusions These changes indicate that many diabetic children, particularly at presentation, may have alterations in cerebral metabolism with implications for the pathogenesis and treatment of the cerebral complications of DKA. In addition, our findings suggest that increased taurine may be one of the important differentiating factors in the response of the brain of diabetic children to DKA that may reflect an increase in their vulnerability to cerebral oedema compared with diabetic adults. [source] Event-related fMRI of Myoclonic Jerks Arising from Dysplastic CortexEPILEPSIA, Issue 9 2006John S. Archer Summary:,Background: Malformations of cortical development can cause epileptiform activity and myoclonic jerks, yet EEG correlates of jerks can be difficult to obtain. Methods: We studied a woman who had frequent episodes of persistent right-foot jerking since childhood. Ictal and interictal EEG had shown no localizing epileptiform activity. Functional imaging experiments were performed with concurrent video monitoring to document the timing of foot jerks. These studies mapped brain regions controlling voluntary right- and left-foot movements, and spontaneous right-foot jerks. Results: High-resolution structural MR imaging revealed a dysplastic gyrus extending anteriorly off the left central sulcus. Event-related analysis of spontaneous jerks revealed prominent activation of the left precentral gyrus (right-foot motor area), bilateral medial frontal regions (supplementary motor area), and the dysplastic gyrus. Hemodynamic response modeling to foot jerks revealed the hemodynamic response peaked earlier in the dysplastic cortex and SMA regions than in the foot area. Discussion: Event-related fMRI in a patient with spontaneous and induced epileptic foot jerks revealed brain regions active during jerks. The results of this analysis allowed us to tailor subsequent intracerebral recordings. Analysis of the timing of the hemodynamic response showed certain brain regions with an earlier rise in BOLD signal, suggesting a possible initiating role, or different hemodynamic response functions. Hemodynamic response timing should be considered carefully when interpreting event-related studies of epileptiform activity. [source] Magnetic Resonance Imaging Follow-up of Progressive Hippocampal Changes in a Mouse Model of Mesial Temporal Lobe EpilepsyEPILEPSIA, Issue 6 2000Viviane Bouilleret Summary: Purpose: Hippocampal sclerosis (HS) is the most frequent lesion found in mesial temporal lobe epilepsy (mTLE). MR imaging is considered to be the most sensitive and specific method to detect HS. Despite extensive studies performed on humans and except in a recent study, the morphologic pattern of HS is usually analyzed when the disease has already fully developed, thus not allowing any insight into the mapping of the progressive morphologic changes inducing the development of mTLE. We have recently characterized a model of mTLE that reproduces the unilateral pattern of HS, induced by intrahippocampal injection of low doses of kainate (KA) in mice. Methods: In this study, we monitored the temporal evolution of the development of HS in this model of mTLE by using T2 -weighted sequence, T2 -relaxation time measurements, and T1 -weighted spin-echo technique after injection of gadolinium, from 1 h to 120 days after KA injection. Results: HS induced by intrahippocampal KA injection occurred in two phases. First, we observed a transient hyperintense T2 -weighted signal in the cortex above the injected hippocampus, most likely indicative of vasogenic edema partly due to the neurotoxic effect of KA. The concomitant increase in the T2 signal in the injected hippocampus and ipsilateral amygdala likely reflects the phase of cytotoxic edema occurring probably in relation to the excitotoxic consequences of both KA and seizure activity. Second, from 15 days on, a persistent unilateral increased T2 signal was detected in the hippocampus, which most probably reflects gliosis. Conclusions: Our findings indicate that longitudinal follow-up would permit a better understanding of the mechanisms underlying the constitution of HS in humans and eventually development of prevention strategies. [source] Antiphospholipid syndrome and endocrine damage: why bilateral adrenal thrombosis?EUROPEAN JOURNAL OF HAEMATOLOGY, Issue 4 2003Kaspar Berneis Abstract: We describe a rare case of bilateral hemorrhagic infarction of the adrenal glands diagnosed in the context of positive antiphospholipid antibodies (aPL). The patient presented atypical clinical symptoms of adrenal insufficiency. Laboratory investigation showed complete adrenal failure and increased aPL, both manifestations persisted 1 yr after the initial event. MR imaging at baseline was compatible with bilateral hemorrhagic infarction and showed almost complete loss of viable adrenal tissue 1 yr later. Although no direct causal effect can be proved, the sequence of events and the exclusion of other common causes of bilateral adrenal hemorrhage (e.g. tuberculosis, severe coagulation disorder) support an association between aPL and adrenal hemorrhagic infarction. A unique link between particular anatomical characteristics of the adrenal fascicular zone and a novel, previously described, explanation model of aPL-thrombosis is hypothesized. It is based on the properties of late endosomes, which are important organelles participating in cholesterol trafficking and protein sorting within cells and express epitopes recognized by aPL. It would be interesting to investigate adrenal tissue for presence of late endosomes and their aPL relevant epitopes for proof of this tempting hypothesis. Focal accumulation of aPL and isolated, simultaneous, bilateral adrenal infarctions could thus be explained. [source] Stereotactic cortical resection in non-lesional extra-temporal partial epilepsyEUROPEAN JOURNAL OF NEUROLOGY, Issue 10 2007D. C. Shields The presentation and treatment of a patient with extra-temporal non-lesional partial epilepsy is discussed herein. His clinical semiology was consistent with supplementary motor area seizures; however, MR imaging did not demonstrate a lesion. A region of stable cortical glucose hypermetabolism in the left frontal region was noted with 2-fluoro-2-deoxy-D-glucose (FDG)-PET. This was consistent with the frequent interictal discharges evident over the left fronto-temporal region and the stereotypic high amplitude ictal discharges arising with highest amplitude from the left frontal region. Epileptiform activity evident on an intracranial 64-point subdural recording grid placed over the left dorsolateral frontal cortex confirmed a distribution concordant with FDG-PET findings. The subsequent resection was guided by the PET and EEG findings rather than structural MR imaging, and a limited cortical resection led to an immediate and substantial reduction in seizure frequency. [source] Diffusion-tensor MR imaging for evaluation of the efficacy of hyperbaric oxygen therapy in patients with delayed neuropsychiatric syndrome caused by carbon monoxide inhalationEUROPEAN JOURNAL OF NEUROLOGY, Issue 7 2007C.-P. Lo The purpose of this study is to assess the efficacy of hyperbaric oxygen therapy (HBOT) in patients with delayed neuropsychiatric syndrome (DNS) caused by carbon monoxide (CO) inhalation using diffusion tensor magnetic resonance (MR) imaging and neuropsychological test. Conventional and diffusion tensor brain MR imaging exams were performed in six patients with DNS immediately before and 3 months after the HBOT to obtain fractional anisotropy (FA) values. Six age- and sex-matched normal control subjects also received MR exams for comparison. Mini-Mental State Examination (MMSE) was also performed in patients immediately before and 3 months after the HBOT. A significantly higher mean FA value was found in control subjects as compared with the patients both before and 3 months after the HBOT (P < 0.001). The mean FA value 3 months after the HBOT was also significantly higher than that before the HBOT in the patient group (P < 0.001). All of the patients regained full scores in the MMSE 3 months after the HBOT. Diffusion tensor MR imaging can be a quantitative method for the assessment of the white matter change and monitor the treatment response in patients of CO-induced DNS with a good clinical correlation. HBO may be an effective therapy for DNS. [source] MR imaging of the brain in patients with hepatic form of Wilson's diseaseEUROPEAN JOURNAL OF NEUROLOGY, Issue 5 2003D. Kozi The aim of this study was to detect the sites and frequency of possible lesions by brain magnetic resonance imaging (MRI; 1,5T) in a group of 16 neurologically asymptomatic patients with hepatic form of Wilson's disease (WD; seven untreated and nine under treatment). Abnormal MR findings of the brain were found in 75% of patients. Lesions in brain parenchyma were detected in all untreated, drug-naive patients and in 44% of treated patients. Abnormal signal in globus pallidus, putamen, and caudate nucleus was revealed in 86, 71 and 71% of treated and in 33, 33 and 22% of untreated patients, respectively. In five of eight patients with putaminal pathology (62.5%) and in four of seven patients with caudate nuclei involvement (57%), only proton density 2-weighted sequence (PDW) exhibited sensitivity for lesion detection, with both T1W and long echo T2W sequences being insensitive. This superiority of PDW sequence was even more pronounced in the group of untreated patients in whom 80% of putaminal pathology was visible exclusively on this sequence. The lower frequency of lesions in the group of treated in comparison with untreated patients indicated that they might be reversible in the course of chronic chelating therapy. [source] Fluorescent Imaging: Surface Modification of Exfoliated Layered Gadolinium Hydroxide for the Development of Multimodal Contrast Agents for MRI and Fluorescence Imaging (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Mater. The synthesis of a new stable colloid of fluorescent LGdH layers through a newly developed surface modification method is reported by Y.-S. Yoon et al. on page 3375. This new method involves layer exfoliation, anion exchange, and PEG coating. The efficient MRI contrast-enhancement of these LGdH layers, both in vitro and in vivo, demonstrates their potential utility as a multimodal probe combining optical and MR imaging. [source] Combined Optical and MR Bioimaging Using Rare Earth Ion Doped NaYF4 NanocrystalsADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Rajiv Kumar Abstract Here, novel nanoprobes for combined optical and magnetic resonance (MR) bioimaging are reported. Fluoride (NaYF4) nanocrystals (20,30,nm size) co-doped with the rare earth ions Gd3+ and Er3+/Yb3+/Eu3+ are synthesized and dispersed in water. An efficient up- and downconverted photoluminescence from the rare-earth ions (Er3+ and Yb3+ or Eu3+) doped into fluoride nanomatrix allows optical imaging modality for the nanoprobes. Upconversion nanophosphors (UCNPs) show nearly quadratic dependence of the photoluminescence intensity on the excitation light power, confirming a two-photon induced process and allowing two-photon imaging with UCNPs with low power continuous wave laser diodes due to the sequential nature of the two-photon process. Furthermore, both UCNPs and downconversion nanophosphors (DCNPs) are modified with biorecognition biomolecules such as anti-claudin-4 and anti-mesothelin, and show in vitro targeted delivery to cancer cells using confocal microscopy. The possibility of using nanoprobes for optical imaging in vivo is also demonstrated. It is also shown that Gd3+ co-doped within the nanophosphors imparts strong T1 (Spin-lattice relaxation time) and T2 (spin-spin relaxation time) for high contrast MR imaging. Thus, nanoprobes based on fluoride nanophosphors doped with rare earth ions are shown to provide the dual modality of optical and magnetic resonance imaging. [source] Superparamagnetic iron oxide,enhanced magnetic resonance images of hepatocellular carcinoma: Correlation with histological gradingHEPATOLOGY, Issue 2 2000Ph.D., Yasuharu Imai M.D. Superparamagnetic iron oxide (SPIO),enhanced magnetic resonance (MR) imaging has been used for the detection of hepatic tumors. However, little is known about this technique in relation to hepatocellular carcinoma (HCC). The aim of this study was to investigate whether SPIO,enhanced MR imaging can be useful in assessing histological grades of HCC. The authors studied histologically proven tumors including 31 HCCs and 6 dysplastic nodules. The ratio of the Kupffer-cell count in the tumorous tissue relative to that in the nontumorous tissue (Kupffer-cell,count ratio) decreased as HCCs became less well differentiated. The ratio of the intensity of the tumorous lesion to that of the nontumorous area on SPIO,enhanced MR images (SPIO intensity ratio) correlated inversely with Kupffer-cell,count ratio in HCCs and dysplastic nodules (r = ,.826, P< .001) and increased as the degree of differentiation of HCCs decreased, indicating that the uptake of SPIO in HCCs decreased as the degree of differentiation of HCCs declined. All of the dysplastic nodules and some well-differentiated HCCs showed hypointense or isointense enhancement, relative to the surrounding liver parenchyma, indicating greater or similar uptake of SPIO in the tumor when compared with nontumorous areas. These results suggest that SPIO,enhanced MR imaging reflects Kupffer-cell numbers in HCCs and dysplastic nodules, and is useful for estimation of histological grading in HCCs, although uncertainties persist in differentiating dysplastic nodules from well-differentiated HCCs. [source] Asynchrony of the early maturation of white matter bundles in healthy infants: Quantitative landmarks revealed noninvasively by diffusion tensor imagingHUMAN BRAIN MAPPING, Issue 1 2008Jessica Dubois Abstract Normal cognitive development in infants follows a well-known temporal sequence, which is assumed to be correlated with the structural maturation of underlying functional networks. Postmortem studies and, more recently, structural MR imaging studies have described qualitatively the heterogeneous spatiotemporal progression of white matter myelination. However, in vivo quantification of the maturation phases of fiber bundles is still lacking. We used noninvasive diffusion tensor MR imaging and tractography in twenty-three 1,4-month-old healthy infants to quantify the early maturation of the main cerebral fascicles. A specific maturation model, based on the respective roles of different maturational processes on the diffusion phenomena, was designed to highlight asynchronous maturation across bundles by evaluating the time-course of mean diffusivity and anisotropy changes over the considered developmental period. Using an original approach, a progression of maturation in four relative stages was determined in each tract by estimating the maturation state and speed, from the diffusion indices over the infants group compared with an adults group on one hand, and in each tract compared with the average over bundles on the other hand. Results were coherent with, and extended previous findings in 8 of 11 bundles, showing the anterior limb of the internal capsule and cingulum as the most immature, followed by the optic radiations, arcuate and inferior longitudinal fascicles, then the spinothalamic tract and fornix, and finally the corticospinal tract as the most mature bundle. Thus, this approach provides new quantitative landmarks for further noninvasive research on brain-behavior relationships during normal and abnormal development. Hum Brain Mapp, 2008. © 2007 Wiley-Liss, Inc. [source] Optic radiation changes after optic neuritis detected by tractography-based group mappingHUMAN BRAIN MAPPING, Issue 3 2005Olga Ciccarelli Abstract Postmortem data suggest that trans-synaptic degeneration occurs in the lateral geniculate nucleus after optic nerve injury. This study investigated in vivo the optic radiations in patients affected by optic neuritis using fast marching tractography (FMT), a diffusion magnetic resonance imaging (MRI) fiber tracking method, and group mapping techniques, which allow statistical comparisons between subjects. Seven patients, 1 year after isolated unilateral optic neuritis, and ten age and gender-matched controls underwent whole-brain diffusion tensor MR imaging. The FMT algorithm was used to generate voxel-scale connectivity (VSC) maps in the optic radiations in each subject in native space. Group maps of the left and right optic radiations were created in the patient and control group in a standardized reference frame using statistical parametric mapping (SPM99). The reconstructed optic radiations in the patient group were localized more laterally in the posterior part of the tracts and more inferiorly than in the control group. Patients showed reduced VSC values in both tracts compared with controls. These findings suggest that the group mapping techniques might be used to assess changes in the optic radiations in patients after an episode of optic neuritis. The changes we have observed may be secondary to the optic nerve damage. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source] In Vivo Determination of Bone Structure in Postmenopausal Women: A Comparison of HR-pQCT and High-Field MR Imaging,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2008Galateia J Kazakia PhD Abstract Bone structural measures obtained by two noninvasive imaging tools,3T MRI and HR-pQCT,were compared. Significant but moderate correlations and 2- to 4-fold discrepancies in parameter values were detected, suggesting that differences in acquisition and analysis must be considered when interpreting data from these imaging modalities. Introduction: High-field MRI and high resolution (HR)-pQCT are currently being used in longitudinal bone structure studies. Substantial differences in acquisition and analysis between these modalities may influence the quantitative data produced and could potentially influence clinical decisions based on their results. Our goal was to compare trabecular and cortical bone structural measures obtained in vivo by 3T MRI and HR-pQCT. Materials and Methods: Postmenopausal osteopenic women (n = 52) were recruited for this study. HR-pQCT imaging of the radius and tibia was performed using the XtremeCT scanner, with a voxel size of 82 × 82 × 82 ,m3. MR imaging was performed on a 3T Signa scanner using SSFP imaging sequences, with a pixel size of 156 × 156 ,m2 and slice thickness of 500 ,m. Structure parameters were calculated using standard HR-pQCT and MRI analysis techniques. Relationships between measures derived from HR-pQCT, MRI, and DXA were studied. Results: Significant correlations between HR-pQCT and MRI parameters were found (p < 0.0001) and were strongest for Tb.N (r2 = 0.52), Ct.Th (r2 = 0.59), and site-specific Tb.Sp (r2 = 0.54,0.60). MRI and HR-pQCT provided statistically different values of structure parameters (p < 0.0001), with BV/TV and Tb.Th exhibiting the largest discrepancies (MR/HR-pQCT = 3,4). Although differences in the Tb.N values were statistically significant, the mean differences were on the order of our reproducibility measurements. Systematic differences between MRI and HR-pQCT analysis procedures leading to discrepancies in cortical thickness values were observed, with MRI values consistently higher. Minimal correlations were found between MRI or HR-pQCT parameters and DXA BMD or T-score, except between HR-pQCT measures at the radius and the ultradistal radius T-scores, where moderate correlations were found (r2 = 0.19,0.58). Conclusions: This study provides unique insight into two emerging noninvasive tools for bone structure evaluation. Our findings highlight the significant influence of analysis technique on results of in vivo assessment and underscore the importance of accounting for these differences when interpreting results from these modalities. [source] Functional and molecular MR imaging of angiogenesis: Seeing the target, seeing it workJOURNAL OF CELLULAR BIOCHEMISTRY, Issue S39 2002Michal NeemanArticle first published online: 16 JAN 200 Abstract Intensive research over the last years led to the discovery of multiple molecular pathways and intricate regulatory network controlling the growth and regression of blood vessels in general and angiogenesis in particular. The difficulties in elucidation of the regulation of angiogenesis, stems from the inherent complexity due to participation of many cell types, under a dominant impact of physiological and environmental effects of flow, perfusion, and oxygenation. Major advances were achieved with the use of sophisticated transgenic mice models engineered so as to provide spatially and temporally controlled expression of specific factors alone or in combination. In vivo analysis of these models frequently requires the use of non-invasive imaging modalities for measurement of functional parameters of the vasculature along with dynamic molecular information. Optical methods are extensively applied for the study of angiogenesis [Brown et al., 2001] but provide very limited tissue penetration. MRI offers the advantage of being non-invasive with uniform and relatively high spatial resolution for deep tissues. Multiple MRI approaches for monitoring angiogenesis were developed over the last years, each looking at a particular step in the process. The aim of this paper is to analyze the clinical, pharmaceutical, and biological needs for imaging of angiogenesis, and to critically evaluate the strengths and weaknesses of functional and molecular imaging for monitoring angiogenesis. The inherent problem of validation of different measures of angiogenesis, and the advantages and limitations associated with application of MRI based methods, as surrogates for other measurements of angiogenesis will be discussed. The terms molecular imaging and functional imaging are frequently loosely defined with a significant overlap between the two. For the sake of this paper we will apply a narrower definition of both terms, where molecular imaging will apply to methods directed towards detection of specific biological molecules that participate directly in (regulation of) a physiological process; while functional imaging will be used to describe those methods that aim to detect the physiological response to a defined (molecular) stimulus. J. Cell. Biochem. Suppl. 39: 11,17, 2002. © 2002 Wiley-Liss, Inc. [source] Nonalcoholic fatty liver disease: Quantitative assessment of liver fat content by computed tomography, magnetic resonance imaging and proton magnetic resonance spectroscopyJOURNAL OF DIGESTIVE DISEASES, Issue 4 2009Liang ZHONG OBJECTIVE: The purpose of this study was to evaluate the clinical application of imaging technology in the quantitative assessment of fatty liver with magnetic resonance imaging (MRI) and proton MR spectroscopy. METHODS: Overall 36 patients with diffuse fatty liver who had undertaken the computed tomography (CT) scan, MRI and proton MR spectroscopy (1H MRS) were analyzed. Their body mass index (BMI) was measured and their liver to spleen CT ratio (L/S) calculated on the plain CT scan. MR T1-weighted imaging (T1WI) was obtained with in-phase (IP) and out-of-phase (OP) images. T2-weighted imaging (T2WI) was acquired with or without the fat-suppression technique. The liver fat content (LFC) was quantified as the percentage of relative signal intensity loss on T1WI or T2WI images. The intrahepatic content of lipid (IHCL) was expressed as the percentage of peak value ratio of lipid to water by 1H MRS. RESULTS: The results of BMI measurement, CT L/S ratio, LFC calculated from MR T1WI and T2WI images, as well as IHCL measured by 1H MRS were 27.26 ± 3.01 kg/m2, 0.88 ± 0.26, 13.80 ± 9.92%, 40.67 ± 16.04% and 30.98 ± 20.43%, respectively. The LFC calculated from MR T1WI, T2WI images and IHCL measured by 1H MRS correlated significantly with the CT L/S ratio (r=,0.830, P= 0.000; r=,0.736, P= 0.000; r=,0.461, P= 0.005, respectively). BMI correlated significantly only with the liver fat contents measured by T1WI IP/OP and 1H MRS (r=,0.347, P= 0.038; r=,0.374, P= 0.025, respectively). CONCLUSION: CT, MR imaging and 1H MRS were effective methods for the quantitative assessment of LFC. The MR imaging, especially 1H MRS, would be used more frequently in the clinical evaluation of fatty liver and 1H MRS could more accurately reflect the severity of fatty liver. [source] 3 Tesla and 7 Tesla MRI of multiple sclerosis cortical lesionsJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2010Emma C. Tallantyre BM Abstract Cortical lesions are prevalent in multiple sclerosis but are poorly detected using MRI. The double inversion recovery (DIR) sequence is increasingly used to explore the clinical relevance of cortical demyelination. Here we evaluate the agreement between imaging sequences at 3 Tesla (T) and 7T for the presence and appearance of individual multiple sclerosis cortical lesions. Eleven patients with demyelinating disease and eight healthy volunteers underwent MR imaging at 3T (fluid attenuated inversion recovery [FLAIR], DIR, and T1 -weighted magnetization prepared rapid acquisition gradient echo [MP-RAGE] sequences) and 7T (T1 -weighted MP-RAGE). There was good agreement between images for the presence of mixed cortical lesions (involving both gray and white matter). However, agreement between imaging sequences was less good for purely intracortical lesions. Even after retrospective analysis, 25% of cortical lesions could only be visualized on a single MRI sequence. Several DIR hyperintensities thought to represent cortical lesions were found to correspond to signal arising from extracortical blood vessels. High-resolution 7T imaging appeared useful for confidently classifying the location of lesions in relation to the cortical/subcortical boundary. We conclude that DIR, FLAIR, and MP-RAGE imaging sequences appear to provide complementary information during the detection of multiple sclerosis cortical lesions. High resolution 7T imaging may facilitate anatomical localization of lesions in relation to the cortical boundary. J. Magn. Reson. Imaging 2010;32:971,977. © 2010 Wiley-Liss, Inc. [source] Can MR fluoroscopic triggering technique and slow rate injection provide appropriate arterial phase images with reducing artifacts on gadoxetic acid-DTPA (Gd-EOB-DTPA)-enhanced hepatic MR imaging?JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2010Hiroki Haradome MD Abstract Purpose: To evaluate whether using MR fluoroscopic triggering technique and slow rate injection improves the quality of arterial phase images in gadoxetic acid-DTPA-enhanced (Gd-EOB-DTPA) MR imaging because of proper acquisition timing and reduction of artifacts. Materials and Methods: Two hundred sixteen patients undergoing examination for liver diseases were retrospectively reviewed. All MR images were obtained with two Gd-EOB-DTPA injection protocols: (i) a combination protocol, in which the MR fluoroscopic triggering technique and slow rate injection (1 mL/s) were used; and for comparison, (ii) a conventional protocol, in which adjusted fixed scan delay and ordinary rate injection (2 mL/s) were adopted. Signal-to-noise ratio (SNR) of aorta, portal vein, and liver parenchyma on arterial phase images were calculated. Two blinded readers independently evaluated the obtained arterial phase images in terms of acquisition timing and degree of artifacts. Results: The SNRs of aorta and portal vein on arterial phase images were significantly higher in the combination protocol group (aorta/portal: 221.9 ± 91.9/197.1 ± 89.8) than that in the conventional protocol group (aorta/portal: 169.8 ± 97.4/92.7 ± 48.5) (P < 0.05). The acquisition timing for arterial phase images with the combination protocol was significantly better than that with the conventional protocol (P < 0.01). The image quality of the combination protocol was significantly higher than that of the conventional protocol (P < 0.01). The occurrence rate of moderate or severe degree of artifacts in the conventional protocol (38.0%) was more prominent than that in the combination protocol (18.5%). Conclusion: The combination of the MR fluoroscopic triggering technique and slow rate injection provides proper arterial phase images and reduces the artifacts in Gd-EOB-DTPA MR imaging. J. Magn. Reson. Imaging 2010;32:334,340. © 2010 Wiley-Liss, Inc. [source] 7 Tesla MR imaging of the human eye in vivoJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 5 2009Kathryn Richdale OD Abstract Purpose: To develop a protocol which optimizes contrast, resolution and scan time for three-dimensional (3D) imaging of the human eye in vivo using a 7 Tesla (T) scanner and custom radio frequency (RF) coil. Materials and Methods: Initial testing was conducted to reduce motion and susceptibility artifacts. Three-dimensional FFE and IR-TFE images were obtained with variable flip angles and TI times. T1 measurements were made and numerical simulations were performed to determine the ideal contrast of certain ocular structures. Studies were performed to optimize resolution and signal-to-noise ratio (SNR) with scan times from 20 s to 5 min. Results: Motion and susceptibility artifacts were reduced through careful subject preparation. T1 values of the ocular structures are in line with previous work at 1.5T. A voxel size of 0.15 × 0.25 × 1.0 mm3 was obtained with a scan time of approximately 35 s for both 3D FFE and IR-TFE sequences. Multiple images were registered in 3D to produce final SNRs over 40. Conclusion: Optimization of pulse sequences and avoidance of susceptibility and motion artifacts led to high quality images with spatial resolution and SNR exceeding prior work. Ocular imaging at 7T with a dedicated coil improves the ability to make measurements of the fine structures of the eye. J. Magn. Reson. Imaging 2009;30:924,932. © 2009 Wiley-Liss, Inc. [source] | |||||||||||||||||||||||||||||||