MDJobScout :: Medicine :: Imaging :: Magnetic Resonance Imaging

PubMed: 0730-725X

Early contrast enhancement of the liver: exact description of subphases using MRI.
Goncalves Neto JA, Altun E, Vaidean G, Elazzazi M, Troy J, Ramachandran S, Semelka RC Related Articles Early contrast enhancement of the liver: exact description of subphases using MRI. Magn Reson Imaging. 2009 Jan 2; Authors: Goncalves Neto JA, Altun E, Vaidean G, Elazzazi M, Troy J, Ramachandran S, Semelka RC PURPOSE: The purpose of this study was to describe the subphases of early post-contrast enhancement of the liver, using vessel enhancement patterns, and correlate these findings with enhancement patterns of abdominal organs. MATERIALS AND METHODS: A total of 114 patients who underwent gadolinium-enhanced abdominal magnetic resonance imaging examinations constituted the final study group, of which 56 were women (age range, 3-94 years; mean, 50 years) and 58 were men (age range, 6-85 years; mean, 54 years). Early post-contrast sequences in all patients were evaluated retrospectively by two reviewers for the determination of the presence of contrast enhancement in predetermined major vessels of the abdomen and qualitative and quantitative extent of enhancement of the renal cortex, spleen, pancreas and liver. Based on the overall findings, subphases of early contrast enhancement of the liver were described and quantitative extent of enhancement of organs was correlated with subphases of early contrast enhancement of the liver. Mann-Whitney U test and one-way unbalanced analysis of variance tests were used for the comparisons. RESULTS: Early hepatic arterial phase was observed in 14/114 patients, mid-hepatic arterial phase in 23/114 patients, late hepatic arterial phase in 33/114 patients, splenic vein only hepatic arterial dominant phase in 20/114 patients and hepatic arterial dominant phase in 24/114 patients. There was an overall association between the subphases of enhancement and the quantitative extent of enhancement for all studied organs (P<.0001). CONCLUSION: The evaluation of vessel and organ enhancement patterns has allowed the characterization of five different subphases in early post-contrast enhancement of the liver. The quantitative extent of enhancement of abdominal organs also demonstrated significant correlation with these five subphases. PMID: 19121908 [PubMed - as supplied by publisher]
Application of FT-based MMSE deconvolution method for cerebral blood flow measurement in patients with leukoaraiosis.
Sakoglu U, Garate BH, Rosenberg GA, Sood R Related Articles Application of FT-based MMSE deconvolution method for cerebral blood flow measurement in patients with leukoaraiosis. Magn Reson Imaging. 2009 Jan 2; Authors: Sakoglu U, Garate BH, Rosenberg GA, Sood R INTRODUCTION: The bolus-tracking (BT) technique is the most popular perfusion-weighted (PW) dynamic susceptibility contrast MRI method used for estimating cerebral blood flow (CBF), cerebral blood volume and mean transit time. The BT technique uses a convolution model that establishes the input-output relationship between blood flow and the vascular tracer concentration. Singular value decomposition (SVD)- and Fourier transform (FT)-based deconvolution methods are popular and widely used for estimating PW MRI parameters. However, from the published literature, it appears that SVD is more widely accepted than other methods. In a previous article, an FT-based minimum mean-squared error (MMSE) technique was proposed and simulation experiments were performed to compare it with the well-established circular SVD (oSVD) method. In this study, the FT-based MMSE method has been used to estimate relative CBF (rCBF) in 13 patients with white matter lesions (WMLs) (leukoaraiosis), and results are compared with the widely used oSVD method. MATERIALS AND METHODS: Thirteen patients with leukoaraiosis were imaged on a 1.5-T Siemens whole-body scanner. After acquiring the localizer and structural scans consisting of FLAIR (fluid attenuated with inversion recovery), T(1)-weighted and T(2)-weighted images, perfusion study was implemented as part of the MRI protocol. For each patient and method, two values were calculated: (a) rCBF for normal white matter (NWM) ROI, obtained by dividing the average CBF value in NWM ROI with average CBF in gray matter (GM) ROI, and (b) rCBF for WML ROI, obtained by dividing the average CBF value in WML ROI with average CBF in GM ROI. Results for the two deconvolution methods were computed. RESULTS AND DISCUSSION: A significant (P<.05) decrease in estimated rCBF was observed in the WML in all the patients using the MMSE method, while for the oSVD method, the decrease was observed in all but one patient. Initial results suggest that the MMSE method is comparable to the oSVD method for estimating rCBF in NMW while it may be better than oSVD for estimating rCBF in lesions of low flow. Studies involving a larger patient population may be required to further validate the findings of this work. PMID: 19121907 [PubMed - as supplied by publisher]

Magnetic Resonance in Medicine

Mapping of brain metabolite distributions by volumetric proton MR spectroscopic imaging (MRSI)
A.A. Maudsley, C. Domenig, V. Govind, A. Darkazanli, C. Studholme, K. Arheart, C. Bloomer Sun, 28 Dec 2008 16:54:00 -0000
Distributions of proton MR-detected metabolites have been mapped throughout the brain in a group of normal subjects using a volumetric MR spectroscopic imaging (MRSI) acquisition with an interleaved water reference. Data were processed with intensity and spatial normalization to enable voxel-based analysis methods to be applied across a group of subjects. Results demonstrate significant regional, tissue, and gender-dependent variations of brain metabolite concentrations, and variations of these distributions with normal aging. The greatest alteration of metabolites with age was observed for white-matter choline and creatine. An example of the utility of the normative metabolic reference information is then demonstrated for analysis of data acquired from a subject who suffered a traumatic brain injury. This study demonstrates the ability to obtain proton spectra from a wide region of the brain and to apply fully automated processing methods. The resultant data provide a normative reference for subsequent utilization for studies of brain injury and disease. Magn Reson Med, 2009. © 2008 Wiley-Liss, Inc.
Retrospective correction for induced magnetic field inhomogeneity in measurements of large-vessel hemoglobin oxygen saturation by MR susceptometry
Michael C. Langham, Jeremy F. Magland, Tom F. Floyd, Felix W. Wehrli Tue, 23 Dec 2008 11:57:00 -0000
MR susceptometry-based blood oximetry relies on phase mapping to measure the difference in magnetic susceptibility between intravascular blood and surrounding tissue. The main source of error in MR susceptometry is the static field inhomogeneity caused by an interface between air and tissue or between adjacent tissue types. High-pass filtering has previously been used in conjunction with shimming to reduce the effect of low spatial-frequency modulations of the phase caused by large-scale induced magnetic fields. We demonstrate that high-pass filtering is not optimum for MR susceptometry because the results are sensitive to filter size. We propose an alternative method that acquires data without scanner-implemented default shimming, and fits, after appropriate weighting and masking, the static field inhomogeneity to a second-order polynomial. Compared to shimming the retrospective correction technique improved agreement between hemoglobin saturations measured in different segments of a vessel (femoral versus popliteal artery and vein) from three standard errors to less than one. Magn Reson Med, 2008. © 2008 Wiley-Liss, Inc.
Investigation of relationships between transverse relaxation rate, diffusion coefficient, and labeled cell concentration in ischemic rat brain using MRI
Hemanthkumar Athiraman, Quan Jiang, Guang Liang Ding, Li Zhang, Zheng Gang Zhang, Lei Wang, Ali S. Arbab, Qingjiang Li, Swayam Panda, Karen Ledbetter, Ali M. Rad, Michael Chopp Tue, 23 Dec 2008 11:58:00 -0000
MRI has been used to evaluate labeled cell migration and distribution. However, quantitative determination of labeled cell concentration using MRI has not been systematically investigated. In the current study, we investigated the relationships between labeled cell concentration and MRI parameters of transverse relaxation rate, R2, and apparent diffusion coefficient (ADC), in vitro in phantoms and in vivo in rats after stroke. Significant correlations were detected between iron concentration or labeled cell concentration and MRI measurements of R2, ADC, and ADC×R2 in vitro. In contrast, in vivo labeled cell concentration did not significantly correlate with R2, ADC, and ADC×R2. A major factor for the absence of a significant correlation between labeled cell concentration and MRI measurements in vivo may be attributed to background effects of ischemic tissue. By correcting the background effects caused by ischemic damage, [Delta]R2 (difference in R2 values in the ischemic tissue with and without labeled cells) exhibited a significant correlation to labeled cell concentration. Our study suggests that MRI parameters have the potential to quantitatively determine labeled cell concentration in vivo. Magn Reson Med, 2009. © 2008 Wiley-Liss, Inc.

Magnetic Resonance Materials in Physics, Biology and Medicine

Monitoring kidney and renal cyst volumes applying MR approaches on a rapamycin treated mouse model of ADPKD
Wed, 24 Dec 2008 08:52:05 -0000
Abstract Object  The aim of our study was to determine total cystic volume in a mouse model of PKD using MR imaging to monitor therapeutic effects in vivo. Materials and methods  We imaged eight female pcy-mice in two groups: four belonged to an untreated control group and four were treated with the anticystic agent rapamycin, which has proven to be effective in reducing cystogenesis in animal models. The mice were imaged using a 9.4 Tesla animal scanner. MRI measurements were taken at six time points during the therapy. Total renal volumes and total cyst volumes were calculated using a thresholding approach. Results  During the course of the treatment, the total cyst volume increased significantly faster than the total renal volume in the untreated group, indicating that growth of the total renal volume in the untreated group was primarily due to the growth of the cysts, rather than the parenchyma. The measured total renal volume in the control (placebo) group was significantly higher than the volume in the treated group. Conclusion  Using MRI, we were able to monitor the cystic volume in a mouse model of PKD to assess the therapeutic effect of anticystic treatment. Content Type Journal ArticleCategory Research ArticleDOI 10.1007/s10334-008-0158-7Authors Wilfried Reichardt, University Hospital Freiburg Department of Diagnostic Radiology, Medical Physics Personalhaus 4, Hugstetter Strasse 55 79106 Freiburg GermanyDaniel Romaker, University Hospital Freiburg Renal Division Freiburg GermanyAnne Becker, University Hospital Freiburg Department of Diagnostic Radiology, Medical Physics Personalhaus 4, Hugstetter Strasse 55 79106 Freiburg GermanyMartin Buechert, University Hospital Freiburg Magnetic Resonance Development and Application Center Freiburg GermanyGerd Walz, University Hospital Freiburg Renal Division Freiburg GermanyDominik von Elverfeldt, University Hospital Freiburg Department of Diagnostic Radiology, Medical Physics Personalhaus 4, Hugstetter Strasse 55 79106 Freiburg Germany Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243
Imaging E-selectin expression following traumatic brain injury in the rat using a targeted USPIO contrast agent
Wed, 24 Dec 2008 08:52:05 -0000
Abstract Introduction  The aim of this work was to map E-selectin expression in a traumatic brain injury model using a newly-designed MR contrast agent. Iron cores, responsible for susceptibility effects and therefore used as T2* contrast agents, need to be coated in order to be stabilized and need to be targeted to be useful. Methods  We have designed a molecule coating composed, at one end, of bisphosphonate to ensure anchorage of the coating on the iron core and, at the other end, of Fukuda’s defined heptapeptide known to target selectin binding sites. Conclusion  The synthesized nanoparticles were able to non-invasively target the traumatic brain lesion, inducing a specific T2* decrease of about 25% up to at least 70 min post-injection of the targeted contrast agent. Content Type Journal ArticleCategory Research ArticleDOI 10.1007/s10334-008-0161-zAuthors Catherine Chapon, INSERM U 646, Ingénierie de la Vectorisation Particulaire 10, rue André Boquel 49100 Angers FranceFlorence Franconi, Université d’Angers Service Commun d’Analyses Spectroscopiques Angers FranceFranck Lacoeuille, INSERM U 646, Ingénierie de la Vectorisation Particulaire 10, rue André Boquel 49100 Angers FranceFrançois Hindré, INSERM U 646, Ingénierie de la Vectorisation Particulaire 10, rue André Boquel 49100 Angers FrancePatrick Saulnier, INSERM U 646, Ingénierie de la Vectorisation Particulaire 10, rue André Boquel 49100 Angers FranceJean-Pierre Benoit, INSERM U 646, Ingénierie de la Vectorisation Particulaire 10, rue André Boquel 49100 Angers FranceJean-Jacques Le Jeune, INSERM U 646, Ingénierie de la Vectorisation Particulaire 10, rue André Boquel 49100 Angers FranceLaurent Lemaire, INSERM U 646, Ingénierie de la Vectorisation Particulaire 10, rue André Boquel 49100 Angers France Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243
A novel continuous arterial spin labeling approach for CBF measurement in rats with reduced labeling time and optimized signal-to-noise ratio efficiency
Thu, 11 Dec 2008 12:12:26 -0000
Abstract Objective  To develop a continuous arterial spin labeling (CASL) perfusion imaging method for cerebral blood flow (CBF) measurement in rats with reduced spin-labeling length and optimized signal-to-noise ratio (SNR f ) per unit time. Materials and methods  In the proposed method, the longitudinal magnetization of brain tissue water in the imaging slice is prepared into a proper state before spin-labeling, and a post-tagging delay is employed after spin-labeling. The method was implemented on a 4.7 T small animal scanner. Numerical simulations and in vivo experiments were used to evaluate the performance of the method proposed. Results  With the proposed method, absolute CBF could be measured accurately from normal rat with a spin-labeling pulse as short as 400 ms, and yet employing the same formula as that used in the conventional CASL perfusion imaging method for calculation. The method also showed improved SNR f per unit time over the conventional CASL perfusion imaging method and the pulsed arterial spin labeling perfusion imaging method FAIR. Conclusion  Compared to the conventional CASL perfusion imaging method, the proposed method would be advantageous for CBF measurement in small animals having short vascular transit time in terms of SNR f per unit time and other benefits brought by shortened spin-labeling pulse. Content Type Journal ArticleCategory Research ArticleDOI 10.1007/s10334-008-0157-8Authors Yuguang Meng, Chinese Academy of Sciences State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics 30# Xiaohongshan 430071 Wuhan Hubei People’s Republic of ChinaHao Lei, Chinese Academy of Sciences State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics 30# Xiaohongshan 430071 Wuhan Hubei People’s Republic of China Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243

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