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

pubmed: 0730-725X

Paradoxical uptake of Gd-EOB-DTPA on the hepatobiliary phase in the evaluation of hepatic metastasis from breast cancer: is the "target sign" a common finding?
Ha S, Lee CH, Kim BH, Park YS, Lee J, Choi JW, Kim KA, Park CM Paradoxical uptake of Gd-EOB-DTPA on the hepatobiliary phase in the evaluation of hepatic metastasis from breast cancer: is the "target sign" a common finding? Magn Reson Imaging. 2012 May 11; Authors: Ha S, Lee CH, Kim BH, Park YS, Lee J, Choi JW, Kim KA, Park CM Abstract PURPOSE: The purpose was to describe magnetic resonance imaging (MRI) findings of breast cancer liver metastasis using gadoxetic acid (Gd-EOB-DTPA) with an emphasis on the added value of the hepatobiliary phase (HBP). MATERIAL AND METHODS: Nine patients with 13 liver metastases were included in the study after the medical records of 29 breast cancer patients who underwent Gd-EOB-DTPA-enhanced MRI between February 2008 and June 2010 were reviewed. The diagnoses of liver metastasis were established by percutaneous liver biopsy or surgery and on the basis of image findings. Two radiologists retrospectively evaluated signal intensity (SI) and sizes of metastases and patterns of enhancement in an HBP. The SI ratio was calculated as the SI of the central hyperintense portion in "target" lesions divided by the SI of nearby normal liver parenchyma on the HBP. We also measured apparent diffusion coefficient (ADC) values from Diffusion Weighted Image (DWI). RESULTS: Liver metastases were all hypointense [n=13/13 (100%)] on T1-weighted imaging (WI), and many lesions had a "target" appearance with a central high SI and a peripheral low SI rim (47%) on T2WI. Dynamic study showed rim enhancement on the arterial phase (85%) and a "target" appearance, consisting of a central enhancing portion with peripheral washout or hypointense rim, on the HBP (62%). The mean SI ratio was 0.7. The mean ADC value of "target" appearing metastases was 1.25 (×10(-3) mm(2)/s; range 1.3-1.6) compared with a mean value of 0.8 (×10(-3) mm(2)/s; range 0.8-1.4) in homogeneous defect on the HBP. There was statistically significant difference (P<.05). CONCLUSION: Breast cancer liver metastases commonly demonstrated as a peripheral ring enhancement on arterial dominant phase and a target sign with a central round enhancing portion and a peripheral hypointense rim on the HBP. PMID: 22578929 [PubMed - as supplied by publisher]
Detecting cortical lesions in multiple sclerosis at 7 T using white matter signal attenuation.
Bluestein KT, Pitt D, Sammet S, Zachariah CR, Nagaraj U, Knopp MV, Schmalbrock P Detecting cortical lesions in multiple sclerosis at 7 T using white matter signal attenuation. Magn Reson Imaging. 2012 May 11; Authors: Bluestein KT, Pitt D, Sammet S, Zachariah CR, Nagaraj U, Knopp MV, Schmalbrock P Abstract Cortical lesions have recently been a focus of multiple sclerosis (MS) MR research. In this study, we present a white matter signal attenuating sequence optimized for cortical lesion detection at 7 T. The feasibility of white matter attenuation (WHAT) for cortical lesion detection was determined by scanning eight patients (four relapsing/remitting MS, four secondary progressive MS) at 7 T. WHAT showed excellent gray matter-white matter contrast, and cortical lesions were hyperintense to the surrounding cortical gray matter, The sequence was then optimized for cortical lesion detection by determining the set of sequence parameters that produced the best gray matter-cortical lesion contrast in a 10-min scan. Despite the B1 inhomogeneities common at ultra-high field strengths, WHAT with an adiabatic inversion pulse showed good cortical lesion detection and would be a valuable component of clinical MS imaging protocols. PMID: 22578928 [PubMed - as supplied by publisher]
Automatic white matter lesion segmentation using an adaptive outlier detection method.
Ong KH, Ramachandram D, Mandava R, Shuaib IL Automatic white matter lesion segmentation using an adaptive outlier detection method. Magn Reson Imaging. 2012 May 11; Authors: Ong KH, Ramachandram D, Mandava R, Shuaib IL Abstract White matter (WM) lesions are diffuse WM abnormalities that appear as hyperintense (bright) regions in cranial magnetic resonance imaging (MRI). WM lesions are often observed in older populations and are important indicators of stroke, multiple sclerosis, dementia and other brain-related disorders. In this paper, a new automated method for WM lesions segmentation is presented. In the proposed method, the presence of WM lesions is detected as outliers in the intensity distribution of the fluid-attenuated inversion recovery (FLAIR) MR images using an adaptive outlier detection approach. Outliers are detected using a novel adaptive trimmed mean algorithm and box-whisker plot. In addition, pre- and postprocessing steps are implemented to reduce false positives attributed to MRI artifacts commonly observed in FLAIR sequences. The approach is validated using the cranial MRI sequences of 38 subjects. A significant correlation (R=0.9641, P value=3.12×10(-3)) is observed between the automated approach and manual segmentation by radiologist. The accuracy of the proposed approach was further validated by comparing the lesion volumes computed using the automated approach and lesions manually segmented by an expert radiologist. Finally, the proposed approach is compared against leading lesion segmentation algorithms using a benchmark dataset. PMID: 22578927 [PubMed - as supplied by publisher]
Compressed sensing MR image reconstruction using a motion-compensated reference.
Du H, Lam F Compressed sensing MR image reconstruction using a motion-compensated reference. Magn Reson Imaging. 2012 May 11; Authors: Du H, Lam F Abstract Compressed sensing (CS)-based methods have been proposed for image reconstruction from undersampled magnetic resonance data. Recently, CS-based schemes using reference images have also been proposed to further reduce the sampling requirement. In this study, we propose a new reference-constrained CS reconstruction method that accounts for the misalignment between the reference and the target image to be reconstructed. The proposed method uses a new image model that represents the target image as a linear combination of a motion-dependent reference image and a sparse difference image. We then use an efficient iterative algorithm to jointly estimate the motion parameters and the difference image from sparsely sampled data. Simulation results from a numerical phantom data set and an in vivo data set show that the proposed method can accurately compensate the motion effects between the reference and the target images and improve reconstruction quality. The proposed method should prove useful for several applications such as interventional imaging, longitudinal imaging studies and dynamic contrast-enhanced imaging. PMID: 22578926 [PubMed - as supplied by publisher]

Magnetic Resonance Materials in Physics, Biology and Medicine (Online Firstâ„¢)

Evaluation of a mobile NMR sensor for determining skin layers and locally estimating the T2eff relaxation time in the lower arm
Sun, 13 May 2012 05:58:46 -0000
Abstract Object  The nuclear magnetic resonance (NMR) mobile-universal-surface-explorer (MOUSE) was evaluated in a pilot study to determine its ability to detect physiological changes in human skin caused by physical or pharmacological interventions. Materials and methods  The left lower arm skin thicknesses of ten male subjects were measured five times using a Profile NMR-MOUSE® (1H, 19 MHz) before and after a venous occlusion manoeuvre. In five of the subjects, the T2eff relaxation times were derived from a bi-exponential fitting and were determined in the dermis and subcutis before and after applying a salve containing capsaicin. Results  The dermis (including the epidermis) showed rather homogeneous signal amplitudes. The subcutis was characterised by higher and more variable amplitudes. The full-skin thickness values were affirmed by ultrasound imaging. The NMR profiles did not show significant skin swelling due to venous occlusion. In the dermis, capsaicin caused significant (p < 0.05) decreases in both components of T 2eff (100 Â± 19 ms–19 Â± 10 ms; 9.5 Â± 0.5 ms–7.2 Â± 1.6 ms). In the subcutis, the T 2eff was not affected. Conclusion  In principle, NMR-MOUSE profiles are capable of detecting skin structure. However, precise measurements are jeopardised by poor reproducibility, long acquisition times, and incompatibility between the geometries of the sensitive area of the instrument and the non-planar structure of the skin. In the dermis, T 2eff contrast could be used to detect the changes in tissue composition caused by inflammatory reactions. Content Type Journal ArticleCategory Research ArticlePages 1-12DOI 10.1007/s10334-012-0317-8Authors Darius Kornetka, Institute of Aerospace Medicine, Deutsches Zentrum für Luft- und Raumfahrt (DLR e.V.), Linder Höhe, 51147 Cologne, GermanyMartin Trammer, Institute of Aerospace Medicine, Deutsches Zentrum für Luft- und Raumfahrt (DLR e.V.), Linder Höhe, 51147 Cologne, GermanyJochen Zange, Institute of Aerospace Medicine, Deutsches Zentrum für Luft- und Raumfahrt (DLR e.V.), Linder Höhe, 51147 Cologne, Germany Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243
The size of cytoplasmic lipid droplets varies between tumour cell lines of the nervous system: a 1H NMR spectroscopy study
Sat, 28 Apr 2012 05:59:18 -0000
Abstract Object  Cytoplasmic lipid droplets (LDs) are dynamic cellular organelles; their accumulation is associated with several cellular processes, such as cell proliferation, apoptosis and necrosis. 1H Nuclear Magnetic Resonance (NMR) spectroscopy detects resonances from lipids present in cytoplasmic (LDs); an understanding of the relationship between LD characteristics and NMR lipid signals is important. Materials and methods  In this study, five nervous system cancer cell lines were investigated. Nile red staining was used to measure the diameter of LDs. High-resolution magic angle spinning NMR (HR-MAS) was performed on harvested cell pellets to quantify the patterns of lipid signals. Results  LDs were present in all five cell lines with different morphology. An average LD diameter of approximately 0.2 Î¼m was found in all cell types. Diameter of the largest LDs varied across the cell lines. The intensity of NMR lipid signals varied greatly between cell types, and a good correlation was found between total volume of LDs and the proton NMR lipid signal intensity at 0.9 and 1.3 ppm. Conclusion  The correlation implied that little NMR signal is detected from LDs of diameters less than approximately 0.34 Î¼m, most likely due to restriction of rotational motion of the lipids. Content Type Journal ArticleCategory Research ArticlePages 1-7DOI 10.1007/s10334-012-0315-xAuthors Xiaoyan Pan, Cancer Sciences, University of Birmingham, Birmingham, UKMartin Wilson, Cancer Sciences, University of Birmingham, Birmingham, UKCarmel McConville, Cancer Sciences, University of Birmingham, Birmingham, UKTheodoros N. Arvanitis, Cancer Sciences, University of Birmingham, Birmingham, UKRisto A. Kauppinen, Electronic, Electrical and Computer Engineering, University of Birmingham, Birmingham, UKAndrew C. Peet, Cancer Sciences, University of Birmingham, Birmingham, UK Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243
Practical considerations for in vivo MRI with higher dimensional spatial encoding
Fri, 06 Apr 2012 15:46:08 -0000
Abstract Object  This work seeks to examine practical aspects of in vivo imaging when spatial encoding is performed with three or more encoding channels for a 2D image. Materials and methods  The recently developed 4-Dimensional Radial In/Out (4D-RIO) trajectory is compared in simulations to an alternative higher-order encoding scheme referred to as O-space imaging. Direct comparison of local k-space representations leads to the proposal of a modification to the O-space imaging trajectory based on a scheme of prephasing to improve the reconstructed image quality. Data were collected using a 4D-RIO acquisition in vivo in the human brain and several image reconstructions were compared, exploiting the property that the dense encoding matrix, after a 1D or 2D Fourier transform, can be approximated by a sparse matrix by discarding entries below a chosen magnitude. Results  The proposed prephasing scheme for the O-space trajectory shows a marked improvement in quality in the simulated image reconstruction. In experiments, 4D-RIO data acquired in vivo in the human brain can be reconstructed to a reasonable quality using only 5 % of the encoding matrix—massively reducing computer memory requirements for a practical reconstruction. Conclusion  Trajectory design and reconstruction techniques such as these may prove especially useful when extending generalized higher-order encoding methods to 3D images. Content Type Journal ArticleCategory Research ArticlePages 1-13DOI 10.1007/s10334-012-0314-yAuthors Daniel Gallichan, University Medical Center Freiburg, Freiburg, GermanyChris A. Cocosco, University Medical Center Freiburg, Freiburg, GermanyGerrit Schultz, University Medical Center Freiburg, Freiburg, GermanyHans Weber, University Medical Center Freiburg, Freiburg, GermanyAnna M. Welz, University Medical Center Freiburg, Freiburg, GermanyJürgen Hennig, University Medical Center Freiburg, Freiburg, GermanyMaxim Zaitsev, University Medical Center Freiburg, Freiburg, Germany Journal Magnetic Resonance Materials in Physics, Biology and MedicineOnline ISSN 1352-8661Print ISSN 0968-5243

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