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Liver Imaging (liver + imaging)
Selected AbstractsCMR2009: 3.04: Mn loaded apoferritin(Mn-Apo): an improved MRI contrast agent for liver imagingCONTRAST MEDIA & MOLECULAR IMAGING, Issue 6 2009S. Aime No abstract is available for this article. [source] Diffusion-weighted imaging of the liver: Comparison of navigator triggered and breathhold acquisitionsJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2009Bachir Taouli MD Abstract Purpose To compare a free breathing navigator triggered single shot echoplanar imaging (SS EPI) diffusion-weighted imaging (DWI) sequence with prospective acquisition correction (PACE) with a breathhold (BH) DWI sequence for liver imaging. Materials and Methods Thirty-four patients were evaluated with PACE-DWI and BH DWI of the liver using b-values of 0, 50, and 500 s/mm2. There were 29 focal liver lesions in 18 patients. Qualitative evaluation was performed on a 3-point scale (1,3) by two independent observers (maximum score 9). Quantitative evaluation included estimated SNR (signal to noise ratio), lesion-to-liver contrast ratio, liver and lesion apparent diffusion coefficients (ADCs), and coefficient of variation (CV) of ADC in liver parenchyma and focal liver lesions (estimate of noise contamination in ADC). Results PACE-DWI showed significantly better image quality, higher SNR and lesion-to-liver contrast ratio when compared with BH DWI. ADCs of liver and focal lesions with both sequences were significantly correlated (r = 0.838 for liver parenchyma, and 0.904 for lesions, P < 0.0001), but lower with the BH sequence (P < 0.02). There was higher noise contamination in ADC measurement obtained with BH DWI (with a significantly higher SD and CV of ADC). Conclusion The use of a navigator echo to trigger SS EPI DWI improves image quality and liver to lesion contrast, and enables a more precise ADC quantification compared with BH DWI acquisition. J. Magn. Reson. Imaging 2009;30:561,568. © 2009 Wiley-Liss, Inc. [source] Focal liver lesions: Breathhold gradient- and spin-echo T2-weighted imaging for detection and characterization ,JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2006Takeshi Yoshikawa MD Abstract Purpose To evaluate breathhold gradient- and spin-echo (GRASE) T2-weighted imaging for the detection and characterization of focal liver lesions. Materials and Methods Two GRASE sequences with different echo times (75 and 90 msec, GRASE75 and GRASE90) were compared with respiratory-triggered fast spin-echo (SE) and breathhold fast SE in 64 patients with 103 malignant and 51 benign lesions. Compared with respiratory-triggered and breathhold fast SE, GRASE reduced scan time by 77% to 82% and 21% to 27%, respectively. Two independent readers evaluated image quality and reviewed 504 liver segments on a segment-by-segment basis. Observer performance was evaluated with receiver operating characteristic (ROC) curve analysis. The signal-to-noise ratio (SNR) of liver and spleen, and lesion-to-liver contrast-to-noise ratio (CNR) were also measured. Results The overall quality of the GRASE images was higher than that of the respiratory-triggered and breathhold fast SE images, although signal inhomogeneities were more frequently observed with GRASE. No significant difference in the values of the area under the ROC curve (Az) for malignant lesion detection was found. The mean SNR and CNR were highest for respiratory-triggered fast SE. Conclusion T2-weighted breathhold GRASE has the potential to provide faster liver imaging. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [source] Magnetic resonance elastography in the liver at 3 Tesla using a second harmonic approachMAGNETIC RESONANCE IN MEDICINE, Issue 2 2009D.A. Herzka Abstract Magnetic resonance elastography (MRE) using mechanical stimulation has demonstrated diagnostic value and clinical promise in breast, liver, and kidney at 1.5 Tesla (T). However, MRE at 1.5T suffers from long imaging times and would benefit from greater signal-to-noise for more robust postprocessing. We present an MRE sequence modified for liver imaging at 3.0T. To avoid artifacts in the phase images, the sequence maintains a short TE by using a second harmonic approach, including stronger motion encoding gradients, shorter radio frequency pulses and an echo-planar readout. Scan time was decreased by a factor of ,2 relative to 1.5T by using an EPI readout and a higher density sampling of the phase waveform was used to calculate shear stiffness and viscosity. Localized (small region of interest) and global (whole-liver region of interest) measurements in normal healthy subjects compared very favorably with previously published results at 1.5T. There was no significant difference between global and localized measures. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source] In vivo study of microbubbles as an MR susceptibility contrast agentMAGNETIC RESONANCE IN MEDICINE, Issue 3 2004Kelvin K. Wong Abstract The potential application of gas microbubbles as a unique intravascular susceptibility contrast agent for MRI has not been fully explored. In this study, the MR susceptibility effect of an ultrasound microbubble contrast agent, Optison®, was studied with rat liver imaging at 7 T. Optison® suspension in two different doses (0.15 mL/kg and 0.4 mL/kg) was injected into rats, and induced transverse relaxation rate increases (,R2*) of 29.1 ± 1.6 s,1 (N = 2) and 61.5 ± 12.9 s,1 (N = 6), respectively, in liver tissue. Liver uptake of intact albumin microbubbles was observed 10 min after injection. Eight of the 16 rats studied showed no susceptibility enhancement. This is probably attributable to the intravascular microbubble growth due to transmural CO2 supersaturation in the cecum and colon in small animals that causes microbubble aggregation and trapping in the inferior vena cava (IVC). In vitro ,R2* measurements of Optison® suspension at different concentrations are also reported. Magn Reson Med 52:445,452, 2004. © 2004 Wiley-Liss, Inc. [source] Measuring SPIO and Gd contrast agent magnetization using 3,T MRINMR IN BIOMEDICINE, Issue 8 2009Pádraig Cantillon-Murphy Abstract Traditional methods of measuring magnetization in magnetic fluid samples, such as vibrating sample magnetometry (VSM), are typically limited to maximum field strengths of about 1,T. This work demonstrates the ability of MRI to measure the magnetization associated with two commercial MRI contrast agents at 3,T by comparing analytical solutions to experimental imaging results for the field pattern associated with agents in cylindrical vials. The results of the VSM and fitted MRI data match closely. The method represents an improvement over VSM measurements since results are attainable at imaging field strengths. The agents investigated are Feridex, a superparamagnetic iron oxide suspension used primarily for liver imaging, and Magnevist, a paramagnetic, gadolinium-based compound used for tumors, inflammation and vascular lesions. MR imaging of the agents took place in sealed cylindrical vials in the presence of a surrounding volume of deionized water where the effects of the contrast agents had a measurable effect on the water's magnetization in the vicinity of the compartment of contrast agent. A pair of phase images were used to reconstruct a B0 fieldmap. The resultant B0 maps in the water region, corrected for shimming and container edge effects, were used to predict the agent's magnetization at 3,T. The results were compared with the results from VSM measurements up to 1.2,T and close correlation was observed. The technique should be of interest to those seeking quantification of the magnetization associated with magnetic suspensions beyond the traditional scope of VSM. The magnetization needs to be sufficiently strong (Ms , 50 Am2/kg Fe for Feridex and Xm , 5 × 10,5 m3/kg Gd for Magnevist) for a measurable dipole field in the surrounding water. For this reason, the technique is mostly suitable for undiluted agents. Copyright © 2009 John Wiley & Sons, Ltd. [source] The Diagnostic Conundrum and Liver Transplantation Outcome for Combined Hepatocellular-CholangiocarcinomaAMERICAN JOURNAL OF TRANSPLANTATION, Issue 5 2010C. Panjala Combined hepatocellular-cholangiocarcinoma (cHCC-CC) is a rare primary liver malignancy with mixed hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC) histological features. It is almost impossible to obtain an accurate, preoperative noninvasive diagnosis of cHCC-CC with tumor markers or cross-sectional abdominal imaging due to the mixed histological features. Despite these difficulties, accurate cHCC-CC diagnosis remains an important goal with prognostic significance. In our study, we retrospectively reviewed the tumor markers: AFP and CA 19-9, and cross-sectional liver imaging, in light of liver explant findings, to identify and characterize cHCC-CC features followed by liver transplantation (LT) outcome analysis. The results from this 12 patient cohort failed to identify characteristic features for cHCC-CC. None of the imaging features helped to identify the cHCC-CC tumor and they mimicked either HCC or CC, depending on the degree of glandular differentiation expressed histologically. In our cHCC-CC LT recipients, the 1-, 3- and 5-year cumulative survival probabilities were 79%, 66% and 16%, respectively with a 5-year survival comparable to or better than LT for intrahepatic CC but poorer than LT for HCC following the Milan criteria. Conceivably explained by its cholangiocarcinoma component the LT outcome for this rare and hard to diagnose tumor appears poor. [source] Superparamagnetic iron oxide particles: contrast media for magnetic resonance imaging,APPLIED ORGANOMETALLIC CHEMISTRY, Issue 10 2004Rüdiger Lawaczeck Abstract The mainstream magnetic iron oxide particles used as contrast media for magnetic resonance (MR) imaging are composed of a magnetic iron oxide core surrounded by a dextran or carboxydextran coat. The core size ranges from 2 nm to less than 10 nm, and the hydrodynamic diameter ranges from 20 nm to about 120 nm. The coat prevents aggregation and sedimentation of the particles in aqueous solutions, achieves high biological tolerance, and prevents toxic side effects. Two kinds of particles are considered: (i) large particles (>30 nm), called superparamagnetic iron oxide particles (SPIOs) for liver imaging; (ii) smaller particles (<30 nm hydrodynamic diameter), called ultrasmall SPIOs (USPIOs), e.g. for MR angiography. To characterize the particles, Mössbauer spectra are presented for the two particle ensembles. These spectra allow insight into the magnetic coupling, the valency of the iron ions and a rough estimate of the core size to be deduced. On the basis of the concentration dependence of the MR signal intensities, two applications are discussed together with two representative clinical examples. Future indications for MR diagnostics, e.g. the labeling and tracking of stem cells during stem-cell therapy control, are outlined. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||