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Objective: To compare prospectively the diagnostic performance of a biparametric (T2‐weighted imaging [T2WI] and diffusion‐weighted imaging [DWI]) 1.5‐T fast magnetic resonance imaging (fMRI) protocol with the standard 3.0‐T multiparametric MRI (mpMRI) protocol of the European Society of Urological Imaging (ESUR) in men referred for a prostate biopsy. Patients and Methods: Ninety patients with a prostate cancer (PCa) risk of ≥10% according to the SWOP calculator 4 underwent first fMRI and then the reference mpMRI. Patients with Prostate Imaging Reporting and Data System (PI‐RADS) v.2 lesions ≥3/5 on the mpMRI were scheduled for MRI/ultrasonography (US) fusion‐guided prostate biopsy. Performance of fMRI was assessed using receiver‐operating characteristic curve analysis and mpMRI as reference. Calculation of inter‐technique agreement on PI‐RADS v.2 score by Cohen's κ. Results: The diagnostic accuracy of fMRI shown by the lesion‐based analysis was excellent: area under the curve (AUC) 0.961 (P < 0.001), sensitivity 95%, specificity 97%, positive predictive value (PPV) 99%, negative predictive value (NPV) 89%. The patient‐based analysis showed an AUC for fMRI of 0.975 (P < 0.001), a sensitivity of 98%, a specificity of 97%, a PPV of 98% and an NPV of 97%. Agreement on the PI‐RADS score between both protocols was found to be good (κ = 0.78 [0.57; 0.99]); fMRI missing PI‐RADS 4 lesions in three patients. Biopsy results showed no cancer in two patients (two cores per nodule) and Gleason 6 cancer in one patient. There was only one false‐positive fMRI, with a PI‐RADS score of 4, whose biopsy was negative. Conclusion: In the triage of men with a high risk of PCa for prostate biopsy, an f MRI protocol (1.5‐T magnet, T2WI + DWI, <15 min) may safely replace the traditional ESUR 3.0‐T mpMRI protocol, saving time and contrast injection. [ABSTRACT FROM AUTHOR]

Purpose To assess which MRI-derived kinetic parameters reflect decreased transvascular and interstitial transport when low- and high-molecular-weight agents are used in rat hepatocellular carcinomas. Materials and Methods Dynamic MRI after injection of a low-molecular-weight contrast agent of 0.56 kDa (Gd-DOTA, gadoterate) and two high-molecular-weight contrast agents of 6.47 kDa (P792, gadomelitol) and 52 kDa (P717, carboxymethyldextran Gd-DOTA) was performed in rats with chemically induced hepatocellular carcinomas. The data were analyzed with the Kety compartmental model, the extended Kety compartmental model in which it is assumed that the tissue voxels contain a vascular component, and the St Lawrence and Lee distributed-parameter model. Results The extravascular extracellular space accessible to the contrast agent v e and the extraction fraction E decreased with increasing molecular weight of the contrast agent. In contrast, the volume transfer constant Ktrans did not differ significantly when low- or high-molecular-weight agents were used. Conclusion In this animal model the results suggest that the accessible extravascular extracellular space and the extraction fraction are more sensitive indicators of decreased transvascular and interstitial transport with high-molecular-weight agents than the volume transfer constant, which is a lumped representation of blood flow and permeability. J. Magn. Reson. Imaging 2008;28:906-914. © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Purpose To determine the correlations between the viscoelastic parameters of the liver measured with in vivo MR elastography and quantitative analysis of liver fibrosis. Materials and Methods MR elastography of the liver was performed in 10 rats with hepatic fibrosis induced by intraperitoneal carbon tetrachloride (CCl4) injections and five normal rats. Longitudinal waves of 200 MHz were transmitted into the liver with a mechanical transducer. Wave propagation into the liver was analyzed with a phase-locked spin-echo sequence at 1.5 T. The viscoelastic parameters, obtained with the Voigt model, were correlated with automatic image analysis of the fibrotic areas and with analysis of the hydroxyproline content of the liver. Results Substantial correlations were observed between the shear viscoelastic parameters and the percentage of fibrosis at automatic image analysis (r = 0.7, P = 0.005 for the elasticity, and r = 0.8, P = 0.001 for the viscosity) and moderate correlations were seen between the shear viscoelastic parameters and the hydroxyproline content (r = 0.6, P = 0.016 for the elasticity and r = 0.5, P = 0.041 for the viscosity). Conclusion The viscoelastic parameters of the liver measured with in vivo MR elastography correlate with quantitative analysis of liver fibrosis. These results suggest that MR elastography is a promising noninvasive method to quantify liver fibrosis. J. Magn. Reson. Imaging 2007;26:956-962. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Purpose To assess whether hepatic fibrosis is associated with a restriction in the diffusion of water that can be analyzed with diffusion-weighted MR imaging (DWI) of the liver. Materials and Methods DWI was performed in 10 normal rats and 15 rats with liver fibrosis. Echo-planar DWI was performed in the living rats at 1.5 T and repeated immediately after the animals were killed. Afterwards the livers were explanted, fixed in Bouin solution, and imaged with a DW spin-echo sequence at 4.7 T. Fibrosis was quantified by densitometry on Sirius red-stained histological sections. Results In living rats the apparent diffusion coefficient (ADC) decreased with the severity of liver fibrosis (controls: 1535 ± 294 mm2/second; CCl4 (5 weeks) 1129 ± 273 mm2/second; CCl4 (9 weeks): 943 ± 132 mm2/second; P = 0.002). An inverse correlation between ADC and liver fibrosis volume density was observed ( r = -0.712, P < 0.001). In contrast, these findings were not observed in the rats after they were killed or in the fixated livers. Conclusion Decreased ADC correlated with increased liver fibrosis in living rats, but not after death. These results suggest that restricted water diffusion cannot be assessed by DWI in liver fibrosis. Other factors, such as a decrease of perfusion, may explain the decrease of the hepatic ADC measured in vivo in rats with liver fibrosis. J. Magn. Reson. Imaging 2007. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the feasibility of using non-invasive MR elastography for determining the stage of liver fibrosis. Twenty-five consecutive patients who had liver biopsy for suspicion of chronic liver disease were included in the study. The stage of fibrosis on the biopsies was assessed according to the METAVIR scoring system from F0, no fibrosis, to F4, cirrhosis. MR elastography was performed by transmitting low-frequency (65 Hz) mechanical waves into the liver with a transducer placed at the back of the patients. The MR pulse sequence was a motion-sensitized spin-echo sequence, phase-locked to the mechanical excitation. The phase maps were processed to obtain shear elasticity and shear viscosity maps. The mean hepatic shear elasticity increased with increasing stage of fibrosis. The mean elasticity was 2.24 ± 0.23 kPa in the 11 patients without substantial fibrosis (F0-F1 grades), 2.56 ± 0.24 kPa in the four patients with substantial fibrosis (F2-F3) and 4.68 ± 1.61 kPa in the 10 patients with cirrhosis (F4). The differences between groups were statistically significant ( p ≤ 0.05). The mean shear viscosity was significantly higher in the patients with cirrhosis (5.19 ± 1.85 Pa · s) than in the patients without cirrhosis (2.39 ± 0.86 Pa · s in F0-F1 and 2.27 ± 0.38 Pa · s in F2-F3 patients). It is concluded that non-invasive MR elastography is a feasible method to assess the stage of liver fibrosis. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Purpose: To describe the use of MRI and a cortical-compartment model to measure the glomerular filtration rate (GFR), and compare the results with those obtained with the Patlak-Rutland model.Materials and Methods: Dynamic MRI of rabbit kidneys was performed during and after injection of gadoterate dimeglumine. The enhancement curves in the aorta and the kidney were analyzed with the cortical-compartment and Patlak-Rutland models to assess the GFR.Results: A substantial correlation was observed between the GFR measured with MRI using the cortical-compartment model and the plasma clearance of 51Cr-EDTA (r=0.821, P=0.004). No significant correlation was observed between the 51Cr-EDTA clearance (r=0.628, P=0.052) and the GFR obtained with the Patlak-Rutland model in regions of interest (ROIs) encompassing the renal cortex and medulla. A Bland and Altman analysis showed that GFR(cortical) (compartment) agreed better with the 51Cr-EDTA clearance compared to GFR(Patlak) when ROIs were limited to the cortex. However, the GFR values obtained by MRI were lower than the plasma clearance of 51Cr-EDTA.Conclusion: MRI with a cortical-compartment model provides more accurate assessments of glomerular filtration than the Patlak-Rutland model. [ABSTRACT FROM AUTHOR]

Inflow effects were studied for T1-weighted, fast gradient-echo, contrast-enhanced MRI. This was done on the basis of realistic simulations (e.g., taking slice profiles into account) for unsteady flow. The area under the point spread function (PSF) was used to estimate the flow-related enhancement. A simple analytical model that accurately describes the inflow effects was derived and validated. This model was used to correct the experimental perfusion calibration curves (signal intensity vs. relaxation rate) for inflow effects. Hepatic perfusion measurements, performed on patients, were analyzed in terms of a dual-input, first-order linear model. It was shown that inflow causes incorrect perfusion input functions. The resulting estimated perfusion parameters displayed a systematic error of typically 30-40%. By performing two extra time-resolved flow measurements during the examination, one can correct the input functions. Magn Reson Med 51:710-717, 2004. © 2004 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The article presents a case study of a 23-year-old man who had a bilateral scleral haemorrhages and haematomas of the lower eyelids associated with fever and fatigue. The patient had complained with nausea and abdominal distension that lead to weight loss. He was diagnosed with acute promyelocytic leukaemia (APL) in bone marrow prognosis. It highlights the thrombotic risk of an APL patient with fatal bleeding symptoms.