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Parameter Maps (parameter + map)

Distribution by Scientific Domains

Medical Sciences	80%

Selected Abstracts

Quantitative contrast-enhanced perfusion measurements of the human lung using the prebolus approach

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2009
Markus Oechsner MS
Abstract Purpose To investigate dynamic contrast-enhanced MRI (DCE-MRI) for quantification of pulmonary blood flow (PBF) and blood volume (PBV) using the prebolus approach and to compare the results to the global lung perfusion (GLP). Materials and Methods Eleven volunteers were examined by applying different contrast agent doses (0.5, 1.0, 2.0, and 3.0 mL gadolinium diethylene triamine pentaacetic acid [Gd-DTPA]), using a saturation-recovery (SR) true fast imaging with steady precession (TrueFISP) sequence. PBF and PBV were determined for single bolus and prebolus. Region of interest (ROI) evaluation was performed and parameter maps were calculated. Additionally, cardiac output (CO) and lung volume were determined and GLP was calculated as a contrast agent,independent reference value. Results The prebolus results showed good agreement with low-dose single-bolus and GLP: PBF (mean ± SD in units of mL/minute/100 mL) = single bolus 190 ± 73 (0.5-mL dose) and 193 ± 63 (1.0-mL dose); prebolus 192 ± 70 (1.0,2.0-mL dose) and 165 ± 52 (1.0,3.0-mL dose); GLP (mL/minute/100 mL) = 187 ± 34. Higher single-bolus resulted in overestimated values due to arterial input function (AIF) saturation. Conclusion The prebolus approach enables independent determination of appropriate doses for AIF and tissue signal. Using this technique, the signal-to-noise ratio (SNR) from lung parenchyma can be increased, resulting in improved PBF and PBV quantification, which is especially useful for the generation of parameter maps. J. Magn. Reson. Imaging 2009;30:104,111. © 2009 Wiley-Liss, Inc. [source]

Detection of changes in articular cartilage proteoglycan by T1, magnetic resonance imaging

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 1 2005
Andrew J. Wheaton
Abstract The purpose of this work is to demonstrate the feasibility of T1, -weighted magnetic resonance imaging (MRI) to quantitatively measure changes in proteoglycan content in cartilage. The T1, MRI technique was implemented in an in vivo porcine animal model with rapidly induced cytokine-mediated cartilage degeneration. Six pigs were given an intra-articular injection of recombinant porcine interleukin-1, (IL-1,) into the knee joint before imaging to induce changes in cartilage via matrix metalloproteinase (MMP) induction. The induction of MMPs by IL-1 was used since it has been extensively studied in many systems and is known to create conditions that mimic in part characteristics similar to those of osteoarthritis. The contralateral knee joint was given a saline injection to serve as an internal control. T1, -weighted MRI was performed on a 4 T whole-body clinical scanner employing a 2D fast spin-echo-based T1, imaging sequence. T1, relaxation parameter maps were computed from the T1, -weighted image series. The average T1, relaxation rate, R1, (1/T1,) of the IL-1,-treated patellae was measured to be on average 25% lower than that of saline-injected patellae indicating a loss of proteoglycan. There was an average reduction of 49% in fixed charge density, measured via sodium MRI, of the IL-1,-treated patellae relative to control corroborating the loss of proteoglycan. The effects of IL-1,, primarily loss of PG, were confirmed by histological and immunochemical findings. The results from this study demonstrate that R1, is able to track proteoglycan content in vivo. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source]

Quantifying spatial heterogeneity in dynamic contrast-enhanced MRI parameter maps

MAGNETIC RESONANCE IN MEDICINE, Issue 2 2009
Chris J. Rose
Abstract Dynamic contrast-enhanced MRI is becoming a standard tool for imaging-based trials of anti-vascular/angiogenic agents in cancer. So far, however, biomarkers derived from DCE-MRI parameter maps have largely neglected the fact that the maps have spatial structure and instead focussed on distributional summary statistics. Such statistics,e.g., biomarkers based on median values,neglect the spatial arrangement of parameters, which may carry important diagnostic and prognostic information. This article describes two types of heterogeneity biomarker that are sensitive to both parameter values and their spatial arrangement. Methods based on Rényi fractal dimensions and geometrical properties are developed, both of which attempt to describe the complexity of DCE-MRI parameter maps. Experiments using simulated data show that the proposed biomarkers are sensitive to changes that distribution-based summary statistics cannot detect and demonstrate that heterogeneity biomarkers could be applied in the drug trial setting. An experiment using 23 DCE-MRI parameter maps of gliomas,a class of tumour that is graded on the basis of heterogeneity,shows that the proposed heterogeneity biomarkers are able to differentiate between low- and high-grade tumours. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source]

Method for quantitative imaging of the macromolecular 1H fraction in tissues

MAGNETIC RESONANCE IN MEDICINE, Issue 5 2003
Stefan Ropele
Abstract A new method was developed for mapping the relative density of the macromolecular protons involved in magnetization transfer (MT). This method employs a stimulated echo preparation scheme in order to modulate the phase distribution within a spin ensemble. This labeled spin ensemble is then used as an intrinsic indicator, which is diluted due to magnetization exchange with macromolecular protons. A pulse sequence is presented which compensates for longitudinal relaxation, allows observation of the dilution effect only, and provides for calculation of parameter maps using indicator dilution theory. Compared to other quantitative MT techniques, neither additional relaxation time measurements nor knowledge regarding the lineshape of the macromolecular proton pool are required. Moreover, the inherent low specific absorption rate and the low sensitivity for B1 errors make this method favorable in a clinical setting. This sequence was used to measure the macromolecular proton density in cross-linked bovine serum albumin. Using a navigated echo planar readout, the sequence was also employed to visualize the macromolecular content of human brain in vivo. Magn Reson Med 49:864,871, 2003. © 2003 Wiley-Liss, Inc. [source]