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Dynamic Contrast (dynamic + contrast)
Selected AbstractsNoncompartmental kinetic analysis of DCE-MRI data from malignant tumors: Application to glioblastoma treated with bevacizumabMAGNETIC RESONANCE IN MEDICINE, Issue 2 2010Ruediger E. Port Abstract Dynamic contrast enhanced MRI contrast agent kinetics in malignant tumors are typically complex, requiring multicompartment tumor models for adequate description. For consistent comparisons among tumors or among successive studies of the same tumor, we propose to estimate the total contrast agent,accessible volume fraction of tumor, including blood plasma, vpe, and an average transfer rate constant across all tumor compartments, Ktrans.av, by fitting a three-compartment tumor model and then calculating the area under the tumor impulse-response function (= vpe) and the ratio area under the tumor impulse response function over mean residence time in tumor (= Ktrans.av). If the duration of dynamic contrast enhanced MRI was too short to extrapolate the tumor impulse-response function to infinity with any confidence, then conditional parameters v and Ktrans.av* should be calculated from the available incomplete impulse response function. Median decreases of 33% were found for both v and Ktrans.av* in glioblastoma patients (n = 16) 24 hours after the administration of bevacizumab (P < 0.001). Median total contrast-enhancing tumor volume was reduced by 18% (P < 0.0001). The combined changes of tumor volume, v, and Ktrans.av* suggest a reduction of true vpe, possibly accompanied by a reduction of true Ktrans.av. The proposed method provides estimates of a scale and a shape parameter to describe contrast agent kinetics of varying complexity in a uniform way. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source] Monitoring angiogenesis in soft-tissue engineered constructs for calvarium bone regeneration: an in vivo longitudinal DCE-MRI studyNMR IN BIOMEDICINE, Issue 1 2010Marine Beaumont Abstract Tissue engineering is a promising technique for bone repair and can overcome the major drawbacks of conventional autogenous bone grafting. In this in vivo longitudinal study, we proposed a new tissue-engineering paradigm: inserting a biological soft-tissue construct within the bone defect to enhance angiogenesis for improved bone regeneration. The construct acts as a resorbable scaffold to support desired angiogenesis and cellular activity and as a vector of vascular endothelial growth factor, known to promote both vessel and bone growth. Dynamic contrast- enhanced magnetic resonance imaging was performed to investigate and characterize angiogenesis necessary for bone formation following the proposed paradigm of inserting a VEGF-impregnated tissue-engineered construct within the critical-sized calvarial defect in the membranous parietal bone of the rabbit. Results show that a model-free quantitative approach, the normalized initial area under the curve metric, provides sensitive and reproducible measures of vascularity that is consistent with known temporal evolution of angiogenesis during bone regeneration. Copyright © 2009 John Wiley & Sons, Ltd. [source] How accurate is dynamic contrast-enhanced MRI in the assessment of renal glomerular filtration rate?JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2008A critical appraisal Abstract Purpose To evaluate the current literature to see if the published results of MRI-glomerular filtration rate (GFR) stand up to the claim that MRI-GFR may be used in clinical practice. Claims in the current literature that Gadolinium (Gd) DTPA dynamic contrast enhanced (DCE) MRI clearance provides a reliable estimate of glomerular filtration are an overoptimistic interpretation of the results obtained. Before calculating absolute GFR from Gd-enhanced MRI, numerous variables must be considered. Materials and Methods We examine the methodology in the published studies on absolute quantification of MRI-GFR. The techniques evaluated included the dose and volume of Gd-DTPA used, the speed of injection, acquisition sequences, orientation of the subject, re-processing, conversion of signal to concentration and the model used for analysis of the data as well as the MRI platform. Results Claims in the current literature that using DCE MRI "Gd DTPA clearance provides a good estimate of glomerular filtration" are not supported by the data presented and a more accurate conclusion should be that "no MRI approach used provides a wholly satisfactory measure of renal GFR function." Conclusion This study suggests that DCE MRI-GFR results are not yet able to be used as a routine clinical or research tool. The published literature does not show what change in DCE MRI-GFR is clinically significant, nor do the results in the literature allow a single DCE MRI-GFR measurement to be correlated directly with a multiple blood sampling technique. J. Magn. Reson. Imaging 2008. © 2008 Wiley-Liss, Inc. [source] Power Doppler sonography in the diagnosis of hemophilic synovitis , a promising toolJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 12 2008S. S. ACHARYA Summary.,Background:,Recurrent hemarthroses in hemophilia results in synovitis and joint arthropathy. Primary prophylaxis when universally instituted at current doses can prevent joint deterioration but is expensive. Alternatively, the selective implementation of prophylaxis would require a more sensitive tool for detecting synovitis than possible with clinical surveillance or plain radiographs. Magnetic resonance imaging (MRI) is such a tool and is utilized for the evaluation of hemophilic joint disease (HJD). However, it is expensive, and requires sedation in younger children precluding its utility for monitoring of synovitis. Ultrasonography (USG) with power Doppler (USG-PDS) has been utilized to detect and quantitate synovial vascularity in other arthritides and could provide an equally effective but less costly tool for HJD, particularly in children who would not require sedation. Objectives:,To determine whether USG-PDS is comparable to MRI in the evaluation of hemophilic synovitis. Patients:,A prospective cohort of 31 subjects including 33 joints (knees, elbows, ankles) underwent dynamic contrast enhanced (DCE)-MRI and USG-PDS. Results:,USG-PDS measurements of synovial thickness(r = 0.70, P < 0.0001) and synovial vascularity (r = 0.73, P < 0.0001) correlated strongly with those obtained with DCE-MRI. A cutoff of PDS intensity of 1.3 decibels (dB) per mm2 was found to yield a sensitivity of 100% and a specificity of 94.1% in 17 joints with/without a history of hemarthroses. Pettersson radiographic scores correlated significantly with synovial thickness in adults but not children. Conclusions:,Our data suggest that USG-PDS may be an inexpensive and easily implemented imaging tool for detecting hemophilic synovitis and could be useful in tailoring effective prophylaxis. [source] Noncompartmental kinetic analysis of DCE-MRI data from malignant tumors: Application to glioblastoma treated with bevacizumabMAGNETIC RESONANCE IN MEDICINE, Issue 2 2010Ruediger E. Port Abstract Dynamic contrast enhanced MRI contrast agent kinetics in malignant tumors are typically complex, requiring multicompartment tumor models for adequate description. For consistent comparisons among tumors or among successive studies of the same tumor, we propose to estimate the total contrast agent,accessible volume fraction of tumor, including blood plasma, vpe, and an average transfer rate constant across all tumor compartments, Ktrans.av, by fitting a three-compartment tumor model and then calculating the area under the tumor impulse-response function (= vpe) and the ratio area under the tumor impulse response function over mean residence time in tumor (= Ktrans.av). If the duration of dynamic contrast enhanced MRI was too short to extrapolate the tumor impulse-response function to infinity with any confidence, then conditional parameters v and Ktrans.av* should be calculated from the available incomplete impulse response function. Median decreases of 33% were found for both v and Ktrans.av* in glioblastoma patients (n = 16) 24 hours after the administration of bevacizumab (P < 0.001). Median total contrast-enhancing tumor volume was reduced by 18% (P < 0.0001). The combined changes of tumor volume, v, and Ktrans.av* suggest a reduction of true vpe, possibly accompanied by a reduction of true Ktrans.av. The proposed method provides estimates of a scale and a shape parameter to describe contrast agent kinetics of varying complexity in a uniform way. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source] Evaluation of the anti-vascular effects of combretastatin in rodent tumours by dynamic contrast enhanced MRINMR IN BIOMEDICINE, Issue 2 2002Ross J. Maxwell The anti-vascular effects of the tubulin binding agent, disodium combretastatin A-4 3- O -phosphate (CA-4-P), have been investigated in the rat P22 carcinosarcoma by measurements of radiolabelled iodoantipyrine uptake and dynamic contrast-enhanced MRI. The iodoantipyrine estimates of absolute tumour blood flow showed a reduction from 0.35 to 0.04,ml g,1 min,1 6,h after 10,mg kg,1 CA-4-P and to <0.01,ml g,1 min,1 after 100,mg kg,1. Tumour blood flow recovered to control values 24,h after 10,mg kg,1 CA-4-P, but there was no recovery by 24,h after the higher dose. Dynamic contrast-enhanced MR images were obtained at 4.7 T, following injection of 0.1,mmol kg,1 Gd-DTPA and analysed assuming a model arterial input function. A parameter, Ktrans, which is related to blood flow rate and permeability of the tumour vasculature to Gd-DTPA, was calculated from the uptake data. Ktrans showed a reduction from 0.34 to 0.11 min,1 6,h after 10,mg kg,1 CA-4-P and to 0.07 min,1 after 100,mg kg,1. Although the magnitude of changes in Ktrans was smaller than that in tumour blood flow, the time course and dose-dependency patterns were very similar. The apparent extravascular extracellular volume fraction, ,e, showed a four-fold reduction 6,h after 100,mg kg,1 CA-4-P, possibly associated with vascular shutdown within large regions of the tumour. These results suggest that Ktrans values for Gd-DTPA uptake into tumours could be a useful non-invasive indicator of blood flow changes induced by anti-vascular agents such as combretastatin. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||