Investigative radiology
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Investigative radiology · Jan 2005
Time-resolved contrast-enhanced three-dimensional magnetic resonance angiography of the chest: combination of parallel imaging with view sharing (TREAT).
In view sharing, some parts of k-space are updated more often than others, leading to an effective shortening of the total acquisition time. Undersampling of high-frequency k-space data, however, can result in artifacts at the edges of blood vessels, especially during the rapid signal intensity changes. The objective of this study was to evaluate a new time-resolved echo-shared angiographic technique (TREAT) combining parallel imaging with view sharing. First, the presence of artifacts arising from different temporal interpolation schemes was evaluated in simulations of the point spread function. Second, the image quality and presence of artifacts of time-resolved parallel three-dimensional magnetic resonance angiography (3D MRA) of the chest, acquired with and without view sharing, was assessed in a clinical study of patients with cardiovascular or pulmonary disease. ⋯ View sharing can be successfully combined with other acceleration techniques, such as parallel imaging. TREAT allows the assessment of the thoracic vasculature with a high temporal and spatial resolution.
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Investigative radiology · Oct 2004
Implantable microstimulator: magnetic resonance safety at 1.5 Tesla.
Ex vivo testing is necessary to characterize implants to determine if it is safe for the patient to undergo a magnetic resonance imaging (MRI) examination. Therefore, the objective of this study was to evaluate MR safety for an implantable microstimulator in association with a 1.5 Tesla MR system. ⋯ The overall findings indicated that it is safe for a patient with the microstimulator to undergo MRI at 1.5 Tesla by following specific safety guidelines described herein.
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Investigative radiology · Oct 2004
ReviewMacrophage imaging in central nervous system and in carotid atherosclerotic plaque using ultrasmall superparamagnetic iron oxide in magnetic resonance imaging.
The long blood circulating time and the progressive macrophage uptake in inflammatory tissues of ultrasmall superparamagnetic iron oxide (USPIO) particles are 2 properties of major importance for magnetic resonance imaging (MRI) pathologic tissue characterization. This article reviews the proof of principle of applications such as imaging of carotid atherosclerotic plaque, stroke, brain tumor characterization, or multiple sclerosis. In the human carotid artery, USPIO accumulation in activated macrophages induced a focal drop in signal intensity compared with preinfusion MRI. ⋯ Several experimental studies and a pilot multiple sclerosis clinical trial in 10 patients have shown that USPIO contrast agents can reveal the presence of inflammatory multiple sclerosis lesions. The enhancement with USPIO does not completely overlap with the gadolinium chelate enhancement. While the proof of concept that USPIO can visualize macrophage infiltrations has been confirmed in animals and patients in several applications (carotid atherosclerotic lesions, stroke, brain tumors and multiple sclerosis), larger prospective clinical studies are needed to demonstrate the clinical benefit of using USPIO as an MRI in vivo surrogate marker for brain inflammatory diseases.
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Investigative radiology · May 2004
Neurostimulation system used for deep brain stimulation (DBS): MR safety issues and implications of failing to follow safety recommendations.
The use of magnetic resonance imaging (MRI) in patients with neurostimulation systems used for deep brain stimulation requires the utmost care, and no individual should undergo an MR examination in the absence of empirical evidence that the procedure can be performed safely. The risks of performing MRI in patients with neurostimulators include those associated with heating, magnetic field interactions, induced currents, and the functional disruption of these devices. The exact safety recommendations for the particular neurostimulation system with regard to the pulse generator, leads, electrodes, operational conditions for the device, the positioning of these components, and the MR system conditions must be carefully followed for MRI. As highlighted by 2 recent accidents, the failure to strictly follow safety recommendations (eg, use a 1.5-T MR system with a send/receive head radiofrequency coil only; limit the specific absorption rate to 0.4 W/kg; etc.) may result in serious, temporary, or permanent injury to the patient including the possibility of transient dystonia, paralysis, coma, or even death.
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Investigative radiology · Mar 2004
Comparative Study Clinical TrialContrast-enhanced three-dimensional pulmonary perfusion magnetic resonance imaging: intraindividual comparison of 1.0 M gadobutrol and 0.5 M Gd-DTPA at three dose levels.
To compare 1.0 M gadobutrol and 0.5 M Gd-DTPA for contrast-enhanced three-dimensional pulmonary perfusion magnetic resonance imaging (3D MRI). ⋯ Higher concentrated gadolinium chelates offer no advantage over standard 0.5 M Gd-DTPA for contrast-enhanced 3D MRI of lung perfusion.