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06:06
Optogenetic Functional MRI
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Cited by 15 •
2016
This protocol describes the steps and data analysis required to successfully perform optogenetic functional magnetic resonance imaging (ofMRI). ofMRI is a novel technique that combines high-field fMRI readout with optogenetic stimulation, allowing for cell type-specific mapping of functional neural circuits and their dynamics across the whole living brain.
08:20
MRI-guided dmPFC-rTMS as a Treatment for Treatment-resistant Major Depressive Disorder
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Cited by 31 •
2015
Here we outline the procedure for MRI-guided repetitive transcranial magnetic stimulation to the dorsomedial prefrontal cortex as an experimental treatment for major depressive disorder.
06:58
Synthesis of an In vivo MRI-detectable Apoptosis Probe
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Cited by 3 •
2012
Early detection of apoptosis may identify at-risk cell populations in a variety of diseases. Here we demonstrate a method to link an early apoptosis-detection protein (Annexin V) to a MRI-detectable iron oxide nanoparticle (SPIO). This method may be extended to other proteins of interest to generate MRI-detectable molecular imaging probes.
09:33
MRI Mapping of Cerebrovascular Reactivity via Gas Inhalation Challenges
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Cited by 78 •
2014
Non-invasive imaging of the brain vasculature’s ability to dilate or constrict may allow a better understanding of cerebrovascular pathophysiology in various neurological diseases. The present report describes a reproducible and patient-comfortable protocol to perform vascular reactivity imaging in humans using magnetic resonance imaging (MRI).
10:26
A Multicenter MRI Protocol for the Evaluation and Quantification of Deep Vein Thrombosis
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Cited by 5 •
2015
The goal of this study is to use magnetic resonance venography with long-circulating gadolinium-based contrast agent and direct thrombus imaging for quantitative evaluation of DVT volume in a multicenter, clinical trial setting. Inter- and intra-observer variability assessments were conducted, and reproducibility of the protocol was determined.
FAQs
Pulse sequences control how radiofrequency pulses and signal measurements are timed, allowing the scanner to emphasize tissue properties such as water content. Because tissues and engineered constructs can differ in these properties, changing the sequence alters their visual contrast. Selecting an appropriate sequence therefore helps investigators examine particular structural features rather than relying on one uniform image.
Magnetic field gradients vary the magnetic field across the subject, so signals from different locations receive distinct spatial information. The scanner uses these variations to encode where the emitted signals originated and form an image. This spatial encoding is essential for separating neighboring tissues, implanted materials, or regions within a regenerated construct.
After radiofrequency excitation temporarily changes hydrogen-nuclei alignment, the nuclei move toward equilibrium and emit measurable signals. The timing and characteristics of this return provide the basis for distinguishing materials and tissues with different water-related properties. In bioengineering studies, that behavior supports visualization of tissue structure and assessment of engineered constructs without ionizing radiation.
The subject is positioned within the scanner's strong magnetic field, after which radiofrequency pulses temporarily alter hydrogen-nuclei alignment. Magnetic field gradients encode the locations of the resulting signals, and the scanner records those signals to generate images. Researchers can repeat the acquisition with different pulse sequences when they need complementary contrast or information about specific tissue properties.
Bioengineers use MRI when they need noninvasive information about tissue structure, biomechanics, vascular function, or implanted and regenerated materials. The method can examine these features in living subjects without ionizing radiation, making it useful for research that follows structural or functional changes over time. Its ability to provide tissue contrast also helps relate construct appearance to surrounding anatomy.
MRI provides imaging information that can guide device design by showing how an implant or engineered material relates to surrounding tissues. It also supports evaluation after implantation by revealing structural features and contributing information about biomechanics or vascular function. These observations help researchers assess how a device or construct performs within the biological environment.
Quantitative imaging extends MRI beyond visual inspection by producing measurements that can be tracked across studies or time points. In bioengineering, those measurements can support assessment of tissue structure, biomechanics, vascular function, and implanted or regenerated materials. Such data may guide device development and help monitor healing as engineered tissues or treated regions change.