-
Notifications
You must be signed in to change notification settings - Fork 2
/
mri_info_OG.html
212 lines (195 loc) · 16.4 KB
/
mri_info_OG.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
<!DOCTYPE HTML>
<html>
<head>
<title>Introduction to MRI</title>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no" />
<link rel="stylesheet" href="assets/css/main.css" />
<noscript><link rel="stylesheet" href="assets/css/noscript.css" /></noscript>
</head>
<body class="is-preload">
<!-- Wrapper -->
<div id="wrapper">
<!-- Header -->
<header id="header">
<div class="inner">
<!-- Logo -->
<a href="index.html" class="logo">
<span class="symbol"><img src="images/NeuroNestLogo.png" alt="NeuroNest Logo" /></span><span class="title">NeuroNest</span>
</a>
<!-- Nav -->
<nav>
<ul>
<li><a href="#menu">Menu</a></li>
</ul>
</nav>
</div>
</header>
<!-- Menu -->
<nav id="menu">
<h2>Menu</h2>
<ul>
<li><a href="index.html">Home</a></li>
<li><a href="resource_menu.html">Resources</a></li>
<li><a href="https://sopkoc.wixsite.com/neuronest/forum">Ask a Question</a></li>
<li><a href="https://sopkoc.wixsite.com/neuronest/about">About NeuroNest</a></li>
<li><a href="https://sopkoc.wixsite.com/neuronest/contact">Contact</a></li>
</ul>
</nav>
<!-- Main -->
<div id="main">
<div class="inner">
<h1>Introduction to MRI</h1>
<span class="image main"><img src="images/mri_info_small.png" alt="" /></span>
<h2>1. MRI Basics</h2>
<p>Atoms are made up of a nucleus and a shell of electrons. Inside the nucleus, there are protons, which have a positive electrical charge. These protons are constantly spinning around an axis, which creates a spin (see figure).</p>
<p>Because protons are moving electrical charges, they generate an electrical current. This current creates a magnetic field, making each proton act like a tiny bar magnet with its own magnetic field.</p>
<p>When protons are placed in an MRI scanner, they align with the external magnetic field. There are two ways they can align:</p>
<ul>
<li>Parallel to the magnetic field (lower energy state)</li>
<li>Anti-parallel to the magnetic field (higher energy state)</li>
</ul>
<p>The protons also precess (spin) along the magnetic field lines, similar to how a spinning top behaves under Earth's gravity.</p>
<p>When a person is inside the MRI machine, a strong magnetic field aligns the protons in their body. If we send a radio-frequency (RF) pulse at the same frequency as the protons' precessing frequency, two things happen:</p>
<ul>
<li><strong>Longitudinal Magnetization Decreases:</strong> More protons align anti-parallel, canceling out some of the parallel protons.</li>
<li><strong>Transversal Magnetization Forms:</strong> The RF pulse synchronizes the protons, causing them to precess together.</li>
</ul>
<img src="images/magnetic_field_MRI.png" alt="Workflow" style="width: 35%;"> <img src="images/magnetization_MRI.png" style="width: 35%;">
<p> </p>
<h2>Key Terms in MRI:</h2>
<ul>
<li><u>Gradients:</u> Gradient magnets are used to spatially encode the signals received from the protons, allowing for the construction of an image.</li>
<li><u>Proton Resonance:</u> Hydrogen protons in the body align with a magnetic field and then resonate when exposed to radiofrequency pulses (RF).</li>
<li><u>Resonance:</u> This phenomenon occurs when the RF pulse matches the protons' frequency, allowing them to absorb energy from the radio waves. This is where the term "resonance" in "magnetic resonance" comes from.</li>
<li><u>T1 (Longitudinal Relaxation Rate):</u> Influenced by the tissue's composition and structure, T1 varies with magnetic field strength and is longer in stronger fields. T1 relaxation is slower than T2 relaxation.</li>
<li><u>T2 (Transversal Relaxation Rate):</u> Occurs when protons get out of sync due to irregularities in the magnetic field or the tissue's local magnetic fields.</li>
</ul>
<h2>Types of MRI Sequences:</h2>
<ul>
<li><strong>T1-Weighted Imaging:</strong> Highlights fat and provides clear images of the brain's anatomy.</li>
<li><strong>T2-Weighted Imaging:</strong> Highlights fluid and is useful for detecting edema and inflammation.</li>
<li><strong>FLAIR (Fluid Attenuated Inversion Recovery):</strong> Suppresses fluids, enhancing the visibility of lesions.</li>
</ul>
<img src="images/t1_t2_flair_sequences.webp" alt="MRI Scanner" style="width: 45%/>
<p>For more information and images about the MRI sequences, visit <a href="https://radiopaedia.org/articles/mri-sequences-overview?lang=us">Radiopaedia</a> and <a href="https://mriquestions.com/hellippulse-sequences.html">MRI Questions</a>.</p>
<p>For more information about the physics of MRI, visit <a href="https://mriquestions.com/hellipthe-nmr-phenomenon.html">MRI Questions - NMR Phenomenon</a>.</p>
<p>For nice illustrations of concepts, check the <a href="https://apps.apple.com/us/app/mri-made-easy-well-almost/id1077847614">MRI Made Easy app</a> (for iOS).</p>
<h2>MRI Equipment and Technologies</h2>
<h3>Main components of an MRI scanner:</h3>
<ul>
<li><strong>Magnet:</strong> The core component of the MRI scanner generating a powerful magnetic field to align the protons in the body. The strength of the magnet is typically measured in tesla (T) with common strengths ranging from 1.5T to 3T in clinical settings and up to 7T or more in research settings.</li>
<li><strong>Gradient Coils:</strong> These coils create variable magnetic fields that allow for spatial encoding of the MRI signal. They are essential for slice selection, spatial resolution, and imaging speed.</li>
<li><strong>Radiofrequency Coils:</strong> These coils transmit and receive radiofrequency pulses that perturb and detect the protons' magnetic alignment. They come in various shapes and sizes tailored for specific body parts or imaging purposes.</li>
<li><strong>Computer System:</strong> The MRI scanner’s computer system controls the hardware, processes the signals received from the radiofrequency coils, and reconstructs the images for display and analysis. It includes powerful processors and advanced software algorithms for image reconstruction and enhancement.</li>
</ul>
<img src="images/MRI_SCANNER.png" alt="MRI Scanner" style="width: 45%/>
<p></p>
<h2>Safety and Precautions in MRI</h2>
<p>MRI is a safe and non-invasive imaging modality, but certain precautions are necessary to ensure patient safety:</p>
<ul>
<li><strong>Compatibility with Metal Implants:</strong> Patients with metal implants, such as pacemakers, cochlear implants, or certain types of aneurysm clips, may be contraindicated for MRI. Thorough screening is essential to identify any potential risks.</li>
<li><strong>Claustrophobia:</strong> Some patients may experience anxiety or claustrophobia during an MRI scan. Providing detailed explanations, using open MRI scanners, or administering mild sedation can help alleviate these issues.</li>
<li><strong>Patient Preparation:</strong>Proper patient preparation, including fasting guidelines, hydration instructions, and positioning tips, is crucial for optimal imaging outcomes and patient comfort.</li>
</ul>
<p>For more detailed information on safety considerations and patient preparation, please refer to the following resources:</p>
<ul>
<li><a href="https://www.ncbi.nlm.nih.gov/books/NBK551669/">Safety Considerations</a></li>
<li><a href="https://www.ncbi.nlm.nih.gov/books/NBK565882/">Patient Preparation</a></li>
<li><a href="https://mriquestions.com/safety-and-screening1.html">MRI Questions - Safety and Screening</a></li>
</ul>
<h2>2. Techniques and Modalities</h2>
<h3>Structural MRI (sMRI):</h3>
<p>OVERVIEW: sMRI utilizes magnetic fields and radio waves to create detailed images of the brain's anatomy. This technique allows for high-resolution examination of brain structures, providing essential information about the size, shape, and integrity of various brain regions.</p>
<p>TECHNIQUES: cortical thickness (CT) [1], diffusion tensor imaging (DTI) [2], surface-based morphometry (SBM) [3,4], and voxel-based morphometry (VBM) [5,6].</p>
<p>APPLICATIONS: It is particularly useful for identifying abnormalities such as tumors, brain injuries, and neurodegenerative diseases.</p>
<p>EXAMPLE: A study using VBM to identify brain volume reductions in patients with Alzheimer's disease.</p>
<h3>Diffusion MRI:</h3>
<p>OVERVIEW: Diffusion MRI maps the local diffusion properties of the water molecules in biological tissues [11].</p>
<p>TECHNIQUES:</p>
<ul>
<li><strong>DWI</strong> (Diffusion Weighted Imaging): Detects differences in the degree of movement of water molecules (speed) [12].</li>
<li><strong>DTI</strong> (Diffusion Tensor Imaging): Maps the diffusion of water along white matter tracts. Reports information on the degree of diffusion (speed) + main (preferential) direction of movement of water molecules [2,13].</li>
<li><strong>DSI</strong> (Diffusion Spectrum Imaging) and <strong>QBI</strong> (Imaging q-ball): Captures more complex diffusion patterns [14,15].</li>
</ul>
<p>COMPUTATIONAL ANALYSIS: Tools like FSL, MRtrix, and DSI Studio for tractography and tensor analysis.</p>
<p>EXAMPLE: DTI used to map white matter changes in patients with multiple sclerosis.</p>
<h3>Functional MRI (fMRI):</h3>
<p>OVERVIEW: fMRI detects changes in blood oxygen levels (BOLD signal) to visualize and measure brain activity in real time [7,8]. There are two main types of fMRI:</p>
<ul>
<li><strong>Task-based</strong> fMRI: Involves participants performing specific tasks while their brain activity is measured, providing insights into brain function related to cognitive and motor tasks [9].</li>
<li><strong>Resting-state</strong> fMRI: Measures brain activity when a person is not performing any explicit tasks, capturing the brain's intrinsic functional connectivity [10].</li>
</ul>
<p>APPLICATIONS: Used in cognitive and behavioral studies, mapping brain functions, and pre-surgical planning.</p>
<p>EXAMPLE: Task-based fMRI identifying regions activated during language tasks in epilepsy patients for surgical planning.</p>
<h2>Clinical Applications of MRI:</h2>
<h3>Neurology:</h3>
<ul>
<li><strong>Diagnosing Brain Tumors:</strong>MRI provides detailed images of brain tumors, helping in diagnosis, treatment planning, and monitoring response to therapy.</li>
<li><strong>Stroke:</strong> MRI, especially diffusion-weighted imaging (DWI), is crucial for detecting acute ischemic strokes, assessing stroke severity, and guiding treatment decisions.</li>
<li><strong>Multiple Sclerosis:</strong> MRI is the gold standard for diagnosing and monitoring multiple sclerosis, identifying lesions, and assessing disease progression.</li>
</ul>
<h3>Cardiology:</h3>
<ul>
<li><strong>Assessing Heart Function:</strong> Cardiac MRI evaluates heart structure, function, and blood flow, providing detailed information on myocardial infarction, cardiomyopathies, and congenital heart disease.</li>
<li><strong>Detecting Myocardial Infarction:</strong> MRI can identify areas of the heart muscle affected by infarction, helping in assessing the extent of damage and planning treatment.</li>
</ul>
<h3>Oncology:</h3>
<ul>
<li><strong>Evaluating Tumors:</strong> MRI is used to visualize and characterize tumors in various organs, including the brain, liver, and prostate. It helps in determining tumor size, extent, and involvement of adjacent structures.</li>
<li><strong>Guiding Biopsies:</strong> MRI-guided biopsies improve the accuracy of sampling suspicious areas, increasing the likelihood of obtaining a definitive diagnosis.</li>
</ul>
<p><strong>Clinical Case Studies:</strong> For a variety of clinical case studies demonstrating MRI applications in different medical conditions, visit <a href="https://radiopaedia.org/search?scope=cases&sort=date_of_publication">Radiopaedia Case Search</a>.</p>
<h2><a href="guide_mri.html">Practical guide on MRI</a></h2>
<h2> Page on <a href="metaanalysis_info.html">META-ANALYSIS in Neuroimaging</a></h2>
</div>
</div>
<!-- Footer -->
<footer id="footer">
<div class="inner">
<section>
<h2>Get in touch</h2>
<form method="post" action="#">
<div class="fields">
<div class="field half">
<input type="text" name="name" id="name" placeholder="Name" />
</div>
<div class="field half">
<input type="email" name="email" id="email" placeholder="Email" />
</div>
<div class="field">
<textarea name="message" id="message" placeholder="Message"></textarea>
</div>
</div>
<ul class="actions">
<li><input type="submit" value="Send" class="primary" /></li>
</ul>
</form>
</section>
<section>
<h2>Follow</h2>
<ul class="icons">
<li><a href="#" class="icon brands style2 fa-twitter"><span class="label">Twitter</span></a></li>
<li><a href="#" class="icon brands style2 fa-facebook-f"><span class="label">Facebook</span></a></li>
<li><a href="#" class="icon brands style2 fa-instagram"><span class="label">Instagram</span></a></li>
<li><a href="#" class="icon brands style2 fa-dribbble"><span class="label">Dribbble</span></a></li>
<li><a href="#" class="icon brands style2 fa-github"><span class="label">GitHub</span></a></li>
<li><a href="#" class="icon brands style2 fa-500px"><span class="label">500px</span></a></li>
<li><a href="#" class="icon solid style2 fa-phone"><span class="label">Phone</span></a></li>
<li><a href="#" class="icon solid style2 fa-envelope"><span class="label">Email</span></a></li>
</ul>
</section>
<ul class="copyright">
<li>© Untitled. All rights reserved</li><li>Design: <a href="http://html5up.net">HTML5 UP</a></li>
</ul>
</div>
</footer>
</div>
<!-- Scripts -->
<script src="assets/js/jquery.min.js"></script>
<script src="assets/js/browser.min.js"></script>
<script src="assets/js/breakpoints.min.js"></script>
<script src="assets/js/util.js"></script>
<script src="assets/js/main.js"></script>
</body>
</html>