10/05/2026
Basic MRI sequences are the fundamental pulse sequences used in routine imaging. Each sequence emphasizes different tissue characteristics (like water, fat, or pathology). Here’s a clear overview:
🧠 1. T1-Weighted Imaging (T1WI)
Key idea: Anatomy (good for structure)
Fat → bright
Water/CSF → dark
White matter → brighter than gray matter
Pathology → usually dark
📌 Uses:
Normal anatomy
Post-contrast imaging (gadolinium enhances lesions)
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💧 2. T2-Weighted Imaging (T2WI)
Key idea: Fluid-sensitive (detects pathology)
Water/CSF → bright
Fat → moderately bright
Gray matter → brighter than white matter
Pathology (edema, tumors, inflammation) → bright
📌 Uses:
Detecting edema, infection, tumors
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🌊 3. FLAIR (Fluid Attenuated Inversion Recovery)
Key idea: T2 with CSF suppressed
CSF → dark (suppressed)
Edema/lesions → bright
📌 Uses:
Brain lesions near CSF (e.g., multiple sclerosis, infarcts)
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⚡ 4. Diffusion-Weighted Imaging (DWI)
Key idea: Movement of water molecules
Restricted diffusion → bright
ADC map → confirms true restriction
📌 Uses:
Acute stroke (very early detection)
Abscess vs tumor differentiation
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🧲 5. Gradient Echo (GRE) / Susceptibility-Weighted Imaging (SWI)
Key idea: Sensitive to blood & metal
Blood, calcium, iron → dark (blooming effect)
📌 Uses:
Hemorrhage
Microbleeds
Calcifications
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💉 6. Post-Contrast T1 (T1 + Gadolinium)
Key idea: Breakdown of blood-brain barrier
Enhancing lesions → bright
📌 Uses:
Tumors
Infection
Inflammation
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🌡️ 7. Proton Density (PD)
Key idea: Proton concentration
CSF → bright (but less than T2)
Good contrast between tissues
📌 Uses:
Joint imaging (e.g., meniscus, cartilage)
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🧾 Quick Comparison Table
Sequence CSF Fat Pathology
T1 Dark Bright Dark
T2 Bright Bright Bright
FLAIR Dark Bright Bright
DWI Variable Variable Bright (acute stroke)
GRE/SWI Dark Dark Dark (blood)
