From the Guidelines
T1 and T2-weighted MRI sequences are essential for visualizing anatomical structures and detecting pathology, with T1-weighted images showing fat as bright and water/fluid as dark, and T2-weighted images displaying the opposite contrast pattern. When interpreting MRI results, it is crucial to understand the basic principles of these sequences, as they provide different types of contrast to visualize anatomical structures 1. T1-weighted images are excellent for visualizing anatomical structures and fat-containing tissues, while T2-weighted images are ideal for detecting pathology, inflammation, and edema 1.
Key Differences Between T1 and T2 Sequences
- T1 measures longitudinal relaxation time (how quickly protons realign with the magnetic field)
- T2 measures transverse relaxation time (how quickly protons dephase from each other)
- Pathologies typically appear dark on T1 and bright on T2, though some exceptions exist such as acute hemorrhage, fat, and melanin
Clinical Applications of T1 and T2 Sequences
- Contrast-enhanced T1-weighted scans and T2-weighted scans can reveal inflammation and the development of new and/or enlarging lesions 1
- T2-weighted fluid-attenuated inversion recovery (FLAIR) MRI uses a combination of T1- and T2-weighting to suppress the signal originating from bulk fluid, including cerebrospinal fluid 1
- T2-weighted FLAIR techniques increase lesion conspicuity, allowing for better visualization of vasogenic edema, surgery-induced and radiation-induced gliosis, and infiltrating tumor 1
Recommendations for MRI Protocols
- Follow-up scans should be conducted at least annually, and as often as every 3–4 months in patients who require enhanced pharmacovigilance 1
- The preferred protocol for T2-weighted FLAIR imaging includes a slice thickness of 3 mm with no interslice gap for 3 T scans, and 1.5 T scanners should acquire images up to 4 mm slice thickness with no interslice gap 1
From the FDA Drug Label
In magnetic resonance imaging (MRI), visualization of normal and pathological tissue depends in part on variations in the radiofrequency signal intensity that occurs with: differences in proton density differences of the spin-lattice or longitudinal relaxation times (T1) differences in the spin-spin or transverse relaxation time (T2) When placed in a magnetic field, gadoterate shortens the T1 and T2 relaxation times in target tissues. At recommended doses, the effect is observed with greatest sensitivity in the T1-weighted sequences.
Gadoterate meglumine affects MRI T1 and T2 relaxation times.
- It shortens both T1 and T2 relaxation times in target tissues.
- The effect is most sensitive in T1-weighted sequences 2 2.
From the Research
MRI T1/T2 Overview
- MRI T1 and T2 are quantitative parameters used in magnetic resonance imaging to characterize the relaxation properties of tissues 3.
- T1 relaxation time, also known as spin-lattice relaxation time, is the time it takes for the longitudinal magnetization to recover after being disturbed by a radiofrequency pulse.
- T2 relaxation time, also known as spin-spin relaxation time, is the time it takes for the transverse magnetization to decay due to interactions between spins.
Clinical Applications of T1/T2
- T1-weighted imaging is commonly used to detect lesions and abnormalities in the brain, such as tumors and multiple sclerosis lesions 4, 5.
- T2-weighted imaging is useful for detecting edema, inflammation, and infection in the body, including musculoskeletal infections 6.
- Fat-suppressed T2-weighted images can help to improve the visibility of lesions and abnormalities in the musculoskeletal system 6.
Comparison of T1/T2 Imaging Techniques
- Gadolinium-enhanced T1-weighted imaging can provide better contrast and visibility of lesions and abnormalities, especially in the brain and musculoskeletal system 4, 6.
- Fast fluid-attenuated inversion-recovery (FLAIR) imaging can provide better visibility of superficial abnormalities, such as meningeal disease, compared to T1-weighted imaging 4.
- Magnetization transfer (MT) imaging can detect gadolinium-related signal changes, but its usefulness in detecting brain gadolinium retention is still being investigated 5.