Areas of high signal on the
Potential causes are diverse, including traumatic, infectious, autoimmune, inflammatory, neoplastic, neurologic, and iatrogenic conditions. Alterations in muscle signal intensity seen in pathologic conditions usually fall into one of three recognizable patterns: muscle edema, fatty infiltration, and mass lesion.
Two types of signal can be detected. T1 signal relates to the speed of realignment with the magnetic field – the more quickly the protons realign the greater the T1 signal. T2 signal relates to the speed of proton spin dephasing – the slower the dephasing the greater the T2 signal.
T1-weighted MRI enhances the signal of the fatty tissue and suppresses the signal of the water. T2-weighted MRI enhances the signal of the water. Consideration of all the information provided by these modalities is conducive to MRI image analysis and diagnosis.
An increase in T2 signal intensity is often associated with chronic compression of the spinal cord, and it is well established that chronic compression results in structural changes to the spinal cord.
Increased signal intensity (ISI) on T2-weighted magnetic resonance imaging (MRI) often indicates severe compression in patients with cervical myelopathy (CM). The optimal surgical approach for CM patients with ISI on T2-weighted MRI remains unclear.
T2 (transverse relaxation time) is the time constant which determines the rate at which excited protons reach equilibrium or go out of phase with each other. It is a measure of the time taken for spinning protons to lose phase coherence among the nuclei spinning perpendicular to the main field. MRI IMAGING SEQUENCES.
T2 is another term for spin-spin relaxation, or transverse relaxation time. Like T1, it is a biological parameter of CMR imaging that is used to identify abnormal myocardial tissues through tissue-specific time parameters.
White matter lesions (WMLs) are areas of abnormal myelination in the brain. These lesions are best visualized as hyperintensities on T2 weighted and FLAIR (Fluid-attenuated inversion recovery) sequences of magnetic resonance imaging. They are considered a marker of small vessel disease.
A T1 MRI image supplies information about current disease activity by highlighting areas of active inflammation. A T2 MRI image provides information about disease burden or lesion load (the total amount of lesion area, both old and new).
When describing most MRI sequences we refer to the shade of grey of tissues or fluid with the word intensity, leading to the following absolute terms: high signal intensity = white. intermediate signal intensity = grey. low signal intensity = black.
Radio waves are then sent from the MRI machine and move these atoms out of the original position. As the radio waves are turned off, the atoms return to their original position and send back radio signals. These signals are received by a computer and converted into an image of the part of the body being examined.
Patients with an increased T2 signal intensity are likely to have a more severe initial neurological deficit but will have relatively minimal early neurological deterioration.
MRI uses magnetic fields and radio waves to measures how much water is in different tissues of the body, maps the location of the water and then uses this information to generate a detailed image.
White matter hyperintensities (WMHs) are lesions in the brain that show up as areas of increased brightness when visualised by T2-weighted magnetic resonance imaging (MRI). WMH's are also referred to as Leukoaraiosis and are often found in CT or MRI's of older patients.
Abstract. White matter lesions, quantified as 'white matter signal abnormalities' (WMSA) on neuroimaging, are common incidental findings on brain images of older adults. This tissue damage is linked to cerebrovascular dysfunction and is associated with cognitive decline.
Hyperintense spinal cord signal on T2-weighted images is seen in a wide-ranging variety of spinal cord processes. Causes including simple MR artefacts, trauma, primary and secondary tumours, radiation myelitis and diastematomyelia were discussed in Part A.
It's all about FAT and WATER
The timing of radiofrequency pulse sequences used to make T1 images results in images which highlight fat tissue within the body. The timing of radiofrequency pulse sequences used to make T2 images results in images which highlight fat AND water within the body.
T2* can be considered an "observed" or "effective" T2, whereas the first T2 can be considered the "natural" or "true" T2 of the tissue being imaged. T2* is always less than or equal to T2. T2* results principally from inhomogeneities in the main magnetic field.
Abnormally decreased T2/T2 FLAIR signal can be seen on brain imaging of patients who are experiencing clinical or subclinical seizures and can be associated with various intracranial pathologies. We identified 29 such patients. The abnormal signal was unilateral in 75.9% of patients.
T2/FLAIR lesions can directly account for some symptoms. For example, a brainstem lesion can cause room spinning sensations and balance problems. Cervical (neck) spinal cord T2/FLAIR lesions could cause tingling and numbness in the hands and legs. Many of the lesions may not be causing obvious symptoms.
Ulnar nerve T2 signal increase is an excellent sign for determining ulnar neuropathy at the elbow (UNE); nerve caliber enlargement allows discrimination between severe and mild UNE.
Digital image signals are typically represented as two-dimensional (2D) arrays of discrete signal samples. If we rearrange the signal samples into a one-dimensional (1D) vector, then every image becomes a single point in a high-dimensional image space, whose dimension equals the number of samples in the image signal.