Inversion recovery is an

MRI sequence An MRI sequence in magnetic resonance imaging (MRI) is a particular setting of pulse sequences and pulsed field gradients, resulting in a particular image appearance. A multiparametric MRI is a combination of two or more sequences, and/or includ ...

that provides high contrast between tissue and lesion. It can be used to provide high T1 weighted image, high T2 weighted image, and to suppress the signals from fat, blood, or

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the ...

(CSF).

Fluid-attenuated inversion recovery

Fluid-attenuated inversion recovery (FLAIR) is an inversion-recovery pulse sequence used to nullify the signal from fluids. For example, it can be used in brain imaging to suppress cerebrospinal fluid so as to bring out periventricular hyperintense lesions, such as multiple sclerosis plaques. By carefully choosing the inversion time TI (the time between the inversion and excitation pulses), the signal from any particular tissue can be suppressed.

Turbo inversion recovery magnitude

Turbo inversion recovery magnitude (TIRM) measures only the magnitude of a turbo spin echo after a preceding inversion pulse, thus is phase insensitive. TIRM is superior in the assessment of

osteomyelitis Osteomyelitis (OM) is an infection of bone. Symptoms may include pain in a specific bone with overlying redness, fever, and weakness. The long bones of the arms and legs are most commonly involved in children e.g. the femur and humerus, while the ...

and in suspected

head and neck cancer Head and neck cancer develops from tissues in the lip and oral cavity (mouth), larynx (throat), salivary glands, nose, sinuses or the skin of the face. The most common types of head and neck cancers occur in the lip, mouth, and larynx. Symptoms ...

. Osteomyelitis appears as high intensity areas. In head and neck cancers, TIRM has been found to both give high signal in tumor mass, as well as low degree of overestimation of tumor size by reactive inflammatory changes in the surrounding tissues.

Double Inversion Recovery

It is a sequence that suppress both

(CSF) and

white matter White matter refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons, also called tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distributi ...

, and samples the remaining transverse magnetisation in fast

spin echo In magnetic resonance, a spin echo or Hahn echo is the refocusing of spin magnetisation by a pulse of resonant electromagnetic radiation. Modern nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) make use of this effect. The NMR ...

, where the majority of the signals are from the

grey matter Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil (dendrites and unmyelinated axons), glial cells (astrocytes and oligodendrocytes), synapses, and capillaries. Grey matter is distingu ...

. Thus, this sequence is useful in detecting small changes on the brain cortex such as focal cortical dysplasia and

hippocampal sclerosis Hippocampal sclerosis (HS) or mesial temporal sclerosis (MTS) is a neuropathological condition with severe neuronal cell loss and gliosis in the hippocampus, specifically in the CA-1 (Cornu Ammonis area 1) and subiculum of the hippocampus. It w ...

in those with

epilepsy Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrica ...

. These lesions are difficult to detect in other MRI sequences.

History

Erwin Han first used inversion recovery technique to determine the value of T1 (the time taken for longitudinal magnetisation to recover 63% of its maximum value) for water in 1949, 3 years after the nuclear magnetic resonance was discovered.

References

{{reflist Magnetic resonance imaging Nuclear magnetic resonance Quantum mechanics