Inversion Recovery Techniques

Magnetic resonance imaging, or MRI scans are used to obtain images of the inside of a patient's body so doctors can diagnose the patient's condition more accurately. Inversion recovery techniques are used to highlight potential problems by making abnormal tissue stand out clearly from normal tissue on the image produced by the MRI.

Magnetic Resonance Imaging

• Magnetic Resonance Imaging scans are used to obtain images of the inside of the body, including the brain, the spine and the heart. The patient is placed into a magnetic field that causes the hydrogen protons in the body to start to spin and give off a magnetic field of their own that matches the field of the MRI scan. A radio frequency pulse is used to change the magnetic field in the area being examined. When the pulse is cut off, the protons in that area emit a radio frequency signal of their own. This RF signal can be measured and used to produce an image of the area.

Inversion Recovery

• Inversion recovery is a method for making MRI diagnostic images easier to read by increasing the contrast between normal and abnormal tissue. Inversion recovery techniques are used to neutralize the signal given off by normal tissue, so it will appear darker on the final image. Diseased tissue will be brighter by comparison, making it easier for the person reading the scan to provide accurate information. Inversion recovery can also be used to darken fat tissue so it doesn't stand out and confuse the analysis.

Inversion Time

• After the radio frequency pulse is applied during an MRI scan, there is a certain interval of time, known as the TI or the inversion time, after which normal tissue will show up on an image as a darker area. This TI interval is most often about 330 miliseconds, but this is not consistent and must be established for each patient individually using an experimental set of test images called the TI scout. After the TI scout has been conducted and the TI for a particular patient has been determined, the image taken at the TI point will show normal tissue as a darker area and abnormal tissue as a brighter area.

Phase Sensitive Inversion Recovery

• Phase sensitive inversion recovery is a more recently developed inversion recovery technique in which a TI scout is not necessary. The process is automated and is capable of distinguishing between normal and abnormal tissue, or between fat and surrounding tissues, without needing to be calibrated separately for each individual patient. This can reduce the amount of time in which the patient needs to remain still in the Magnetic Resonance Imaging scan.