Magnetic Resonance Imaging (MRI) Practice Test

Which imaging technique would typically use a 180-degree inversion pulse?

1. Fast Spin Echo (FSE)

2. Turbo Spin Echo (TSE)

3. Inversion Recovery (IR)

4. Gradient Echo Sequence

The correct answer is: Inversion Recovery (IR)

The use of a 180-degree inversion pulse is a defining characteristic of Inversion Recovery (IR) imaging techniques. This pulse is utilized to achieve tissue contrast enhancement based on the T1 relaxation times of different tissues. In an inversion recovery sequence, the initial 180-degree pulse inverts the longitudinal magnetization of the tissue, and following this pulse, a variable delay (referred to as the inversion time, TI) is incorporated before a standard excitation pulse, commonly a 90-degree pulse, is applied. This delay allows for the different tissues to recover at their specific rates, thereby enhancing the contrast between them when the image is captured. IR sequences are particularly useful for suppressing signals from specific tissues, such as fat or fluid, making it an effective modality in various clinical situations, including brain imaging, where it helps in distinguishing between white matter and grey matter or identifying pathologies like edema and demyelination. Other imaging techniques, such as Fast Spin Echo (FSE) and Turbo Spin Echo (TSE) sequences, while they may incorporate variations of refocusing pulses, do not specifically utilize the inversion pulse configuration. Gradient Echo sequences utilize variable flip angles and do not typically involve 180-degree inversion pulses. Therefore, the characteristic application of