Magnetic Resonance Imaging (MRI) Practice Test

What is the role of Inversion Time (TI) in inversion recovery sequences?

1. To determine acquisition duration

2. To selectively null signals from specific tissues

3. To establish imaging plane orientation

4. To optimize signal-to-noise ratio

The correct answer is: To selectively null signals from specific tissues

Inversion Time (TI) plays a crucial role in inversion recovery sequences by selectively nulling signals from specific tissues. This technique allows practitioners to enhance contrast in images by manipulating the timing of the radiofrequency pulse in relation to the tissue's relaxation times. By choosing a TI that corresponds to the T1 relaxation time of a particular tissue, such as fat or fluid, the signal from that tissue can be effectively suppressed. This is particularly useful in MRI to distinguish between different types of tissues or pathologies. It enhances the visibility of other tissues by reducing the contribution of the nulled signals to the overall image, thus improving diagnostic capacity. The other choices do touch upon important aspects of MRI imaging, but they do not accurately capture the primary function of TI in inversion recovery sequences. Selection of acquisition duration is more related to the overall imaging protocol rather than the specific timing of an inversion pulse. Imaging plane orientation is determined by other parameters such as gradient selection and does not directly pertain to TI. Optimizing the signal-to-noise ratio involves various factors including coil sensitivity and imaging parameters, which are separate from the specific role of TI in nulling signals.