Magnetic Resonance Imaging (MRI) Practice Test

To acquire an intracranial arterial blood flow sequence, a presaturation pulse would be applied in which location?

1. In the slice group

2. Inferior to the slice group

3. Superior to the slice group

4. Lateral to the slice group

The correct answer is: Superior to the slice group

Applying a presaturation pulse superior to the slice group is a strategic approach in MRI sequences aimed at reducing unwanted signal from certain areas, such as static tissues or flowing blood from nearby structures, which could obscure the imaging of the target vessels. In the context of intracranial arterial blood flow, positioning the presaturation pulse above the slice group effectively saturates the signal from the vessels that are flowing into the area of interest. This allows for a clearer depiction of the arterial blood flow within the designated slice by minimizing the signal from arteries that are not part of the focus of the scan. In this scenario, if the presaturation pulse were placed inferior, lateral, or within the slice group, it may not adequately suppress the unwanted signals from the superior vessels, potentially leading to artifacts or diminished clarity in the imaging of the targeted arteries. Positioning above the slice group optimally targets the desired signal while suppressing irrelevant contributions.