Magnetic Resonance Imaging (MRI) Practice Test

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How can scan time be reduced in a FSE sequence that acquires T2 weighted images with a long TE?

Using a shorter ETL
Using a longer ETL
Increasing the TR
Reducing the bandwidth

The correct answer is: Using a longer ETL

Reducing scan time in a Fast Spin Echo (FSE) sequence that acquires T2 weighted images can be effectively achieved by using a longer Echo Train Length (ETL). The ETL refers to the number of echoes that are collected after a single excitation pulse during the spin echo sequence. By increasing the ETL, more data is collected with each repetition time (TR), which allows for multiple lines of k-space to be filled in a single scan. This efficiency means that the overall scan time can be shortened because fewer TRs are required to acquire the same amount of imaging information. However, it is essential to consider that while longer ETLs can expedite the process, it may also influence image quality. Typically, longer ETLs can lead to some degree of signal loss and increased risk of motion artifacts, particularly in cases where the T2 relaxation times are significantly different in tissues. Careful optimization of the ETL is crucial for balancing scan time and image quality when acquiring T2-weighted images. In contrast, other options do not effectively contribute to reducing scan time in the context provided. For example, using a shorter ETL would decrease the amount of information per TR, potentially increasing the number of TRs needed to produce a complete image.