In a Fast Spin Echo (FSE) sequence with a long TE yielding T2 weighted images, how can scan time be reduced?

In a Fast Spin Echo (FSE) sequence, the Effective Echo Train Length (ETL) is a critical factor that influences scan time. Choosing to use a longer ETL can help to reduce the total acquisition time for a number of reasons, primarily because it acquires multiple echoes in a single repetition time (TR).

When a longer ETL is employed, more data points are collected during each sequence of the echo train, effectively increasing the number of phase-encoding steps that can be completed within the same TR. This means that while the sequence captures more information in one go – resulting in a denser dataset for T2-weighted imaging – it does so in a way that can condense the overall time required for the scan.

In contrast, options that involve increasing the field of view (FOV) or the number of excitations (NEX) would generally lead to an increase in scan time, as they expand the volume of tissue being imaged or require multiple acquisitions respectively. Utilizing a shorter ETL would instead mean fewer echoes are captured per TR, which can prolong the scan time as more repetition times would be needed to acquire the same amount of data. Hence, opting for a longer ETL is a strategic choice in