What happens to scan time as the field of view (FOV) increases while other parameters remain constant?

• A. Scan time decreases
• B. Scan time remains the same
• C. Scan time increases
• D. Scan time only increases with TR

Answer: (C)

When the field of view (FOV) increases while keeping other imaging parameters constant, the scan time tends to increase. This is primarily because a larger FOV means that the MRI system must capture and process a greater volume of tissue.

In MRI, the spatial resolution is determined by the size of the FOV and the matrix size. When the FOV increases without changing the matrix size, the resolution per unit area decreases, but the total area being imaged increases. Consequently, the system requires more time to acquire sufficient data across the larger area.

Moreover, the data collection process involves several factors, such as the number of phase encoding steps and the repetition time (TR). If those elements are held constant, the longer scan time is directly related to the need to collect more data points to fully represent the larger volume of tissue being imaged. This relationship is key in understanding how FOV impacts overall scan efficiency and time. Thus, increasing the FOV leads to an increased scan time when other parameters remain constant.