As the TR is increased, which outcomes are expected?

When the repetition time (TR) is increased in an MRI scan, there are several outcomes that can be expected. One of the primary effects of increasing TR is an improvement in signal-to-noise ratio (SNR). The longer TR allows for more time for the longitudinal magnetization to recover before the next radiofrequency pulse is applied, which results in a greater amount of net magnetization and consequently a stronger signal, enhancing the SNR.

Additionally, increasing TR also affects the available number of slices that can be acquired. A longer TR means that there is more time between the application of radiofrequency pulses, thereby allowing for the collection of slices in a multi-slice acquisition protocol without compromising the image quality. This means that more slices can be acquired during the same period since each slice has a longer recovery time before being excited again.

Therefore, the expected outcomes of increasing TR are both an increase in SNR and an increase in the available number of slices, supporting the conclusion that the correct answer is a combination of these effects.