Questions and Answers from the Pulse-programming Workshop
Q: How does one do a real simulation in WTools with respect to entering multiple slice locations?
A: A real simulation can be done in terms of writing slice location infomation into structure scan_info and rsp_info. To do this, set the CV use_myscan to 1 in EvalTool. When use_myscan is set to 1, the sequence will call the function myscan, which proceeds to calculate scan_info based on slice thickness and a slice location.
Q: What does view or frame mean in epic terminology?
A:In epic terminology, view or frame refers to the phase encoding step.
Q: What does phases or multiphase mean in epic terminology?
A: This has nothing to do with phase encoding. It actually refers to the number of repeated scans acquired over multiple time points. This is equivalent to hitting the scan button repeatedly.
Q: What does echoes mean in epic terminology?
A: This can be confusing. Generally, the number of echoes refers to the number of images acquired with different TEs. The standard CV for this is opnecho. In a normal sequence with one phase encode per shot this would simply be the number of readouts. For example, for opnecho=2, there would be two readouts. The readouts are placed at different times within the sequence so the effective TE for each is different. After N shots and N phase-encode steps, two images with different effective TEs can be reconstructed. Where things get complicated is when there is more than one phase encode per shot, i.e., when different readouts are used for different phase encodes. In sequences such as EPI, multiple readouts are used for multiple phase encodes within a single shot rather than to acquire images with different TEs. If , as in EPI, a single image with a single effective TE is reconstructed, then we would consider this as a single echo (opnecho=1) even though there were multiple readouts.