Search found 485 matches

by Dave Higgins
Wed Nov 15, 2017 8:30 am
Forum: MRI Physics Questions and Answers
Topic: Heating effects of RF pulses
Replies: 4
Views: 3950

Re: Heating effects of RF pulses

You can reduce energy deposition, and therefore heating, with a reduction of flip angle. But this also affects image contrast.
by Dave Higgins
Tue Oct 31, 2017 2:38 pm
Forum: MRI Physics Questions and Answers
Topic: Echo planar Imaging- Echo Train Length
Replies: 6
Views: 1578

Re: Echo planar Imaging- Echo Train Length

No, the effective echo time for EPI is whenever the central k-space line is acquired.
For a single shot EPI, this would be half way along the echo train.
by Dave Higgins
Tue Oct 31, 2017 12:23 pm
Forum: MRI Physics Questions and Answers
Topic: Echo planar Imaging- Echo Train Length
Replies: 6
Views: 1578

Re: Echo planar Imaging- Echo Train Length

Assuming no partial Fourier, yes
by Dave Higgins
Tue Oct 31, 2017 9:36 am
Forum: MRI Physics Questions and Answers
Topic: Echo planar Imaging- Echo Train Length
Replies: 6
Views: 1578

Re: Echo planar Imaging- Echo Train Length

63 x 1 ms? (63 spacings in 64 echo readout)
by Dave Higgins
Fri Oct 27, 2017 3:15 pm
Forum: MRI Physics Questions and Answers
Topic: Shim volumes?
Replies: 1
Views: 648

Re: Shim volumes?

Balanced SSFP (FIESTA, on GE).
But also think about which body parts or measurements require a good shim. E.g. the heart requires volume shimming (B0) and at 3T RF (B1) volume shimming too.
by Dave Higgins
Mon May 22, 2017 10:20 am
Forum: MRI Physics Questions and Answers
Topic: Is "asymmetric readout" and "partial echo" the same thing? Effect on scan time?
Replies: 1
Views: 973

Re: Is "asymmetric readout" and "partial echo" the same thing? Effect on scan time?

If TR needs to be as short as possible, then yes, a shorter TE does affect TR.
If the scan time is dependent on TR (it often is), then yes, it does affect scan time.
Partial echo and asymmetric readout are the same thing: partial Fourier in the kx direction.

Dave