Some examples of spin echo pulse sequences (spins are rephased by a 180º rephasing pulse):

141

• conventional spin echo
• fast or turbo spin echo
• inversion recovery

Some examples of gradient echo pulse sequences (spins are rephased by a gradient):

141

• coherent gradient echo
• incoherent gradient echo
• steady state free precession
• balanced gradient echo
• fast gradient echo
• echo planar imaging

___________ pulse sequences are the gold standard for most imaging.

142

__________ is a spin echo pulse sequence, but with scan times that are much shorter than conventional spin echo.

143

In ___________, the scan time is reduced by performing more than one phase encoding step and subsequently filling more than one line of K space per TR.

143

The number of 180º rephasing pulses performed per TR corresponds to the number of echoes produced and the number of lines of K space filled. This number is called the ___________ or the ____________.

144

The TE selected is only an _________ TE. In other words, it is the TE at which the operator wishes to weight the resultant image.

144-145

In fast spin echo, fat remains dark/bright on T2 weighted images due to the multiple RF pulses, with reduce the effects of spin-spin interactions in fat. This is called ____________.

146

In fast spin echo, the repeated 180º pulses can increase magnetization transfer effects so that muscle, for example, appears darker/lighter on fast spin echo images than in conventional spin echo.

146

What are some advantages of using fast spin echo?

148

• scan times greatly reduced
• high-resolution matrices and multiple NEX can be used
• image quality improved
• increased T2 information

What are some disadvantages of using fast spin echo?

149

• some flow and motion affects increased
• incompatible with some imaging options
• fat bright on T2 weighted images
• image blurring with very long echo trains

_______________ is a scan technique in which all the lines of K space are acquired in one TR.

150

__________ combines a partial Fourier technique with fast spin echo; however, there is a SNR penalty.

150

The ___________ is significantly increased by applying so many successive 180º pulses.

150

In another modification of FSE, a reverse flip angle excitation pulse is applied at the end of the echo train to drive any transverse magnetization into the longitudinal plane so that it is available for excitation at the beginning of the next TR period. This is called _______________.

151