Time-Varying Gradient Basics: Parameter Interactions

Question 1

How does increasing TE affect peripheral nerve stimulation risk?

Answer 1

Increasing TE decreases PNS

Question 2

How does decreasing receiver bandwidth affect peripheral nerve stimulation risk?

Answer 2

Decreasing bandwidth decreases PNS

Question 3

How does decreasing frequency encoding affect peripheral nerve stimulation risk?

Answer 3

decreasing frequency encoding decreases PNS

Question 4

How does decreasing phase encoding affect peripheral nerve stimulation risk?

Answer 4

decreasing phase encoding decreases PNS

Question 5

How does using thicker slices affect peripheral nerve stimulation risk?

Answer 5

Thicker slices decrease PNS

Question 6

How does running a slower scan affect peripheral nerve stimulation risk?

Answer 6

slower pulse sequences decrease PNS

Question 7

What causes PNS in the patient?

Answer 7

Peripheral nerve stimulation is produced during a changing magnetic field

Question 8

What factors cause a steeper gradient slope (and therefore more chance for PNS)

Answer 8

Shorter TE, increased receiver bandwidth, increased phase and frequency encoding, thinner slices, faster sequences

Question 9

The louder the sequence the ______ the gradients are working (easier or harder).

Answer 9

harder

Question 10

Is an EPI, like the DWI, more or less likely to create PNS?

Answer 10

More likely to create PNS because of the stronger gradient activation

Question 11

Other than EPI (like DWI), what other sequences are likely to cause PNS?

Answer 11

Single shot scans like HASTE

Question 12

What type of pulse sequence would be a good choice to reduce PNS?

Answer 12

Spine echo

Question 13

What units is Gradient Maximum measured in?

Answer 13

mT/m

Question 14

What units is Slew Rate measured in?

Answer 14

T/m/s

Question 15

What units is Rise Time measured in?

Answer 15

Milliseconds

Question 16

What units is Magnetic Spacial Gradient measured in?

Answer 16

T/m (or g/cm)

Question 17

What units is B0 measured in?

Answer 17

Tesla