DTI scan protocol considerations

A DTI scan is an EPI-based acquisition, and therefore suffers from image distortion. A good compromise between the level of distortion and the level of noise is critical to warrant good parametric data and accuracy for fiber tracking.

Consider these tradeoffs as you change scan parameters for images that are post processed with the READY View DTI protocol.

• As the Receive Bandwidth increases, SNR decreases, chemical shift artifact decreases, minimum TE decreases (which means that the echo space decreases). As echo space decreases, geometric distortion decreases.
• Do not select Interleave for spacing because images may be lost and tensor maps will not be processed. The system acquires the first phase at each location (pass 1) and then goes back and acquires the second phase at each location (pass 2) and so on. Select 0 for spacing if contiguous slices are desired.
• Increasing the TR increases the amount of available slices. Select a TR long enough to cover the imaging area within a single acquisition.
• In DTI, the frequency and phase matrix values default to 128 (the matrix values range from 64 to 256). Images acquired with a 128×128 matrix provide adequate resolution in a reasonable scan time.