A single oscillating waveform-based gradient delay estimation

Purpose

We present a time efficient method to estimate gradient delay using a single oscillating waveform.

Methods

Single oscillating waveform-based gradient delay estimation algorithm (SODA) was proposed. It estimated gradient delays by measuring the relative shifts of echoes acquired at consecutive time points. An acceleration was achieved by a three spin-echo sequence acquiring measurements for all gradient channels within a single excitation. Simulations and phantom experiments were carried out to compare SODA with a reference method. In addition, we monitored the change of the gradient delay over time using an integrated sequence with high gradient amplitude on a 3 T scanner. High-resolution imaging was performed for phantom and in vivo studies to compare images quality with and without gradient delay correction (GDC).

Results

Simulations showed no significant difference in gradient delay estimates when comparing SODA with the reference method for noise levels 1 to 5. The phantom results confirmed strong agreements on delay estimates between SODA with the three spin-echo sequence and the reference method with six pulse repetitions. The gradient delays were observed nearly consistent over time for the scanner. For high-resolution imaging, the reconstruction with GDC exhibit sharper and clearer depictions of images structures than reconstruction without GDC.

Conclusion: SODA can provide accurate gradient delay estimates with short calibration scan time. The three spin-echo sequence can be seamlessly integrated with any host sequence to measure the gradient delay and provide accurate spiral trajectory. It may be a valuable tool for gradient delay correction in spiral imaging.