A single oscillating waveform-based gradient delay estimation.

Abstract

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.