Bootstrap quantification of cardiac pulsation artifact in DTI

While several studies have shown the benefit of cardiac gating in diffusion MRI with single-shot EPI acquisition, cardiac gating is still not commonly used. This is probably because it requires additional time and many investigators may not be convinced that cardiac gating is worth the extra effort. Here, we tested a clinically feasible protocol with a minimal increase in scan time, and quantified the effect of cardiac gating under partial or full Fourier acquisition. Eight volunteers were scanned on a 3 T scanner with a SENSE 8-channel head coil. Diffusion-weighted, single-shot spin-echo EPI images were acquired along 32 gradient directions, with or without cardiac gating and with partial or full Fourier acquisition. Vectorcardiography (VCG) was used to trigger acquisition at a minimum delay (30 ms). The uncertainties of DTI derived parameters were estimated using residual bootstrap. With partial Fourier, cardiac gating reduced the uncertainties, and better efficiency in reducing DTI parameter variability was also achieved even allowing for the increase in total scan time. For full Fourier acquisition, minimum time gating slightly decreased the uncertainties but the efficiency was worse. A minimum trigger delay might not be the optimal scheme to avoid the majority of systole but it allows clinically acceptable scan times. We have demonstrated that cardiac gating, especially of partial Fourier acquisitions, can reduce the uncertainties of DTI derived parameters in a time-efficient manner.