Four‐dimensional flow MRI using spiral acquisition

Abstract

Time-resolved three-dimensional phase contrast MRI is an important tool for physiological as well as clinical studies of flow in the heart and vessels. The application of the technique is, however, limited by the long scan times required.In the present work, we investigate the feasibility of using spiral readouts to reduce the scan time of 4D flow MRI without sacrificing quality. Three spiral approaches are presented and evaluated in-vivo and in-vitro against a conventional Cartesian acquisition. In-vivo, the performance of each method was assessed in the thoracic aorta in ten volunteers using pathline based analysis and cardiac output analysis. SNR and background phase errors were investigated invitro.Using spiral readouts, the scan times of a 4D flow acquisition of the thoracic aorta could be reduced two to threefold, with no statistically significant difference in pathline validity or cardiac output. The shortened scan time improves the applicability of 4D flow MRI, which may allow the technique to become a part of a clinical workflow for cardiovascular functional imaging.

Volumetric velocity measurements in restricted geometries using spiral sampling: a phantom study

“…A major obstacle to wide-spread clinical use of 4D PC is the long acquisitions times. However, volumetric non-cartesian sequences in combination with PC (such as PC-VIPR) have been shown able to greatly reduce acquisition times compared to traditional Cartesian readout schemes, while maintaining accuracy in flow quantification [28,29], and 4D PC have also been successfully combined with spiral readouts for in-vivo measurements [30,31].…”

“…Simulations performed on our MR system indicates that both 3D throughplane PC and 4D PC sequences used in this work can be used with a spectral-spatial excitation pulse [30] and still achieve TE below 2 ms. We also observed a less smooth background phase offset variation in the spiral datasets as compared to the Cartesian sequences, with minor streak artifacts present. This type of background phase offset variations are likely more difficult to correct for using polynomial fitting procedures.…”

Assessment of flow and hemodynamics in the carotid artery using a reduced TE 4D flow spiral phase-contrast MRI

“…Previously, Sigfridsson et al [19] proposed a 4D Spiral flow sequence and used their method for imaging and visualization of flow through the aorta. In this paper, a 4D spiral flow MRI technique was designed which through combination of bipolar and slice select gradient further reduces the TE in comparison to Sigfridsson et al's implementation.…”

4D ultra-short TE (UTE) phase-contrast MRI for assessing stenotic flow and hemodynamics.

“…Figure 40 displays the proposed 4D spiral flow sequence, designed using a 3D stack of spirals trajectory. A stack of spirals trajectory was also adopted in [164]; however, as shown in Figure 40, the TE is now further shortened through combination of the flow encoding/compensated gradient with the refocusing portion of slice select gradient. Further reduction in TE is possible using higher values of Velocity encoding (Venc).…”