Breath-hold spiral tissue phase velocity mapping (TPVM) with non-Cartesian SENSE
Journal of Cardiovascular Magnetic Resonance volume 16, Article number: P40 (2014)
TPVM is the only MR technique capable of measuring regional myocardial mechanics over the entire cardiac cycle [1, 2]. Previous Cartesian breath-hold TPVM sequences have had low temporal resolution (eg ), limiting temporal detail, while navigator sequences are long and difficult to use clinically. This abstract presents a new spiral TPVM sequence which is capable of acquiring high temporal resolution TPVM data over the entire cardiac cycle within a clinically acceptable breath-hold duration.
K-space is fully sampled with 8 spiral interleaves (14 ms duration, TR 24 ms) but only 3 spirals are acquired and reconstructed using non-Cartesian SENSE  implemented on the Gadgetron GPU framework . Velocity compensated and encoded (30 cm/s through plane, 20 cm/s in-plane) data are acquired in consecutive heartbeats, with an initial heartbeat used to collect coil sensitivity information (total breath-hold duration 13 heartbeats). Acquired spatial resolution is 1.7 × 1.7 mm. Retrospective cardiac gating is used to cover the entire cycle (50 reconstructed phases). Basal, mid and apical short-axis slices were acquired in 10 volunteers and from the mid-slice of 1 early stage DCM patient (LVEF 49%, EDV 188 mL, ESV 96 mL) and one late stage DCM patient (LVEF 21%, EDV 326 mL, ESV 258 mL) on a Siemens Skyra 3T scanner. Global peak and time to peak (TTP) velocities were extracted. In one healthy volunteer a stack of 9 short axis slices were also acquired, providing full LV coverage.
Figure 1a shows global velocities measured from the 9 short axis slices in one volunteer with velocity peaks labelled. This shows smooth changes from base to apex that have only previously been seen in lengthy 3D acquisitions . Figure 1b shows mid-slice healthy mean (+/- SD) peak and time to peak velocities as well as the individual patient values. Longitudinal peaks in the early DCM patient are normal but radial values are clearly reduced. For the late stage patient, velocities in all directions are reduced. Figure 2 shows regional velocity variation (y-axis) over time (x-axis) in the mid slice of one volunteer and both patients. Regional abnormalities can be seen in the radial direction of the early DCM example, although longitudinal velocities are normal. The late DCM patient has clearly abnormal regional variation in all directions, particularly in early diastole.
Spiral trajectories and non-Cartesian SENSE has allowed acquisition of high temporal resolution TPVM images within a clinically achievable breath-hold and allows acquisition and reconstruction of a full short axis stack within 30 minutes. Initial clinical examples indicate that this technique is capable of detecting reduced radial velocities in early DCM when global parameters of motion are still within the normal range.
HRUK Grant RG2584. NHLI CBRU Royal Brompton Hospital and Imperial College.
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Simpson, R., Keegan, J., Gatehouse, P. et al. Breath-hold spiral tissue phase velocity mapping (TPVM) with non-Cartesian SENSE. J Cardiovasc Magn Reson 16 (Suppl 1), P40 (2014). https://doi.org/10.1186/1532-429X-16-S1-P40