Respiratory and cardiac self-gated free-breathing cardiac CINE imaging with multiecho 3D hybrid radial SSFP acquisition

Abstract

A respiratory and cardiac self-gated free-breathing three-dimensional cine steady-state free precession imaging method using multiecho hybrid radial sampling is presented. Cartesian mapping of the k-space center along the slice encoding direction provides intensity-weighted position information, from which both respiratory and cardiac motions are derived. With in plan radial sampling acquired at every pulse repetition time, no extra scan time is required for sampling the k-space center. Temporal filtering based on density compensation is used for radial reconstruction to achieve high signal-to-noise ratio and contrast-to-noise ratio. High correlation between the self-gating signals and external gating signals is demonstrated. This respiratory and cardiac self-gated, free-breathing, three-dimensional, radial cardiac cine imaging technique provides image quality comparable to that acquired with the multiple breath-hold two-dimensional Cartesian steady-state free precession technique in short-axis, four-chamber, and two-chamber orientations. Functional measurements from the three-dimensional cardiac short axis cine images are found to be comparable to those obtained using the standard two-dimensional technique.

Figure 1

Respiratory and cardiac self-gating signals were derived from the center of mass of the z-intensity profile in multi-echo hybrid 3D radial imaging. a) k-space sampling trajectories, b) z-intensity profile evolving over time, c) center of mass of b) along z, d) respiratory motion, e) cardiac motion.

Figure 2

The respiratory gating was determined based on the histogram of the respiratory motion signal. Sampling projections were divided into multiple bins according to the position of the respiratory motion (left). A histogram (right) was generated for employing a respiratory gating window, such as 30% (dotted line) and 50% (dashed line). Note that the gating windows are expressed as the fraction of the total amount of the acquired data.

Figure 3

Respiratory and cardiac self-gating signals were compared with bellows and ECG signals. Cardiac self-gating (solid line) and ECG (dashed line) signals were synchronized in a), presented by stars and circles, respectively. Respiratory self-gating (solid line) and bellows (dashed line) signals were synchronized in b). Amplitudes of all curves were rescaled for display purposes only.

Figure 4

Short axis views acquired with respiratory and cardiac self-gated free-breathing 3D technique were compared by using different respiratory gating windows: a) 20%, b) 50%, c) 75%, d) 100%, and e) 50% with temporal filtering. Data were acquired in a healthy volunteer with a heart rate of 75 bpm and a respiratory rate of 11 bpm. Images at end systole are shown.

Figure 5

Short axis cine images obtained with the proposed self-gated free-breathing 3D technique (right block) were compared with those with ECG-gated multiple breath-hold 2D technique (left block). Data were acquired from a healthy volunteer with a heart rate of 53 bpm and a respiratory of 19 bpm. Images of three representative slices (rows) at end diastole and end systole are shown. A temporal filter and a respiratory gating window of 50% was used for the 3D results.

Figure 6

Four-chamber (left block) and two-chamber views (right block) obtained with ECG-gated breath-hold 2D technique a)c) and the proposed self-gated free-breathing 3D technique b)d) are shown.

Figure 7

Reformatted four-chamber views of the standard 2D and the proposed 3D short axis images were compared. The multiple breath-hold 2D imaging a) suffered slice misregistration errors, which were not presented in 3D imaging, b).

Figure 8

Comparisons of functional measurements obtained with the standard 2D method and the proposed self-gated 3D technique are presented. The first row exhibits the LVEDV, LVESV, LVEF, and LVEDM measurements of the two techniques, with the 2D measurements along the horizontal axis and 3D measurements along the vertical axis. The second row shows the Bland-Altman plots of those measurements. The dashed lines show the mean bias and the confidence interval.