2D Steady-state Free Precession Imaging Research Articles

Free breathing 2D multi-slice real-time gradient-echo cardiovascular magnetic resonance imaging: impact on left ventricular function measurements compared with standard multi-breath hold 2D steady-state free precession imaging

Objective Multi-breath hold cine-imaging (standard-2D-SSFP) is the standard technique for ventricular function assessment. However, image acquisition is time-consuming and breath holding is required. Ultrafast 2D real-time imaging (2D real time-SSFP) does not require breath holding, but spatial resolution is sacrifi ced. The accuracy of 2D real time-SSFP free-breathing ventricular function assessment by using an automated contour detection programme has not been systematically studied.Methods and results Twenty-eight subjects (14 with impaired LV function) were investigated by 1.5 Tesla magnetic resonance imaging. Left ventricular short-axis images were acquired with multi-breath hold standard 2D-SSFP and free-breathing 2D real time-SSFP. LV-volumes (EDV, ESV), EF, and mass were determined using a semi-automated contour detection programme.EDV, ESV, EF, and mass were not signifi cantly diff erent between real time- and standard 2D-SSFP in subjects (absolute diff erences: EDV 3.2 ± 0.7 mL, ESV 3.0 ± 0.3 mL, EF 1.9 ± 0.4 %, mass 0.8 ± 0.4 g; P≥ 0.78) and patients (absolute diff erences: EDV = 3.0 ± 0.8 mL, ESV 3.3 ± 1.0 mL, EF 0.9 ± 0.5 %, mass 0.9 ± 0.5 g; P≥ 0.73). Automated contour detection required extensive manual correction for real-time imaging (≤ 86%).Conclusions Diff erences in LV function measurements between real-time and standard 2D-SSFP are small, and not signifi cant. Real-time SSFP may be used for rapid LV function assessment when examination time is limited.

Influence of adenosine on ventricular function measurements as part of a comprehensive stress perfusion magnetic resonance imaging study

Stress-rest perfusion magnetic resonance imaging (MRI) has become one of the major indications for cardiovascular MRI. Standard multibreath hold short-axis image acquisition is the gold standard for LV function assessment and part of a comprehensive stress-rest perfusion MRI study, but takes up to 10 min. The total scan time could significantly be shortened when cine imaging would be performed between stress and rest perfusion. To systematically study whether adenosine, albeit its short half-life time, influences LV function measurements in this setting. Thirty-nine patients with suspected and/or known coronary artery disease underwent 3-Tesla adenosine (140 µg/min/kg) stress-rest perfusion MRI. A stack of short-axis slices covering the entire ventricles was acquired before and ≥3 min after adenosine infusion using standard multibreath-hold 2D steady-state free precession imaging. LV volumes (EDV, ESV), EF, and mass were calculated by the slice summation method, and wall motion was assessed using a 4-point scoring scale. Reproducibility was assessed by Bland-Altman statistics. EDV, ESV, EF, and mass were not significantly different between the two imaging time points (before versus after adenosine administration) in all patients (P ≥ 0.346) and patients with impaired LV function (P ≥ 0.718). Wall motion scores did not differ either (P ≥ 0.124). Inter-observer variability before (P ≥ 0.468) and after (P ≥ 0.451) adenosine infusion was low. Short-axis cine imaging for LV function assessment can accurately be performed between stress and rest imaging. These data demonstrate that potential effects of adenosine on LV function are of short duration, and propose a new time-saving imaging protocol without compromising accuracy.

Fast 3D Cine Steady-State Free Precession Imaging with Sensitivity Encoding for Assessment of Left Ventricular Function in a Single Breath-Hold

This study compares single breath-hold 3D cine steady-state free precession (SSFP) MRI using sensitivity encoding (SENSE) with standard 2D cine SSFP imaging in the quantitative evaluation of global left ventricular (LV) function. The LV function of 22 healthy volunteers and 15 patients was evaluated using a standard 2D SSFP sequence and a 3D SSFP sequence with SENSE at 1.5 T. Ventricular volume, ejection fraction, and LV mass were calculated with each method, and signal-to-noise ratios (SNRs) and myocardium-to-blood contrast-to-noise ratios (CNRs) were measured. Agreement between the two methods was assessed using Bland-Altman analysis, and results were compared using a paired Student's t test (p < 0.05). The local institutional review board approved the study protocol, and all participants gave signed informed consent. The study complied with the Health Insurance Portability and Accountability Act. Both techniques produced similar estimates of ejection fraction (mean bias +/- SD, -1.2% +/- 3.6%) and LV mass (mean bias, +/- SD-1.2 +/- 10.9 g). No significant differences were found in calculated volumes, ejection fraction, or LV mass between the two methods. Acquisition time was reduced by 82%, to a single breath-hold (18 +/- 3 seconds), with the 3D SSFP technique. SNR and CNR were significantly lower with the 3D method than with the standard method. Three-dimensional SSFP imaging with SENSE can reduce acquisition time to a single breath-hold and can provide LV function quantification comparable to that obtained with conventional 2D SSFP imaging.

Catheter-directed MR Angiography and Cross-sectional Imaging for the Assessment of Renal Artery Stenosis

Catheter-directed intraarterial (IA) gadolinium (Gd)-enhanced gradient-echo (GRE) imaging has been used in the setting of magnetic resonance (MR) imaging-guided endovascular procedures for two-dimensional (2D) or three-dimensional (3D) depiction of blood vessels. In a swine model, the hypothesis was tested that the combination of 2D IA GRE and 2D cross-sectional steady-state free precession (SSFP) imaging improves assessment of renal artery stenosis (RAS) compared with 3D IA GRE imaging alone. Bilateral RAS was surgically induced in seven pigs. Detection of stenoses was then compared between the combination of 2D projection IA GRE and cross-sectional 2D SSFP imaging without contrast agent and 3D IA GRE alone. Radiographic digital subtraction angiography (DSA) was employed as the reference standard. Linear regression was used to compare stenosis measurements, with an alpha of 0.05. Radiographic DSA and MR imaging were successful in the seven animals (14 stenoses). With use of linear regression analysis, the combination of 2D IA GRE and 2D SSFP imaging had a higher r(2) (0.87 vs 0.72) and a slope closer to unity (1.02 vs 0.77) compared with 3D IA GRE imaging alone. When comparing intercepts, the regression line for SSFP significantly differed from that of 3D IA GRE imaging (P < .05). The combination of 2D IA GRE and cross-sectional 2D SSFP imaging improves the accuracy of RAS detection compared with IA 3D IA-GRE alone.

Effects of view ordering and dummy pulse rate on two-dimensional and three-dimensional steady-state free precession imaging 1

Rationale and Objective. To assess the effects of view ordering and dummy pulse rate on the image quality of steady-state free precession (SSFP) imaging. Material and Methods. Two- and three-dimensional (2D and 3D) SSFP imaging with various view orderings (eg, centric, sequential, reverse centric) and dummy pulse rates were performed in the phantom including several concentrations of gadolinium and patients. Results. Centric view orderings increased the noise in 3D SSFP images in the phantom. In the patients studied, the centric view ordering increased the signals obtained from abdominal organs in 2D and 3D SSFP and the background signal in 3D images, without changing the vascular signals. An increased dummy pulse rate reduced the background signal in 2D SSFP, but not in 3D SSFP. Conclusion. Sequential ordering is recommended for both 2D and 3D SSFP, and centric view ordering combined with an increase in dummy pulse rate can be used for 2D imaging.