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Clinical validation of free breathing Respiratory Triggered Retrospectively Cardiac Gated Cine Steady-State Free Precession (RT-SSFP) imaging in sedated children
Journal of Cardiovascular Magnetic Resonance volume 15, Article number: O98 (2013)
Cine steady-state free precession (SSFP) is the preferred sequence for ventricular function evaluation. However, SSFP demands uninterrupted RF excitation to maintain steady-state (SS) during suspended respiration. This is feasible in adults who can perform breath-holding (BH), but is difficult to accomplish in sedated or uncooperative children. To overcome this, many pediatric groups routinely perform multi-NSA acquisitions (MN) during free breathing. In this work, we validate a respiratory triggered (RT) SSFP sequence that drives the magnetization to steady-state before commencing cardiac gated cine acquisition in sedated pediatric population.
This prospective study was performed on 12 sedated children with congenital heart disease (age: 7±3 yrs) with IRB approval.
All imaging was performed on a commercial MR scanner (1.5 T, Achieva, Philips Healthcare). Identical imaging parameters were used for MN and RT cine SSFP sequences  covering both the ventricles in short-axis (SA) orientation (TR/TE/flip angle: 3/1.5/60; acquired voxel size: 1.5-1.9 x 1.5-2.1 x 7-8 mm3; SENSE acceleration factor: 2; temporal resolution: 30-45 ms; acquisition time: 8-10 RR intervals/slice).
Image quality assessment (Figure 1) and quantitative volumetric analysis was performed on the datasets by independent blinded users. One-sided Wilcoxon signed rank test and Box plot analysis were performed to compare the RT-SSFP clinical scores against MN-SSFP. Bland-Altman (BA) analysis was performed on LV and RV volumes.
The clinical scores for RT-SSFP were consistently better than MN-SSFP (Figure 1). BA analysis (Table. 1) indicates that variability between RT and MN acquisitions is comparable to inter and intra-observer variability reported in the literature . In sedated children, the BMC (p=0.06) and EDef (p=0.06) scores were significantly better for RT-SSFP than MN-SSFP while ISA (p=0.5) was comparable. The ISA due to inconsistent respiration level leads to inconsistent estimation of basal LV volume which can explain the variability in EDV and ESV using two different acquisitions. Total score (with equal weights to each clinical score category) was significantly better for RT compared to MN (p=0.03). Total scan duration for SA stack using RT-SSFP (4.1±0.97 min) was slightly shorter than MN-SSFP (4.6±0.9 min) acquisitions.
The free breathing RT-SSFP sequence allows clinically diagnostic images in sedated children without any penalty for total scan time, and offers improved myocardial blood-pool contrast, and edge definition when compared to MN-SSFP.
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Krishnamurthy, R., Pednekar, A., Vogelius, E. et al. Clinical validation of free breathing Respiratory Triggered Retrospectively Cardiac Gated Cine Steady-State Free Precession (RT-SSFP) imaging in sedated children. J Cardiovasc Magn Reson 15, O98 (2013). https://doi.org/10.1186/1532-429X-15-S1-O98
- Image Quality Assessment
- Free Breathing
- Blinded User
- Respiratory Trigger
- Sedate Child