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  • Workshop presentation
  • Open Access

Highly accelerated real-time T2-weighted imaging with through-time radial GRAPPA and low-latency GPU reconstruction

  • 1,
  • 2,
  • 3,
  • 4,
  • 4,
  • 4,
  • 5, 6,
  • 6 and
  • 1
Journal of Cardiovascular Magnetic Resonance201416 (Suppl 1) :W33

https://doi.org/10.1186/1532-429X-16-S1-W33

  • Published:

Keywords

  • Acute Myocardial Infarction
  • High Temporal Resolution
  • Acute Injury
  • Radial Sequence
  • Latency Reconstruction

Background

T2-weighted cardiac images are commonly used for edema detection [14]. However, neither black-blood TSE nor cine images can offer real-time edema monitoring, and are therefore not suitable for the guidance of cardiac ablation procedures. We proposed a radial T2-weighted interrupted balanced SSFP (rT2W-iSSFP), a real-time high temporal resolution sequence targeted at monitoring edema.

Methods

Sequence

rT2W-iSSFP generates T2-weighting with a series of 180° RF pulses. TE-effective for the radial sequence is defined as the time from the beginning of the train to the median imaging echo. rT2W-iSSFP also incorporates through-time radial GRAPPA to achieve high temporal resolution with high degrees of acceleration (R = 8) [5], (Figure 1) which was implemented on a 48-core hybrid system with a GPU (Tesla C1060, NVIDIA), achieving 10-20 fps image acquisition with 20 ms latency reconstruction and image display [6].
Figure 1
Figure 1

Illustration of the acquisition scheme, flip angles and k-space sampling pattern of rT 2 W-iSSFP. Four-fold acceleration is shown in this example. Images were reconstructed using through-time radial GRAPPA with a low-latency implementation. Typically a 192 × 192 matrix and an acceleration rate of R = 8 is used.

Simulations

Bloch equation simulations were performed to evaluate the T2-weighting and the image quality of rT2W-iSSFP using a variant of the Shepp-Logan phantom containing 3 ellipsoids with different T1s and T2s to represent cerebrospinal fluid (CSF), liver, and myocardium (Figure 2a) [7, 8]. T2-weighted turbo spin echo (T2W-TSE) was also simulated [3, 9]. TE-effective was 60 ms for both T2W-TSE and rT2W-iSSFP.
Figure 2
Figure 2

(a) Illustration of the Shepp-Logan phantom used for simulation. (b) T2W-TSE and (c) r T2W-iSSFP were simulated. Swine with acute injury was scanned by (d) breath-hold T2W-TSE and (e) free-breathing r T2W-iSSFP as well. The edema (the arrows in d) is depicted in both d and e. In both simulation and in-vivo imaging, T2W-TSE was used as the reference of T2-weighting. Tacq - acquisition time.

Animal Model

Swine with acute injury (N = 2) were imaged on a 1.5T scanner (Avanto, Siemens, Germany). Free-breathing ECG-triggered single-shot rT2W-iSSFP was acquired (TE-effective = 80 ms; TR = 3 ms; matrix = 192 × 192; 3 slices per heartbeats). ECG-triggered, breath-held T2W-TSE (TE = 80 ms, resolution = 1 × 1 mm2, matrix = 192 × 192) was used as a reference.

Results

The results from simulation of T2W-TSE and rT2W-iSSFP are shown in Figures 2b and 2c. The intensity difference between CSF and liver is similar in T2W-TSE and rT2W-iSSFP. Streaking artifacts are seen in Figure 2c, but these are not pronounced in in vivo images. Four-chamber views of swine heart from T2W-TSE (breath-hold) and rT2W-iSSFP (free-breathing) are shown in Figures 2d and 2e. Edema at the anteroseptal region due to acute myocardial infarction is depicted (the arrows in d).

Conclusions

rT2W-iSSFP offers high temporal resolution T2-weighted imaging with image quality sufficient for visualization of edema from acute injury. rT2W-iSSFP can be applied to real-time monitoring of edema formation during cardiac interventions.

Authors’ Affiliations

(1)
Biomedical Engineering, The Johns Hopkins School of Medicine, Baltimore, Maryland, USA
(2)
Biomedical Engineering, Tsinghua University, Beijing, China
(3)
Siemens Healthcare USA, Inc., Chicago, Illinois, USA
(4)
Cardiology, The Johns Hopkins School of Medicine, Baltimore, Maryland, USA
(5)
Radiology, Case Western Reserve University, Cleveland, Ohio, USA
(6)
Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA

References

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  3. Simonetti, et al: Radiology. 1996Google Scholar
  4. Dharmakumar, et al: MRM. 2006Google Scholar
  5. Seiberlich, et al: MRM. 2011Google Scholar
  6. Saybasili, et al: ISMRM. 2013Google Scholar
  7. Paul, et al: MRM. 2006Google Scholar
  8. Derbyshire, et al: MRM. 2005Google Scholar
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Copyright

© Xu et al.; licensee BioMed Central Ltd. 2014

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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