Skip to main content

Advertisement

  • Poster presentation
  • Open Access

Self-navigated three-dimensional cardiac T2 mapping at 3T

  • 1, 2,
  • 2, 3,
  • 1, 2,
  • 4 and
  • 1, 2
Journal of Cardiovascular Magnetic Resonance201315 (Suppl 1) :P51

https://doi.org/10.1186/1532-429X-15-S1-P51

  • Published:

Keywords

  • Healthy Adult Subject
  • Affine Registration
  • Isotropic Spatial Resolution
  • Radial Acquisition
  • Proximal Left Circumflex

Background

Cardiac T2 mapping using a variable T2 preparation module (T2Prep) has recently gained attention for its ability to quantify the extent of edema (Giri, JCMR 2009). Due to time constraints, the T2 maps are commonly acquired as one or several two-dimensional slices, while the underlying pathology has a three-dimensional (3D) structure. The next logical step would therefore be to exploit recent hardware and software advances to directly acquire 3D T2 maps. To this end, we tested the feasibility of using a self-navigated 3D radial acquisition with a variable T2Prep for 3D T2 mapping at 3T.

Methods

Approval was obtained from the institutional review board. A 3D self-navigated undersampled balanced steady-state free precession (bSSFP) sequence (TR/TE=2.6/1.33ms, matrix 1283, flip angle 70°) with a spiral phyllotaxis radial 3D trajectory (Piccini, MRM 2011) was implemented on a 3T clinical system (Skyra, Siemens AG). This self-navigated pulse sequence allows free breathing acquisitions with 100% scan efficiency, while ECG triggering every 2 heartbeats and TET2Prep=60/30/0ms allow for a total acquisition time of ~18min with an isotropic spatial resolution of (1.7mm)3. The datasets were registered using 3D affine registration (Studholme, Med Image Anal 1996). Through Bloch equation simulations, the heart-rate-dependent T1 -relaxation-related offset in the T2-fitting equation was ascertained. Subsequently, the validity and accuracy of the T2 fitting was tested in a phantom whose "true" T2 values were previously determined. The in vivo robustness of the T2 determination was then tested in 9 healthy adult subjects. Finally, the sequence was applied for the detection of edema in a 75-year-old male infarct patient after revascularization of his proximal left circumflex.

Results

The Bloch equation simulations of the pulse sequence demonstrated that the input T2 value could be accurately fitted from the magnetization M with the equation [M=M 0e -TET2Prep/T2 +0.08M0], while the fitted T2 had only a ~3% variation over the common range of heart rates (Fig.1A). The phantom T2 maps demonstrated high homogeneity and fitting accuracy with the 3D sequence matching the ‘true' value to within 1% (Fig.1B). The volunteer study (Fig.2A-C) suggested good agreement with previously reported T2 values at T2=39.3±3.9ms (Van Heeswijk, JACC Imaging 2012, in press). A region of significantly elevated T2 (60.4±9.1 vs. 41.0±4.5ms) was identified in the patient in the infero-lateral myocardium of the left ventricle (Fig.2D,E), consistent with the findings on X-ray coronary angiography.
Figure 1
Figure 1

A) Bloch equation simulation demonstrating that the dependence of the T2 fit of the magnetization on the heart rate due to varying T1 relaxation is relatively low (between 43 and 46ms, a variation of 3%), while the "true" input T2 was 45ms. B) T2 map of a phantom that approximates arterial blood and myocardium. The T2 values of the two ‘myocardium' compartments (turquoise) are very similar at 35.3±2.1ms and 35.5±2.4ms and within 1% of the "‘true" T2 value of 35.6ms.

Figure 2
Figure 2

A-C) Axial, sagittal and coronal multi-planar reformatted T2 maps through the LV of a healthy volunteer. The myocardium is well defined and T2=41.3±2.1ms. D) A sagittal T2 map of a patient with a subacute myocardial infarction demonstrates elevated T2=62.4±9.2ms in the inferior and infero-lateral segments (arrows). E) 3D segmented LV at a sub-endocardial surface as seen from a posterior position, with a clearly visible inferior and infero-lateral infarction.

Conclusions

The proposed technique provides an easy and time-efficient way to obtain accurate isotropic T2 maps of the whole heart. Accurate T2 values were obtained in the phantom, while those in volunteers are consistent with previously reported values. The preliminary patient study demonstrated elevated T2 in the infarcted region as expected.

Funding

Foundation Emma Muschamp

Authors’ Affiliations

(1)
Department of Radiology, University Hospital (CHUV) and University (UNIL) of Lausanne, Lausanne, Switzerland
(2)
Center for Biomedical Imaging (CIBM), Lausanne, Switzerland
(3)
Siemens Schweiz AG, Healthcare Sector, Lausanne, Switzerland
(4)
Cardiology and Cardiac MR Center, University Hospital of Lausanne (CHUV), Lausanne, Switzerland

Copyright

© van Heeswijk et al; licensee BioMed Central Ltd. 2013

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.

Advertisement