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R2* for myocardial iron quantification at 3T CMR using an advanced shimming algorithm

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Journal of Cardiovascular Magnetic Resonance201315 (Suppl 1) :P38

https://doi.org/10.1186/1532-429X-15-S1-P38

  • Published:

Keywords

  • Hemochromatosis
  • Chelate Therapy
  • Diagnostic Image Quality
  • Strong Linear Correlation
  • Iron Chelate Therapy

Background

Quantification of myocardial iron overload is critical for the management of patients with hemochromatosis. T2* relaxation time or its inverse R2*, are currently the non-invasive gold standard at 1.5T, as they strongly correlate with myocardial iron concentration, and are obtained using a fast single breath-hold ECG-gated multi-echo GRE sequence. However, due to high sensitivity to B0 inhomogeneities, R2* (1/T2*) quantification at 3T is still challenging. We aimed to evaluate if a recently developed advanced shimming protocol based on a GRE double-echo fieldmap acquisition, can improve the performance of R2* quantification at 3T.

Methods

A total of 15 normal volunteers and 7 hemochromatosis patients (with a myocardial T2* measure <20 ms in the last 2 years, five of these on iron chelating therapy) were scanned at 1.5T and 3T (MAGNETOM Symphony and Verio respectively, Siemens, Erlangen, Germany) using breath-hold multi-echo GRE sequences, under standard entire FOV shimming (Protocol1). The same sequence was repeated at 3T after a double-echo GRE fieldmap guided a novel 3D shimming with the shim volume limited to the heart (Protocol2). All ROIs were placed at mid-interventricular septum, carefully avoiding the blood pool and all analyses were blinded.

Results

All patients were at sinus rhythm and their MRI scans had diagnostic image quality. Mean myocardial R2* values were not statistically different between protocols 1 and 2 (65.2±51.3 Hz and 68.6±56.8 Hz respectively, p=0.83). R2* in both 3T protocols showed strong linear correlation with R2* at 1.5T, with r=0.98 in both cases (Figure 1). R2* measurements with and without advanced shimming had excellent correlation with each other (r=0.99), with small bias (mean difference of 3.5±8.6 ms) as shown in Figure 2.
Figure 1
Figure 1

Linear regression between R2* measurements at 3T with standard shimming and R2* at 1.5T

Figure 2
Figure 2

Bland-Altman plot of the R2* measurements at 3T performed with and without GRE shimming.

Conclusions

In sustained shimmed 3T systems, R2* quantification can be reliably performed using standard shimming protocol, in strong correlation with 1.5T reference values. Our results do not show improvement in performance of R2* measurement using a new volume targeted shimming algorithm developed for 3T.

Funding

Internal

Authors’ Affiliations

(1)
CDPI - Clínica de Diagnóstico por Imagem, Rio de Janeiro, Brazil
(2)
Siemens LTDA, São Paulo, Brazil
(3)
Siemens Healthcare, Erlangen, Germany
(4)
Cardiology, Johns Hopkins University, Baltimore, MD, USA

Copyright

© Camargo 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.

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