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Cardiac T2-mapping using a fast gradient echo spin echo sequence - first in vitro and in vivo experience.

Baeßler B, Schaarschmidt F, Stehning C, Schnackenburg B, Maintz D, Bunck AC - J Cardiovasc Magn Reson (2015)

Bottom Line: Both, GraSE and T2prep resulted in an overestimation of T2 times compared to MESE.In general, T2prep resulted in lowest (52.4 ± 2.8 ms) and GraSE in highest T2 estimates (59.3 ± 4.0 ms).Our study revealed significant differences of derived mean T2 values when applying different sequence designs.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, University Hospital of Cologne, Kerpener Str. 62, D-50937, Cologne, Germany. bettina.baessler@uk-koeln.de.

ABSTRACT

Background: The aim of this study was the evaluation of a fast Gradient Spin Echo Technique (GraSE) for cardiac T2-mapping, combining a robust estimation of T2 relaxation times with short acquisition times. The sequence was compared against two previously introduced T2-mapping techniques in a phantom and in vivo.

Methods: Phantom experiments were performed at 1.5 T using a commercially available cylindrical gel phantom. Three different T2-mapping techniques were compared: a Multi Echo Spin Echo (MESE; serving as a reference), a T2-prepared balanced Steady State Free Precession (T2prep) and a Gradient Spin Echo sequence. For the subsequent in vivo study, 12 healthy volunteers were examined on a clinical 1.5 T scanner. The three T2-mapping sequences were performed at three short-axis slices. Global myocardial T2 relaxation times were calculated and statistical analysis was performed. For assessment of pixel-by-pixel homogeneity, the number of segments showing an inhomogeneous T2 value distribution, as defined by a pixel SD exceeding 20 % of the corresponding observed T2 time, was counted.

Results: Phantom experiments showed a greater difference of measured T2 values between T2prep and MESE than between GraSE and MESE, especially for species with low T1 values. Both, GraSE and T2prep resulted in an overestimation of T2 times compared to MESE. In vivo, significant differences between mean T2 times were observed. In general, T2prep resulted in lowest (52.4 ± 2.8 ms) and GraSE in highest T2 estimates (59.3 ± 4.0 ms). Analysis of pixel-by-pixel homogeneity revealed the least number of segments with inhomogeneous T2 distribution for GraSE-derived T2 maps.

Conclusions: The GraSE sequence is a fast and robust sequence, combining advantages of both MESE and T2prep techniques, which promises to enable improved clinical applicability of T2-mapping in the future. Our study revealed significant differences of derived mean T2 values when applying different sequence designs. Therefore, a systematic comparison of different cardiac T2-mapping sequences and the establishment of dedicated reference values should be the goal of future studies.

No MeSH data available.


Assessment of segmental pixel-by-pixel homogeneity. Percentage of segments demonstrating a pixel SD exceeding 20 % of the corresponding observed T2 times (orange; inhomogeneous) and not exceeding 20 % of the corresponding observed T2 times (green, homogeneous), separately for each sequence
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Fig4: Assessment of segmental pixel-by-pixel homogeneity. Percentage of segments demonstrating a pixel SD exceeding 20 % of the corresponding observed T2 times (orange; inhomogeneous) and not exceeding 20 % of the corresponding observed T2 times (green, homogeneous), separately for each sequence

Mentions: Analysis of pixel-by-pixel homogeneity per segment revealed a variability of T2 values by a standard deviation of more than 20 % of the mean T2 time of the corresponding segment in 8 % of all analyzed myocardial segments. The highest number of segments meeting the definition of inhomogeneity was found for T2prep (14 %), followed by MESE (10 %) (Fig. 4). Conversely, GraSE showed only a relatively small number of segments affected by inhomogeneity (5 %). The difference in the number of inhomogeneous segments between GraSE and T2prep proved to be significant at the 5 % level (p = 0.027).Fig. 4


Cardiac T2-mapping using a fast gradient echo spin echo sequence - first in vitro and in vivo experience.

Baeßler B, Schaarschmidt F, Stehning C, Schnackenburg B, Maintz D, Bunck AC - J Cardiovasc Magn Reson (2015)

Assessment of segmental pixel-by-pixel homogeneity. Percentage of segments demonstrating a pixel SD exceeding 20 % of the corresponding observed T2 times (orange; inhomogeneous) and not exceeding 20 % of the corresponding observed T2 times (green, homogeneous), separately for each sequence
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4522069&req=5

Fig4: Assessment of segmental pixel-by-pixel homogeneity. Percentage of segments demonstrating a pixel SD exceeding 20 % of the corresponding observed T2 times (orange; inhomogeneous) and not exceeding 20 % of the corresponding observed T2 times (green, homogeneous), separately for each sequence
Mentions: Analysis of pixel-by-pixel homogeneity per segment revealed a variability of T2 values by a standard deviation of more than 20 % of the mean T2 time of the corresponding segment in 8 % of all analyzed myocardial segments. The highest number of segments meeting the definition of inhomogeneity was found for T2prep (14 %), followed by MESE (10 %) (Fig. 4). Conversely, GraSE showed only a relatively small number of segments affected by inhomogeneity (5 %). The difference in the number of inhomogeneous segments between GraSE and T2prep proved to be significant at the 5 % level (p = 0.027).Fig. 4

Bottom Line: Both, GraSE and T2prep resulted in an overestimation of T2 times compared to MESE.In general, T2prep resulted in lowest (52.4 ± 2.8 ms) and GraSE in highest T2 estimates (59.3 ± 4.0 ms).Our study revealed significant differences of derived mean T2 values when applying different sequence designs.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, University Hospital of Cologne, Kerpener Str. 62, D-50937, Cologne, Germany. bettina.baessler@uk-koeln.de.

ABSTRACT

Background: The aim of this study was the evaluation of a fast Gradient Spin Echo Technique (GraSE) for cardiac T2-mapping, combining a robust estimation of T2 relaxation times with short acquisition times. The sequence was compared against two previously introduced T2-mapping techniques in a phantom and in vivo.

Methods: Phantom experiments were performed at 1.5 T using a commercially available cylindrical gel phantom. Three different T2-mapping techniques were compared: a Multi Echo Spin Echo (MESE; serving as a reference), a T2-prepared balanced Steady State Free Precession (T2prep) and a Gradient Spin Echo sequence. For the subsequent in vivo study, 12 healthy volunteers were examined on a clinical 1.5 T scanner. The three T2-mapping sequences were performed at three short-axis slices. Global myocardial T2 relaxation times were calculated and statistical analysis was performed. For assessment of pixel-by-pixel homogeneity, the number of segments showing an inhomogeneous T2 value distribution, as defined by a pixel SD exceeding 20 % of the corresponding observed T2 time, was counted.

Results: Phantom experiments showed a greater difference of measured T2 values between T2prep and MESE than between GraSE and MESE, especially for species with low T1 values. Both, GraSE and T2prep resulted in an overestimation of T2 times compared to MESE. In vivo, significant differences between mean T2 times were observed. In general, T2prep resulted in lowest (52.4 ± 2.8 ms) and GraSE in highest T2 estimates (59.3 ± 4.0 ms). Analysis of pixel-by-pixel homogeneity revealed the least number of segments with inhomogeneous T2 distribution for GraSE-derived T2 maps.

Conclusions: The GraSE sequence is a fast and robust sequence, combining advantages of both MESE and T2prep techniques, which promises to enable improved clinical applicability of T2-mapping in the future. Our study revealed significant differences of derived mean T2 values when applying different sequence designs. Therefore, a systematic comparison of different cardiac T2-mapping sequences and the establishment of dedicated reference values should be the goal of future studies.

No MeSH data available.