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Assessment of Myocardial Fibrosis in Mice Using a T2*-Weighted 3D Radial Magnetic Resonance Imaging Sequence.

van Nierop BJ, Bax NA, Nelissen JL, Arslan F, Motaal AG, de Graaf L, Zwanenburg JJ, Luijten PR, Nicolay K, Strijkers GJ - PLoS ONE (2015)

Bottom Line: Detection of short T2* species resulting from fibrotic tissue may provide an attractive non-contrast-enhanced alternative to directly visualize the presence of both replacement and interstitial fibrosis.Infarct T2*slow decreased significantly, while a moderate decrease was observed in remote tissue in post-MI hearts and in TAC hearts.However, in vivo contrast on subtraction images was rather poor, hampering a straightforward visual assessment of the spatial distribution of the fibrotic tissue.

View Article: PubMed Central - PubMed

Affiliation: Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.

ABSTRACT

Background: Myocardial fibrosis is a common hallmark of many diseases of the heart. Late gadolinium enhanced MRI is a powerful tool to image replacement fibrosis after myocardial infarction (MI). Interstitial fibrosis can be assessed indirectly from an extracellular volume fraction measurement using contrast-enhanced T1 mapping. Detection of short T2* species resulting from fibrotic tissue may provide an attractive non-contrast-enhanced alternative to directly visualize the presence of both replacement and interstitial fibrosis.

Objective: To goal of this paper was to explore the use of a T2*-weighted radial sequence for the visualization of fibrosis in mouse heart.

Methods: C57BL/6 mice were studied with MI (n = 20, replacement fibrosis), transverse aortic constriction (TAC) (n = 18, diffuse fibrosis), and as control (n = 10). 3D center-out radial T2*-weighted images with varying TE were acquired in vivo and ex vivo (TE = 21 μs-4 ms). Ex vivo T2*-weighted signal decay with TE was analyzed using a 3-component model. Subtraction of short- and long-TE images was used to highlight fibrotic tissue with short T2*. The presence of fibrosis was validated using histology and correlated to MRI findings.

Results: Detailed ex vivo T2*-weighted signal analysis revealed a fast (T2*fast), slow (T2*slow) and lipid (T2*lipid) pool. T2*fast remained essentially constant. Infarct T2*slow decreased significantly, while a moderate decrease was observed in remote tissue in post-MI hearts and in TAC hearts. T2*slow correlated with the presence of diffuse fibrosis in TAC hearts (r = 0.82, P = 0.01). Ex vivo and in vivo subtraction images depicted a positive contrast in the infarct co-localizing with the scar. Infarct volumes from histology and subtraction images linearly correlated (r = 0.94, P<0.001). Region-of-interest analysis in the in vivo post-MI and TAC hearts revealed significant T2* shortening due to fibrosis, in agreement with the ex vivo results. However, in vivo contrast on subtraction images was rather poor, hampering a straightforward visual assessment of the spatial distribution of the fibrotic tissue.

No MeSH data available.


Related in: MedlinePlus

In vivo T2*-weighted images in control heart, a MI heart and a TAC heart.Examples of a short-axis cross-section of a control heart (top row), a MI heart (middle row) and a TAC heart (bottom row) obtained with the T2*-weighted 3D sequence (short-TE, long-TE and ΔUTE image). LGE scans were obtained in control and post-MI mice (right column). The arrows indicate the infarcted areas.
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pone.0129899.g005: In vivo T2*-weighted images in control heart, a MI heart and a TAC heart.Examples of a short-axis cross-section of a control heart (top row), a MI heart (middle row) and a TAC heart (bottom row) obtained with the T2*-weighted 3D sequence (short-TE, long-TE and ΔUTE image). LGE scans were obtained in control and post-MI mice (right column). The arrows indicate the infarcted areas.

Mentions: Direct visual assessment of the fibrosis in the in vivo ΔUTE images, however, proved more challenging (Fig 5). ΔUTE images of the post-MI hearts revealed areas with hyperenhancement, which co-localized with the MI as independently determined by LGE. However, ΔUTE contrast was significantly less pronounced compared to the ex vivo measurements and in many cases difficult to distinguish visually. As expected for diffuse fibrosis, in the TAC hearts no focal hyperenhancement was observed (Fig 5). Nevertheless, an ROI-based ΔUTE signal differences of control, post-MI and TAC mice (Fig 6) demonstrated that ΔUTE signal in the MI (0.26±0.10) was significantly higher than that in remote tissue (0.20±0.06, P<0.05). Moreover, the ΔUTE signal in the remote tissue of the post-MI hearts (0.20±0.06) and that in the TAC hearts (0.21±0.07) was larger as compared to that in the control hearts (0.13±0.04, P<0.001 vs. post-MI, and P<0.001 vs. TAC). We attribute the latter signal difference to the presence of diffuse fibrosis in these hearts, in line with the ex vivo results of Fig 3.


Assessment of Myocardial Fibrosis in Mice Using a T2*-Weighted 3D Radial Magnetic Resonance Imaging Sequence.

van Nierop BJ, Bax NA, Nelissen JL, Arslan F, Motaal AG, de Graaf L, Zwanenburg JJ, Luijten PR, Nicolay K, Strijkers GJ - PLoS ONE (2015)

In vivo T2*-weighted images in control heart, a MI heart and a TAC heart.Examples of a short-axis cross-section of a control heart (top row), a MI heart (middle row) and a TAC heart (bottom row) obtained with the T2*-weighted 3D sequence (short-TE, long-TE and ΔUTE image). LGE scans were obtained in control and post-MI mice (right column). The arrows indicate the infarcted areas.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4482648&req=5

pone.0129899.g005: In vivo T2*-weighted images in control heart, a MI heart and a TAC heart.Examples of a short-axis cross-section of a control heart (top row), a MI heart (middle row) and a TAC heart (bottom row) obtained with the T2*-weighted 3D sequence (short-TE, long-TE and ΔUTE image). LGE scans were obtained in control and post-MI mice (right column). The arrows indicate the infarcted areas.
Mentions: Direct visual assessment of the fibrosis in the in vivo ΔUTE images, however, proved more challenging (Fig 5). ΔUTE images of the post-MI hearts revealed areas with hyperenhancement, which co-localized with the MI as independently determined by LGE. However, ΔUTE contrast was significantly less pronounced compared to the ex vivo measurements and in many cases difficult to distinguish visually. As expected for diffuse fibrosis, in the TAC hearts no focal hyperenhancement was observed (Fig 5). Nevertheless, an ROI-based ΔUTE signal differences of control, post-MI and TAC mice (Fig 6) demonstrated that ΔUTE signal in the MI (0.26±0.10) was significantly higher than that in remote tissue (0.20±0.06, P<0.05). Moreover, the ΔUTE signal in the remote tissue of the post-MI hearts (0.20±0.06) and that in the TAC hearts (0.21±0.07) was larger as compared to that in the control hearts (0.13±0.04, P<0.001 vs. post-MI, and P<0.001 vs. TAC). We attribute the latter signal difference to the presence of diffuse fibrosis in these hearts, in line with the ex vivo results of Fig 3.

Bottom Line: Detection of short T2* species resulting from fibrotic tissue may provide an attractive non-contrast-enhanced alternative to directly visualize the presence of both replacement and interstitial fibrosis.Infarct T2*slow decreased significantly, while a moderate decrease was observed in remote tissue in post-MI hearts and in TAC hearts.However, in vivo contrast on subtraction images was rather poor, hampering a straightforward visual assessment of the spatial distribution of the fibrotic tissue.

View Article: PubMed Central - PubMed

Affiliation: Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.

ABSTRACT

Background: Myocardial fibrosis is a common hallmark of many diseases of the heart. Late gadolinium enhanced MRI is a powerful tool to image replacement fibrosis after myocardial infarction (MI). Interstitial fibrosis can be assessed indirectly from an extracellular volume fraction measurement using contrast-enhanced T1 mapping. Detection of short T2* species resulting from fibrotic tissue may provide an attractive non-contrast-enhanced alternative to directly visualize the presence of both replacement and interstitial fibrosis.

Objective: To goal of this paper was to explore the use of a T2*-weighted radial sequence for the visualization of fibrosis in mouse heart.

Methods: C57BL/6 mice were studied with MI (n = 20, replacement fibrosis), transverse aortic constriction (TAC) (n = 18, diffuse fibrosis), and as control (n = 10). 3D center-out radial T2*-weighted images with varying TE were acquired in vivo and ex vivo (TE = 21 μs-4 ms). Ex vivo T2*-weighted signal decay with TE was analyzed using a 3-component model. Subtraction of short- and long-TE images was used to highlight fibrotic tissue with short T2*. The presence of fibrosis was validated using histology and correlated to MRI findings.

Results: Detailed ex vivo T2*-weighted signal analysis revealed a fast (T2*fast), slow (T2*slow) and lipid (T2*lipid) pool. T2*fast remained essentially constant. Infarct T2*slow decreased significantly, while a moderate decrease was observed in remote tissue in post-MI hearts and in TAC hearts. T2*slow correlated with the presence of diffuse fibrosis in TAC hearts (r = 0.82, P = 0.01). Ex vivo and in vivo subtraction images depicted a positive contrast in the infarct co-localizing with the scar. Infarct volumes from histology and subtraction images linearly correlated (r = 0.94, P<0.001). Region-of-interest analysis in the in vivo post-MI and TAC hearts revealed significant T2* shortening due to fibrosis, in agreement with the ex vivo results. However, in vivo contrast on subtraction images was rather poor, hampering a straightforward visual assessment of the spatial distribution of the fibrotic tissue.

No MeSH data available.


Related in: MedlinePlus