Magnetic resonance imaging of chronic myocardial infarcts in formalin-fixed human autopsy hearts.

Hsu, Jung-Cheng; Johnson, G. Allan; Smith, William M.; Reimer, Keith A.; Re, Ideker

doi:10.1161/01.cir.89.5.2133

Cited by 22 publications

(12 citation statements)

References 31 publications

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“…As shown in the studies of the effect of immersion time, T1 and T2 continued to decrease when tissues remained in the fixative mixture (also shown by Hsu et al (15)). This suggests that a storage method is necessary to establish equilibrium between the tissues and the medium, and to maintain the desirable relaxation times achieved by the staining in the long term.…”

Section: Methodssupporting

confidence: 54%

Staining methods for magnetic resonance microscopy of the rat fetus

Petiet

Hedlund

Johnson

2007

Magnetic Resonance Imaging

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Purpose: To develop a magnetic resonance histology (MRH) staining and fixation method by immersion to enhance the signal-to-noise ratio (SNR) with a paramagnetic contrast agent permitting microscopic acquisition within a 3-hour scan time. Materials and Methods:Methods were optimized for embryonic day 18.5 (E18.5) rat fetuses and imaging at 9.4T with an RF refocused spin-echo pulse sequence (TR/TE ϭ 75 msec/5.2 msec). Fixation/staining was performed by immersion in Bouin's fixative containing varied concentrations of ProHance (from 10:1 to 500:1 Bouin's:ProHance) and for varied immersion durations (up to 24 hours). Results:The results showed a significant change in T1 and T2 relaxation times as a function of concentration of contrast agent and immersion duration. As the contrast agent penetrated the tissues, T1 was reduced as desired (typically by 10ϫ), but at the same time T2 was profoundly reduced (typically by 3ϫ) due to both protein cross-linking from the fixative and the high concentration of contrast agent. A systematic assessment of this staining protocol showed an increased SNR (by 5ϫ) over that in unstained specimens. Conclusion:This staining protocol reduced scan time for very-high-resolution images (19.5 m) to only 3 hours, making MRH a routine tool for evaluating fetal development.

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Section: Methodssupporting

confidence: 54%

Staining methods for magnetic resonance microscopy of the rat fetus

Petiet

Hedlund

Johnson

2007

Magnetic Resonance Imaging

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“…A previous study looking at T1 of formalin fixed infarcted myocardium stored for between 1 and 9 years, found significantly shorter T1 values with a T1 of 272 ± 163 ms in non-infarcted tissue and 459 ± 266 ms in infarct tissue [38]. Some previous evidence suggests that while organ iron concentration is lower after fixation in formalin or histological processing, the difference is not significant [39],[40].…”

Section: Discussionmentioning

confidence: 99%

“…The fact that a very short T1 (independent of iron concentration) was found in all the hearts which had been stored in formalin for greater than a year, suggests that the T1 shortening effect was likely to be due to the effects of formalin, but the precise reasons for this remain unclear. T2 in formalin-fixed myocardium is less affected but is also slightly shorter than the normal in-vivo level (which is around 70 ms) [38],[43]. …”

Section: Discussionmentioning

confidence: 99%

Calibration of myocardial T2 and T1 against iron concentration

Carpenter

Kirk

et al. 2014

Journal of Cardiovascular Magnetic Resonance

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BackgroundThe assessment of myocardial iron using T2* cardiovascular magnetic resonance (CMR) has been validated and calibrated, and is in clinical use. However, there is very limited data assessing the relaxation parameters T1 and T2 for measurement of human myocardial iron.MethodsTwelve hearts were examined from transfusion-dependent patients: 11 with end-stage heart failure, either following death (n = 7) or cardiac transplantation (n = 4), and 1 heart from a patient who died from a stroke with no cardiac iron loading. Ex-vivo R1 and R2 measurements (R1 = 1/T1 and R2 = 1/T2) at 1.5 Tesla were compared with myocardial iron concentration measured using inductively coupled plasma atomic emission spectroscopy.ResultsFrom a single myocardial slice in formalin which was repeatedly examined, a modest decrease in T2 was observed with time, from mean (±SD) 23.7 ± 0.93 ms at baseline (13 days after death and formalin fixation) to 18.5 ± 1.41 ms at day 566 (p < 0.001). Raw T2 values were therefore adjusted to correct for this fall over time. Myocardial R2 was correlated with iron concentration [Fe] (R2 0.566, p < 0.001), but the correlation was stronger between LnR2 and Ln[Fe] (R2 0.790, p < 0.001). The relation was [Fe] = 5081•(T2)-2.22 between T2 (ms) and myocardial iron (mg/g dry weight). Analysis of T1 proved challenging with a dichotomous distribution of T1, with very short T1 (mean 72.3 ± 25.8 ms) that was independent of iron concentration in all hearts stored in formalin for greater than 12 months. In the remaining hearts stored for <10 weeks prior to scanning, LnR1 and iron concentration were correlated but with marked scatter (R2 0.517, p < 0.001). A linear relationship was present between T1 and T2 in the hearts stored for a short period (R2 0.657, p < 0.001).ConclusionMyocardial T2 correlates well with myocardial iron concentration, which raises the possibility that T2 may provide additive information to T2* for patients with myocardial siderosis. However, ex-vivo T1 measurements are less reliable due to the severe chemical effects of formalin on T1 shortening, and therefore T1 calibration may only be practical from in-vivo human studies.

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“…In normal myocardium the normal wash out of the contrast reduces the presence of contrast molecules to a non significant level. With this technique the necrotic tissue can be directly visualised with the superior spatial resolution of MRI images so that subendocardic necrosis can be identified [57][58][59][60][61][62][63][64][65][66][67][68]. The extent of necrosis, as percent of the entire wall thickness, has a good predictive value for the functional improvement after revascularisation [69].…”

Section: Myocardial Viabilitymentioning

confidence: 99%

Contrast Media in Cardiovascular Magnetic Resonance

Lombardi¹,

Aquaro²,

Favilli

2005

CPD

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Among the available imaging techniques, Magnetic Resonance Imaging (MRI) is gaining an increasing role in the cardiologic setting because its specific properties such as the use of non ionising energies, the natural strong contrast between different tissues, the absence of spatial limitations, the good spatial and temporal resolution, the reduced operator dependency. To further improve the images quality and the histopathologic characterisation of tissues the use of contrast media (molecules containing gadolinium, manganese, iron, dysprosium ions) has been proposed both in the experimental and in the clinical settings. Among these ions gadolinium, which having 7 odd electrons in the external orbit has a strong magnetic momentum, is the most used. Gadolinium by itself is extremely toxic but once it is linked with a chelanting agent such as DTPA (Dietilen-Triamin-Penta-Acetic acid) the resulting complex shows a very low toxicity. The number of Gadolinium based compound is growing together with the use of contrast agents in MRI. These contrast agents are routinely used to perform Magnetic Resonance Angiography (MRA) and to a better definition of several cardiac diseases such as the presence of a intra- or paracardiac mass, the evaluation of myocardial perfusion and the evaluation of viability. Both the latter applications have relevant clinical implications. In fact the assessment of myocardial perfusion is one of the most used approach for detecting inducible myocardial ischemia due to major coronary artery disease or to assess the presence of a microvascular disease. The presence and the extent of viable myocardium is deeply modifying the clinical decision making as this viable tissue can recruit a normal function spontaneously or after revascularisation. Furthermore, the extent of viable myocardium has a strong correlation with negative prognosis. Clinical events are also time related to the detection of viable tissue. These evidences imply that the diagnostic procedure needs the highest level of accuracy. Either in the case of myocardial perfusion and in that of myocardial viability the advantages of MRI with respect to the others techniques are the use of non ionising radiations, the superior spatial resolution, an overall cost/benefit favourable ratio which explains the growing interest among cardiologists toward this new diagnostic tool.

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Magnetic resonance imaging of chronic myocardial infarcts in formalin-fixed human autopsy hearts.

Cited by 22 publications

References 31 publications

Staining methods for magnetic resonance microscopy of the rat fetus

Staining methods for magnetic resonance microscopy of the rat fetus

Calibration of myocardial T2 and T1 against iron concentration

Contrast Media in Cardiovascular Magnetic Resonance

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