Related Experiment Videos
Detection of intramyocardial hemorrhage using high-field proton (1H) nuclear magnetic resonance imaging
C S Lotan1, S K Miller, A Bouchard
1Department of Medicine, University of Alabama, Birmingham 35294.
Insights
Proton magnetic resonance imaging (MRI) reveals decreased signal intensity in myocardial infarction zones, indicating intramyocardial hemorrhage. This finding aids in defining infarct characteristics and associated blood flow changes.
Area of Science:
- Cardiovascular Imaging
- Magnetic Resonance Imaging
- Myocardial Infarction Research
Background:
- Proton (1H) nuclear magnetic resonance (NMR) imaging identifies myocardial infarction (MI) zones by increased signal intensity (SI).
- Decreased SI zones within infarcts are hypothesized to represent intramyocardial hemorrhage.
Purpose of the Study:
- To investigate the phenomenon of decreased SI within MI zones using ex vivo proton NMR imaging.
- To correlate imaging findings with the presence and extent of intramyocardial hemorrhage.
Main Methods:
- Ex vivo spin-echo 1H NMR imaging at 1.5 Tesla was performed on 17 dogs post-coronary artery occlusion (24 hr and 72 hr).
- Signal intensity, gross inspection, histological assessment, myocardial flow, and T2 relaxation times were analyzed.
Main Results:
- All dogs showed increased SI in the infarct zone; 12/17 exhibited decreased SI zones within or around the infarct.
- Hemorrhage was typically found in decreased SI regions, which also showed higher myocardial flow and shortened T2 relaxation times compared to increased SI zones.
- Absence of decreased SI correlated with smaller infarcts and minimal or no hemorrhage.
Conclusions:
- Decreased SI on proton NMR imaging is a reliable indicator of intramyocardial hemorrhage in myocardial infarction.
- Hemorrhagic infarct regions exhibit distinct imaging characteristics, including altered T2 relaxation times and increased blood flow.
Abstract:
Proton (1H) nuclear magnetic resonance (NMR) imaging has been used to define zones of myocardial infarction (MI), which appear as areas of relatively increased signal intensity (SI). However, zones of decreased SI have been observed within the areas of infarction and have been postulated to result from intramyocardial hemorrhage. To explore this phenomenon further, ex vivo spin-echo 1H NMR imaging at 1.5 Tesla was performed in 17 dogs after 24 hr (n = 9) and after 72 hr (n = 8) of coronary artery occlusion. In all dogs, a zone of increased SI (118 +/- 9% compared with normal myocardium) was observed in the distribution of the occluded coronary artery. In 12 of the 17 dogs, zones of decreased SI (92 +/- 8% compared with normal) were seen within or around the central zone of increased SI. Gross inspection and histological assessment of sliced myocardium usually disclosed hemorrhage in the regions of decreased SI. In three of the five dogs with no apparent zones of decreased SI on NMR, the infarct was small, and only minor hemorrhage was observed by gross inspection, whereas in the remaining two dogs no hemorrhage was seen. Myocardial flow in the hemorrhagic regions was significantly higher than in the necrotic core (59 +/- 29% vs. 31 +/- 24% compared with control, P less than 0.05). Image-derived calculation of T2 relaxation times in the different infarcted regions revealed a significant shortening of T2 in the infarcted hemorrhagic zones with decreased SI compared with the infarct zones with increased SI (49 +/- 8 msec vs. 66 +/- 8 msec, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)