Quantification of infarct size and myocardium at risk: evaluation of different techniques and its implications.
OBJECTIVE
The aim of this study was to evaluate seven methods for quantifying myocardial oedema [2 standard deviation (SD), 3 SD, 5 SD, full width at half maximum (FWHM), Otsu method, manual thresholding, and manual contouring] from T2-weighted short tau inversion recovery (T2w STIR) and also to reassess these same seven methods for quantifying acute infarct size following ST-segment myocardial infarction (STEMI). This study focuses on test-retest repeatability while assessing inter- and intraobserver variability. T2w STIR and late gadolinium enhancement (LGE) are the most widely used cardiovascular magnetic resonance (CMR) techniques to image oedema and infarction, respectively. However, no consensus exists on the best quantification method to be used to analyse these images. This has potential important implications in the research setting where both myocardial oedema and infarct size are increasingly used and measured as surrogate endpoints in clinical trials.


RESULTS
Forty patients day 2 following acute reperfused STEMI were scanned for myocardial oedema and infarction (LGE). All patients had a second CMR scan on the same day >6 h apart from the first one. Images were analysed offline by two independent observers using the semi-automated software. Both oedema and LGE were quantified using seven techniques (2 SD, 3 SD, 5 SD, Otsu, FWHM, manual threshold, and manual contouring). Interobserver, intraobserver and test-retest agreement and variability for both infarct size and oedema quantification were assessed. Infarct size and myocardial quantification vary depending on the quantification method used. Overall, manual contouring provided the lowest inter-, intraobserver, and interscan variability for both infarct size and oedema quantification. The FWHM method for infarct size quantification and the Otsu method for myocardial oedema quantification are acceptable alternatives.


CONCLUSIONS
This study determines that, in acute myocardial infarction (MI), manual contouring has the lowest overall variability for quantification of both myocardial oedema and MI when analysed by experienced observers.
NIHR Bristol Cardiovascular Biomedical Research Unit, Bristol Heart Institute, Level 7 Queens Building, Bristol Royal Infirmary, Bristol BS2 8HW, UK.
Elisa
E
McAlindon
Clinical Trial and Evaluation Unit (CTEU), University of Bristol, Bristol, UK.
Maria
M
Pufulete
NIHR Bristol Cardiovascular Biomedical Research Unit, Bristol Heart Institute, Level 7 Queens Building, Bristol Royal Infirmary, Bristol BS2 8HW, UK.
Chris
C
Lawton
NIHR Bristol Cardiovascular Biomedical Research Unit, Bristol Heart Institute, Level 7 Queens Building, Bristol Royal Infirmary, Bristol BS2 8HW, UK.
Gianni D
GD
Angelini
NIHR Bristol Cardiovascular Biomedical Research Unit, Bristol Heart Institute, Level 7 Queens Building, Bristol Royal Infirmary, Bristol BS2 8HW, UK c.bucciarelli-ducci@bristol.ac.uk.
Chiara
C
Bucciarelli-Ducci
D000368:Aged; D015331:Cohort Studies; D004489:Edema, Cardiac / Q000175:diagnosis* / Q000401:mortality; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000401:mortality* / Q000628:therapy; D015425:Myocardial Reperfusion / Q000379:methods; D009206:Myocardium / Q000473:pathology; D015588:Observer Variation; D011446:Prospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D015996:Survival Rate; D016896:Treatment Outcome; D020107:Troponin T / Q000097:blood
D020107:Troponin T
Cardiac magnetic resonance; Infarct size; Myocardial oedema; Quantification