T₁ mapping for assessment of myocardial injury and microvascular obstruction at one week post myocardial infarction.
OBJECTIVE
To compare 3T T1 mapping to conventional T2-weighted (T2W) imaging for delineating myocardial oedema one week after ST-elevation myocardial infarction (STEMI), and to explore the confounding effects of microvascular obstruction (MVO) on each technique.


METHODS
T2W spectral attenuated inversion recovery and native T1 mapping were applied in 10 healthy volunteers and 62 STEMI patients, and late gadolinium enhancement was included for infarct localisation at 1 week and at 6 months post-STEMI. Segmental T1 values and T2W signal intensity ratios were calculated; oedema volumes and salvage indices were determined in patients using image thresholding-a receiver operator characteristic (ROC) derived T1 threshold, and a 2SD T2W threshold; and the results were compared between patients with/without MVO (n=35/27).


RESULTS
Native T1 mapping delineated oedema with significantly better discriminatory power than T2W-as indicated by ROC analysis (area-under-the-curve, AUC=0.89 versus 0.83, p=0.009; and sensitivity/specificity=83/83% versus 73/73%). The optimal ROC threshold derived for T1 mapping was 1241ms, which gave significantly larger oedema volumes than 2SD T2W (p=0.006); with this threshold, patients with and without MVO showed similar oedema volumes, but patients with MVO had significantly poorer salvage indices (p<0.05) than those without. Neither method was significantly affected by MVO, the volume of which was seen to increase exponentially with infarct size.


CONCLUSIONS
Native T1 mapping at 3T can delineate oedema one week post-STEMI, showing larger oedema volumes and better discriminatory power than T2W imaging, and it is suitable for quantitative thresholding. Both techniques are robust against MVO-related magnetic susceptibility.
Department of Cardiovascular Medicine, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK. Electronic address: d.cameron.09@aberdeen.ac.uk.
Donnie
D
Cameron
Department of Cardiovascular Medicine, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK. Electronic address: n.siddiqi@abdn.ac.uk.
Nishat
N
Siddiqi
Department of Cardiovascular Medicine, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK. Electronic address: ctop1@me.com.
Christopher J
CJ
Neil
Department of Cardiovascular Medicine, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK. Electronic address: b.jagpal@abdn.ac.uk.
Baljit
B
Jagpal
Department of Cardiovascular Medicine, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK. Electronic address: maggie.bruce2@nhs.net.
Margaret
M
Bruce
Philips Healthcare, Guildford Business Park, Guildford, Surrey GU2 8XH, UK. Electronic address: David.Higgins@philips.com.
David M
DM
Higgins
Department of Cardiovascular Medicine, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK. Electronic address: jiabao.he@abdn.ac.uk.
Jiabao
J
He
Department of Cardiovascular Medicine, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK. Electronic address: s.singh@abdn.ac.uk.
Satnam
S
Singh
Department of Cardiovascular Medicine, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK. Electronic address: t.redpath@abdn.ac.uk.
Thomas W
TW
Redpath
Department of Cardiovascular Medicine, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK. Electronic address: m.p.frenneaux@abdn.ac.uk.
Michael P
MP
Frenneaux
Department of Cardiovascular Medicine, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK. Electronic address: dana.dawson@abdn.ac.uk.
Dana K
DK
Dawson
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003331:Coronary Vessels / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D055806:Microvessels / Q000473:pathology*; D008875:Middle Aged; D009203:Myocardial Infarction / Q000473:pathology*; D009206:Myocardium / Q000473:pathology; D012372:ROC Curve; D012680:Sensitivity and Specificity; D013997:Time Factors
Acute myocardial infarction; Magnetic resonance imaging; Microvascular obstruction; Myocardial oedema; Myocardium at risk; T(1) mapping