Several pulse sequences are available for T2-weighted imaging. The oldest are fast (turbo) spin-echo sequences with long TR's/ TE's. These are typically preceded by an inversion module to suppress blood (double inversion recovery, DIR) and/or fat (triple inversion recovery, TIR). The latter method has contrast features similar to short-TI inversion recovery (STIR) imaging in that T1- and T2- signal contributions are additive.
T2-weighted SSFP methods are also available in which one or more driven equilibrium (DE) "T2-prep" modules are used in conjunction with a balanced-SSFP readout. Hybrid T2-weighted sequences have also been developed (e.g. ACUT2E), where a turbo spin-echo and SSFP are used together for signal generation.
To overcome some of these difficulties and allow more consistency of diagnosis, T2-mapping has been recommended. T2-mapping is typically performed using a balanced SSFP readout sequence preceded by a multinomial T2-preparation module. Signals are sampled at several different TE's and fitted to an exponential decay curve of the form:
Si = Mo e−TEi / T2
to determine T2. The results are displayed on a pixel-by-pixel base in a color map, from which T2-values can be directly measured.
Advanced Discussion (show/hide)»
Aletras AH, Kellman P, Derbyshire JA, Arai AE. ACUT2E TSE-SSFP: a hybrid method for T2-weighted imaging of edema in the heart. Magn Reson Med 2008; 59:229-235.
Croisille P, Kim HW, Kim RJ. Controversies in cardiovascular MR imaging. T2-weighted imaging should not be used to delineate the area at risk in ischemic myocardial injury. Radiology 2012; 265:12-22.
Eitel I, Friedrich MG. T2-weighted cardiovascular magnetic resonance in acute cardiac disease. J Cardiovasc Magn Reson 2011; 13:13.
Giri S, Chung Y-C, Merchant A, et al. T2 quantification for improved detection fo myocardial edema. J Cardiovasc Magn Reson 2009; 11:56.
McAlindon EJ, Pufulete M, Harris JM, et al. Measurement of myocardium at risk with cardiovascular MR: comparison of techniques for edema imaging. Radiology 2015; 275:61-70. (In setting of STEMI, myocardial edema is detected most reproducibly using T2 mapping over STIR and early gadolinium enhancement).
Verhaert D, Thavendiranathan P, Giri S, et al. Direct T2 quantification of myocardial edema in acute ischemic injury. JACC Cardiovasc Imaging 2011; 4:269-278.
How is cardiac T1 mapping performed? When is it useful?
How and why is T2*-myocardial mapping performed?