ABSTRACT
MRI tagging is a unique technique that provides the opportunity to noninvasively tag the myocardium in a predened pattern prior to imaging (Zerhouni et al. 1988, Axel and Dougherty 1989, Ibrahim 2011). The tagging pattern spatially labels the myocardium, and as the heart deforms, the tagging pattern deforms accordingly. The motion of the tagging pattern can be observed in the subsequently acquired time-resolved (cine) images. The full potential of this tool, however, is not ful-lled unless the tagging pattern matches both the myocardial geometry and motion. The geometry of healthy and unhealthy hearts are largely circular (in short-axis (SAX) views), where the underlying motion pattern can be compactly described in a polar coordinate system. Specically, it is apparent in a SAX
12.12 Radial Tagging ............................................................................................................................................................... 528 12.12.1 Alternate Implementation ................................................................................................................................. 528 12.12.2 Nonuniform Radial Tagging ..............................................................................................................................531 12.12.3 Complementary Radial Tagging (CTR) ........................................................................................................... 532
12.12.3.1 Basic Idea and Implementation ........................................................................................................ 532 12.12.3.2 Alternative CRT Implementation ..................................................................................................... 533
12.13 Analysis Methods Specic to Polar-Tagged Images ...................................................................................................... 533 12.13.1 Polar HARP ...................................................................................................................................................... 533 12.13.2 High-Resolution Circular Tagging ................................................................................................................... 534 12.13.3 CIRCOME ........................................................................................................................................................ 537
12.13.3.1 Basic Idea.......................................................................................................................................... 537 12.13.3.2 Circular Band-Pass Filtering of the K-Space ................................................................................... 538 12.13.3.3 Calculation of Circumferential Strain .............................................................................................. 538 12.13.3.4 Technique’s Efciency and Validation ............................................................................................. 540 12.13.3.5 Parameters Affecting CIRCOME .................................................................................................... 540
12.14 Toward Real-Time Strain Imaging with Polar Tagging ................................................................................................. 542 12.14.1 Inline Circular Density Maps ........................................................................................................................... 542 12.14.2 Real-Time Circular Tagging ............................................................................................................................. 543 12.14.3 Real-Time Radial Tagging ................................................................................................................................ 545
12.15 Clinical Applications of Polar Tagging .......................................................................................................................... 545 12.16 Summary and Key Points .............................................................................................................................................. 549
12.16.1 Summary .......................................................................................................................................................... 549 12.16.2 Key Points ......................................................................................................................................................... 549
Acknowledgment ...................................................................................................................................................................... 552 References ................................................................................................................................................................................. 552
view that the heart grossly contracts in the circumferential direction and thickens in the radial direction.
