Myocardial tagging, introduced over 25 years ago, is universally implemented on all manufacturers’ MRI scanners^1-3. Despite extensive validation as the best method for clinical quantitative measure of myocardial wall deformation, tagging is limited to a research context due to the time intensive analysis and need to acquire additional sequences. Cardiac MRI (CMR) sequences must provide maximum diagnostic information, and maximum patient throughput, with minimum operator effort and time (cost)⁴. We developed a CMR cine sequence with an added “hidden” capability to acquire cardiac strain data while requiring no extra operator effort. Called Cine Watermark (CWM), this method produces normal (qualitative) cine magnitude images, plus a grid pattern of tags added only in the phase (watermark) information for quantitative cine strain capability.Fig 1 presents the ECG-triggered CWM sequence that acquires both normal and complimentary spatial modulation of magnetization (SPAMM/CSPAMM) prepared cine image sets. A classic “1-1” saturation SPAMM was used were each non-selective Rect RF pulse had a flip angle of 45°. The sequence alternated the acquisition of SPAMM or CSPAMM on every other ECG trigger. The cine readout used a standard, low flip angle, spoiled GRE method. CWM acquisition runs were acquired with the cosine modulation in the readout (RO) axis and then phase encode (PE) axis directions to create a grid-tag pattern. Two rats were scanned in a 7T human-size scanner with a birdcage 1-chan small animal RF coil and two healthy human volunteers, with informed consent, were scanned in a 3T Verio scanner with a 32-chan anterior/posterior RF coil array (both scanners: Siemens, Erlangen, Germany). All CWM scan slice locations were mid-left ventricular (LV), short-axis. Scan parameters for rats (humans): field-of-view = 64x40(264x198) mm, slice thickness = 2(8) mm, matrix = 256x160(176x132), in-plane pixel size = 0.25x0.25(1.5x1.5) mm, flip angle = 8(10)°, BW = 488(406) Hz/pix, averages = 4(1), cine phases = 15(20), tag spacing = 1.5(5) mm, ECG-triggered, free-breathing(11 breath holds). All CWM image reconstruction was performed offline using customized Matlab programs (Mathworks, Natick, MA). During image reconstruction, the sum of the SPAMM + CSPAMM raw k-space data eliminated the cosine modulation components leaving only the conventional (central k-space) T1-weighted cine image component. The magnitude images of this sum’s inverse Fourier transform provided the pure cardiac cine image set without tag pattern lines. Conversely, the difference of SPAMM – CSPAMM raw k-space eliminated the central k-space T1-weighted component leaving only the cosine modulation components. The phase images of this difference’s inverse Fourier transform provided strong and persistent (0°/180°) phase-only tag lines that tracked cardiac displacement and allowed subsequent strain calculation. The myocardial strain analysis was implemented in C++ using the ITK⁵ and OpenCV⁶ libraries. Magnitude and phase images were weighted to create synthetic tag images. Dense displacement fields were obtained between successive frames using the Farneback optical flow algorithm (5 pyramids, 7px window). Principal strain values were then calculated pixelwise for each image, and the median value within each anatomical segment was calculated. A weighted sum of forward and reverse registrations was calculated to avoid propagation of error.Both rat and human CWM scans gave cine magnitude and displacement cine phase image sets suitable for analysis. Fig 2 shows the in vivo rat SPAMM/CSPAMM k-space sum effectively isolated the central k-space component (magnitude cine) and the k-space difference isolated the simultaneous RO and PE axes cosine modulation components (for strain). Fig 3 presents example rat CWM images at end-diastole (ED) and end-systole (ES) time points. The rat CWM exhibited some signal loss in the myocardium that is common at 7T due to susceptibility B0 inhomogeneities. Fig 4 presents similar human CWM ED and ES image results. Both Figs 3&4 show observable displacement of the phase grid-tag patterns evident at ES compared to the ED starting point, with regionalized displacement (quiver maps) displayed at far-right. The calculated peak principle strain, averaged around the LV, for rat = -16.5±2.4 % and human = -17.8±6.2 % (mean±StdDev).These preliminary results provided an in vivo demonstration that CWM can be used to obtain anatomical cine and tagged phase images in a single scan, although with some short-comings that need correction and optimization. The phase-tag displacements are much more obvious in the phase cine loop playback (not shown). Proper strain calculation was problematic and attributed to be from phase tags discontinuities. This CWM Encode method is likely compatible with SSFP cine and such an integration should be investigated.We developed and demonstrated a CMR cine sequence with added “hidden” capability to acquire strain data. Future development effort will improve its performance.