Motion‐corrected free‐breathing delayed enhancement imaging of myocardial infarction

Abstract

Following administration of Gd-DTPA, infarcted myocardium exhibits delayed enhancement and can be imaged using an inversion-recovery sequence. A conventional segmented acquisition requires a number of breath-holds to image the heart. Single-shot phase-sensitive inversion-recovery (PSIR) true-FISP may be combined with parallel imaging using SENSE to achieve high spatial resolution. SNR may be improved by averaging multiple motion-corrected images acquired during free breathing. PSIR techniques have demonstrated a number of benefits including consistent contrast and appearance over a relatively wide range of inversion recovery times (TI), improved contrast-to-noise ratio, and consistent size of the enhanced region. Comparison between images acquired using segmented breath-held turbo-FLASH and averaged, motion-corrected, free-breathing true-FISP show excellent agreement of measured CNR and infarct size. In this study, motion correction was implemented using image registration postprocessing rather than navigator correction of individual frames. Myocardial viability assessment using Gd-DTPA enhancement MRI is gaining clinical acceptance (1,2). Using recent MRI methods (3) myocardial infarction (MI) may be imaged with high spatial resolution and good contrast. Following administration of Gd-DTPA, infarcted myocardium exhibits delayed enhancement and can be imaged using an inversion-recovery (IR) sequence (1-3). Using a conventional segmented acquisition requires a number of breathholds to image the heart. This paper introduces a method for free-breathing acquisition of delayed enhancement imaging and a quantitative evaluation is presented. Single-shot IR true-FISP may be combined with parallel imaging using SENSE to achieve high spatial resolution (4,5) comparable to conventional segmented IR turbo-FLASH. A single-shot acquisition eliminates the requirement for breath-holding. A phasesensitive inversion-recovery (PSIR) method (6) combined with parallel imaging reconstruction was used. PSIR techniques have demonstrated a number of benefits including consistent contrast and appearance over a relatively wide range of inversion recovery times (TI), improved contrastto-noise ratio (CNR), and accurate depiction of the enhanced region. Enhanced signal-to-noise ratio (SNR) may be achieved by averaging multiple motion-corrected images acquired during free breathing. Multiple free-breathing images were motion corrected using a multiscale, subpixel, intensity-based image registration method (7,8). Image registration was constrained to rigid body transformation.Averaged free-breathing images were compared with images acquired using a standard breath-held segmented IR turbo-FLASH sequence. While true-FISP has a ͌(T 2 /T 1 ) dependence in steady state, Scheffler and Hennig (9) have shown that inversion recovery with true-FISP readout closely follows the predicted T 1 -weighted recovery and is actually more accurate than the standard IR turbo-FLASH. Comparison between the two sequences included measurement of CNR between normal and...

Rapid Detection of Myocardial Infarction by Subsecond, Free-Breathing Delayed Contrast-Enhancement Cardiovascular Magnetic Resonance

“…New approaches in which SNR is improved further by averaging multiple single-shot images after motion correction may hold promise. 26 In summary, subsecond imaging has both advantages and disadvantages compared with standard imaging. Therefore, the results suggest that the choice of technique should be based on multiple factors, including logistical issues at the CMR center, the technical knowledge level of the CMR operators, and patient-specific concerns such as the presence of arrhythmia, ability to breath-hold, and acuity of illness.…”

Free‐breathing delayed hyperenhanced imaging of the myocardium: A clinical application of real‐time navigator echo imaging

“…These include singleshot imaging (11,12), real-time imaging (29), and motion-corrected imaging (30). Two-dimensional steadystate free precession (SSFP) imaging has been explored for single-heartbeat imaging.…”

Motion corrected free‐breathing delayed‐enhancement imaging of myocardial infarction using nonrigid registration

“…Experiments were conducted using a 1.5-T Siemens Sonata MR imaging system. Custom modification to the Siemens product inversion-recovery true-FISP sequence and phase-sensitive inversion recovery (PSIR) reconstruction software was made to incorporate parallel imaging using sensitivity encoding (SENSE) as previously described (5). Raw data including prescan noise was acquired for all scans, and images were reconstructed offline.…”

“…Respiratory motion-corrected averaging of multiple images acquired while free-breathing may be used to substantially improve the image quality (5). The motivation for motion-corrected averaging with single-shot delayed-enhancement imaging is to improve the signalto-noise ratio (SNR).…”

“…In prior work, rigid body image registration was used to correct respiratory motion in the heart region, based on a user-defined bounding box (5). In this work, nonrigid body image registration is used to correct respiratory motion across the full field-of-view (FOV).…”