Image quality improvement in MDCT cardiac imaging via SMART-RECON method

Li, Yinsheng; Cao, Ximiao; Xing, Z; Sun, Xuguang; Hsieh, Jiang; Chen, Guang-Hong

doi:10.1117/12.2254644

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“…14 The temporal resolution of 4DCT is complex; motion artifacts seen in reconstructed CT images are due to the combined effect of gantry position as a function of time and the relative direction of wall motion. 15,16 Edge locations in reconstructed CT images are updated every time the X-ray beam is tangent to the particular edge; therefore, depending on their orientation, different edges are updated at different points in time in a continuous 4DCT movie, giving the false impression of dyssynchronous contraction (Section 2.5 provides further insight into the source of the false dyssynchrony artifact). These artifacts are usually not crucial in the assessment of global LV function; however, they impede the ability to accurately and precisely measure mechanical activation times at different locations on the LV wall.…”

Section: Introductionmentioning

confidence: 99%

Four‐dimensional computed tomography of the left ventricle, Part II: Estimation of mechanical activation times

et al. 2022

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Purpose We demonstrate the viability of a four‐dimensional X‐ray computed tomography (4DCT) imaging system to accurately and precisely estimate mechanical activation times of left ventricular (LV) wall motion. Accurate and reproducible timing estimates of LV wall motion may be beneficial in the successful planning and management of cardiac resynchronization therapy (CRT). Methods We developed an anthropomorphically accurate in silico LV phantom based on human CT images with programmed septal‐lateral wall dyssynchrony. Twenty‐six temporal phases of the in silico phantom were used to sample the cardiac cycle of 1 s. For each of the 26 phases, 1 cm thick axial slabs emulating axial CT image volumes were extracted, 3D printed, and imaged using a commercially available CT scanner. A continuous dynamic sinogram was synthesized by blending sinograms from these static phases; the synthesized sinogram emulated the sinogram that would be acquired under true continuous phantom motion. Using the synthesized dynamic sinogram, images were reconstructed at 70 ms intervals spanning the full cardiac cycle; these images exhibited expected motion artifact characteristics seen in images reconstructed from real dynamic data. The motion corrupted images were then processed with a novel motion correction algorithm (ResyncCT) to yield motion corrected images. Five pairs of motion uncorrected and motion corrected images were generated, each corresponding to a different starting gantry angle (0 to 180 degrees in 45 degree increments). Two line profiles perpendicular to the endocardial surface were used to sample local myocardial motion trajectories at the septum and the lateral wall. The mechanical activation time of wall motion was defined as the time at which the endocardial boundary crossed a fixed position defined on either of the two line profiles while moving toward the center of the LV during systolic contraction. The mechanical activation times of these myocardial trajectories estimated from the motion uncorrected and the motion corrected images were then compared with those derived from the static images of the 3D printed phantoms (ground truth). The precision of the timing estimates was obtained from the five different starting gantry angle simulations. Results The range of estimated mechanical activation times observed across all starting gantry angles was significantly larger for the motion uncorrected images than for the motion corrected images (lateral wall: 58 ± 15 ms vs 12 ± 4 ms, p < 0.005; septal wall: 61 ± 13 ms vs 13 ± 9 ms, p < 0.005). Conclusions 4DCT images processed with the ResyncCT motion correction algorithm yield estimates of mechanical activation times of LV wall motion with significantly improved accuracy and precision. The promising results reported in this study highlight the potential utility of 4DCT in estimating the timing of mechanical events of interest for CRT guidance.

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Section: Introductionmentioning

confidence: 99%