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

Manohar, Ashish; Pack, Jed D.; Schluchter, Andrew; McVeigh, Elliot R.

doi:10.1002/mp.15550

Cited by 10 publications

(21 citation statements)

References 38 publications

(81 reference statements)

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“…Unfortunately, 37 of the 147 subjects (25%) had severe step artifacts due to beat-to-beat irregularities, rendering the images not usable for dyssynchrony analysis. Despite the excellent temporal resolution of the dual-source scanner (66 ms per frame), wider detector scanners (256 or 320 detector-rows) with full heart coverage from a single table position may be better suited for this application, especially with the recent innovations in motion estimation and motion compensation technology [25], [26].…”

Section: Discussionmentioning

confidence: 99%

Prediction of CRT Response Using a Lead Placement Score Derived from 4DCT

Manohar

Colvert

Yang

et al. 2022

Preprint

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Background: Cardiac resynchronization therapy (CRT) is an effective treatment for patients with heart failure; however, 30% of patients do not respond to the treatment. We sought to derive patient-specific left-ventricle (LV) maps of lead placement scores (LPS) that highlight target pacing lead sites for achieving a higher probability of CRT response. Methods: Eighty-two subjects recruited for the ImagingCRT trial were retrospectively analyzed. All 82 subjects had two contrast-enhanced full-cardiac cycle 4DCT scans: a baseline and a 6-month follow-up scan. CRT response was defined as a reduction in CT-derived end-systolic volume ≥15%. Eight LV features derived from the baseline scans were used to train a support vector machine (SVM) via a bagging approach. An LPS map over the LV was created for each subject as a linear combination of the SVM feature weights and the subject's own feature vector. Performance for distinguishing responders was performed on the original 82 subjects. Results: Fifty-two (63%) subjects were responders. Subjects with an LPS ≤ Q1 (lower-quartile) had a posttest probability of responding of 14% (3/21), while subjects with an LPS ≥ Q3 (upper-quartile) had a posttest probability of responding of 90% (19/21). Subjects with Q1 < LPS < Q3 had a posttest probability of responding that was essentially unchanged from the pretest probability (75% vs 63%, p=0.2). An LPS threshold that maximized the geometric mean of true-negative and true-positive rates identified 26/30 of the non-responders. The AUC of the ROC curve for identifying responders with an LPS threshold was 87%. Conclusions: An LPS map was defined using 4DCT-derived features of LV mechanics. The LPS correlated with CRT response, reclassifying 25% of the subjects into low-probability of response, 25% into high-probability of response, and 50% unchanged. These encouraging results highlight the potential utility of 4DCT in guiding patient selection for CRT. The present findings need verification in larger independent data sets and prospective trials.

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Section: Discussionmentioning

confidence: 99%

Prediction of CRT Response Using a Lead Placement Score Derived from 4DCT

Manohar

Colvert

Yang

et al. 2022

Preprint

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“…These gantry position induced artifacts make it very difficult to accurately measure the mechanical activation time of regions of the LV because of the uncertainty of endocardial wall position in the images. The uncorrected images were processed with a motion correction algorithm called ResyncCT [21] to yield motion corrected images. ResyncCT is a newly developed cardiac CT motion correction algorithm that leverages the power of conjugate pairs of partial angle reconstruction images for motion estimation and motion compensation.…”

Section: Methodsmentioning

confidence: 99%

“…Figure 5A shows bullseye maps of the difference in TOS estimates between the uncorrected and the ResyncCT images over all 72 endocardial segments for all 24 subjects; virtually all of the patients have substantial changes to the TOS values. We have previously evaluated the effect of ResyncCT under controlled phantom experiments [21],…”

Section: Effect Of Resyncct On Accuracy Of Mechanical Activation Time...mentioning

confidence: 99%

“…We previously reported that out of 147 subjects recruited for a retrospective CRT study, 37 subjects (25%) had severe step-artifacts preventing the precise estimation of LV mechanics [16]. With the advances made in 4DCT motion correction technology [17], wide detector scanners can now yield high temporal resolution images, together with the advantages of single-heartbeat and single-table position acquisitions [18]; the 'false dyssynchrony' artifact [19], [20] can also be significantly reduced [21]. These favorable features of 4DCT are of particular value in the accurate and precise estimation of LV mechanical activation times, highlighting the potential utility of wide detector 4DCT systems in guiding CRT planning.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the objective of this study was to assess the effect of a newly developed cardiac CT motion correction algorithm called ResyncCT on the computed TOS estimates in a clinical cohort of 25 subjects. ResyncCT has previously been validated using a set of controlled phantom experiments [21]; this study presents new results which focus on the clinical applicability and the effect of ResyncCT on routinely acquired retrospective cardiac 4DCT images in human subjects.…”

Section: Introductionmentioning

confidence: 99%

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Estimation of Left Ventricular Mechanical Activation Times from Motion-Corrected Cardiac 4DCT Images

Manohar

Yang

Pack

et al. 2022

Preprint

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BackgroundMechanical activation times of the left ventricle (LV) are strongly correlated with patient response to cardiac resynchronization therapy (CRT); however, there remains an unmet clinical need for a simple, robust imaging modality that yields accurate and reproducible estimates of LV mechanical activation times. Modern four-dimensional computed tomography (4DCT) imaging systems with effective motion correction could fulfill this need.PurposeTo demonstrate the clinical utility of a newly developed cardiac motion correction algorithm called ResyncCT and to investigate its effect on estimating mechanical activation times of the LV.MethodsTwenty-four subjects with full cardiac volume, full cardiac cycle 4DCT images were retrospectively analyzed in this study. The reconstructed 4DCT images exhibited typical motion artifact characteristics that were dependent on the direction of LV wall motion with respect to the gantry position at each cardiac phase; these artifacts rotated synchronously with the gantry. The motion corrupted images, referred to as the uncorrected images, were processed with a novel cardiac motion correction algorithm called ResyncCT to yield motion corrected images (referred to as the ResyncCT images). Regional shortening (RSCT) of the LV was calculated over a 72-segment model for both the uncorrected and the ResyncCT images; each segment contained RSCT vs time data. From these RSCT vs time curves, LV mechanical activation was estimated as the time point at which the RSCT vs time curve shortened by 10% of its full dynamic range during systolic contraction; we refer to this time point as the time to onset of shortening (TOS). A shift in TOS > |35| ms has a significant effect on reclassifying patients based on their probabilities of responding to CRT; we investigated the effect of ResyncCT on the measured values of TOS over the LV.ResultsResyncCT had a pronounced effect on the TOS estimates; ResyncCT could potentially reclassify 23/24 (96%) subjects as either responders or non-responders to CRT. In 16/24 (67%) subjects, the differences in TOS that were sufficient to bring about a reclassification of CRT response were at least as large in surface area of the LV as one entire American Heart Association segment.ConclusionsWe demonstrated the clinical utility of ResyncCT in estimating LV mechanical activation times as ‘times to onset of shortening’ in 24 human subjects. ResyncCT has a pronounced effect on the estimation of LV mechanical activation times; the differences in activation times between the ResyncCT and uncorrected images are heterogenous and subject specific. The effect of ResyncCT could potentially reclassify 96% of the subjects used in this study based on their probabilities of responding to CRT. The results reported in this study highlight the potential utility of ResyncCT in estimating timing of mechanical events of interest of the LV for CRT planning.

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Four‐dimensional computed tomography of the left ventricle, Part I: Motion artifact reduction

et al. 2022

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Purpose Standard four‐dimensional computed tomography (4DCT) cardiac reconstructions typically include spiraling artifacts that depend not only on the motion of the heart but also on the gantry angle range over which the data was acquired. We seek to reduce these motion artifacts and, thereby, improve the accuracy of left ventricular wall positions in 4DCT image series. Methods We use a motion artifact reduction approach (ResyncCT) that is based largely on conjugate pairs of partial angle reconstruction (PAR) images. After identifying the key locations where motion artifacts exist in the uncorrected images, paired subvolumes within the PAR images are analyzed with a modified cross‐correlation function in order to estimate 3D velocity and acceleration vectors at these locations. A subsequent motion compensation process (also based on PAR images) includes the creation of a dense motion field, followed by a backproject‐and‐warp style compensation. The algorithm was tested on a 3D printed phantom, which represents the left ventricle (LV) and on challenging clinical cases corrupted by severe artifacts. Results The results from our preliminary phantom test as well as from clinical cardiac scans show crisp endocardial edges and resolved double‐wall artifacts. When viewed as a temporal series, the corrected images exhibit a much smoother motion of the LV endocardial boundary as compared to the uncorrected images. In addition, quantitative results from our phantom studies show that ResyncCT processing reduces endocardial surface distance errors from 0.9 ± 0.8 to 0.2 ± 0.1 mm. Conclusions The ResyncCT algorithm was shown to be effective in reducing motion artifacts and restoring accurate wall positions. Some perspectives on the use of conjugate‐PAR images and on techniques for CT motion artifact reduction more generally are also given.

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

Cited by 10 publications

References 38 publications

Prediction of CRT Response Using a Lead Placement Score Derived from 4DCT

Prediction of CRT Response Using a Lead Placement Score Derived from 4DCT

Estimation of Left Ventricular Mechanical Activation Times from Motion-Corrected Cardiac 4DCT Images

Four‐dimensional computed tomography of the left ventricle, Part I: Motion artifact reduction

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