Cine Acquisition Research Articles

Achieving reduced radiation exposure with maintained fluoroscopy effectiveness using ultralow‐dose settings in cryoballoon ablation

AbstractBackground and AimsOptimization of fluoroscopic image quality for reducing radiation exposure in cryoballoon pulmonary vein isolation (CB‐PVI) has not yet been fully investigated. Therefore, we tried to compare the radiation doses among three different X‐ray system settings.MethodsConsecutive 148 patients scheduled for their first CB‐PVI were prospectively enrolled: low dose with the use of an anti‐scatter grid for the first 51 patients (LD + G group), low dose without an anti‐scatter grid for the subsequent 46 patients (LD‐G group), and ultralow dose (ULD group) with an anti‐scatter grid for the remaining 51 patients. We compared the radiation doses required to complete CB‐PVI procedures among the groups. There were 27 patients for whom CB‐PVI was performed without cine acquisition, but with fluoroscopy only, and the radiation doses were also compared.ResultsThe median procedure time and fluoroscopy time were 119 and 35.5 min, respectively, with no significant differences among the groups. The median cumulative air Kerma (AK) decreased in both the LD‐G group (71.8 mGy, p < .001) and the ULD group (73.0 mGy, p < .001), compared to the LD + G group (145.0 mGy). Among 27 patients who underwent CB‐PVI without cine acquisition, the median cumulative AK further decreased in both the LD‐G group (31.4 mGy, p < .05) and the ULD group (22.7 mGy, p < .01), compared to the LD + G group (64.6 mGy).ConclusionUsing an ULD X‐ray setting and avoiding cine acquisition, we can reduce radiation exposure, while ensuring the necessary fluoroscopy time for the CB‐PVI procedure.

Evaluation of the impact of cardiac implantable electronic devices on cine MRI for real-time adaptive cardiac radioablation on a 1.5 T MR-linac.

Stereotactic arrhythmia radioablation (STAR) is a novel treatment approach for refractory ventricular tachycardia (VT). The risk of treatment-induced toxicity and geographic miss can be reduced with online MRI-guidance on an MR-linac. However, most VT patients carry cardiac implantable electronic devices (CIED), which compromise MRimages. Robust MR-linac imaging sequences are required for cardiac visualization and accurate motion monitoring in presence of a CIED during MRI-guided STAR. We optimized two clinically available cine sequences for cardiorespiratory motion estimation in presence of a CIED on a 1.5 T MR-linac. The image quality, motion estimation accuracy, and geometric fidelity using these cine sequences wereevaluated. Clinically available 2D balanced steady-state free precession (bSSFP, voxel size = 3.0 3.0 10 mm3, Tscan = 96 ms, bandwidth (BW) = 1884 Hz/px) and -spoiled gradient echo ( -GRE, voxel size = 4.0 4.0 10 mm3, Tscan = 97 ms, BW = 500 Hz/px) sequences were adjusted for real-time cardiac visualization and cardiorespiratory motion estimation on a 1.5 T Unity MR-linac (Elekta AB, Stockholm, Sweden), while complying with safety guidelines for MRI in presence of CIEDs (specific absorption rate 2 W/kg and 80 mT/s). Cine acquisitions were performed in five healthy volunteers, with and without an implantable cardioverter- defibrillator (ICD) placed on the clavicle, and a VT patient. Generalized divergence-curl (GDC) deformable image registration (DIR) was used for automated landmark motion estimation in the left ventricle (LV). Gaussian processes (GP), a machine-learning technique, was trained using GDC landmarks and deployed for real-time cardiorespiratory motion prediction. -mapping was performed to assess geometric image fidelity in the presence ofCIEDs. CIEDs introduced banding artifacts partially obscuring cardiac structures in bSSFP acquisitions. In contrast, the -GRE was more robust to CIED-induced artifacts at the expense of a lower signal-to-noise ratio. In presence of an ICD, image-based cardiorespiratory motion estimation was possible for 85% (100%) of the volunteers using the bSSFP ( -GRE) sequence. The in-plane 2D root-mean-squared deviation (RMSD) range between GDC-derived landmarks and manual annotations using the bSSFP (T1-GRE) sequence was 3.1-3.3 (3.3-4.1) mm without ICD and 4.6-4.6 (3.2-3.3) mm with ICD. Without ICD, the RMSD between the GP-predictions and GDC-derived landmarks ranged between 0.9 and 2.2 mm (1.3-3.0 mm) for the bSSFP (T1-GRE) sequence. With ICD, the RMSD between the GP-predictions and GDC-derived landmarks ranged between 1.3 and 2.2 mm (1.2-3.2 mm) using the bSSFP (T1-GRE) sequence resulting in an RMSD-increase of 42%-143% (bSSFP) and -61%-142% (T1-GRE). Lead-induced spatial distortions ranged between -0.2 and 0.2 mm (-0.7-1.2 mm) using the bSSFP ( -GRE) sequence. The 98th percentile range of the spatial distortions in the gross target volume of the patient was between 0.0 and 0.4 mm (0.0-1.8 mm) when using bSSFP ( -GRE). Tailored bSSFP and -GRE sequences can facilitate real-time cardiorespiratory estimation using GP trained with GDC-derived landmarks in the majority of landmark locations in the LV despite the presence of CIEDs. The need for high temporal resolution noticeably reduced achievable spatial resolution of the cine MRIs. However, the effect of the CIED-induced artifacts is device, patient and sequence dependent and requires specific assessment percase.

Rationale and design of RESILIENCE: A prospective randomized clinical trial evaluating remote ischaemic conditioning for the prevention of anthracycline cardiotoxicity.

There is a lack of therapies able to prevent anthracycline cardiotoxicity (AC). Remote ischaemic conditioning (RIC) has shown beneficial effects in preclinical models of AC. REmote iSchemic condItioning in Lymphoma PatIents REceiving ANthraCyclinEs (RESILIENCE) is a multinational, prospective, phase II, double-blind, sham-controlled, randomized clinical trial that evaluates the efficacy and safety of RIC in lymphoma patients receiving anthracyclines. Patients scheduled to undergo ≥5 chemotherapy cycles including anthracyclines and with ≥1 AC-associated risk factors will be randomized to weekly RIC or sham throughout the chemotherapy period. Patients will undergo three multiparametric cardiac magnetic resonance (CMR) studies, at baseline, after the third cycle (intermediate CMR), and 2 months after the end of chemotherapy. Thereafter, patients will be followed up for clinical events over an anticipated median of ≥24 months. The primary endpoint is the absolute change from baseline in CMR-based left ventricular ejection fraction (LVEF). The main secondary outcome is the incidence of AC events, defined as (1) a drop in CMR-based LVEF of ≥10 absolute points, or (2) a drop in CMR-based LVEF of ≥5 and <10 absolute points to a value <50%. Intermediate CMR will test the ability of T2 mapping to predict AC versus classical markers (left ventricular strain and cardiac injury biomarkers). A novel CMR sequence allowing ultrafast cine acquisition will be validated in this vulnerable population. The RESILIENCE trial will test RIC (a novel non-invasive intervention to prevent AC) in a cohort of high-risk patients. The trial will also test candidate markers for their capacity to predict AC and will validate a novel CMR sequence reducing acquisition time in a vulnerable population.

Accelerated cardiac magnetic resonance imaging using deep learning for volumetric assessment in children

BackgroundVentricular volumetry using a short-axis stack of two-dimensional (D) cine balanced steady-state free precession (bSSFP) sequences is crucial in any cardiac magnetic resonance imaging (MRI) examination. This task becomes particularly challenging in children due to multiple breath-holds.ObjectiveTo assess the diagnostic performance of accelerated 3-RR cine MRI sequences using deep learning reconstruction compared with standard 2-D cine bSSFP sequences.Material and methodsTwenty-nine consecutive patients (mean age 11 ± 5, median 12, range 1–17 years) undergoing cardiac MRI were scanned with a conventional segmented 2-D cine and a deep learning accelerated cine (three heartbeats) acquisition on a 1.5-tesla scanner. Short-axis volumetrics were performed (semi-)automatically in both datasets retrospectively by two experienced readers who visually assessed image quality employing a 4-point grading scale. Scan times and image quality were compared using the Wilcoxon rank-sum test. Volumetrics were assessed with linear regression and Bland–Altman analyses, and measurement agreement with intraclass correlation coefficient (ICC).ResultsMean acquisition time was significantly reduced with the 3-RR deep learning cine compared to the standard cine sequence (45.5 ± 13.8 s vs. 218.3 ± 44.8 s; P < 0.001). No significant differences in biventricular volumetrics were found. Left ventricular (LV) mass was increased in the deep learning cine compared with the standard cine sequence (71.4 ± 33.1 g vs. 69.9 ± 32.5 g; P < 0.05). All volumetric measurements had an excellent agreement with ICC > 0.9 except for ejection fraction (EF) (LVEF 0.81, RVEF 0.73). The image quality of deep learning cine images was decreased for end-diastolic and end-systolic contours, papillary muscles, and valve depiction (2.9 ± 0.5 vs. 3.5 ± 0.4; P < 0.05).ConclusionDeep learning cine volumetrics did not differ significantly from standard cine results except for LV mass, which was slightly overestimated with deep learning cine. Deep learning cine sequences result in a significant reduction in scan time with only slightly lower image quality.Graphical

The impact of clinical audits on patient radiation exposure for device procedures

Abstract Background Clinical audits aim to ensure ideal use of ionizing radiation in clinical practice. Since it became mandatory by Swiss law in 2018, such an audit also took place in our Cardiac Pacing and Electrophysiology Division at the University Heart Center. Purpose To establish local diagnostic reference levels (DRLs) for specific procedures and to examine if patient radiation exposure was reduced after the clinical audit. Methods Retrospective cohort study including patients from October 2018 to October 2020 who underwent device implantation, including pacemakers, implantable cardioverter defibrillators (ICD), cardiac resynchronization therapy (CRT), or lead extraction / device explantation. Main measures to reduce radiation exposure after the audit were lower pulsed fluoroscopy frame rates and dose characteristics at baseline. Patient radiation exposure was evaluated with the dose-area product (DAP), cumulative dose, fluoroscopy time, and the number of cine acquisitions. Secondary endpoints included the effective dose, the acute procedural success rate and 30-day complications. Data were collected from a dose management system and cross-checked for accuracy with the patient information system. The third quartiles were set as local DRLs. Data before and after the clinical audit were compared. Results A total of 541 patients (45.7 % before the audit, 54.3% after the audit) were included. 28.3% had a conventional pacemaker, 22.0% a leadless pacemaker, 21.1% an ICD, and 17.2% a CRT implantation. Lead extraction / device explantation was undergone by 11.5% of patients. The local DRLs (including all procedures before and after the audit) for the DAP were significantly lower as compared to national DRLs (6.2 dGy.cm2 versus 300 dGy.cm2 for conventional pacemakers; 7.6 dGy.cm2 versus 200 dGy.cm2 for ICDs, 203 dGy.cm2 versus 570 dGy.cm2 for CRTs). After the audit, DAP (Figure 1), cumulative dose, effective dose and the number of cine acquisition significantly decreased for conventional pacemakers (p-value ≤ 0.04), whereas no significant differences were observed for the other procedures. The acute procedural success rate (98.4 vs 98.9%) and the 30-day complications (4.0 vs 7.8%) were not significantly different before and after the audit. Conclusions The clinical audit in our institution led to a significant reduction of radiation exposure for patients during pacemaker implantations. Regarding DRLs, local values were far below national DRLs, which suggests that national DRLs need to be updated more regularly. Our study highlights the importance of clinical audits and the need for more research in this field.

ECG-free cine MRI with data-driven clustering of cardiac motion for quantification of ventricular function.

Despite the widespread use of cine MRI for evaluation of cardiac function, existing real-time methods do not easily enable quantification of ventricular function. Moreover, segmented cine MRI assumes periodicity of cardiac motion. We aim to develop a self-gated, cine MRI acquisition scheme with data-driven cluster-based binning of cardiac motion. A Cartesian golden-step balanced steady-state free precession sequence with sorted k-space ordering was designed. Image data were acquired with breath-holding. Principal component analysis and k-means clustering were used for binning of cardiac phases. Cluster compactness in the time dimension was assessed using temporal variability, and dispersion in the spatial dimension was assessed using the Caliński-Harabasz index. The proposed and the reference electrocardiogram (ECG)-gated cine methods were compared using a four-point image quality score, SNR and CNR values, and Bland-Altman analyses of ventricular function. A total of 10 subjects with sinus rhythm and 8 subjects with arrhythmias underwent cardiac MRI at 3.0 T. The temporal variability was 45.6 ms (cluster) versus 24.6 ms (ECG-based) (p< 0.001), and the Caliński-Harabasz index was 59.1 ± 9.1 (cluster) versus 22.0 ± 7.1 (ECG based) (p< 0.001). In subjects with sinus rhythm, 100% of the end-systolic and end-diastolic images from both the cluster and reference approach received the highest image quality score of 4. Relative to the reference cine images, the cluster-based multiphase (cine) image quality consistently received a one-point lower score (p< 0.05), whereas the SNR and CNR values were not significantly different (p= 0.20). In cases with arrhythmias, 97.9% of the end-systolic and end-diastolic images from the cluster approach received an image quality score of 3 or more. The mean bias values for biventricular ejection fraction and volumes derived from the cluster approach versus reference cine were negligible. ECG-free cine cardiac MRI with data-driven clustering for binning of cardiac motion is feasible and enables quantification of cardiac function.

Clinical utility of a rapid two-dimensional balanced steady-state free precession sequence with deep learning reconstruction

BackgroundCardiovascular magnetic resonance (CMR) cine imaging is still limited by long acquisition times. This study evaluated the clinical utility of an accelerated two-dimensional (2D) cine sequence with deep learning reconstruction (Sonic DL) to decrease acquisition time without compromising quantitative volumetry or image quality. MethodsA sub-study using 16 participants was performed using Sonic DL at two different acceleration factors (8x and 12x). Quantitative left-ventricular volumetry, function and mass measurements were compared between the two acceleration factors against a standard cine method. Following this sub-study, 108 participants were prospectively recruited and imaged using a standard cine method and the Sonic DL method with the acceleration factor that more closely matched the reference method. Two experienced clinical readers rated images based on their diagnostic utility and performed all image contouring. Quantitative contrast difference and endocardial border sharpness were also assessed. Left- and right-ventricular volumetry, left-ventricular mass and myocardial strain measurements were compared between cine methods using Bland-Altman plots, Pearson’s correlation, and paired t-tests. Comparative analysis of image quality was measured using Wilcoxon-signed-rank tests and visualized using bar graphs. ResultsSonic DL at an acceleration factor of 8 more closely matched the reference cine method. There were no significant differences found across left ventricular volumetry, function, or mass measurements. In contrast, an acceleration factor of 12 resulted in a 6% reduction of measured ejection fraction when compared to the standard cine method and a 4% reduction of measured ejection fraction when compared to Sonic DL at an acceleration factor of 8. Thus, Sonic DL at an acceleration factor of 8 was chosen for downstream analysis. In the larger cohort, this accelerated cine sequence was successfully performed in all participants and significantly reduced the acquisition time of cine images compared to the standard 2D method (reduction of 40%, p < 0.0001). Diagnostic image quality ratings and quantitative image quality evaluations were statistically not different between the two methods (p > 0.05). Left- and right-ventricular volumetry and circumferential and radial strain were also similar between methods (p > 0.05) but left-ventricular mass and longitudinal strain were over-estimated using the proposed accelerated cine method (mass over-estimated by 3.36g/m2, p < 0.0001; longitudinal strain over-estimated by 1.97%, p = 0.001). ConclusionsThis study found that an accelerated 2D cine method with DL reconstruction at an acceleration factor of 8 can reduce CMR cine acquisition time by 40% without significantly affecting volumetry or image quality. Given the increase of scan time efficiency, this undersampled acquisition method using deep learning reconstruction should be considered for routine clinical CMR.

Two-center validation of Pilot Tone based cardiac triggering of a comprehensive cardiovascular magnetic resonance examination.

The electrocardiogram (ECG) signal is prone to distortions from gradient and radiofrequency interference and the magnetohydrodynamic effect during cardiovascular magnetic resonance imaging (CMR). Although Pilot Tone Cardiac (PTC) triggering has the potential to overcome these limitations, effectiveness across various CMR techniques has yet to be established. To evaluate the performance of PTC triggering in a comprehensive CMR exam. Fifteen volunteers and 20 patients were recruited at two centers. ECG triggered images were collected for comparison in a subset of sequences. The PTC trigger accuracy was evaluated against ECG in cine acquisitions. Two experienced readers scored image quality in PTC-triggered cine, late gadolinium enhancement (LGE), and T1- and T2-weighted dark-blood turbo spin echo (DB-TSE) images. Quantitative cardiac function, flow, and parametric mapping values obtained using PTC and ECG triggered sequences were compared. Breath-held segmented cine used for trigger timing analysis was collected in 15 volunteers and 14 patients. PTC calibration failed in three volunteers and one patient; ECG trigger recording failed in one patient. Out of 1987 total heartbeats, three mismatched trigger PTC-ECG pairs were found. Image quality scores showed no significant difference between PTC and ECG triggering. There was no significant difference found in quantitative measurements in volunteers. In patients, the only significant difference was found in post-contrast T1 (p = 0.04). ICC showed moderate to excellent agreement in all measurements. PTC performance was equivalent to ECG in terms of triggering consistency, image quality, and quantitative image measurements across multiple CMR applications.

3-dimensional ct versus angiography guided pci for ostial rca lesions

Abstract Background Geographical stent-ostium mismatch is an important predictor of target lesion failure (TLF) after PCI of an aorto-ostial right coronary artery (RCA) lesion. Purpose We hypothesize that a pre-procedural 3-dimensional coronary CT angiography (3DCT) to determine the optimal C-arm angle of the X-ray system with the most accurate visualization of the aorto-ostial angle could allow optimal stent implantation at the level of the ostium and avoid excessive use of radiation and contrast. Methods This is a single centre trial randomizing 30 patients with an indication for non-emergent PCI of an ostial RCA lesion between 3DCT (intervention group) versus angiography guided strategy (control group). While in the control group the C-arm angle was at the operators’ discretion, in the intervention group the angle was determined based on a pre-PCI CT scan with 3D reconstruction using Materialise Mimics Innovation Suite software. A pre- and post-PCI IVUS is performed in all patients and analyzed by a blinded core lab. The primary endpoint is absence of geographical mismatch on IVUS defined as full stent coverage of the ostium and maximal aortic protrusion equal or less than 3mm. Secondary, we also aim to investigate whether a pre-procedural 3DCT may reduce procedural radiation, contrast use, may predict IVUS parameters (minimal luminal area (MLA), calcification), stent sizing and may promote stent expansion. Finally, MACE rate is evaluated at 1 month. Results The full patient dataset (n=30) including primary and all secondary endpoints will be available for presentation at the ESC congress. Currently, 27 patients were randomized. An interim analysis shows the following findings. There is significant patient heterogeneity considering the optimal angle for stent implantation, underscoring the potential benefit for individualized pre-procedural CT planning. In general, more extreme LAO angles were used in patients randomized to the intervention group (picture 1). While the stent was implanted in optimal position in 13/13 (100%) patients randomized to the intervention group, geographical stent mismatch was present in 5/14 (36%) patients randomized to the control group (interim p-value 0.07) (picture 2). The number of cine acquisitions performed before stent implantation (1±1.87 vs. 3.5±0.60; p=0.0007), the amount of contrast used (60±24.5 vs. 114±37.8 mL; p=0.0002), radiation dose (209 [186,315] vs. 497 [411,678] mGy; p=0.01) and procedure time (30 [20,38] vs. 50 [39,66] min; p=0.005) were significantly lower in patients randomized to the intervention group. There was a highly significant correlation between the calcium arc determined by CT and IVUS (R² = 0.84). No MACE occurred at 1 month. Conclusion We showed that pre-procedural CT planning for PCI of aorto-ostial RCA lesions allowed for optimal stent positioning while reducing procedure time, contrast and radiation use.Picture 1Picture 2

K-t PCA accelerated in-plane balanced steady-state free precession phase-contrast (PC-SSFP) for all-in-one diastolic function evaluation.

Diastolic function evaluation requires estimates of early and late diastolic mitral filling velocities (E and A) and of mitral annulus tissue velocity (e'). We aimed to develop an MRI method for simultaneous all-in-one diastolic function evaluation in a single scan by generating a 2D phase-contrast (PC) sequence with balanced steady-state free precession (bSSFP) contrast (PC-SSFP). E and A could then be measured with PC, and e' estimated by valve tracking on the magnitude images, using an established deep learning framework. Our PC-SSFP used in-plane flow-encoding, with zeroth and first moment nulling over each TR. For further acceleration, different k-t principal component analysis (PCA) methods were investigated with both retrospective and prospective undersampling. PC-SSFP was compared to separate balanced SSFP cine and PC-gradient echo acquisitions in phantoms and in 10 healthy subjects. Phantom experiments showed that PC-SSFP measured accurate velocities compared to PC-gradient echo (r = 0.98 for a range of pixel-wise velocities -80 cm/s to 80 cm/s). In subjects, PC-SSFP generated high SNR and myocardium-blood contrast, and excellent agreement for E (limits of agreement [LOA] 0.8 ± 2.4 cm/s, r = 0.98), A (LOA 2.5 ± 4.1 cm/s, r = 0.97), and e' (LOA 0.3 ± 2.6 cm/s, r = 1.00), versus the standard methods. The best k-t PCA approach processed the complex difference data and substituted in raw k-space data. With prospective k-t PCA acceleration, higher frame rates were achieved (50 vs. 25 frames per second without k-t PCA), yielding a 13% higher e'. The proposed PC-SSFP method achieved all-in-one diastolic function evaluation.

Feature-Tracking Strain Parameters Differ Between Highly Accelerated and Conventional Acquisitions: A Multisoftware Assessment.

Cardiac magnetic resonance imaging protocols have been adapted to fit the needs for faster, more efficient acquisitions, resulting in the development of highly accelerated, compressed sensing-based (CS) sequences. The aim of this study was to evaluate intersoftware and interacquisition differences for postprocessing software applied to both CS and conventional cine sequences. A total of 106 individuals (66 healthy volunteers, 40 patients with dilated cardiomyopathy, 51% female, 38±17y) underwent cardiac magnetic resonance at 3T with retrospectively gated conventional cine and CS sequences. Postprocessing was performed using 2 commercially available software solutions and 1 research prototype from 3 different developers. The agreement of clinical and feature-tracking strain parameters between software solutions and acquisition types was assessed by Bland-Altmann analyses and intraclass correlation coefficients. Differences between softwares and acquisitions were assessed using Kruskal-Wallis analysis of variances. In addition, receiver operating characteristic curve-derived cutoffs were used to evaluate whether sequence-specific cutoffs influence disease classification. There were significant intersoftware ( P <0.002 for all except LV end-diastolic volume per body surface area) and interacquisition differences ( P <0.02 for all except end-diastolic volume per body surface area from Neosoft, left ventricular mass per body surface area from cvi42 and TrufiStrain and global circumferential strain from Neosoft). However, the intraclass correlation coefficients between acquisitions were strong-to-excellent for all parameters (all ≥0.81). In comparing individual softwares to a pooled mean, Bland-Altmann analyses revealed smaller magnitudes of bias for cine acquisition than for CS acquisition. In addition, the application of conventional cutoffs to CS measurements did not result in the false reclassification of patients. Significantly lower magnitudes of strain and volumetric parameters were observed in retrospectively gated CS acquisitions, despite strong-to-excellent agreement amongst software solutions and acquisition types. It remains important to be aware of the acquisition type in the context of follow-up examinations, where different cutoffs might lead to misclassifications.

Automated segmentation of 3D cine cardiovascular magnetic resonance imaging.

As the life expectancy of children with congenital heart disease (CHD) is rapidly increasing and the adult population with CHD is growing, there is an unmet need to improve clinical workflow and efficiency of analysis. Cardiovascular magnetic resonance (CMR) is a noninvasive imaging modality for monitoring patients with CHD. CMR exam is based on multiple breath-hold 2-dimensional (2D) cine acquisitions that should be precisely prescribed and is expert and institution dependent. Moreover, 2D cine images have relatively thick slices, which does not allow for isotropic delineation of ventricular structures. Thus, development of an isotropic 3D cine acquisition and automatic segmentation method is worthwhile to make CMR workflow straightforward and efficient, as the present work aims to establish. Ninety-nine patients with many types of CHD were imaged using a non-angulated 3D cine CMR sequence covering the whole-heart and great vessels. Automatic supervised and semi-supervised deep-learning-based methods were developed for whole-heart segmentation of 3D cine images to separately delineate the cardiac structures, including both atria, both ventricles, aorta, pulmonary arteries, and superior and inferior vena cavae. The segmentation results derived from the two methods were compared with the manual segmentation in terms of Dice score, a degree of overlap agreement, and atrial and ventricular volume measurements. The semi-supervised method resulted in a better overlap agreement with the manual segmentation than the supervised method for all 8 structures (Dice score 83.23 ± 16.76% vs. 77.98 ± 19.64%; P-value ≤0.001). The mean difference error in atrial and ventricular volumetric measurements between manual segmentation and semi-supervised method was lower (bias ≤ 5.2 ml) than the supervised method (bias ≤ 10.1 ml). The proposed semi-supervised method is capable of cardiac segmentation and chamber volume quantification in a CHD population with wide anatomical variability. It accurately delineates the heart chambers and great vessels and can be used to accurately calculate ventricular and atrial volumes throughout the cardiac cycle. Such a segmentation method can reduce inter- and intra- observer variability and make CMR exams more standardized and efficient.

Real Time Volumetric MRI for MR-Guided 3D Motion Tracking via Sparse Prior-Augmented Neural Representation Learning

To reconstruct volumetric MRI from orthogonal cine acquisition aided by sparse priors of 2 static 3D MRI through implicit neural representation (NeRP) learning, with the goal of eliminating large-scale training datasets for data-driven sparse MRI reconstruction and supporting clinical workflow of real time 3D motion tracking during MR-guided radiotherapy. A multi-layer perceptron network was trained to learn the NeRP of a patient-specific MRI dataset, where the network takes 4D data coordinates of voxel locations and motion states as inputs and outputs corresponding voxel intensities. By first learning the NeRP of 2 static 3D MRI with different breathing motion states, prior knowledge of patient breathing motion was embedded into network weights through optimization. The prior knowledge was then augmented from 2 to 31 motion states by querying the optimized network at interpolated/extrapolated motion state coordinates. Starting from the prior-augmented network as an initialization point, the network was further trained using sparse samples of 2 orthogonal cine slices. The final volumetric reconstruction was obtained by querying the trained network at desired 3D spatial locations. We evaluated the proposed method using 5-minute volumetric MRI time series with 340 ms temporal resolution collected from 7 liver carcinoma patients. The time series was acquired using golden-angle radial MRI sequence and reconstructed through retrospective sorting. Two MRI with inhale and exhale states respectively were selected from the first 30 sec of the time series for prior embedding and augmentation. The remaining 4.5-min time series was used for volumetric reconstruction evaluation, where we retrospectively subsampled each MRI to 2 orthogonal slices and compared network-reconstructed images to ground truth images in terms of image quality and the capability of supporting 3D target motion tracking. Across the 7 patients evaluated, the peak signal to noise ratio between model reconstruction and ground truth was 54.66 ± 6.16 dB and the structural similarity index measure was 0.99 ± 0.01. Gross tumor volume (GTV) contours estimated by deforming a reference state MRI to model-reconstructed and ground truth MRI showed good consistency. The 95-percentile Hausdorff distance between GTV contours was 1.89 ± 1.13 mm, which is less than the voxel dimension. The mean GTV centroid position difference between ground truth and model estimation was less than 1 mm in all 3 orthogonal directions. Volumetric MRI from orthogonal cine acquisition with sparse priors is feasible by modeling prior knowledge through implicit neural representation learning. The model-reconstructed images showed sufficient accuracy in supporting 3D motion tracking of abdominal targets. By eliminating the need for large scale training datasets, the method promises to enable clinical implementation of 3D motion tracking for precision radiation therapy.

MRI detects increased aortic stiffening and myocardial dysfunction after TEVAR of blunt injury in young patients.

Background: Thoracic endovascular aortic repair (TEVAR) is a well-established technique for the management of blunt thoracic aortic injury (BTAI). Despite improvements in vascular imaging, graft material properties, and implant techniques, stent-graft deployment artificially induces aortic stiffening. This study aimed to evaluate the midterm effect of thoracic endovascular aortic repair after blunt thoracic aortic injury on aortic stiffness and cardiac function in young patients using cardiovascular magnetic resonance (CMR) imaging. Patients and methods: From all patients who underwent TEVAR for BTAI between 2009 and 2019 in a single institution, 10 patients with no other comorbidities affecting arterial stiffness were sex-, age-, height-, and body surface area-matched to 10 healthy controls. Comprehensive CMR examination was performed in all controls and patients. The mean follow-up period was 5.4±1.8 years; the mean age at the time of TEVAR was 30.3±8.7 years. Results: Four patients who underwent TEVAR developed arterial hypertension. 4D flow CMR-based analysis demonstrated higher global pulse wave velocity (PWV) in TEVAR patients than in controls (p=0.012). Segmental analysis showed a higher PWV in the descending and abdominal aorta. The indexed diameter of the ascending aorta was larger in TEVAR patients than in controls (p=0.007). The CINE acquisitions demonstrated increased left ventricular myocardial thickness (p<0.001). The 3D global diastolic strain rate and diastolic longitudinal velocity (e') decreased, and the A-wave velocity increased. Native myocardial T1 values were significantly higher in TEVAR patients (p=0.037). Conclusions: Young patients with TEVAR after BTAI are at an increased risk of developing vascular and myocardial dysfunction due to increased aortic stiffness. CMR follow-up allows for a comprehensive and radiation-free evaluation of vascular stiffness and associated myocardial changes, especially at the early and subclinical stages.

Cardiovascular magnetic resonance derived biventricular strain in healthy adolescents: reference values and comparison between myocardial tagging and feature-tracking

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Instituto de Salud Carlos III (ISCIII) European Regional Development Fun/European Social Fund (A way to make Europe/Investing in your future). Background Strain measurements have demonstrated to be earlier and more sensitive markers of contractile dysfunction than ejection fraction (EF) alone. Myocardial tagging (MT) is considered the reference standard for CMR strain measurements, but its clinical application is limited because acquisition and analysis are laborious and time consuming. Feature-tracking (FT) CMR allows strain quantification using steady-state in free-precession (SSFP) sequence, which is obtained in routine CMR protocols, being easily applicable in clinical practice. Literature regarding reference strain values in pediatric populations is scarce and, to the best of our knowledge, there are no studies comparing FT and MT in healthy adolescents. Purpose To provide CMR strain reference values in healthy adolescents and compare FT to MT results. Methods A CMR study was performed in healthy adolescents enrolled in the "Early ImaginG Markers of unhealthy lifestyles in Adolescents" (EnIGMA) project using a 3-Tesla CMR scanner between March and October 2021. The imaging protocol included a cine SSFP to provide images for chamber size and function, including FT; and MT acquisitions using spatial modulation of magnetization (SPAMM) technique. Cine acquisitions included the entire left ventricular (LV) short axis and long-axis 4 chamber (4c)- and 2 chamber (2c)-views, while MT acquisitions included three short axis slices (basal, mid and apical) and long-axis 4c-view. Endo- and epicardial borders were manually contoured in the end-diastolic (ED) phase. A non-rigid, elastic algorithm was used for segmentation and registration for strain quantification. If tracking was suboptimal, the software only allowed adaptations of the contours on the ED image. Longitudinal (LS) and circumferential (CS) strains were obtained for the LV and right ventricle (RV). Results CMR scans were performed in 123 adolescents (64 girls, 52.0%) with a mean age of 16.0 years (standard deviation [SD]=0.4), a mean LVEF of 62.5% (SD=4.1) and a mean RVEF of 56.2% (SD=4.6). Reference percentiles (P) 3, 10, 25, 50, 90 and 97 for strain values by sex are provided in Figure 1. FT-measured LVLS and LVCS were higher in girls than in boys (-19.8 vs -17.8%, p&amp;lt;0.01; and -22.2 vs -21.0%, p&amp;lt;0.01; respectively), and these differences were confirmed with MT analysis. There were no consistent between-sex differences for RVLS and RVCS. Bland-Altman analyses showed reasonable agreement between FT and MT for LVLS, LVCS, RVLS and RVCS (Figure 2 A, B, C and D). Conclusions This study provided CMR derived reference values for left and right ventricle strain in adolescents aged 15 to 18 years. This work suggests that FT is a reasonably valid technique to measure LV and RV strain in this population. This information may be useful for diagnostic and prognostic implications in adolescent patients.

C49 NO CONTRAST TAVI

Abstract Background Chronic renal failure is a common comorbidity in patients undergoing TAVI. Large amounts of contrast media are generally needed to safely perform TAVI with potential deleterious effects on renal function and long term life quality. Objectives Every step of the procedure can be safely replaced by no contrast techniques: ultrasound guided vascular puncture and final check, alignement of 3 guides in Valsalva sinuses to check coplanarity or cusp overlap, coupling of hemodynamics and transthoracic echocardiography to check the results and need of postdilatation, measure of gradient across the arterial puncture to rule out iatrogenic stenosis. Matherials and Methods 3 patients with severe renal failure (GFR &amp;lt; 30 ml/min/ 1.73 m2) and 1 patient with moderate renal failure and previous double renal transplantation underwent TAVI with protocol without contrast in our center in the last year. All cases were performed with local anesthesia and conscious sedation. 3 cases were performed with balloon expandable bioprosthesis and 1 with self expandable bioprosthesis. Results We were able to perform TAVI procedure without contrast in all 4 patients in which the technique was attempted without complications. Hemodynamics was excellent in all cases with no residual gradient or significant leaks. No vascular complication occured. Procedural time was generally 20% longer than average procedure but X rays dose exposure was reduced because less cine acquisitions were needed. Conclusions TAVI with no use of contrast media is feasible and safe by extensive use of vascular ultrasound, hemodynamics, transthoracic echocardiography and multiple guides to depict coronary sinuses and assure correct prothesis implantation.

Comparison of Biplane Area-Length Method and 3D Volume Quantification by Using Cardiac MRI for Assessment of Left Atrial Volume in Atrial Fibrillation

To compare maximum left atrial (LA) volume (LAV) from the routinely used biplane area-length (BAL) method with three-dimensional (3D)-based volumetry from late gadolinium-enhanced MRI (3D LGE MRI) and contrast-enhanced MR angiography (3D CE-MRA) in patients with atrial fibrillation (AF). Sixty-four patients with AF (mean age, 63 years ± 9 [SD]; 40 male patients) were retrospectively included from a prospective cohort acquired between October 2018 and February 2021. All patients underwent a research MRI examination that included standard two- and four-chamber cine acquisitions, 3D CE-MRA, and 3D LGE MRI performed prior to the atrial kick. Contour delineation on cine imaging and LA 3D segmentations were performed by a radiologist. Maximum LAV (BALmax) was extracted from the BAL volume-time curve and compared with LAV from 3D CE-MRA and 3D LGE MRI. The Kruskal-Wallis test was performed, followed by the Dunn post hoc test and Bland-Altman analyses. Interobserver variability was assessed in 10 patients. BALmax underestimated LAV compared with 3D CE-MRA (bias: -23.5 mL ± 46.2, P < .001) and 3D LGE MRI (bias: -31.3 mL ± 58.3, P < .001), whereas 3D LGE MRI volumes showed no evidence of a difference from 3D CE-MRA (bias: 7.8 mL ± 45.7, P = .38). Interobserver variability yielded excellent agreement for each method (intraclass correlation coefficient, 0.96-0.98). BALmax underestimated LAV in patients with AF compared with 3D LGE MRI and 3D CE-MRA, suggesting that the geometric assumption of an ellipsoidal LA shape in BAL does not reflect LA geometry in patients with AF.Keywords: Left Atrial Volume, Biplane Area-Length, Late Gadolinium-enhanced 3D MRI, Contrast-enhanced 3D MR Angiography, Atrial Fibrillation Supplemental material is available for this article. © RSNA, 2023.

Safety and efficacy of an ultra low dose fluoroscopic protocol for chronic total occlusion recanalization.

Chronic total occlusion (CTO) revascularization is a major source of radiation for both patients and physicians. Therefore, efforts to minimize radiation during CTOpercutaneous coronary intervention (PCI) are highly encouraged. To evaluate the impact of an Ultra Low fluoroscopic Dose Protocol (ULDP), based on 3.75 frames per second for the fluoroscopy and 7.5 frames per second for the cine acquisition, during CTO PCI. One hundred fiftyconsecutive patients who underwent CTO PCI were retrospectively enrolled. Eighty-fiveunderwent standard dose protocol (SDP) and 65 ULDP. Radiation exposure and acute clinical outcomes were compared between groups. Results were stratified according to lesion complexity. Patients undergoing ULDP, as compared to those undergoing SDP, showed a significant reduction of kerma area product, both for simple lesions (6861.0 vs. 13236.0 mGy × cm2 ; p = 0.014) and complex lesions (CL) (8865.0 vs. 16618.0 mGy × cm2 ; p < 0.001). Similarly, Air Kerma (AK) was lower when ULDP was used (1222.5 vs. 2015.0 cGy in SL, p = 0.134; 1499.0 vs. 2794.0 cGy in CL, p < 0.001). No significant differences were reported regarding procedural success and in-hospital major adverse cardiovascular eventsbetween groups. Notably, there was not any crossover from ULDO to SDP due to poor quality images. Interestingly, fluoroscopy time, procedural time and contrast volume was significantly lower in patients undergoing ULDP only for CLs. ULDP significantly reduces radiation exposure in the setting of high complexity procedures such as CTO PCI. This reduction seemed to be greater with increased procedural complexity and did not impact acute success or adverse clinical events.

Feasibility of delivered dose reconstruction for MR-guided SBRT of pancreatic tumors with fast, real-time 3D cine MRI

Background and purposeIn MR-guided SBRT of pancreatic cancer, intrafraction motion is typically monitored with (interleaved) 2D cine MRI. However, tumor surroundings are often not fully captured in these images, and motion might be distorted by through-plane movement. In this study, the feasibility of highly accelerated 3D cine MRI to reconstruct the delivered dose during MR-guided SBRT was assessed. Materials and methodsA 3D cine MRI sequence was developed for fast, time-resolved 4D imaging, featuring a low spatial resolution that allows for rapid volumetric imaging at 430 ms. The 3D cines were acquired during the entire beam-on time of 23 fractions of online adaptive MR-guided SBRT for pancreatic tumors on a 1.5 T MR-Linac. A 3D deformation vector field (DVF) was extracted for every cine dynamic using deformable image registration. Next, these DVFs were used to warp the partial dose delivered in the time interval between consecutive cine acquisitions. The warped dose plans were summed to obtain a total delivered dose. The delivered dose was also calculated under various motion correction strategies. Key DVH parameters of the GTV, duodenum, small bowel and stomach were extracted from the delivered dose and compared to the planned dose. The uncertainty of the calculated DVFs was determined with the inverse consistency error (ICE) in the high-dose regions. ResultsThe mean (SD) relative (ratio delivered/planned) D99% of the GTV was 0.94 (0.06), and the mean (SD) relative D0.5cc of the duodenum, small bowel, and stomach were respectively 0.98 (0.04), 1.00 (0.07), and 0.98 (0.06). In the fractions with the lowest delivered tumor coverage, it was found that significant lateral drifts had occurred. The DVFs used for dose warping had a low uncertainty with a mean (SD) ICE of 0.65 (0.07) mm. ConclusionWe employed a fast, real-time 3D cine MRI sequence for dose reconstruction in the upper abdomen, and demonstrated that accurate DVFs, acquired directly from these images, can be used for dose warping. The reconstructed delivered dose showed only a modest degradation of tumor coverage, mostly attainable to baseline drifts. This emphasizes the need for motion monitoring and development of intrafraction treatment adaptation solutions, such as baseline drift corrections.

Cardiac MRI-based right-to-left ventricular blood pool T2 relaxation times ratio correlates with exercise capacity in patients with chronic heart failure

BackgroundMRI T2 mapping has been proven to be sensitive to the level of blood oxygenation. We hypothesized that impaired exercise capacity in chronic heart failure is associated with a greater difference between right (RV) to left ventricular (LV) blood pool T2 relaxation times due to a higher level of peripheral blood desaturation, compared to patients with preserved exercise capacity and to healthy controls. MethodsPatients with chronic heart failure (n = 70) who had undergone both cardiac MRI (CMR) and a 6-min walk test (6MWT) were retrospectively identified. Propensity score matched healthy individuals (n = 35) served as control group. CMR analyses included cine acquisitions and T2 mapping to obtain blood pool T2 relaxation times of the RV and LV. Following common practice, age- and gender-adjusted nominal distances and respective percentiles were calculated for the 6MWT. The relationship between the RV/LV T2 blood pool ratio and the results from 6MWT were evaluated by Spearman's correlation coefficients and regression analyses. Inter-group differences were assessed by independent t-tests and univariate analysis of variance. ResultsThe RV/LV T2 ratio moderately correlated with the percentiles of nominal distances in the 6MWT (r = 0.66) while ejection fraction, end-diastolic and end-systolic volumes showed no correlation (r = 0.09, 0.07 and − 0.01, respectively). In addition, there were significant differences in the RV/LV T2 ratio between patients with and without significant post-exercise dyspnea (p = 0.001). Regression analyses showed that RV/LV T2 ratio was an independent predictor of the distance walked and the presence of post-exercise dyspnea (p < 0.001). ConclusionThe proposed RV/LV T2 ratio, obtained by two simple measurements on a routinely acquired four-chamber T2 map, was superior to established parameters of cardiac function to predict exercise capacity and the presence of post-exercise dyspnea in patients with chronic heart failure.