Carr, James

Foundation models can streamline imaging workflows, improve diagnostic accuracy, enable personalized treatment, and, via integrated generative artificial intelligence, create synthetic images to augment scarce real-world data; however, successful adoption requires explainability, trust, and workflow integration.

BackgroundDoxorubicin and doxorubicin‐trastuzumab combination chemotherapy have been associated with cardiotoxicity that eventually leads to heart failure and may limit dose‐effective cancer treatment. Current diagnostic strategies rely on decreased ejection fraction (EF) to diagnose cardiotoxicity.PurposeThe aim of this study is to explore the potential of cardiac MR (CMR) imaging to identify imaging biomarkers in a mouse model of chemotherapy‐induced cardiotoxicity.MethodsA cumulative dose of 25 mg/kg doxorubicin was administered over three weeks using subcutaneous pellets (n = 9, Dox). Another group (n = 9) received same dose of Dox and a total of 10 mg/kg trastuzumab (DT). Mice were imaged at baseline, 5/6 weeks and 10 weeks post‐treatment on a 7T MRI system. The protocol included short‐axis cine MRI covering the left ventricle (LV) and mid‐ventricular short‐axis tissue phase mapping (TPM), pre‐ and post‐contrast T1 mapping, T2 mapping and Displacement Encoding with Stimulated Echoes (DENSE) strain encoded MRI. EF, peak myocardial velocities, native T1, T2, extracellular volume (ECV), and myocardial strain were quantified. N = 7 mice were sacrificed for histopathologic assessment of apoptosis at 5/6 weeks.ResultsGlobal peak systolic longitudinal velocity was reduced at 5/6 weeks in Dox (0.6 ± 0.3 vs 0.9 ± 0.3, p = 0.02). In the Dox group, native T1 was reduced at 5/6 weeks (1.3 ± 0.2 ms vs 1.6 ± 0.2 ms, p = 0.02), and relatively normalized at week 10 (1.4 ± 0.1 ms vs 1.6 ± 0.2 ms, p > 0.99). There was no change in EF and other MRI parameters and histopathologic results demonstrated minimal apoptosis in all mice (~1–2 apoptotic cell/high power field), suggesting early‐stage cardiotoxicity.ConclusionsIn a mouse model of chemotherapy‐induced cardiotoxicity using doxorubicin and trastuzumab, advanced CMR shows promise in identifying treatment‐related decrease in myocardial velocity and native T1 prior to the onset of cardiomyocyte apoptosis and reduction of EF.

Background: Four-dimensional (D) flow magnetic resonance imaging (MRI) is limited by time-consuming and nonstandardized data analysis. We aimed to test the efficiency and interobserver reproducibility of a dedicated 4D flow MRI analysis workflow. Materials and Methods: Thirty retrospectively identified patients with bicuspid aortic valve (BAV, age=47.8±11.8 y, 9 male) and 30 healthy controls (age=48.8±12.5 y, 21 male) underwent Aortic 4D flow MRI using 1.5 and 3 T MRI systems. Two independent readers performed 4D flow analysis on a dedicated workstation including preprocessing, aorta segmentation, and placement of four 2D planes throughout the aorta for quantification of net flow, peak velocity, and regurgitant fraction. 3D flow visualization using streamlines was used to grade aortic valve outflow jets and extent of helical flow. Results: 4D flow analysis workflow time for both observers: 5.0±1.4 minutes per case (range=3 to 10 min). Valve outflow jets and flow derangement was visible in all 30 BAV patients (both observers). Net flow, peak velocity, and regurgitant fraction was significantly elevated in BAV patients compared with controls except for regurgitant fraction in plane 4 (91.1±29.7 vs. 62.6±19.6 mL/s, 37.1% difference; 121.7±49.7 vs. 90.9±26.4 cm/s, 28.9% difference; 9.3±10.1% vs. 2.0±3.4%, 128.0% difference, respectively; P <0.001). Excellent intraclass correlation coefficient agreement for net flow: 0.979, peak velocity: 0.931, and regurgitant fraction: 0.928. Conclusion: Our study demonstrates the potential of an efficient data analysis workflow to perform standardized 4D flow MRI processing in under 10 minutes and with good-to-excellent reproducibility for flow and velocity quantification in the thoracic aorta.

Abstract Aims While right ventricular (RV) dysfunction is associated with worse prognosis in co-morbid pulmonary hypertension and heart failure with preserved ejection fraction (PH-HFpEF), the mechanisms driving RV dysfunction are unclear. We evaluated the extent and clinical correlates of diffuse RV myocardial fibrosis in PH-HFpEF, as measured by cardiovascular magnetic resonance-derived extracellular volume (ECV). Methods and results We prospectively enrolled participants with PH-HFpEF (n = 14), pulmonary arterial hypertension (PAH; n = 13), and controls (n = 8). All participants underwent high-resolution cardiovascular magnetic resonance, and case subjects (PH-HFpEF and PAH) additionally underwent right heart catheterization. T1 mapping was performed using high-resolution modified look-locker inversion recovery with a 1 × 1 mm2 in-plane resolution. RV free wall T1 values were quantified, and ECV was calculated. Participants with PH-HFpEF were older and carried higher rates of hypertension and obstructive sleep apnoea than those with PAH. While RV ECV was similar between PH-HFpEF and PAH (33.1 ± 8.0 vs. 34.0 ± 4.5%; P = 0.57), total pulmonary resistance was lower in PH-HFpEF compared with PAH [PH-HFpEF: 5.68 WU (4.70, 7.66 WU) vs. PAH: 8.59 WU (8.14, 12.57 WU); P = 0.01]. RV ECV in PH-HFpEF was associated with worse indices of RV structure (RV end-diastolic volume: r = 0.67, P = 0.01) and RV function (RV free wall strain: r = 0.59, P = 0.03) but was not associated with RV afterload (total pulmonary resistance: r = 0.08, P = 0.79). Conversely, there was a strong correlation between RV ECV and RV afterload in PAH (r = 0.57, P = 0.04). Conclusions Diffuse RV fibrosis, as measured by ECV, is present in PH-HFpEF and is associated with adverse RV structural and functional remodelling but not degree of pulmonary vasculopathy. In PH-HFpEF, diffuse RV fibrosis may occur out of proportion to the degree of RV afterload.

AbstractIntroductionA recent study reported that diffuse left ventricular (LV) fibrosis is a predictor of atrial fibrillation (AF) recurrence following catheter ablation, by measuring postcontrast cardiac T1 (an error prone metric as per the 2017 Society for Cardiovascular Magnetic Resonance consensus statement) using an inversion‐recovery pulse sequence (an error prone method in arrhythmia) in AF ablation candidates. The purpose of this study was to verify the prior study, by measuring extracellular volume (ECV) fraction (an accurate metric) using a saturation‐recovery pulse sequence (accurate method in arrhythmia).Methods and ResultsThis study examined 100 AF patients (mean age = 62 ± 11 years, 69 males and 31 females, 67 paroxysmal [pAF] and 33 persistent [peAF]) who underwent a preablation cardiovascular magnetic resonance (CMR) exam. LV ECV and left atrial (LA) and LV functional parameters were quantified using standard analysis methods. During an average follow‐up period of 457 ± 261 days with 4 ± 3 rhythm checks per patient, 72 patients maintained sinus rhythm. Between those who maintained sinus rhythm (n = 72) and those who reverted to AF (n = 28), the only clinical characteristic that was significantly different was age (60 ± 12 years vs 66 ± 9 years); for CMR metrics, neither mean LV ECV (25.1 ± 3.3% vs 24.7 ± 3.7%), native LV T1 (1093.8 ± 73.5 ms vs 1070.2 ± 115.9 ms), left ventricular ejection fraction (54.1 ± 11.2% vs 55.7 ± 7.1%), nor LA end diastolic volume/body surface area (42.4 ± 14.8 mL/m2 vs 43.4 ± 19.6 mL/m2) were significantly different (P ≥ .23). According to Cox regression tests, none of the clinical and imaging variables predict AF recurrence.ConclusionNeither LV ECV nor other CMR metrics predict recurrence of AF following catheter ablation.

BackgroundSystematic evaluation of complex flow in the true lumen and false lumen (TL, FL) is needed to better understand which patients with chronic descending aortic dissection (DAD) are predisposed to complications.PurposeTo develop quantitative hemodynamic maps from 4D flow MRI for evaluating TL and FL flow characteristics.Study TypeRetrospective.PopulationIn all, 20 DAD patients (age = 60 ± 11 years; 12 male) (six medically managed type B AD [TBAD], 14 repaired type A AD [rTAAD] now with ascending aortic graft [AAo] or elephant trunk [ET1] repair) and 21 age‐matched controls (age = 59 ± 10 years; 13 male) were included.Field Strength/Sequence1.5T, 3T, 4D flow MRI.Assessment4D flow MRI was acquired in all subjects. Data analysis included 3D segmentation of TL and FL and voxelwise calculation of forward flow, reverse flow, flow stasis, and kinetic energy as quantitative hemodynamics maps.Statistical TestsAnalysis of variance (ANOVA) or Kruskal–Wallis tests were performed for comparing subject groups. Correlation and Bland–Altman analysis was performed for the interobserver study.ResultsPatients with rTAAD presented with elevated TL reverse flow (AAo repair: P = 0.004, ET1: P = 0.018) and increased TL kinetic energy (AAo repair: P = 0.0002, ET1: P = 0.011) compared to controls. In addition, TL kinetic energy was increased vs. patients with TBAD (AAo repair: P = 0.021, ET1: P = 0.048). rTAAD was associated with higher FL kinetic energy and lower FL stasis compared to patients with TBAD (AAo repair: P = 0.002, ET1: P = 0.024 and AAo repair: P = 0.003, ET1: P = 0.048, respectively).Data ConclusionQuantitative maps from 4D flow MRI demonstrated global and regional hemodynamic differences between DAD patients and controls. Patients with rTAAD vs. TBAD had significantly altered regional TL and FL hemodynamics. These findings indicate the potential of 4D flow MRI‐derived hemodynamic maps to help better evaluate patients with DAD.Level of Evidence: 3Technical Efficacy Stage: 1J. Magn. Reson. Imaging 2020;51:1357–1368.