Browsing by Author "Nadel, James"

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    Automated Segmentation of Thoracic Aortic Lumen and Vessel Wall on 3D Bright- and Black-Blood MRI using nnU-Net
    (2025) Cesario, Matteo; Littlewood, Simon J.; Nadel, James; Fletcher, Thomas J.; Fotaki, Anastasia; Castillo Passi, Carlos; Hajhosseiny, Reza; Pouliopoulos, Jim; Jabbour, Andrew; Olivero, Ruperto; Rodríguez Palomares, José; Kooi, M. Eline; Prieto Vásquez, Claudia; Botnar, René Michael
    BACKGROUND: Magnetic resonance angiography (MRA) is an important tool for aortic assessment in several cardiovascular diseases. Assessment of MRA images relies on manual segmentation; a time-intensive process that is subject to operator variability. We aimed to optimize and validate two deep-learning models for automatic segmentation of the aortic lumen and vessel wall in high-resolution ECG-triggered free-breathing respiratory motion-corrected 3D bright- and black-blood MRA images. METHODS: Manual segmentation, serving as the ground truth, was performed on 25 bright-blood and 15 black-blood 3D MRA image sets acquired with the iT2PrepIR-BOOST sequence (1.5T) in thoracic aortopathy patients. The training was performed with nnU-Net for bright-blood (lumen) and black-blood image sets (lumen and vessel wall). Training consisted of a 70:20:10% training: validation: testing split. Inference was run on datasets (single vendor) from different centres (UK, Spain, and Australia), sequences (iT2PrepIR-BOOST, T2 prepared CMRA, and TWIST MRA), acquired resolutions (from 0.9 mm 3 to 3 mm 3), and field strengths (0.55T, 1.5T, and 3T). Predictive measurements comprised Dice Similarity Coefficient (DSC), and Intersection over Union (IoU). Postprocessing (3D slicer) included centreline extraction, diameter measurement, and curved planar reformatting (CPR). RESULTS: The optimal configuration was the 3D U-Net. Bright blood segmentation at 1.5T on iT2PrepIR-BOOST datasets (1.3 and 1.8 mm 3) and 3D CMRA datasets (0.9 mm 3) resulted in DSC ≥ 0.96 and IoU ≥ 0.92. For bright-blood segmentation on 3D CMRA at 0.55T, the nnUNet achieved DSC and IoU scores of 0.93 and 0.88 at 1.5 mm³, and 0.68 and 0.52 at 3.0 mm³, respectively. DSC and IoU scores of 0.89 and 0.82 were obtained for CMRA image sets (1 mm 3) at 1.5T (Barcelona dataset). DSC and IoU score of the BRnnUNet model were 0.90 and 0.82 respectively for the contrast-enhanced dataset (TWIST MRA). Lumen segmentation on black blood 1.5T iT2PrepIR-BOOST image sets achieved DSC ≥ 0.95 and IoU ≥ 0.90, and vessel wall segmentation resulted in DSC ≥ 0.80 and IoU ≥ 0.67. Automated centreline tracking, diameter measurement and CPR were successfully implemented in all subjects. CONCLUSION: Automated aortic lumen and wall segmentation on 3D bright- and black-blood image sets demonstrated excellent agreement with ground truth. This technique demonstrates a fast and comprehensive assessment of aortic morphology with great potential for future clinical application in various cardiovascular diseases.
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    Molecular magnetic resonance imaging of myeloperoxidase activity identifies culprit lesions and predicts future atherothrombosis
    (2024) Nadel, James; Wang, Xiaoying; Saha, Prakash; Bongers, André; Tumanov, Sergey; Giannotti, Nicola; Chen, Weiyu; Vigder, Niv; Chowdhury, Mohammed; Lima da Cruz, Gastao; Velasco Jimeno, Carlos; Prieto Vasquez, Claudia; Jabbour, Andrew; Botnar, Rene Michael; Stocker, Roland; Phinikaridou, Alkystis
    Aims Unstable atherosclerotic plaques have increased activity of myeloperoxidase (MPO). We examined whether molecular magnetic resonance imaging (MRI) of intraplaque MPO activity predicts future atherothrombosis in rabbits and correlates with ruptured human atheroma. Methods and results Plaque MPO activity was assessed in vivo in rabbits (n = 12) using the MPO-gadolinium (Gd) probe at 8 and 12 weeks after induction of atherosclerosis and before pharmacological triggering of atherothrombosis. Excised plaques were used to confirm MPO activity by liquid chromatography–tandem mass spectrometry (LC–MSMS) and to determine MPO distribution by histology. MPO activity was higher in plaques that caused post-trigger atherothrombosis than plaques that did not. Among the in vivo MRI metrics, the plaques’ R1 relaxation rate after administration of MPO-Gd was the best predictor of atherothrombosis. MPO activity measured in human carotid endarterectomy specimens (n = 30) by MPO-Gd–enhanced MRI was correlated with in vivo patient MRI and histological plaque phenotyping, as well as LC–MSMS. MPO-Gd retention measured as the change in R1 relaxation from baseline was significantly greater in histologic and MRI-graded American Heart Association (AHA) type VI than type III–V plaques. This association was confirmed by comparing AHA grade to MPO activity determined by LC–MSMS. Conclusion We show that elevated intraplaque MPO activity detected by molecular MRI employing MPO-Gd predicts future atherothrombosis in a rabbit model and detects ruptured human atheroma, strengthening the translational potential of this approach to prospectively detect high-risk atherosclerosis.
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    Site-specific analysis of thoracic aortic aneurysm and cardiovascular mortality: Insights from the National Echo Database Australia
    (2025) Nadel, James; Suinesiaputra, Avan; Paratz, Elizabeth D.; Humphries, Juile; Young, Alistair; Botnar, René Michael; Celermajer, David S.; Strange, Geoff; Playford, David
    Background Aortic diameter remains the most utilised criterion for considering surgical correction. In uncomplicated cases guidelines do not differentiate between the size of aneurysms at the root and ascending aorta. In order to improve practice, greater understanding of site-specific TAA is needed. A nationwide echocardiographic dataset linked to mortality outcomes was examined to determine how TAA affects cardiovascular (CVD) mortality.Methods The National Echo Database Australia (NEDA) was examined for aortic dimensions at the sinuses of Valsalva (SoV), sinotubular junction (STJ) and ascending aorta (AscAo). Patients were stratified according to absolute aortic diameters and grouped as normal (<4cm), mild (4.0-4.5cm), moderate (4.5-5cm) and severely (>5cm) dilated at the prescribed thoracic aortic sites. Mortality data was linked from the National Death Index.Results 477,501 echocardiographs from 175,158 patients with 2,897,357 patient-years of follow-up were included. Severe TAA at any site increased likelihood of 10-year CVD mortality compared to normal aortic diameters (31% vs. 14%, p<0.0001), with incremental increase in probability of CVD death when moving from the proximal to distal ascending aorta; CVD mortality at SoV 30% (HR 1.79; CI 1.2-2.67; p=0.004), STJ 41% (HR 1.91; CI 1.11-3.29; p=0.002) and AscAo 45% (HR 3.96; CI 2.06-7.64; p<0.001).Conclusions Severe TAA increases the probability of cardiovascular mortality. Given the low event rate of aortic death (0.2%) this is not solely explained by increased dissection risk. Interestingly, there is a doubling of CVD mortality likelihood when moving from the proximal to distal ascending aorta. These results suggest those with severe AscAo dilatation may be at higher CVD risk compared to those with aortic root aneurysms, identifying new considerations for risk stratification and surgical management.
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    The future of MRI in thoracic aortopathy: blueprint for the paradigm shift to improve management
    (2025) Nadel, James; Rodríguez Palomares, José; Phinikaridou, Alkystis; Prieto Vásquez, Claudia Del Carmen; Masci, Pier Giorgio; Botnar, René Michael
    Thoracic aortopathies result in aneurysmal expansion of the aorta that can lead to rapidly fatal aortic dissection or rupture. Despite the availability of abundant non-invasive imaging tools, the greatest contemporary challenge in the management of thoracic aortic aneurysm (TAA) is the lack of reliable metrics for risk stratification, with absolute aortic diameter, growth rate and syndromic factors remaining the primary determinants by which prophylactic surgical intervention is adjudged. Advanced MRI techniques present as a potential key to unlocking insights into TAA that could guide disease surveillance and surgical intervention. MRI has the capacity to encapsulate the aorta as a complex biomechanical structure, permitting the determination of aortic volume, morphology, composition, distensibility and fluid dynamics in a time-efficient manner. Nevertheless, current standard-of-care imaging protocols do not harness its full capacity. This state-of-the-art review explores the emerging role of MRI in the assessment of TAA and presents a blueprint for the required paradigm shift away from aortic size as the sole metric for risk stratifying TAA.