Deep learning-based left ventricular segmentation demonstrates improved performance on respiratory motion-resolved whole-heart reconstructions

IntroductionDeep learning (DL)-based segmentation has gained popularity for routine cardiac magnetic resonance (CMR) image analysis and in particular, delineation of left ventricular (LV) borders for LV volume determination. Free-breathing, self-navigated, whole-heart CMR exams provide high-resolution, isotropic coverage of the heart for assessment of cardiac anatomy including LV volume. The combination of whole-heart free-breathing CMR and DL-based LV segmentation has the potential to streamline the acquisition and analysis of clinical CMR exams. The purpose of this study was to compare the performance of a DL-based automatic LV segmentation network trained primarily on computed tomography (CT) images in two whole-heart CMR reconstruction methods: (1) an in-line respiratory motion-corrected (Mcorr) reconstruction and (2) an off-line, compressed sensing-based, multi-volume respiratory motion-resolved (Mres) reconstruction. Given that Mres images were shown to have greater image quality in previous studies than Mcorr images, we hypothesized that the LV volumes segmented from Mres images are closer to the manual expert-traced left ventricular endocardial border than the Mcorr images.MethodThis retrospective study used 15 patients who underwent clinically indicated 1.5 T CMR exams with a prototype ECG-gated 3D radial phyllotaxis balanced steady state free precession (bSSFP) sequence. For each reconstruction method, the absolute volume difference (AVD) of the automatically and manually segmented LV volumes was used as the primary quantity to investigate whether 3D DL-based LV segmentation generalized better on Mcorr or Mres 3D whole-heart images. Additionally, we assessed the 3D Dice similarity coefficient between the manual and automatic LV masks of each reconstructed 3D whole-heart image and the sharpness of the LV myocardium-blood pool interface. A two-tail paired Student’s t-test (alpha = 0.05) was used to test the significance in this study.Results & DiscussionThe AVD in the respiratory Mres reconstruction was lower than the AVD in the respiratory Mcorr reconstruction: 7.73 ± 6.54 ml vs. 20.0 ± 22.4 ml, respectively (n = 15, p-value = 0.03). The 3D Dice coefficient between the DL-segmented masks and the manually segmented masks was higher for Mres images than for Mcorr images: 0.90 ± 0.02 vs. 0.87 ± 0.03 respectively, with a p-value = 0.02. Sharpness on Mres images was higher than on Mcorr images: 0.15 ± 0.05 vs. 0.12 ± 0.04, respectively, with a p-value of 0.014 (n = 15).ConclusionWe conclude that the DL-based 3D automatic LV segmentation network trained on CT images and fine-tuned on MR images generalized better on Mres images than on Mcorr images for quantifying LV volumes

Elettronica biointegrata per applicazioni mediche

I tessuti e gli organi del corpo umano sono curvilinei ed elastici; al contrario, i wafer di silicio e i circuiti elettronici sono piatti e rigidi. Il proposito di questa tesi è di illustrare i materiali, i design e le tecniche costruttive che permettono lo sviluppo di dispositivi biomedicali ad alte prestazioni, elastici, biocompatibili, biodegradabili e che siano capaci di interfacciarsi con gli organi del corpo uman

Geometric Misalignment Calibration and Detector Lag Effect Artifact Correction in a Cone-Beam Flat Panel micro-CT System for Small Animal Imaging

The cone-beam flat panel micro-CT is a high definition imaging system. It acquires projections of an object or animal to reconstruct a 3D image of its internal structure. The device is basically composed by a radiation tube and a detector panel, which are fixed to a gantry that rotates all around the test subject. The micro-CT system is affected by several imperfections and problems, that might lead to serious artifacts that deteriorate the quality of the reconstructed image. In particular, two issues have been discussed in the present work: the source-panel geometric misalignment and the detector lag effect. The first problem concerns the consequences of systems where the different elements are not perfectly aligned to each other. The second issue regards the residual signal, left in the detector's sensor after a projection acquisition, which affects the following frames with ghost images. Both these arguments have been investigated to describe their characteristics and behaviour in a typical acquisition protocol. Then two correction methods have been presented and tested on a real micro-CT device to verify their effectiveness in the artifacts compensation. In the end, a comparison between images before and after the corrections is provided and future prospects are discussed

FREE-RUNNING FRAMEWORK FOR AUTOMATED MULTIDIMENSIONAL AND COMPREHENSIVE MAGNETIC RESONANCE IMAGING OF THE HEART

Cardiovascular disease is the leading cause of morbidity and mortality globally, contributing to an estimated 31% of all deaths. According to the most recent statistics of the American Heart Association, almost 50% of these deaths are at- tributable to coronary artery diseases (CAD). Magnetic resonance imaging (MRI) has emerged as a promising imaging modality for the detection and diagnosis of CADs, as it can generate 3D images and 2D slices along any arbitrary plane, it provides high contrast for soft tissues, and the exam is safe and noninvasive. Furthermore, besides coronary vessel visualization, multiple assessments are en- abled within the same MR examination, such as whole-heart anatomy, cardiac function, tissue characterization, and perfusion. While MRI offers many advantages, the relatively long acquisition time repre- sents one of the main limitations. This aspect becomes particularly challenging when imaging the heart, as it is characterized by rapid and complex movements (bulk, respiratory, and cardiac motion), which can corrupt images with blurring artifacts. For this reason, several techniques to avoid, correct, or resolve motion have been proposed in the past decades, most of which require external devices for motion tracking and numerous manual interactions from experienced operators. Conversely, a novel approach to cardiac MRI is presented in this thesis: the free-running framework. The goal is to provide efficient motion-resolved imaging of the whole heart within a fully automated single-click acquisition and recon- struction, which does not require external devices for motion synchronization. Furthermore, the developed framework aims at providing the most comprehensive diagnostic information, including (but not limited to) anatomical and functional assessment. To illustrate the context and set the starting point of the work presented in this thesis, an overview of the milestones that led to the formulation of the free-running framework is given in the first chapter. In the second chapter, two studies present the first complete formulation of an automated and fully self-gated free-running framework for motion-resolved 5D whole-heart MRI. In particular, the first study developed a robust and precise self-gating technique to resolve cardiac motion, as an alternative to the gold- standard electrocardiogram (ECG) signals. The retrospective image reconstruc- tion pipeline was also automated to minimize the number of manual adjustments required. With this implementation, all external gating or triggering devices are no longer mandatory. In the second study, made in a collaborative effort with the Children’s Hospital of Philadelphia (Pennsylvania, USA), the free-running framework was modified and successfully tested in a cohort of congenital heart disease pediatric patients with contrast agent for motion-resolved 5D coronary angiography. These projects proved that the free-running framework is robust and flexible under various scan- ning conditions, while providing an automated and easy-to-use solution for car- diac MRI with excellent delineation of the coronary arteries. The third chapter presents four different studies that either enhance the per- formance of or extend the information provided by the free-running framework. In the first two studies, two alternative acquisition pulse sequences (FISS and LIBRE) have provided effective fat suppression in motion-resolved whole-heart 5D images for coronary MR angiography without contrast agent injection. The third project presented in this chapter, 5D flow MRI, is the result of a collaboration with Northwestern University (Illinois, USA). In this study, a 6th dimension for the resolution of cardiovascular flow dynamics was added to the free-running framework, expanding its dimensionality. The fourth project, 5D T1-mapping MRI, proposed an extension of the free- running approach to include a 6th dimension for whole-heart isotropic T1-mapping in addition to motion-resolved 5D images. In summary, the four studies presented in this chapter demonstrate how the framework first developed for 5D imaging already enabled and accelerated the research in the domain of cardiac MRI both inside and outside of our institution. In the last project included in this thesis, presented in the fourth chapter, the free-running framework was successfully adapted and applied to motion-resolved imaging of the human eye, removing the necessity for anesthesia or stable fixation that still are a requirement for current MRI protocols in ophthalmology. In conclusion, the free-running framework presented in this thesis has the potential to help simplify and disseminate MRI of the heart (and potentially other moving organs) in both research and clinical practice, where a single-click acquisition and automated reconstruction provide images with comprehensive diagnostic information. -- Les maladies cardiovasculaires constituent aujourd’hui la première cause de mor- bidité et de mortalité dans le monde: l’American Heart Association les estime responsables de 31% des décès, dont plus de la moitié sont attribués à une patholo- gie touchant les artères coronaires. L’Imagerie par Résonance Magnétique (IRM) est apparue comme une technique prometteuse pour la détection et le diagnostic des maladies coronariennes, car permettant la génération d’images 2D (dans toutes les directions) et 3D au con- traste élevé, lors d’un examen clinique non-invasif et sûr. En parallèle de la visualisation des vaisseaux du cœur, plusieurs évaluations cliniques peuvent être réalisées lors d’un même examen IRM, entre autres: appréciation de l’anatomie cardiaque globale, évaluation de la fonction cardiaque, caractérisation des tissus, évaluation du mécanisme de perfusion. La technique d’IRM offre de nombreux avantages, mais présente l’inconvénient majeur d’un temps d’acquisition relativement long. Dans le cas de l’examen du cœur, un organe sujet à des mouvements à la fois rapides et complexes car multi- ples (battements cardiaques, mouvement respiratoire, mouvements aléatoires du patient), la question de la méthode d’acquisition est dès lors cruciale, car la qual- ité des images est facilement altérée par des artéfacts liés au mouvement. Ces dernières décennies ont vu naître de nombreuses techniques permettant de cor- riger ou d’empêcher la création des artéfacts de mouvement, voire même de ren- dre possible la visualisation des mouvements en question. Cependant, la grande majorité de ces techniques requièrent un ou plusieurs appareils externes pour la détection du mouvement, et augmentent de fait la contribution et l’expertise devant être fournies par les techniciens en radiologie lors de l’examen. Dans cette thèse, une approche nouvelle de l’IRM cardiaque est présentée, où l’acquisition est continue et suivie d’un canal de reconstruction sophistiqué permettant l’extraction des mouvements cardiaque et respiratoire. Cet ensem- ble de techniques allant de l’acquisition au traitement de l’image forme un cadre de fonctionnement IRM qui fut intitulé en anglais ‘Free-Running Framework’ (FRF). L’objectif est de produire des images dynamiques et multidimensionnelles du cœur entier à partir d’une unique acquisition ininterrompue, complètement au- tomatisée, sans appareils externes, et qui peut être lancée d’un seul clic. Le cadre d’acquisition et de reconstruction est développé dans une optique d’optimisation de l’information extraite, notamment au niveau anatomique et fonctionnel (mais sans se limiter à ces deux aspects), pour le diagnostic clinique. Afin d’illustrer le contexte de l’émergence du FRF et de donner un point de dé- part au travail présenté dans cette thèse, un aperçu chronologique des développements théoriques et techniques d’IRM cardiovasculaire ayant précédé cette thèse est rapporté dans le premier chapitre. Dans le deuxième chapitre, la première formulation complète d’un cadre au- tomatisé et entièrement autonome dans l’extraction des signaux physiologiques et du mouvement pour la production d’images 5D du cœur humain par résonance magnétique est présentée en deux études. La première étude se concentre sur le développement d’une méthode robuste et précise d’auto-gating pour l’extraction du mouvement cardiaque, en la présen- tant comme une alternative à la méthode de référence utilisant les signaux de l’électrocardiogramme (ECG). Lors de ce travail, le canal de reconstruction d’ima- ges fut automatisé afin de réduire le nombre d’ajustements manuels requis. Avec cette implémentation, tous les appareils externes de détection, dont l’ECG, de- viennent superflus. Dans la deuxième étude, réalisé en collaboration avec le Children’s Hospital of Philadelphia (Pennsylvania, USA), une version modifiée du FRF fut testée au sein d’un panel de patients pédiatriques atteints de cardiopathie congénitale. La réalisation d’un examen IRM de coronarographie avec injection d’un agent de contraste chez ces patients a démontré l’applicabilité et la performance du FRF dans les conditions cliniques standard rencontrées en imagerie cardiaque. Ces deux projets ont prouvé le caractère à la fois robuste et flexible du FRF, qui a été facilement adapté à différentes conditions d’imagerie et a produit une ex- cellente délinéation des vaisseaux coronaires. Ils ont démontré le positionnement du FRF en tant que solution automatisée et facile d’usage pour l’IRM cardiovas- culaire. Le troisième chapitre est constitué de quatre études dans lesquelles les perfor- mances ainsi que la quantité et la qualité d’information obtenue avec le FRF ont été accrues. Les deux premières de ces études concernent l’utilisation de deux séquences d’acquisition (FISS et LIBRE) visant à supprimer le signal indésirable provenant des tissus adipeux. La conjonction de ces séquences et du FRF a per- mis d’obtenir des images 5D du cœur entier et des vaisseaux, sans gras ni artéfacts de mouvement, et cela sans nécessiter l’injection d’un agent de contraste. Le troisième projet, intitulé ‘5D flow MRI’ et réalisé en collaboration avec l’Uni- versité de Northwestern (Illinois, USA), propose une extension du FRF dans laquelle l’ajout d’une sixième dimension permet l’étude de la dynamique des flux sanguins. Dans une approche similaire, la quatrième et dernière étude de ce chapitre, in- titulée ‘5D T1-mapping’ exploite une sixième dimension, cette fois-ci pour car- tographier quantitativement le temps de relaxation longitudinale T1 des différents tissus cardiaques. Pour résumer, les quatre projets présentés dans le troisième chapitre de cette thèse ont montré comment le FRF a pu être étendu, à la fois dans sa dimension- nalité et dans son domaine d’application, afin d’accélérer la recherche en IRM cardiaque, au sein et au-delà de notre institution. Le quatrième et ultime chapitre de cette thèse concerne l’adaptation du FRF à l’étude d’un autre organe mouvant: l’œil humain. Dans ce cadre, l’usage de la technique d’extraction du mouvement a rendu possible une acquisition ne néces- sitant ni anesthésie ni positionnement fixe de l’œil, des conditions normalement requises par les protocoles IRM standards en ophtalmologie. En conclusion, le cadre FRF développé et présenté dans cette thèse a le po- tentiel d’aider à la simplification ainsi qu’à la diffusion de l’IRM cardiovasculaire, à la fois dans les projets de recherche et dans la pratique clinique

Deep Learning to Automate Reference-Free Image Quality Assessment of Whole-Heart MR Images

Purpose: To develop and characterize an algorithm that mimics human expert visual assessment to quantitatively determine the quality of three-dimensional (3D) whole-heart MR images

Free-running cardiac and respiratory motion-resolved 5D whole-heart coronary cardiovascular magnetic resonance angiography in pediatric cardiac patients using ferumoxytol

Abstract Background Coronary cardiovascular magnetic resonance angiography (CCMRA) of congenital heart disease (CHD) in pediatric patients requires accurate planning, adequate sequence parameter adjustments, lengthy scanning sessions, and significant involvement from highly trained personnel. Anesthesia and intubation are commonplace to minimize movements and control respiration in younger subjects. To address the above concerns and provide a single-click imaging solution, we applied our free-running framework for fully self-gated (SG) free-breathing 5D whole-heart CCMRA to CHD patients after ferumoxytol injection. We tested the hypothesis that spatial and motion resolution suffice to visualize coronary artery ostia in a cohort of CHD subjects, both for intubated and free-breathing acquisitions. Methods In 18 pediatric CHD patients, non-electrocardiogram (ECG) triggered 5D free-running gradient echo CCMRA with whole-heart 1 mm3 isotropic spatial resolution was performed in seven minutes on a 1.5T CMR scanner. Eleven patients were anesthetized and intubated, while seven were breathing freely without anesthesia. All patients were slowly injected with ferumoxytol (4 mg/kg) over 15 minutes. Cardiac and respiratory motion-resolved 5D images were reconstructed with a fully SG approach. To evaluate the performance of motion resolution, visibility of coronary artery origins was assessed. Intubated and free-breathing patient sub-groups were compared for image quality using coronary artery length and conspicuity as well as lung-liver interface sharpness. Results Data collection using the free-running framework was successful in all patients in less than 8 min; scan planning was very simple without the need for parameter adjustments, while no ECG lead placement and triggering was required. From the resulting SG 5D motion-resolved reconstructed images, coronary artery origins could be retrospectively extracted in 90% of the cases. These general findings applied to both intubated and free-breathing pediatric patients (no difference in terms of lung-liver interface sharpness), while image quality and coronary conspicuity between both cohorts was very similar. Conclusions A simple-to-use push-button framework for 5D whole-heart CCMRA was successfully employed in pediatric CHD patients with ferumoxytol injection. This approach, working without any external gating and for a wide range of heart rates and body sizes provided excellent definition of cardiac anatomy for both intubated and free-breathing patients

Respiratory Motion-Registered Isotropic Whole-Heart T₂ Mapping in Patients With Acute Non-ischemic Myocardial Injury.

Background: T <sub>2</sub> mapping is a magnetic resonance imaging technique that can be used to detect myocardial edema and inflammation. However, the focal nature of myocardial inflammation may render conventional 2D approaches suboptimal and make whole-heart isotropic 3D mapping desirable. While self-navigated 3D radial T <sub>2</sub> mapping has been demonstrated to work well at a magnetic field strength of 3T, it results in too noisy maps at 1.5T. We therefore implemented a novel respiratory motion-resolved compressed-sensing reconstruction in order to improve the 3D T <sub>2</sub> mapping precision and accuracy at 1.5T, and tested this in a heterogeneous patient cohort. Materials and Methods: Nine healthy volunteers and 25 consecutive patients with suspected acute non-ischemic myocardial injury (sarcoidosis, n = 19; systemic sclerosis, n = 2; acute graft rejection, n = 2, and myocarditis, n = 2) were included. The free-breathing T <sub>2</sub> maps were acquired as three ECG-triggered T <sub>2</sub> -prepared 3D radial volumes. A respiratory motion-resolved reconstruction was followed by image registration of the respiratory states and pixel-wise T <sub>2</sub> mapping. The resulting 3D maps were compared to routine 2D T <sub>2</sub> maps. The T <sub>2</sub> values of segments with and without late gadolinium enhancement (LGE) were compared in patients. Results: In the healthy volunteers, the myocardial T <sub>2</sub> values obtained with the 2D and 3D techniques were similar (45.8 ± 1.8 vs. 46.8 ± 2.9 ms, respectively; P = 0.33). Conversely, in patients, T <sub>2</sub> values did differ between 2D (46.7 ± 3.6 ms) and 3D techniques (50.1 ± 4.2 ms, P = 0.004). Moreover, with the 2D technique, T <sub>2</sub> values of the LGE-positive segments were similar to those of the LGE-negative segments (T <sub>2LGE-</sub> = 46.2 ± 3.7 vs. T <sub>2LGE+</sub> = 47.6 ± 4.1 ms; P = 0.49), whereas the 3D technique did show a significant difference (T <sub>2LGE-</sub> = 49.3 ± 6.7 vs. T <sub>2LGE+</sub> = 52.6 ± 8.7 ms, P = 0.006). Conclusion: Respiratory motion-registered 3D radial imaging at 1.5T led to accurate isotropic 3D whole-heart T <sub>2</sub> maps, both in the healthy volunteers and in a small patient cohort with suspected non-ischemic myocardial injury. Significantly higher T <sub>2</sub> values were found in patients as compared to controls in 3D but not in 2D, suggestive of the technique's potential to increase the sensitivity of CMR at earlier stages of disease. Further study will be needed to demonstrate its accuracy

A proposito di spazio, limite, reinvenzione

Qusto libro include 60 profili di artiste nell'area romana e non solo; contributi critici di 15 fra studiose e studiosi di discipline storico-artistiche, filosofiche, sociologiche, antropologiche, psicologiche. Questi sono i numeri di FEMM[E]: un progetto - e un libro - nato sotto la denominazione e l'intento di una "ricerca sulla specificità (eventuale) dell'arte femminile", realizzata dal 2016 al 2018 su iniziativa e cura della storica dell'arte Anna Maria Panzera e dell'artista Veronica Montanino. Il mio testo parla del tema dell'abitazione e in specifico di «casa» che è riccorente nelle opere di artiste in tutto il mondo. Dopo gli esempi conosciuti della storia dell'arte contemporanea, il testo prosegue con le storie degli artisti con cui l'autrice ha collaborato sul tema di "Casa"