Single-image Tomography: 3D Volumes from 2D Cranial X-Rays

As many different 3D volumes could produce the same 2D x-ray image, inverting this process is challenging. We show that recent deep learning-based convolutional neural networks can solve this task. As the main challenge in learning is the sheer amount of data created when extending the 2D image into a 3D volume, we suggest firstly to learn a coarse, fixed-resolution volume which is then fused in a second step with the input x-ray into a high-resolution volume. To train and validate our approach we introduce a new dataset that comprises of close to half a million computer-simulated 2D x-ray images of 3D volumes scanned from 175 mammalian species. Applications of our approach include stereoscopic rendering of legacy x-ray images, re-rendering of x-rays including changes of illumination, view pose or geometry. Our evaluation includes comparison to previous tomography work, previous learning methods using our data, a user study and application to a set of real x-rays

Three-Dimensional In vivo Magnetic Resonance Imaging (MRI) of Mouse Facial Nerve Regeneration

MRI (magnetic resonance imaging) is an indispensable tool in the diagnosis of centrals nervous system (CNS) disorders such as spinal cord injury and multiple sclerosis (MS). In contrast, diagnosis of peripheral nerve injuries largely depends on clinical and electrophysiological parameters. Thus, currently MRI is not regularly used which in part is due to small nerve calibers and isointensity with surrounding tissue such as muscles. In this study we performed translational MRI research in mice to establish a novel MRI protocol visualizing intact and injured peripheral nerves in a non-invasive manner without contrast agents. With this protocol we were able to image even very small nerves and nerve branches such as the mouse facial nerve (diameter 100–300 μm) at highest spatial resolution. Analysis was performed in the same animal in a longitudinal study spanning 3 weeks after injury. Nerve injury caused hyperintense signal in T2-weighted images and an increase in nerve size of the proximal and distal nerve stumps were observed. Further hyperintense signal was observed in a bulb-like structure in the lesion site, which correlated histologically with the production of fibrotic tissue and immune cell infiltration. The longitudinal MR representation of the facial nerve lesions correlated well with physiological recovery of nerve function by quantifying whisker movement. In summary, we provide a novel protocol in rodents allowing for non-invasive, non-contrast agent enhanced, high-resolution MR imaging of small peripheral nerves longitudinally over several weeks. This protocol might further help to establish MRI as an important diagnostic and post-surgery follow-up tool to monitor peripheral nerve injuries in humans

Prognostic significance of cardiac magnetic resonance imaging: Update 2010

Cardiac magnetic resonance imaging (CMR) has become an indispensible imaging technique for the diagnosis and treatment of patients with cardiovascular diseases. Technical advances in the past have rendered CMR unique in the evaluation of cardiovascular anatomy, physiology, and pathophysiology due to its unique ability to produce high resolution tomographic images of the human heart and vessels in any arbitrary orientation, with soft tissue contrast that is superior to competing imaging modalities without the use of ionizing radiation. CMR imaging is the gold standard for assessing left and right ventricular function and for detecting myocardial tissue abnormalities like edema, infarction, or scars. For prognostic reasons abnormal structure and dysfunction of the heart, and the detection of myocardial ischemia and/or myocardial scars are the main targets for CMR imaging. In this review we briefly describe the prognostic significance of several CMR imaging techniques and special CMR parameters in patients with coronary artery disease (CAD), with cardiomyopathies, and with chronic heart failure. Myocardial ischemia proved to be a strong predictor of an adverse outcome in patients with CAD. Microvascular obstruction in acute myocardial infarction is a new and independent parameter of negative left ventricular remodeling and a worse prognosis. Myocardial scars in patients with CAD and unrecognized myocardial infarction heralds a negative outcome. Scar in patients with dilated or hypertrophic cardiomyopathy are a strong predictor of both life-threatening ventricular tachyarrhythmias and prognosis. CMR imaging may improve the assessment of inter- and intraventricular dyssynchrony and provide prognostic information by detecting myocardial scars. (Cardiol J 2010; 17, 6: 549-557

Ageing-induced shrinkage of intervessel pit membranes in xylem of Clematis vitalba modifies its mechanical properties as revealed by atomic force microscopy

Bordered pit membranes of angiosperm xylem are anisotropic, mesoporous media between neighbouring conduits, with a key role in long distance water transport. Yet, their mechanical properties are poorly understood. Here, we aim to quantify the stiffness of intervessel pit membranes over various growing seasons. By applying an AFM-based indentation technique “Quantitative Imaging” we measured the effective elastic modulus (Eeffective) of intervessel pit membranes of Clematis vitalba in dependence of size, age, and hydration state. The indentation-deformation behaviour was analysed with a non-linear membrane model, and paired with magnetic resonance imaging to visualise sap-filled and embolised vessels, while geometrical data of bordered pits were obtained using electron microscopy. Eeffective was transformed to the geometrically independent apparent elastic modulus Eapparent and to aspiration pressure Pb. The material stiffness (Eapparent) of fresh pit membranes was with 57 MPa considerably lower than previously suggested. The estimated pressure for pit membrane aspiration was 2.20+28 MPa. Pit membranes from older growth rings were shrunken, had a higher material stiffness and a lower aspiration pressure than current year ones, suggesting an irreversible, mechanical ageing process. This study provides an experimental-stiffness analysis of hydrated intervessel pit membranes in their native state. The estimated aspiration pressure suggests that membranes are not deflected under normal field conditions. Although absolute values should be interpreted carefully, our data suggest that pit membrane shrinkage implies increasing material stiffness, and highlight the dynamic changes of pit membrane mechanics and their complex, functional behaviour for fluid transport

Current and future options for the management of phantom-limb pain

Phantom-limb pain (PLP) belongs among difficult-to-treat chronic pain syndromes. Treatment options for PLP are to a large degree implicated by the level of understanding the mechanisms and nature of PLP. Research and clinical findings acknowledge the neuropathic nature of PLP and also suggest that both peripheral as well as central mechanisms, including neuroplastic changes in central nervous system, can contribute to PLP. Neuroimaging studies in PLP have indicated a relation between PLP and the neuroplastic changes. Further, it has been shown that the pathological neuroplastic changes could be reverted, and there is a parallel between an improvement (reversal) of the neuroplastic changes in PLP and pain relief. These findings facilitated explorations of novel neuromodulatory treatment strategies, adding to the variety of treatment approaches in PLP. Overall, available treatment options in PLP include pharmacological treatment, supportive non-pharmacological non-invasive strategies (eg, neuromodulation using transcranial magnetic stimulation, visual feedback therapy, or motor imagery; peripheral transcutaneous electrical nerve stimulation, physical therapy, reflexology, or various psychotherapeutic approaches), and invasive treatment strategies (eg, surgical destructive procedures, nerve blocks, or invasive neuromodulation using deep brain stimulation, motor cortex stimulation, or spinal cord stimulation). Venues of further development in PLP management include a technological and methodological improvement of existing treatment methods, an implementation of new techniques and products, and a development of new treatment approaches

Znaczenie prognostyczne obrazowania metodą kardiologicznego rezonansu magnetycznego: uaktualnienie informacji na 2010 rok

Obrazowanie metodą kardiologicznego rezonansu magnetycznego (CMR) stało się niezbędną techniką w diagnostyce i leczeniu pacjentów z chorobami sercowo-naczyniowymi. Postępy techniczne sprawiły, że CMR jest wyjątkową metodą oceny budowy anatomicznej, fizjologii i patofizjologii układu sercowo-naczyniowego. Pozwala bowiem na uzyskanie obrazów tomograficznych ludzkiego serca i naczyń o wysokiej rozdzielczości w dowolnej płaszczyźnie. Ponadto, kontrast w obrazowaniu tkanek miękkich przewyższa inne konkurencyjne metody, bez konieczności stosowania promieniowania jonizującego. Obrazowanie CMR stanowi referencyjną metodę oceny funkcji lewej i prawej komory serca oraz wykrywania nieprawidłowości tkanki mięśnia sercowego, takich jak obrzęk, martwica czy blizna. Dla celów prognostycznych największe znaczenie w obrazowaniu CMR ma wykrycie nieprawidłowej budowy lub dysfunkcji serca, a także niedokrwienia i/lub blizny pozawałowej w obrębie mięśnia sercowego. W niniejszym artykule krótko opisano znaczenie prognostyczne obrazowania CMR z zastosowaniem kilku technik oraz scharakteryzowano obrazy obserwowane u pacjentów z chorobą wieńcową (CAD), kardiomiopatiami i przewlekłą niewydolnością serca. Niedokrwienie mięśnia sercowego okazało się silnym czynnikiem predykcyjnym niekorzystnych zdarzeń sercowo- -naczyniowych u pacjentów z CAD. Uszkodzenie mikrokrążenia u chorych z ostrym zawałem serca jest nowym, niezależnym czynnikiem zapowiadającym negatywną przebudowę lewej komory serca oraz pogarszającym rokowanie. Również obecność blizny oraz nierozpoznany zawał serca wiążą się z ryzykiem niekorzystnych zdarzeń sercowo-naczyniowych. Obecność włóknienia u pacjentów z kardiomiopatią rozstrzeniową czy przerostową stanowi silny czynnik ryzyka zagrażających życiu tachyarytmii komorowych i obciąża rokowanie. Obrazowanie CMR pozwala na dokładniejszą ocenę między- i śródkomorowej dyssynchronii skurczu i identyfikuje obszary włóknienia w mięśniu sercowym, które mają znaczenie prognostyczne. (Folia Cardiologica Excerpta 2011; 6, 1: 17–27