2,389 research outputs found

    Fast and radiation-free high-resolution MR cranial bone imaging for pediatric patients

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    AbstractEach year, 2.2 million pediatric head computed tomography (CT) scans are performed in the United States. Head trauma and craniosynostosis are two of the most common pediatric conditions requiring head CT scans. Head trauma is common in children and one-third of the patients that present to the emergency room undergoes head CT imaging. Craniosynostosis is a congenital disability defined by a prematurely fused cranial suture. Standard clinical care for pediatric patients with head trauma or craniosynostosis uses high-resolution head CT to identify cranial fractures or cranial sutures. Unfortunately, the ionizing radiation of CT imaging imposes a risk to patients, particularly pediatric patients who are vulnerable to radiation. Moreover, multiple CT scans are often performed during follow-up, exacerbating their cumulative risk. The National Cancer Institute reported that radiation exposure from multiple head CT scans will triple the risk of leukemia and brain cancer. Many medical centers have recently removed CT from the postoperative care of craniosynostosis, limiting postoperative evaluation and highlighting the urgent need for radiation-free imaging. Several “Black bone” magnetic resonance imaging (MRI) methods have been introduced as radiation-free alternatives. Despite the initially encouraging results, these methods have not translated into clinical practice due to several challenges, including 1) subjective manual image processing; 2) long acquisition time. Due to poor signal contrast between bone and its surrounding tissues in MR images, existing post-processing methods rely on extensive manual MR segmentation which is subjective, prone to noise and artifacts, hard to reproduce, and time-consuming. As a result, they do not meet the need for clinical diagnosis and have not been employed clinically. A CT scan takes tens of seconds; however, a high-resolution MR scan takes minutes, which may be challenging for pediatric subject compliance and limit clinical adoption. The overall objective of this study is to develop rapid and radiation-free 3D high-resolution MRI methods to provide CT-equivalent information in diagnosing cranial fractures and cranial suture patency for pediatric patients. Two specific aims are proposed to achieve the overall objective. Aim 1: Develop a fully automated deep learning method to synthesize high-resolution pseudo-CT (pCT) of pediatric cranial bone from MR images. Aim 2: Develop a deep learning image reconstruction method to reduce MR acquisition time. Aim 1 is to address the issues of subjective manual image processing. In this aim, we developed a robust and fully automated deep learning method to create pCT images from MRI, which facilitates translating MR cranial bone imaging into clinical practice for pediatric patients. Two 3D patch-based ResUNets were trained using paired MR and CT patches randomly selected from the whole head (NetWH) or in the vicinity of bone, fractures/sutures, or air (NetBA) to synthesize pCT. A third ResUNet was trained to generate a binary brain mask using only MRI. The pCT images from NetWH (pCTNetWH) in the brain area and NetBA (pCTNetBA) in the non-brain area were combined to generate pCTCom. A manual processing method using inverted MR images (iMR) was also employed for comparison. pCTCom had significantly smaller mean absolute errors (MAE) than pCTNetWH and pCTNetBA in the whole head. Dice Similarity Coefficient (DSC) of the segmented bone was significantly higher in pCTCom than in pCTNetWH, pCTNetBA, and iMR. DSC from pCTCom demonstrated significantly reduced age dependence than iMR. Furthermore, pCTCom provided excellent suture and fracture visibility comparable to CT. A fast MR acquisition is highly desirable to translate novel MR cranial to clinical practice in place of CT. However, fast MR acquisition usually results in under-sampled data below the Nyquist rate, leading to artifacts and high noise. Recently, numerous deep learning MR reconstruction methods have been employed to mitigate artifacts and minimize noise. Despite many successes, existing deep learning methods have not accounted for MR k-space sampling density variations. In aim 2, we developed a self-supervised and physics-guided deep learning method by weighting k-space sampling Density in network training Loss (wkDeLo). The proposed method uses an unrolled network with a data consistency (DC) and a regularization (R). A forward Fourier model was used to transform the reconstructed image into k-space. The data consistency between the transformed k-space and the acquired k-space data is enforced in the DC layer. This unrolled network is regularized by k-space deep-learning prior using a convolution neural network. In total, 400 radial spokes were acquired with an acquisition time of 5 minutes. Two disjoint k-space data sets, including the first 1 minute (80 radial spokes) and the remaining 4 minutes (320 radial spokes), were used as the network training input and target. A unique feature of our proposed method is to use a L1 loss weighted by k-space sampling density in an end-to-end training of the unrolled network. Moreover, we also reconstructed images using the same unrolled network structure but without accounting for the k-space sampling density variations in the loss for comparison. In other words, a uniform weighted k-space is used in the training loss (un-wkDeLo). Furthermore, we implemented a well-accepted deep learning reconstruction method, Self-Supervision via Data Undersampling (SSDU) as a baseline method reference. Using the images reconstructed from a 5-min scan as the gold standard, we computed the structural similarity index measure (SSIM) and peak signal-to-noise ratio (PSNR) for reconstructed images from 1-min k-space data using SSDU, un-wkDeLo, and wkDeLo. The SSIM and PSNR of the wkDeLo images are significantly higher than both SSDU and un-wkDeLo. Moreover, the wkDeLo reconstructed images have the highest sharpness and the least artifacts and noise. In aim 2, we have demonstrated that high quality MR images at a spatial resolution of 0.6x0.6x0.8 mm3 could be achieved using only 1 min acquisition time. Finally, we evaluated the clinical utility of the proposed MR cranial bone imaging in identifying cranial fractures and cranial suture patency. Clinicians by consensus evaluated the MR-derived pCT images. Acceptable image quality was achieved in greater than 90% of all MR scans; diagnoses were 100% accurate in the subset of patients with acceptable image quality. We have demonstrated that the proposed 3D high-resolution MR cranial bone method provided CT-equivalent images for pediatric patients with head trauma or craniosynostosis. This work will have a profound impact on pediatric health by providing clinicians with a rapid diagnostic tool without radiation safety concerns

    The Development And Application Of A Statistical Shape Model Of The Human Craniofacial Skeleton

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    Biomechanical investigations involving the characterization of biomaterials or improvement of implant design often employ finite element (FE) analysis. However, the contemporary method of developing a FE mesh from computed tomography scans involves much manual intervention and can be a tedious process. Researchers will often focus their efforts on creating a single highly validated FE model at the expense of incorporating variability of anatomical geometry and material properties, thus limiting the applicability of their findings. The goal of this thesis was to address this issue through the use of a statistical shape model (SSM). A SSM is a probabilistic description of the variation in the shape of a given class of object. (Additional scalar data, such as an elastic constant, can also be incorporated into the model.) By discretizing a sample (i.e. training set) of unique objects of the same class using a set of corresponding nodes, the main modes of shape variation within that shape class are discovered via principal component analysis. By combining the principal components using different linear combinations, new shape instances are created, each with its own unique geometry while retaining the characteristics of its shape class. In this thesis, FE models of the human craniofacial skeleton (CFS) were first validated to establish their viability. A mesh morphing procedure was then developed to map one mesh onto the geometry of 22 other CFS models forming a training set for a SSM of the CFS. After verifying that FE results derived from morphed meshes were no different from those obtained using meshes created with contemporary methods, a SSM of the human CFS was created, and 1000 CFS FE meshes produced. It was found that these meshes accurately described the geometric variation in human population, and were used in a Monte Carlo analysis of facial fracture, finding past studies attempting to characterize the fracture probability of the zygomatic bone are overly conservative

    Promoting ossification of calvarial defects in craniosynostosis surgery by demineralized bone plate and bone dust in different age groups

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    Correction of calvarial defects after calvarial vault reconstruction (CVR) is challenging in craniosynostosis patients of advanced age and typically employs autologous bone. Demineralized bone matrix (DBM) is a potential alternative material for autologous bone, but its use has not been extended to correct calvarial defects. CVR patients operated at the Department of Plastic Surgery, Helsinki University Hospital, during 2008-2010 were retrospectively reviewed. Inclusion criteria of the study were CVR patients who received DBM plate, with or without bone dust, on calvarial defects and who had suitable uncovered defect on the contralateral side as control. This study included 17 craniosynostosis and one positional plagiocephaly patient, whose mean age was 6.9 years (range 0.9-19 years). The mean follow-up time was 5.6 years. The fusion degree of all defects was measured from 1 week to 1 year postoperatively using three-dimensional computed tomography (3D CT) images by the OsiriX (R) method. Medical records were reviewed for DBM-related complications. A total of 26 defects were covered with a DBM plate (mean area 11.1 cm(2)) and 26 control defects were identified (mean area 7.8 cm2). The mean fusion degree of the DBM defects was 74% and 54% for the controls (p 30 months) than in younger patients or when used with bone dust. (C) 2016 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.Peer reviewe

    CT Scanning

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    Since its introduction in 1972, X-ray computed tomography (CT) has evolved into an essential diagnostic imaging tool for a continually increasing variety of clinical applications. The goal of this book was not simply to summarize currently available CT imaging techniques but also to provide clinical perspectives, advances in hybrid technologies, new applications other than medicine and an outlook on future developments. Major experts in this growing field contributed to this book, which is geared to radiologists, orthopedic surgeons, engineers, and clinical and basic researchers. We believe that CT scanning is an effective and essential tools in treatment planning, basic understanding of physiology, and and tackling the ever-increasing challenge of diagnosis in our society

    Development of image-based surgical planning software for bone-conduction implants

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    The BONEBRIDGE bone-conduction device is used to treat conductive and mixed hearing losses. The size of its floating mass transducer (FMT) can preclude implantation in certain anatomies, necessitating comprehensive surgical planning. Current techniques are time consuming and difficult to transfer to the operating room. The objective of this thesis was to develop software for calculating skull thickness to the dura mater to find locations for the FMT and to the first air cells which guarantee sufficient bone for the implant screws to grasp. Temporal bone computed tomography (CT) images were segmented and processed and custom Matlab code was written to generate and test thickness colormaps. For validation, measurements performed by a trained otologist were compared to the algorithm estimations achieving sub-millimeter accuracy. Results suggest this software can be used in the surgical workflow to automate thickness estimation and aid in finding an ideal location for the BONEBRIDGE device and screws

    Subcutaneous Adipose Tissue Plays A Beneficial Effect On Subclinical Atherosclerosis In Young Survivors Of Acute Lymphocytic Leukemia.

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    The aim of this study was to evaluate the relationship between body composition, metabolic profile, adipokines, and carotid intima-media thickness (cIMT) in young survivors of childhood acute lymphocytic leukemia (ALL). This cross-sectional study compared 55 ALL survivors, of chronological age between 15 years and 24 years, assigned into two groups according to the exposure to cranial radiation therapy (CRT; 25 irradiated and 30 nonirradiated) with 24 leukemia-free controls, and assessed body fat mass (dual-energy X-ray absorptiometry), computed tomography scan-derived abdominal adipose tissue, lipid profile, blood pressure (BP), adipokines, and cIMT by a multiple regression analysis. Treatment with CRT had an effect on all of the variables derived from the computed tomography scan: visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) (P<0.050). In a multiple linear regression model, cIMT positively correlated with exposure to CRT (P=0.029), diastolic BP (P=0.016), and leptin-to-adiponectin ratio (P=0.048), while negatively related to SAT (P=0.007). In young survivors of childhood ALL, CRT modified the distribution of fat and played a critical role in determining cIMT. Leptin-to-adiponectin ratio, a biomarker of abdominal obesity and metabolic syndrome, and diastolic BP also influenced cIMT, a marker of subclinical atherosclerosis. Nonetheless, adiposity-associated vascular disease might be attenuated by SAT. Changes in body fat must be evaluated in this group of patients in the early course of survivorship in order to avoid premature cardiovascular disease associated with atherosclerosis. Yet, further research as regards the possible protective effect of SAT on vascular disease is warranted.11479-48

    Tibial ultrasonometry in children

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    Postnatal development of the human nasal septum and its related structures

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