The Picture Administration and Communications System (PACS) was designed to replace the old film archiving system in hospitals in order to store and move varying medical image modalities. Using the standard Internet transport protocol, PACS creators designed a robust digital signaling platform to optimize media use, availability, and confidentiality. Nowadays PACS has become ubiquitous in medical facilities but lacks imaging analytical capabilities. A myriad of initiatives have been launched in the hope of achieving this goal, but current solutions face issues with security and ease-of-use that have precluded their widespread adoption.
Here, we present a PACS-based image processing tool that safeguards patient confidentiality, is user-friendly and is easy to implement. The final product is platform-independent, has a small degree of intrusiveness and is well suited to clinical and research work flows.
KEYWORDS: Picture Archiving and Communication System, Medical imaging, Standards development, Medical research, Medicine, Surgery, Health informatics, Interfaces, Cancer, Web services
PACS provides a consistent model to communicate and to store images with recent additions to fault
tolerance and disaster reliability. However PACS still lacks fine granulated user based authentication and
authorization, flexible data distribution, and semantic associations between images and their embedded
information. These are critical components for future Enterprise operations in dynamic medical research
and health care environments. Here we introduce a flexible Grid based model of a PACS in order to add
these methods and to describe its implementation in the Children's Oncology Group (COG) Grid. The
combination of existing standards for medical images, DICOM, and the abstraction to files and meta
catalog information in the Grid domain provides new flexibility beyond traditional PACS design. We
conclude that Grid technology demonstrates a reliable and efficient distributed informatics infrastructure
which is well applicable to medical informatics as described in this work. Grid technology will provide
new opportunities for PACS deployment and subsequently new medical image applications.
KEYWORDS: Magnetic resonance imaging, Functional magnetic resonance imaging, Neuroimaging, Diffusion tensor imaging, Brain, Information fusion, Data storage, Visualization, Picture Archiving and Communication System, Diffusion
MRI Neuroimaging provides a rich source of image content including structural (MRI, Diffusion DTI), functional (fMRI, Perfusion ASL), and metabolic (MRS) information. Today MRI capabilities allow to acquire these imaging techniques in one session in most cases. In order to be of diagnostic value, the immense and diverse data needs to be (i) automatically post-processed to extract the relevant information, e.g. 3D brain maps from 4D fMRI, and to be (ii) fused and visualized to correlate the voxel-based findings. The purpose of this study is to demonstrate the feasibility of automatic relevant information retrieval and fusion of MRI, fMRI, DTI, ASL, and MRS data of a pediatric population into a single semantic data representation. By using advanced imaging, we may able to detect a larger spectrum of abnormalities in the neonatal brain. Each imaging application, provides unique information about the physiology (fMRI, ASL), the anatomy (DTI), and the biochemistry (MRS) of the newborn brain in relation to normal development and brain injury. By being able to integrate this technology, we will be able to combine biochemical, physiologic and anatomic information which can provide unique insight about not only the normal development of the brain, but also injury of the neonatal brain.
Functional Magnetic Resonance Imaging (fMRI) provides the location and regional extent of a task correlated activation in the brain. Recently we have demonstrated, that fMRI of passive sensory tasks (visual, auditory, motor) can be successfully used to map cortical activation in the newborn brain. However the interpretation of the functional response in the immature brain is difficult, as the blood oxygen level dependent (BOLD) physiological signal and location of the activation is quite different compared to adult fMRI responses of similar tasks. We expect, that the major reason for these differences are primarily caused by the immature myelination of the white matter tracts at this age. Diffusion tensor imaging (DTI) can be used to measure the white matter tract development in the newborn brain. The purpose of this paper is to report how to obtain and to combine fMRI and DTI data processing to enhance functional brain mapping in newborns. We obtained simultaneous fMRI and DTI data of 18 newborns, post-conceptional age (gestational age at study) between 34-week and 52-week, which were referred for clinical indicated MRI. 16 out of 18 subjects have been successfully investigated with combined fMRI and DTI and functional activation could be obtained. Fiber tracking was successfully in the visual and auditory cortex, but proofed difficult in the motor-cortex. The additional tract information supported the functional findings and the interpretation in the immature brain. The novel functional imaging in newborn is challenging because of the yet unknown physiological response and location of activation in the newborn brain. Therefore one need additional evidence that the functional findings are valid in the context of structural development. The maturation of myelination is an essential information to compare and to interpret fMRI in newborns. We conclude that the proposed method of combined fMRI and DTI, derived from adult neuroimaging, will be most relevant to understand the physiological response and thus the neurodevelopment of the newborn brain.
We have investigated the feasibility of obtaining high-quality Diffusion Tensor Magnetic Resonance Imaging (DTI) data in newborn humans. We show that the use of an MR-compatible incubator with customized RF headcoils can provide diffusion tensor maps of sufficient quality for quantitative DTI measurements and 3D fiber tracking. We have also investigated the effect of performing affine co-registration on the diffusion-weighted images, as is conventionally believed to be necessary to correct for eddy current distortion effects. We have found that co-registration indeed successfully eliminates the well-known bright band of high anisotropy that forms in the peripheral brain regions, and that such co-registration also reduces smaller interior regions of artifactually high diffusion anisotropy. In addition, we have investigated whether non-affine distortions exist in the diffusion-weighted images, as might be expected due to the existence of large susceptibility gradients. The results of performing 2nd order mutual information polynomial registration of the diffusion-weighted images to the non-diffusion-weighted (b=0) image in each slice show that subtle differences between affine and 2nd order co-registration do exist, which suggests that care must be taken when interpreting FA values in cortical brain regions. Finally, we present results of 3D white matter fiber tracking in the newborn brain. To preserve the full information content of the DTI data, we used simple Euler integration without noise filtering or fiber crossing detection. Our results show that the directionality of the major white matter pathways can be visualized in newborns.
KEYWORDS: Picture Archiving and Communication System, Personal digital assistants, Medicine, Medical imaging, Radiology, Control systems, Databases, Internet, Image processing, Wireless communications
Image workflow in today's Picture Archiving and Communication Systems (PACS) is controlled from fixed Display Workstations (DW) using proprietary control interfaces. A remote access to the Hospital Information System (HIS) and Radiology Information System (RIS) for urgent patient information retrieval does not exist or gradually become available. The lack for remote access and workflow control for HIS and RIS is especially true when it comes to medical images of a PACS on Department or Hospital level. As images become more complex and data sizes expand rapidly with new image techniques like functional MRI, Mammography or routine spiral CT to name a few, the access and manageability becomes an important issue. Long image downloads or incomplete work lists cannot be tolerated in a busy health care environment. In addition, the domain of the PACS is no longer limited to the imaging department and PACS is also being used in the ER and emergency care units. Thus a prompt and secure access and manageability not only by the radiologist, but also from the physician becomes crucial to optimally utilize the PACS in the health care enterprise of the new millennium. The purpose of this paper is to introduce a concept and its implementation of a remote access and workflow control of the PACS combining wireless, Internet and Internet2 technologies. A wireless device, the Personal Digital Assistant (PDA), is used to communicate to a PACS web server that acts as a gateway controlling the commands for which the user has access to the PACS server. The commands implemented for this test-bed are query/retrieve of the patient list and study list including modality, examination, series and image selection and pushing any list items to a selected DW on the PACS network.
Brain imaging and particular functional MRI (fMRI), which acquires brain volumes in time, reveals new understanding of the functional/structural relation in neuroscience. During fMRI imaging physiological state changes occur in the brain regions activated from the task paradigm which the subject performs in the scanner. These state changes can be depicted in the small veins of the activated region due to the blood oxygen level dependent (BOLD) effect. For each brain voxel in the fMRI experiment one accumulates a time series vector which has to be analyzed for similarity to the original task paradigm vector and its characteristic hemodynamic response function (HRF). Various analysis methods have been discussed for fMRI analysis, model-based statistical or unsupervised data-driven techniques. The purpose of this paper is to introduce a new method which combines two different approaches. We use an unsupervised self-organizing map (SOM) neural network to reduce the time series vector space by non-linear pattern recognition into a 2D table of representative time series wave-forms. Using a-priori knowledge of the HRF, either derived from a theoretical wave-form model or estimated from a brain region of interest (ROI), one can use correlation analysis between the time series patterns of the SOM table and the HRF to depict regions of activation specific to the HRF. An optional second SOM training with a reduce number of neurons of the best-matching time series to the HRF classification refines the second neural network pattern table. The learned time series pattern of each neuron and the corresponding brain voxels are superimposed onto the subject's brain image for visual investigation.
Among the methods proposed for the analysis of functional MR we have previously introduced a model-independent analysis based on the self-organizing map (SOM) neural network technique. The SOM neural network can be trained to identify the temporal patterns in voxel time-series of individual functional MRI (fMRI) experiments. The separated classes consist of activation, deactivation and baseline patterns corresponding to the task-paradigm. While the classification capability of the SOM is not only based on the distinctness of the patterns themselves but also on their frequency of occurrence in the training set, a weighting or selection of voxels of interest should be considered prior to the training of the neural network to improve pattern learning. Weighting of interesting voxels by means of autocorrelation or F-test significance levels has been used successfully, but still a large number of baseline voxels is included in the training. The purpose of this approach is to avoid the inclusion of these voxels by using three different levels of segmentation and mapping from Talairach space: (1) voxel partitions at the lobe level, (2) voxel partitions at the gyrus level and (3) voxel partitions at the cell level (Brodmann areas). The results of the SOM classification based on these mapping levels in comparison to training with all brain voxels are presented in this paper.
In the last few years more and more University Hospitals as well as private hospitals changed to digital information systems for patient record, diagnostic files and digital images. Not only that patient management becomes easier, it is also very remarkable how clinical research can profit from Picture Archiving and Communication Systems (PACS) and diagnostic databases, especially from image databases. Since images are available on the finger tip, difficulties arise when image data needs to be processed, e.g. segmented, classified or co-registered, which usually demands a lot computational power. Today's clinical environment does support PACS very well, but real image processing is still under-developed. The purpose of this paper is to introduce a parallel cluster of standard distributed systems and its software components and how such a system can be integrated into a hospital environment. To demonstrate the cluster technique we present our clinical experience with the crucial but cost-intensive motion correction of clinical routine and research functional MRI (fMRI) data, as it is processed in our Lab on a daily basis.
Functional magnetic resonance imaging (fMRI) becomes a common method to study task induced brain activation. Using rapid Echo Planar Imaging (EPI) sequences one can obtain a higher MR-Signal under a task condition close by activated areas as a result of susceptibility changes in blood oxygenation (BOLD effect). Beside the commonly used blocked task designs, event- related paradigms gain more importance for activation of higher cognitive functions enabling more sophisticated and complex paradigms. For the analysis of event-related fMRI data one can use statistical tests, in example t-test used by SPM Software. The introduced analysis method based on an artificial neural network algorithm, a self-organizing map (SOM), is capable to distinguish between task related activation, deactivation and baseline patterns from the time series. This is achieved by temporal sorting and projection of all events from one condition into one combined hemodynamic response sampling for each voxel. These responses, having individual patterns can be separated by their pattern features and is done by training of the neural network. After training the SOM consists of a pattern-to-voxel mapping which is superimposed onto either an anatomical or EPI image of the subject for the task evaluation.
The structure of an fMRI time series coregistration algorithm can be divided into modules (preprocessing, minimization procedure, interpolation method, cost function), for each of which there are many different approaches. In our study we implemented some of the most recent techniques and compared their combinations with regard to both registration accuracy and runtime performance. Bidirectional inconsistency and difference image analysis served as quality measures. The result shows that with an appropriate choice of methods realignment results can be improved by far compared with standard solutions. Finally, an automatic parameter adaptation method was incorporated. Additionally, the algorithm was implemented to run on a distributed 48 processor PC cluster, surpassing the performance of conventional applications running on high end workstations.
Functional magnet resonance imaging (fMRI) has become a standard non invasive brain imaging technique delivering high spatial resolution. Brain activation is determined by magnetic susceptibility of the blood oxygen level (BOLD effect) during an activation task, e.g. motor, auditory and visual tasks. Usually box-car paradigms have 2 - 4 rest/activation epochs with at least an overall of 50 volumes per scan in the time domain. Statistical test based analysis methods need a large amount of repetitively acquired brain volumes to gain statistical power, like Student's t-test. The introduced technique based on a self-organizing neural network (SOM) makes use of the intrinsic features of the condition change between rest and activation epoch and demonstrated to differentiate between the conditions with less time points having only one rest and one activation epoch. The method reduces scan and analysis time and the probability of possible motion artifacts from the relaxation of the patients head. Functional magnet resonance imaging (fMRI) of patients for pre-surgical evaluation and volunteers were acquired with motor (hand clenching and finger tapping), sensory (ice application), auditory (phonological and semantic word recognition task) and visual paradigms (mental rotation). For imaging we used different BOLD contrast sensitive Gradient Echo Planar Imaging (GE-EPI) single-shot pulse sequences (TR 2000 and 4000, 64 X 64 and 128 X 128, 15 - 40 slices) on a Philips Gyroscan NT 1.5 Tesla MR imager. All paradigms were RARARA (R equals rest, A equals activation) with an epoch width of 11 time points each. We used the self-organizing neural network implementation described by T. Kohonen with a 4 X 2 2D neuron map. The presented time course vectors were clustered by similar features in the 2D neuron map. Three neural networks were trained and used for labeling with the time course vectors of one, two and all three on/off epochs. The results were also compared by using a Kolmogorov-Smirnov statistical test of all 66 time points. To remove non- periodical time courses from training an auto-correlation function and bandwidth limiting Fourier filtering in combination with Gauss temporal smoothing was used. None of the trained maps, with one, two and three epochs, were significantly different which indicates that the feature space of only one on/off epoch is sufficient to differentiate between the rest and task condition. We found, that without pre-processing of the data no meaningful results can be achieved because of the huge amount of the non-activated and background voxels represents the majority of the features and is therefore learned by the SOM. Thus it is crucial to remove unnecessary capacity load of the neural network by selection of the training input, using auto-correlation function and/or Fourier spectrum analysis. However by reducing the time points to one rest and one activation epoch either strong auto- correlation or a precise periodical frequency is vanishing. Self-organizing maps can be used to separate rest and activation epochs of with only a 1/3 of the usually acquired time points. Because of the nature of the SOM technique, the pattern or feature separation, only the presence of a state change between the conditions is necessary for differentiation. Also the variance of the individual hemodynamic response function (HRF) and the variance of the spatial different regional cerebral blood flow (rCBF) is learned from the subject and not compared with a fixed model done by statistical evaluation. We found that reducing the information to only a few time points around the BOLD effect was not successful due to delays of rCBF and the insufficient extension of the BOLD feature in the time space. Especially for patient routine observation and pre-surgical planing a reduced scan time is of interest.
Functional Magnetic Resonance Imaging (fMRI) data of the brain includes activated parenchymal voxels, corresponding to the paradigm performed, non-activated parenchymal voxels and background voxels. Statistical tests, e.g. using the general linear model approach of SPM or the Kolmogorov-Smirnov (KS) non-parametric statistic, are common 'supervised' techniques to look for activation in functional brain MRI. Selection of voxel type by comparing the voxel time course with a model of the expected hemodynamic response function (HRF) from the task paradigm has proven to be difficult due to individual and spatial variance of the measured HRF. For the functional differentiation of brain voxels we introduce a method separating brain voxels based on their features in the time domain using a self-organizing map (SOM) neural network technique without modeling the HRF. Since activation measured by fMRI is related to magnetic susceptibility changes in venous blood which represents only 2 - 5% of brain matter, preprocessing is required to remove the majority of non- activated voxels which dominate learning instead of real activation patterns. Using the auto-correlation function one can select voxels which are candidates of being activated. Features of the time course of the selected voxels can be learned with the SOM. In the first step the SOM is trained by the voxels time course, fitting its neurons to the input. After learning, the neurons have adapted to the intrinsic features space of the voxel time courses. Using the trained SOM, voxel time courses are presented again, now labeled by the neuron having the smallest Euclidean distance to the presented voxel time course. The result of the labeling and the learned feature time course vectors are compared visually with the p-value map of the KS statistic. With the SOM map one can visually separate the voxels based on their features in the time domain into different functional task related classes.
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