Current Medical Imaging - Volume 2, Issue 4, 2006

Portal vein embolization (PVE) has become an important tool in the preoperative management of select patients prior to major hepatic resection. PVE redirects portal flow to the intended remnant liver to induce hypertrophy of the nondiseased portion of the liver and thereby may reduce complications and shorten hospital stays after surgery. This article reviews the rationale and existing literature on PVE, including the mechanisms and rates of liver regeneration, the pathophysiology of PVE, the importance of liver volumetric measurements to best estimate functional hepatic reserve, and the technical aspects of PVE including the use of state-of-the-art imaging techniques to guide the procedure. Also, the indications and contraindications for performing PVE in patients with and without chronic liver disease and the multidisciplinary approach required for the treatment of these complex cases are emphasized.

After we briefly review representative analytic and iterative reconstruction algorithms for X-ray computed tomography (CT), we address the need for faster reconstruction by parallel computing techniques. For a decent, a conebeam reconstruction usually takes hours on a regular PC, since most of algorithms take more than 60 iterations even longer. In order to speedup the performance, people introduce various acceleration methodologies including algorithm improvements, chip utilization, and parallel computing technique. This paper focuses on the speedup the computation using parallel computing. The first generation of parallel computing systems was based on a centralized parallel configuration. The second generation of such systems employed a cluster of general-purpose computers that are connected by a fast local area network (LAN). Hereby, we highlight distributed parallel computing techniques: from a locally distributed client-server topology to a peer-to-peer (P2P) enhanced network model. With the P2P technology, the client would be directly connected to all other computing peers seamlessly, forming a virtual parallel computer. There are multiple Internet connections between the client and other computing peers. This way, a single failure of node wouldn’t cause the entire failure of computation. Finally, we state that by integrating the large-scale geographically distributed systems such as Grid computing technology the future of the CT reconstruction will be highly parallel, efficient, scalable over the Internet, so will be other biomedical imaging tasks.

Reconstruction of vascular trees from digital diagnostic images is a challenging task in the development of tools for simulation and procedural planning for clinical use. Improvements in quality and resolution of acquisition modalities are constantly increasing the fields of application of computer assisted techniques for vascular modeling and a lot of Computer Vision and Computer Graphics research groups are currently active in the field, developing methodologies, algorithms and software prototypes able to recover models of branches of human vascular system from different kinds of input images. Reconstruction methods can be extremely different according to image type, accuracy requirements and level of automation. Some technologies have been validated and are available on medical workstation, others have still to be validated in clinical environments. It is difficult, therefore, to give a complete overview of the different approach used and results obtained, this paper just presents a short review including some examples of the principal reconstruction approaches proposed for vascular reconstruction, showing also the contribution given to the field by the Medical Application Area of CRS4, where methods to recover vascular models have been implemented and used for blood flow analysis, quantitative diagnosis and surgical planning tools based on Virtual Reality.

Vasculitis is inflammation of blood vessel walls, which produces dysfunction in both the peripheral and central nervous system (CNS). In CNS, cerebral ischemia is the major cause for neurological manifestations. Vasculitis affecting the CNS alone is referred to as primary angiitis of the CNS. The pathogenesis of vasculitis includes different immunological mechanisms. Diagnosis of CNS vasculitis depends on a combination of clinical, radiographic and pathologic features, but the gold standard is confirmation of vasculitis in a biopsy specimen. However, before conducting biopsies, imaging study, especially MRI, is essential for diagnosis of CNS vasculitis. In this review, a wide spectrum of MRI features of CNS vasculitis are presented and discussed.

In the past, many aspects concerning specific cerebral activation patterns and cross-modal plasticity in blind subjects have been reported. Experimental data on cortical reorganization in blind subjects, using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), has revealed activation of the visual cortex related to Braille reading and tactile discrimination tasks in congenitally and early blind subjects. In addition to the cortical activity in sensorimotor and visual areas, an increased global activation of the cerebellum has been shown during Braille reading in blind subjects. Our studies addressed the two aspects mentioned above: early blind and normal sighted subjects were studied with fMRI during Braille reading, tactile discrimination of nonsense dots, sensory electrical stimulation and finger tapping to reveal specific cerebral and cerebellar activation and further insights into cross modal plasticity. Findings of specific cortical and cerebellar activation during Braille reading in normal volunteers and blind subjects are discussed in light of the current literature concerning cross modal plasticity and the hypothesis of cerebellar involvement in language processing.

Syntactic structures relate the meanings of the individual words in sentences to one another, thus allowing sentences to express propositions that can be entered into memory, used in reasoning and planning, and serve as the basis for much of human thought and expression. Syntactic structures are abstract, unique types of representations that are not found in non-humans. How the brain is organized to support syntactic processing is thus of neurobiological interest. Functional neuroimaging studies of the neural basis for syntactic processing have resulted in a number of theoretical positions, but the data supporting these positions is generally weak. This review presents a selective and critical review of important recent contributions to this literature. We focus on psychological methodology and interpretation of results and suggest several new approaches to the study of syntactic processing that might avoid some of the problems with existing work.

Bioluminescence tomography (BLT) is a new molecular imaging tool. Using a modality fusion approach, we built the first BLT prototype that combines BLI data and micro-CT and micro-MRI images for proof of concept, established a theoretical framework for BLT, and reported encouraging preliminary results. In this overview, we highlight our key results and discuss further directions.