Contrast-Enhanced Ultrasound

Isolated bilateral optic neuropathy is an exceedingly rare presentation of perinuclear-antineutrophil cytoplasmic autoantibody (p-ANCA) vasculitis. We report one such case with MRI documentation of a compressive mechanism mediated by pachymeningitis. A 69-year-old woman had a 6-month history of progressive visual failure caused by bilateral optic neuropathy. Cranial MRI showed diffuse contrast enhancement of the dura mater extending to the perioptic sheaths bilaterally with encasement of the optic nerves. Extensive laboratory study showed increased levels of p-ANCA titres and autoimmune markers. Corticosteroid treatment improved both visual acuity and the neuroradiological signs of active pachymeningitis. In conclusion, our case demonstrates that bilateral optic neuropathy may be the presenting symptom of p-ANCAassociated pachymeningitis, whose causative role may be demonstrated by MRI.

BACKGROUND AND PURPOSE: Radiologic evaluation of CSF leaks is a diagnostic challenge that often involves multiple imaging studies with the associated expense and patient discomfort. We evaluated the use of screening noncontrast high-resolution CT in identifying the presence and site of CSF rhinorrhea and otorrhea and compared it with contrast-enhanced CT cisternography and radionuclide cisternography.

Nanoparticle-based photonic explorers have been developed for intracellular sensing and photodynamic therapy (PDT). The design employs nanoparticles made of various matrices as multifunctional nanoplatforms, loading active components by encapsulation or covalent attachment. The nanoplatform for biosensing has been successfully applied to intracellular measurements of important ionic and molecular species. The nanoplatform for PDT has shown high therapeutic efficacy in a rat 9L gliosarcoma model. Specifically, a multifunctional nanoplatform that encompasses magnetic resonance imaging (MRI) and PDT agents inside, as well as targeting ligands on the surface, has been developed and applied in vivo, resulting in much improved MRI contrast enhancement and PDT efficacy.

Purpose: Tookad® is a novel intravascular photosensitizer. When activated by 763 nm light, it destroys tumors by damaging their blood supply. It then clears rapidly from the circulatory system. To our knowledge we report the first application of Tookad vascular targeted photodynamic therapy in humans. We assessed the safety, pharmacokinetics and preliminary treatment response as a salvage procedure after external beam radiation therapy. Materials and Methods: Patients received escalating drug doses of 0.1 to 2 mg/kg at a fixed light dose of 100 J/cm or escalated light doses of 230 and 360 J/cm at the 2 mg/kg dose. Four optical fibers were placed transperineally in the prostate, including 2 for light delivery and 2 for light dosimetry. Treatment response was assessed primarily by hypovascular lesion formation on contrast enhanced magnetic resonance imaging and transrectal ultrasound guided biopsies targeting areas of lesion formation and secondarily by serum prostate specific antigen changes. Results: Tookad vascular targeted photodynamic therapy was technically feasible. The plasma drug concentration was negligible by 2 hours after infusion. In the drug escalation arm 3 of 6 patients responded, as seen on magnetic resonance imaging, including 1 at 1 mg/kg and 2 at 2 mg/kg. The light dose escalation demonstrated an increasing volume of effect with 2 of 3 patients in the first light escalation cohort responding and all 6 responding at the highest light dose with lesions encompassing up to 70% of the peripheral zone. There were no serious adverse events, and continence and potency were maintained. Conclusions: Tookad vascular targeted photodynamic therapy salvage therapy is safe and well tolerated. Lesion formation is strongly drug and light dose dependent. Early histological and magnetic resonance imaging responses highlight the clinical potential of Tookad vascular targeted photodynamic therapy to manage post-external beam radiation therapy recurrence.

Extraction of anatomical structures (landmarks), such as optic disk (OD), fovea and blood vessels, from fundus images is useful in automatic diagnosis. Current approaches largely use spatial relationship among the landmarks' position for detection. In this paper, we present an appearance-based method for detecting fovea and OD from colour images. The strategy used for detection is based on improving the local contrast which is achieved by combining information from two spectral channels of the given image. The proposed method has been successfully tested on different datasets and the results show 96% detection for fovea and 91% detection for OD (a total of 502 and 531 images for fovea and OD are taken respectively).

Objective: The microscopic study of the various components of joints provide a proper basis for understanding the nature of pathologic lesions to which they are subject and their imaging appearances. This study was designed to correlate MR imaging with a systematic histological study of the normal sacroiliac joint (SIJ), which to our knowledge is not available in the literature. Design and patients: Five male cadavers, aged 20 to 45 years, and seven male and seven female volunteers, aged 23 to 44 years, were investigated with oblique transaxial and coronal MR imaging of the SIJs. A variety of sequences including pre-and post-contrast T1 fat-saturated studies in the volunteers were used. Cryosectioning was performed in six SIJs of the five cadavers and compared with the MR images for the microscopic joint anatomy and assessed for the presence of abnormalities resembling those associated with sacroiliitis. Results: Throughout the SIJ, the hyaline cartilage of the sacral bone and the proximal third of the hyaline iliac cartilage was strongly attached to the surrounding stabilizing ligaments, forming wide margins of fibrocartilage. In the distal one-third of the joint only, the margins of the iliac joint facet resemble that of a synovial joint, which include an inner capsule with synovial cells. The MR anatomy of the ventral and dorsal nal MR imaging does not allow assessment of normal anatomy, variants or abnormalities of the ventral and dorsal margins of the cartilaginous SIJ.

We studied the role of duplex Doppler ultrasonography in the diagnosis of renal obstruction caused by ureteral calculi. Using duplex Doppler sonography, we evaluated the intrarenal hemodynamics of 27 patients who presented to the emergency department with renal colic. We performed Doppler ultrasonography on patients in whom US did not reveal any pathology causing renal colic and calculated and compared mean RI values of normal and obstructed kidneys and ΔRI values of each group. Threshold levels for the diagnosis of urinary tract obstruction (mean RI ≥ 0.70 and ΔRI ≥ 0.08) were used to determine the sensitivity and specificity of Doppler sonography for the diagnosis of urinary tract obstruction. Patients were investigated for revealing calculi diagnosis either by stone excretion history, intravenous pyelography or non contrast enhanced urinary computed tomography. A total of 162 intrarenal arterial Doppler recordings were made on 54 kidneys. Of the 16 patients with urinary obstruction, 11 (68%) had sonographic evidence of pelvicalyceal dilatation. The mean RI of the 16 obstructed and 11 unobstructed kidneys was 0.69 ± 0.04 and 0.61 ± 0.06 (mean ± standard deviation), respectively. The difference between the mean RI values for each group was statistically significant (P P P 

| The increased use of abdominal imaging techniques for a variety of indications has contributed to more-frequent detection of renal cell carcinoma (RCC). Ultrasonography has been used to characterize the solid versus cystic nature of renal masses. This modality has limitations, however, in further characterization of solid tumors and in staging of malignancy, although contrast-enhanced ultrasonography has shown promise. Crosssectional imaging with multiplanar reconstruction capability via CT or MRI has become the standard-bearer in the diagnosis, staging and surveillance of renal cancers. The use of specific protocols and the exploitation of different imaging characteristics of RCC subtypes, including variations in contrast agent timing, MRI weighting and digital subtraction, have contributed to this diagnostic capability. Cystic renal masses are a special case, evaluation of which can require multiple imaging modalities. Rigorous evaluation of these lesions can provide information that is crucial to prediction of the likelihood of malignancy. Such imaging is not without risk, however, as radiation from frequent CT imaging has been implicated in the development of secondary malignancies, and contrast agents for CT and MRI can pose risks, particularly in patients with compromised renal function.

Optics has played a key role in the rapidly developing field of molecular imaging. The spectroscopic nature and high-resolution imaging capabilities of light provide a means for probing biological morphology and function at the cellular and molecular levels. While

Purpose: The objective of this study was to evaluate white matter tissue damage in patients with Alzheimer's disease (AD) and in patients with mild cognitive impairment (MCI) using diffusion tensor imaging (DTI). Materials and Methods: Forty-seven subjects were evaluated: 14 patients with AD, 15 with MCI, and 18 healthy volunteers. All subjects were studied using conventional magnetic resonance imaging and DTI (32 directions) with a 1.5-T magnet. Fractional anisotropy (FA) was measured in the following regions: frontal, occipital, parietal, and temporal white matter and in the genu and splenium of the corpus callosum. The results were compared between the different groups and correlated with the Mini-Mental State Evaluation (MMSE) scores. Results: A statistically significant difference was obtained between controls and MCI patients (Pb.007) and between controls and AD patients (Pb.05) with regard to FA of the white matter in the splenium. A statistically significant difference was obtained between controls and AD patients with regard to FA in the genu (Pb.016). Moreover, there was a statistically significant difference between controls and AD patients considering the genu (Pb.016) and the frontal white matter on the right side (Pb.024). The MMSE scores correlated with the FA values measured in the genu, the splenium, and frontal white matter on the right side. No significant differences were identified between patients with AD and those with MCI. Conclusions: DTI could be of value in the early detection of white-matter damage in patients with MCI and AD. The DTI values correlate with the neuropsychological tests. Tissue characterization of head and neck lesions using diffusion-weighted MR imaging with SPLICE

In humans, contrast-enhanced fluid-attenuated inversion recovery (FLAIR) imaging plays an important role in detecting brain disease. The aim of this study was to define the clinical utility of contrast-enhanced FLAIR imaging by comparing the results with those with contrast-enhanced spin echo T1-weighted images (SE T1WI) in animals with different brain disorders. Forty-one dogs and five cats with a clinical suspicion of brain disease and 30 normal animals (25 dogs and five cats) were evaluated using a 0.2 T permanent magnet. Before contrast medium injection, spin echo T1-weighted, SE T1WI, and FLAIR sequences were acquired in three planes. SE T1WI and FLAIR images were also acquired after gadolinium injection. Sensitivity in detecting the number, location, margin, and enhancement pattern and rate were evaluated. No lesions were found in a normal animal. In affected animals, 48 lesions in 34 patients were detected in contrast-enhanced SE T1WI whereas 81 lesions in 44 patients were detected in contrast-enhanced FLAIR images. There was no difference in the characteristics of the margins or enhancement pattern of the detected lesions. The objective enhancement rate, the mean value between lesion-to-white matter ratio and lesion-to-gray matter ratio, although representing an overlap of T1 and T2 effects and not pure contrast medium shortening of T1 relaxation, was better in contrast-enhanced FLAIR images. These results suggest a superiority of contrast-enhanced FLAIR images as compared with contrastenhanced SE T1WI in detecting enhancing brain lesions.

Computed tomography (CT; unenhanced, followed by contrast-enhanced examinations) is the cornerstone of imaging of adrenal tumours. Attenuation values of !10 Hounsfield units on an unenhanced CT are practically diagnostic for adenomas. When lesions cannot be characterised adequately with CT, magnetic resonance imaging (MRI) evaluation (with T1-and T2-weighted sequences and chemical shift and fat-suppression refinements) is sought. Functional nuclear medicine imaging is useful for adrenal lesions that are not adequately characterised with CT and MRI. Scintigraphy with [ 131 I]-6-iodomethyl norcholesterol (a labelled cholesterol analogue) can differentiate adrenal cortical adenomas from carcinomas. Phaeochromocytomas appear as areas of abnormal and/or increased uptake of [ 123 I]-and [ 131 I]-meta-iodobenzylguanidine (a labelled noradrenaline analogue). The specific and useful roles of adrenal imaging include the characterisation of tumours, assessment of true tumour size, differentiation of adenomas from carcinomas and metastases, and differentiation of hyperfunctioning from non-functioning lesions. Adrenal imaging complements and assists the clinical and hormonal evaluation of adrenal tumours.

In this work we propose a comprehensive study of Digital Stent Enhancement (DSE), from the analysis of requirements to the validation of the proposed solution. First, we derive the stent visualization requirements in the context of the clinical application and workflow. Then, we propose a DSE algorithm combining automatic detection, tracking, registration and contrast enhancement. The most original parts of our solution: landmark segmentation and non-linear image registration are detailed. Finally, we validate the algorithm on a large number of synthetic and clinical cases. Performance is characterized in terms of image quality, automation, and execution time. This work is, to the best of our knowledge, the first comprehensive article on DSE, covering problem statement, proposed solution, and validation strategies.

The extent and degree of myocardial injury after an ischemic event are strong predictors of patient's outcome. After acute infarction, delayed contrast enhancement magnetic resonance imaging allows clinicians to distinguish between viable and non-viable myocardium and can delineate with high precision the infarcted tissue. The aim of this study is to provide a quantitative method based on the fuzzy c-means clustering algorithm to assess the location and the extent of the infarcted area. Segmental infarct trasmurality was visually assessed on a 5-point scale for the 288 segments. The agreement between visual and quantitative analyses was good: 84% of the segments were categorized similarly by quantitative and visual analyses.

| The increased use of abdominal imaging techniques for a variety of indications has contributed to more-frequent detection of renal cell carcinoma (RCC). Ultrasonography has been used to characterize the solid versus cystic nature of renal masses. This modality has limitations, however, in further characterization of solid tumors and in staging of malignancy, although contrast-enhanced ultrasonography has shown promise. Crosssectional imaging with multiplanar reconstruction capability via CT or MRI has become the standard-bearer in the diagnosis, staging and surveillance of renal cancers. The use of specific protocols and the exploitation of different imaging characteristics of RCC subtypes, including variations in contrast agent timing, MRI weighting and digital subtraction, have contributed to this diagnostic capability. Cystic renal masses are a special case, evaluation of which can require multiple imaging modalities. Rigorous evaluation of these lesions can provide information that is crucial to prediction of the likelihood of malignancy. Such imaging is not without risk, however, as radiation from frequent CT imaging has been implicated in the development of secondary malignancies, and contrast agents for CT and MRI can pose risks, particularly in patients with compromised renal function.

Confluent hepatic fibrosis (CHF) is usually a feature of advanced cirrhosis, while occurrence in early stage compensated cirrhosis is uncommon. We report the imaging findings of masslike CHF in a patient with previously unsuspected compensated alcoholic cirrhosis. The combination of partially wedge shape, minimal capsular retraction, and homogeneous delayed enhancement on multiphase contrast-enhanced spiral CT led to the characterization of the lesions and establishment of the diagnosis of cirrhosis. D 2004 Elsevier Inc. All rights reserved.

Concerns over the health effects of nanomaterials in the environment have created a need for microscopy methods capable of examining the biological interactions of nanoparticles (NP). Unfortunately, NP are beyond the diffraction limit of resolution for conventional light microscopy (~200 nm). Fluorescence and electron microscopy techniques commonly used to examine NP interactions with biological substrates have drawbacks that limit their usefulness in toxicological investigation of NP. EM is labor intensive and slow, while fluorescence carries the risk of photobleaching the sample and has size resolution limits. In addition, many relevant particles lack intrinsic fluorescence and therefore can not be detected in this manner. To surmount these limitations, we evaluated the potential of a novel combination of darkfield and confocal laser scanning microscopy (DF-CLSM) for the efficient 3D detection of NP in human lung cells. The DF-CLSM approach utilizes the contrast enhancements of da...

Tone-mapping operators are used to produce low dynamic range versions of the high dynamic range images, while preserving as much details as possible. We have proposed a tonemapping operator which is built on an existing histogram adjustment technique. It incorporates certain characteristics of the human visual system, to restrain the problem of extreme contrast enhancement of certain segments and intensive compression of others, associated with histogram equalization based techniques. Test results show significant improvement over traditional histogram adjustment. The proposed method also does quite well compared to the other state of the art tonemapping operators.

The introduction of multidetector-row CT (MDCT) has provided the abdominal radiologists with dramatic changes for the imaging of the liver. At just present, establishment of new and optimal injection protocol in multiphasic contrast-enhanced MDCT of the liver has been yearned because the difficulty and the importance to optimize the scan timing for each phase imaging have obviously increased because of the extremely rapid scan speed with MDCT scanners. Among technical factors employed in an injection protocol for multiphasic contrastenhanced MDCT of the liver, to make an injection duration of contrast material fixed is the most important for the precise estimation of the scan timing for each phase imaging. With the fixed injection duration, the peak enhancement time of the aorta, portal vein, and liver constantly appear approximately 10, 20, and 30 s after the any fixed injection durations (completion of injection of contrast material), respectively. Moreover, using a combination of the fixed injection duration and patients' body-weight-tailored dose of contrast material, similarity of time-density curves of each organ in shape and pattern can be achieved for individual patient with different body weight. In this issue, we will attempt to determine an ultimately optimal, but practical injection/scan protocol to successfully realize multiphasic contrast-enhanced MDCT of the liver based on the contrast-enhancement theory.

Hemophagocytic lymphohistiocytosis (HLH) is a rare disease with rarer neurological presentation. When this occurs, diagnosis may be delayed. This report aims to call attention to clinical, laboratory, and radiological features that should prompt the correct diagnosis. A 13-yearold girl presented with progressive increase in intracranial pressure and ataxia. MRI showed a diffuse tumor-like swelling of the cerebellum with tonsillar herniation and patchy white matter post-contrast enhancement. Regression of swelling with steroids ruled out glioma and medulloblastoma, and brain lymphoma was considered. Diagnosis of HLH was reached 2 months after onset when uncontrolled fever and severe elevation of liver enzymes occurred. Two bone marrow biopsies were needed to demonstrate hemophagocytosis. Familial HLH was confirmed by perforin gene mutations. Bone marrow transplantation was performed. The early diagnosis of HLH may be life saving. Awareness of the disease is necessary to investigate its characteristic findings, thus avoiding a delay in diagnosis.

In this letter, a new satellite image contrast enhancement technique based on the discrete wavelet transform (DWT) and singular value decomposition has been proposed. The technique decomposes the input image into the four frequency subbands by using DWT and estimates the singular value matrix of the low-low subband image, and, then, it reconstructs the enhanced image by applying inverse DWT. The technique is compared with conventional image equalization techniques such as standard general histogram equalization and local histogram equalization, as well as state-of-the-art techniques such as brightness preserving dynamic histogram equalization and singular value equalization. The experimental results show the superiority of the proposed method over conventional and state-of-the-art techniques.

The Teager-Kaiser operator is a discrete version of Teager's energy operator, advanced about 16 years ago. It is a filter of the moving window type and is commonly used as an estimator of the local energy contents of a signal; it is also used as a contrast enhancer of gray level images. We state some properties of a 2D version of the operator and its responses to common images. We characterize some of its root and preconstant images, and consider the case of separable images.

Extravasation of contrast material is a well-recognized complication of contrast-enhanced imaging studies. The management of this complication is contentious; therefore, the Contrast Media Safety Committee of The European Society of Urogenital Radiology decided to review the literature and issue guidelines. A comprehensive literature search was carried out. The resulting report was discussed at the 8th European Symposium on Urogenital Radiology in Genoa, Italy. Automated power injection may result in extravasation of large volumes and may or can lead to severe tissue damage. Infants, young children and unconscious and debilitated patients are particularly at risk of extravasation during contrast media injection. Fortunately, most extravasations result in minimal swelling or erythema, with no long-term sequelae; however, severe skin necrosis and ulceration may occur. Large volumes of high osmolar contrast media are known to induce significant tissue damage. Compartment syndrome may b...

In the unsharp masking approach for image enhancement, a fraction of the highpass filtered version of the image is added to the original image to form the enhanced version. The method is simple, but it suffers from two serious drawbacks. First, it enhances the contrast in the darker areas perceptually much more strongly than that in the lighter areas. Second, it enhances the noise and/or digitization effects, particularly in the darker regions, resulting in visually less pleasing enhanced images. In general, noise can be suppressed with lowpass filters, which are associated with the blurring of the edges. On the other hand, contrast can be enhanced with highpass filters, which are associated with noise amplification. A reasonable solution, therefore, is to use suitable nonlinear filters which combine the features of both highpass and lowpass filters. This paper outlines several new methods of unsharp masking based on the use of such nonlinear filters. Computer simulations have verified the superior results obtained using these filters. In addition, a new measure of contrast enhancement is introduced which quantitatively supports the improvement obtained using the proposed methods. © 1996 SPIE and IS&T.

The main objective of image enhancement is to improve some characteristic of an image to make it visually better one. This paper proposes a method for enhancing the color images based on nonlinear transfer function and pixel neighborhood by preserving details. In the proposed method, the image enhancement is applied only on the V (luminance value) component of the HSV color image and H and S component are kept unchanged to prevent the degradation of color balance between HSV components. The V channel is enhanced in two steps. First the V component image is divided into smaller overlapping blocks and for each pixel inside the block the luminance enhancement is carried out using nonlinear transfer function. In the second step, each pixel is further enhanced for the adjustment of the image contrast depending upon the center pixel value and its neighborhood pixel values. Finally, original H and S component image and enhanced V component image are converted back to RGB image. The subjective and objective performance evaluation shows that the proposed enhancement method yields better results without changing image original color in comparison with the conventional methods.

Image processing is an engineering field where stored image data is readily available for parallel processing. Basically data processing algorithms developed in sequential approach are not capable of harnessing the computing power of individual cores present in a single-chip multicore processor. To utilize the multicore processor efficiently on windows platform for color image processing applications, a lock-free multithreading approach was developed using Visual C++ with Microsoft Foundation Class (MFC) support. This approach distributes the image data processing task on multicore Central Processing Unit (CPU) without using parallel programming framework like Open Multi-Processing (OpenMP) and reduces the algorithm execution time. In image processing, each pixel is processed using same set of high-level instruction which is time consuming. Therefore to increase the processing speed of the algorithm in a multicore CPU, the entire image data is partitioned into equal blocks and copy of the algorithm is applied on each block using separate worker thread. In this paper, multithreaded color image processing algorithms namely contrast enhancement using fuzzy technique and edge detection were implemented. Both the algorithms were tested on an Intel Core i5 Quad-core processor for ten different images of varying pixel size and their performance results are presented. A maximum of 71% computing performance improvement and speedup of about 3.4 times over sequential approach was obtained for large-size images using four thread model.

Our purpose was to prospectively compare MRI findings with histopathologic findings in the evaluation of suspected acute cholecystitis. Fourteen patients with clinically suspected acute cholecystitis were entered into the study. MR sequences included T,-weighted fat-suppression and breath-hold spoiled gradient echo (SGE) before and after intravenous gadolhdum chelate administration. Percent contrast enhancement ( %CE) of the gallbladder wall and gallbladder wall thickness (WT) were measured and liver enhancement patterns determined prospectively on MR images. Correlation was obtained with pathological findings at cholecytectomy in all patients. In a second phase of the study MR images on 10 additional subjects who underwent MR examination for reasons other than hepatobiliary disease were analyzed to determine normal values for %CE and gallbladder wall thickness. Mean %CE was 124.0% in patients with acute cholecystitis (10 patients), 58.0% in patients with chronic cholecystitis (2 patients), and 73.0% in patients with gallbladder malignancy (2 patients). Mean gallbladder WT was 6.1 mm in acute cholecystitis, 4.5 mm in chronic cholecystitis, and 6.0 mm in malignant disease. There was a significant difference in %CE between acute and chronic cholecystitis 0, = 0.03) ; no other significant differences in %CE or WT were observed among the patients with gallbladder disease. Patients without biliary disease had %CE of 37.3% and WT of 2.9 mm, which were both significantly less @ < 0.001) than in patients with acute cholecystitis. Transient enhancement of pericholecystic hepatic parenchyma on immediate postgadolinlum SGE images was seen in 7 of 10 patients with acute cholecystitis, and not observed in other patients. Patients with acute cholecystitis had increased %CE and WT on MR images that were significantly greater than normal and %CE that was significantly greater than in patients with chronic cholecystitis. Transient increased pericholecystic hepatic enhancement was observed in 70% of acute cholecystitis patients and in no other patient groups.

A method of analysing timbre in melody that takes account of its multidimensional characteristic is described. The aim of this analysis technique is to uncover the role of timbre as a structural element in melody. Gaining an understanding of how an abstract, multidimensional sound phenomenon such as timbre is used in a structured manner can lead to important insights into potential cognitive abilities; our ability to form mental representations of abstract phenomena so that they can be conserved and, subsequently, used in an organised or structured manner. This method of analysis comprises two main components, a first which carries out a time-frequency analysis of the melodic signal and processes the signal data using DSP techniques that model aspects of auditory processing before calculating the timbre descriptors, and a second that represents the melody in terms of its timbral changes rather than its absolute timbral values. A self-organising feature map is used to reduce the timbral detail and the dimensionality of the timbral representation, and to contrast-enhance the timbral changes. An example of the implementation of this analysis technique is presented using an extract from a Japanese shakuhachi honkyoku melody, chosen because of its accepted exploitation of timbre.

Magnetic resonance imaging (MRI) is a non-invasive clinical imaging modality, which has become widely used in the diagnosis and/or staging of human diseases around the world. Some MRI examinations include the use of contrast agents. The categorizations of currently available contrast agents have been described according to their effect on the image, magnetic behavior and biodistribution in the body, respectively. In this field, superparamagnetic iron oxide particles and soluble paramagnetic metal chelates are two main classes of contrast agents for MRI. This review outlines the research and development of MRI contrast agents. In future, the ideal MRI contrast agent will be focused on the neutral tissue-or organ-targeting materials with high relaxivity and specificity, low toxicity and side effects, suitable long intravascular duration and excretion time, high contrast enhancement with low dose in vivo, and with minimal cost.

Propos. -La tuberculose du système nerveux central (SNC) demeure un problème de santé publique paticulièrement dans les pays en voie de développement. Le but de ce travail est de caractériser les anomalies neuroradiologiques des différentes lésions tuberculeuses intracrâniennes.

In this paper a novel approach is proposed to approximate the exponential correction factor of grayscale images which maximizes the contrast of the image in the class of exponential intensity mapping functions. The error of approximation is less than 10% compared to the optimal exponent determined by the iterative bisection method. Besides the method maximizes the contrast in the class of exponential functions, it can be used to restore under-and over-exposed images. In the tests well exposed images were exponentially distorted and the result of contrast enhancement using the proposed method and histogram equalization are compared. Alghough the contrast provided by the proposed method is smaller, the resulting images are smoother than in the case of histogram equalization, furthermore the results of the exponential contrast maximization have higher correlation with the original images than histogram equalized distorted images.

Gadolinium (Gd)-based contrast agents are a valuable diagnostic aid for magnetic resonance imaging (MRI). The amount of free Gd deposited in tissues following contrast enhanced MRI is of toxicological concern. The McMaster University in vivo prompt gamma neutron activation analysis facility has been adapted for the detection of Gd in the kidney, liver, and the leg muscle. A simple model of the HPGe detector used for detection of the prompt c-rays following Gd neutron capture has been created using Monte Carlo simulation. A separate simulation describing the neutron collimation and shielding apparatus has been modified to determine the neutron capture rate in the Gd phantoms. The MCNP simulation results have been confirmed by experimental measurement. The deviations between MCNP and the experiment were between 1% and 18%, with an average deviation of 3.8 ± 6.7%. The validated MCNP model is to be used to improve the Gd in vivo measurement sensitivity by determining the best neutron moderator/reflector arrangement.

Digital Image enhancement provides a multitude of choices for improving the visual quality of radiographic images. When the details of radiographic image are lost due to various reasons, image enhancement has been applied. Many algorithms have been proposed for image enhancement in the past decade. Contrast improvement algorithms are used to enhance image contrast and some algorithms come with undesired drawbacks like the loss of tiny details, enhancement of image noise, occasional over enhancement and unnatural look of the processed images. This paper proposes new algorithms for contrast enhancement of radiographic images in spatial domain based on edge operators. Experimental results show that the proposed algorithms provide a flexible and reliable way for contrast enhancement over the traditional high pass filter.

Gourtsoyiannis, N. (Heraklion) 94 Lymph Node Clearance after Total Mesorectal Excision for Rectal Cancer: Laparoscopic versus Open Approach Pechlivanides, G.; Gouvas, N.; Tsiaoussis, J.; Tzortzinis, A.; Tzardi, M.; Moutafidis, M.; Dervenis, C.; Xynos, E. (Athens) Souglakos, J.; Vardakis, N.; Androulakis, N.; Kakolyris, S.; Kourousis, C.; Mavroudis, D.; Pallis, A.; Agelaki, S.; Kalbakis, K.; Georgoulias

Image registration techniques are used routinely in a variety of today's medical imaging diagnosis. Since the problem is ill-posed, one may like to add additional information about distortions. This applies, for example, to the registration of contrast enhanced images, where variations of substructures are not related to patient motion but to contrast uptake. Here, one may only be interested in registrations which do not alter the volume of any substructure. In this paper we discuss image registration techniques with a focus on volume preserving constraints. These constraints can reduce the non-uniqueness of the registration problem significantly. Our implementation is based on a constrained optimization formulation. Upon discretization, we obtain a large, discrete, highly nonlinear optimization problem and the necessary conditions for the solution form a discretize nonlinear partial differential equation. To solve the problem we use a variant of Sequential Quadratic Programming method. Moreover, we present results on synthetic as well as on real life data.

BACKGROUND AND PURPOSE: Radiologic evaluation of CSF leaks is a diagnostic challenge that often involves multiple imaging studies with the associated expense and patient discomfort. We evaluated the use of screening noncontrast high-resolution CT in identifying the presence and site of CSF rhinorrhea and otorrhea and compared it with contrast-enhanced CT cisternography and radionuclide cisternography.

Advances in conformal radiation therapy and advancements in pre-clinical radiotherapy research have recently stimulated the development of precise micro-irradiators for small animals such as mice and rats. These devices are often kilovolt x-ray radiation sources combined with high-resolution CT imaging equipment for image guidance, as the latter allows precise and accurate beam positioning. This is similar to modern human radiotherapy practice. These devices are considered a major step forward compared to the current standard of animal experimentation in cancer radiobiology research. The availability of this novel equipment enables a wide variety of pre-clinical experiments on the synergy of radiation with other therapies, complex radiation schemes, sub-target boost studies, hypofractionated radiotherapy, contrast-enhanced radiotherapy and studies of relative biological effectiveness, to name just a few examples. In this review we discuss the required irradiation and imaging capabilities of small animal radiation research platforms. We describe the need for improved small animal radiotherapy research and highlight pioneering efforts, some of which led recently to commercially available prototypes. From this, it will be clear that much further development is still needed, on both the irradiation side and imaging side. We discuss at length the need for improved treatment planning tools for small animal platforms, and the current lack of a standard therein. Finally, we mention some recent experimental work using the early animal radiation research platforms, and the potential they offer for advancing radiobiology research.

Vascular diseases are among the most important public health problems in developed countries. Given the size and complexity of modern angiographic acquisitions, segmentation is a key step toward the accurate visualization, diagnosis and quantification of vascular pathologies.

The aim of this study was to assess the diagnostic value of integrated whole body positron emission tomography/contrast-enhanced CT (PET/CECT) as a one step examination in the initial staging of oral and oropharyngeal squamous cell carcinoma (OOSCC). Seventy three consecutive OOSCC patients who underwent PET/CECT for initial staging and tumour resection and neck dissection as primary treatment, were included. For each PET/CECT result, the contribution of fluorine-18 fluorodeoxyglucose ((18)F-FDG)-uptake and radiologic criteria was assessed. PET/CECT results were correlated to histological specimens obtained with tumour resection and neck dissection. For detecting the primary tumour PET/CECT showed a sensitivity of 96% and for detecting cervical metastases a sensitivity and specificity of 89% and 81%, respectively. In the clinically N0 subgroup (n=37), PET/CECT showed a sensitivity and specificity of 64% and 81%, respectively. In five of six patients PET/CECT detected a second primar...

The current study investigates whether texture properties of the tissue surrounding microcalcification (MC) clusters can contribute to breast cancer diagnosis. The case sample analyzed consists of 100 mammographic images, originating from the Digital Database for Screening Mammography (DDSM). All mammograms selected correspond to heterogeneously and extremely dense breast parenchyma and contain subtle MC clusters (46 benign and 54 malignant, according

The purpose of this study was to present the variation of clinical target volume (CTV) with different computed tomography (CT) slice thicknesses and the impact of CT slice thickness on 3-dimensional (3D) conformal radiotherapy treatment planning. Fifty patients with brain tumors were selected and CT scans with 2.5-, 5-, and 10-mm slice thicknesses were performed with non-ionic contrast enhancement. The patients were selected with tumor volume ranging from 2.54 cc to 222 cc. Three-dimensional treatment planning was performed for all three CT datasets. The target coverage and the isocenter shift between the treatment plans for different slice thickness were correlated with the tumor volume. An important observation from our study revealed that for volume < 25 cc, most of the cases were underdosed by 18% with 5-mm slice thickness and 27% with 10-mm slickness. For volume > 25 cc, the target underdosage was less than 6.7% for 5-mm slice thickness and 8% for 10-mm slice thickness. For 3D conformal radiotherapy treatment planning (3DCRT), a CT slice thickness of 2.5 mm is optimum for tumor volume < 25 cc, and 5 mm is optimum for tumor volume > 25 cc.