Improved Imaging Methods Research Articles

An Improved Method for Calculating Wave Velocity Fields in Fractured Rock Based on Wave Propagation Probability

Ultrasonic velocity field imaging offers a robust tool for characterizing and analyzing damage and its evolution within fractured rock masses. The combined application of ultrasonic first arrival waves and coda waves can significantly enhance the accuracy and range of velocity field imaging. This manuscript introduces an improved imaging method that integrates the propagation probability distribution of the first arrival and coda waves to calculate the velocity field. The proposed method was applied to the velocity field imaging of a medium with multiple scatterers and varying degrees of fracturing. The overall error and calculation unit error of the proposed method were analyzed, and its improvement in calculation accuracy and applicable scope was verified. Additionally, this method was employed to image the velocity field during the damage process of fractured rock masses. The imaging results were compared against digital speckle patterns to confirm the method’s suitability. Finally, we discussed the impact of measurement errors and sensor missing on the accuracy of the computational outcomes presented in this method. These two situations will affect the calculation results, and the influence of reducing the number of sensors is smaller than that of measuring time shifts with error.

An Improved Imaging Method Based on Optimal Topographic Imaging Plane Reconstruction for Nonlinear Trajectory SAR

An Improved Imaging Method Based on Optimal Topographic Imaging Plane Reconstruction for Nonlinear Trajectory SAR

CD46-Targeted Theranostics for PET and 225Ac-Radiopharmaceutical Therapy of Multiple Myeloma.

Multiple myeloma is a plasma cell malignancy with an unmet clinical need for improved imaging methods and therapeutics. Recently, we identified CD46 as an overexpressed therapeutic target in multiple myeloma and developed the antibody YS5, which targets a cancer-specific epitope on this protein. We further developed the CD46-targeting PET probe [89Zr]Zr-DFO-YS5 for imaging and [225Ac]Ac-DOTA-YS5 for radiopharmaceutical therapy of prostate cancer. These prior studies suggested the feasibility of the CD46 antigen as a theranostic target in multiple myeloma. Herein, we validate [89Zr]Zr-DFO-YS5 for immunoPET imaging and [225Ac]Ac-DOTA-YS5 for radiopharmaceutical therapy of multiple myeloma in murine models. In vitro saturation binding was performed using the CD46 expressing MM.1S multiple myeloma cell line. ImmunoPET imaging using [89Zr]Zr-DFO-YS5 was performed in immunodeficient (NSG) mice bearing subcutaneous and systemic multiple myeloma xenografts. For radioligand therapy, [225Ac]Ac-DOTA-YS5 was prepared, and both dose escalation and fractionated dose treatment studies were performed in mice bearing MM1.S-Luc systemic xenografts. Tumor burden was analyzed using BLI, and body weight and overall survival were recorded to assess antitumor effect and toxicity. [89Zr]Zr-DFO-YS5 demonstrated high affinity for CD46 expressing MM.1S multiple myeloma cells (Kd = 16.3 nmol/L). In vitro assays in multiple myeloma cell lines demonstrated high binding, and bioinformatics analysis of human multiple myeloma samples revealed high CD46 expression. [89Zr]Zr-DFO-YS5 PET/CT specifically detected multiple myeloma lesions in a variety of models, with low uptake in controls, including CD46 knockout (KO) mice or multiple myeloma mice using a nontargeted antibody. In the MM.1S systemic model, localization of uptake on PET imaging correlated well with the luciferase expression from tumor cells. A treatment study using [225Ac]Ac-DOTA-YS5 in the MM.1S systemic model demonstrated a clear tumor volume and survival benefit in the treated groups. Our study showed that the CD46-targeted probe [89Zr]Zr-DFO-YS5 can successfully image CD46-expressing multiple myeloma xenografts in murine models, and [225Ac]Ac-DOTA-YS5 can effectively inhibit the growth of multiple myeloma. These results demonstrate that CD46 is a promising theranostic target for multiple myeloma, with the potential for clinical translation.

Improved Segmentation of Pulmonary Nodules Using Soft Computing Techniques with SegNet and Adversarial Networks

Lung cancer is seen as one of the most common lung diseases. For the patients having symptoms, the presence of lung nodules is checked by using various imaging techniques. Pulmonary nodules are detected in most of the cases having symptoms. But identifying the type of the nodule and the categorization still remains as a challenge. After confirming the presence of a nodule (benign or malignant) it takes several other steps to identify its characteristics. Improved imaging methods produce results within a short span of time. Research works are being conducted to increase the overall efficiency of the system. The proposed system considers authentic data sources for the study. The benign and malignant samples are considered for the generation of realistic large image sets. The generation of a large data set with the help of a generative adversarial network (GAN) is the first part of the work. The generated images using GAN cannot be differentiated from the original images even by a trained radiologist. This proves the importance of images generated using GAN. A GAN is able to generate 1024 × 1024 resolutions for natural images. Real data images are used to finetune the SegNet output. Through transfer learning, these weights are transferred to the system for segmentation of the images. The training process use real and generated images, which improve theefficiency of the network. The original data from LUNA 16 was used to further generate benign and malignant samples using GAN. A total of 440 images and their augmented images were used for training the GAN, and it generated 1,001,000 images. Hence the overall efficiency of the system was improved. To verify the results, the same various combinations and methods were considered and tabulated with various parameters. Methods with SegNet, GAN, and other combinations were evaluated to verify the efficiency of the system. Receiver operating characteristics were also plotted and compared with the area under the curve for verification of the results.

Novel Surrogate Markers of Cardiovascular Risk in the Setting of Autoimmune Rheumatic Diseases: Current Data and Implications for the Future.

Patients suffering from rheumatologic diseases are known to have an increased risk for cardiovascular disease (CVD). Although the pathological mechanisms behind this excess risk have been increasingly better understood, there still seems to be a general lack of consensus in early detection and treatment of endothelial dysfunction and CVD risk in patients suffering from rheumatologic diseases and in particular in those who haven't yet shown symptoms of CVD. Traditional CVD prediction scores, such as Systematic Coronary Risk Evaluation (SCORE), Framingham, or PROCAM Score have been proposed as valid assessment tools of CVD risk in the general population. However, these risk calculators developed for the general population do not factor in the effect of the inflammatory burden, as well as other factors that can increase CVD risk in patients with rheumatic diseases, such as glucocorticoid therapy, abnormal lipoprotein function, endothelial dysfunction or accelerated atherosclerosis. Thus, their sole use could lead to underestimation of CVD risk in patients with rheumatic diseases. Therefore, there is a need for new biomarkers which will allow a valid and early assessment of CVD risk. In recent years, different research groups, including ours, have examined the value of different CVD risk factors such as carotid sonography, carotid-femoral pulse wave velocity, flow-mediated arterial dilation and others in the assessment of CVD risk. Moreover, various novel CVD laboratory markers have been examined in the setting of autoimmune diseases, such as Paraoxonase activity, Endocan and Osteoprotegerin. Dyslipidemia in rheumatoid arthritis (RA) is for instance better quantified by lipoproteins and apolipoproteins than by cholesterol levels; screening as well as pre-emptive carotid sonography hold promise to identify patients earlier, when prophylaxis is more likely to be effective. The early detection of subtle changes indicating CVD in asymptomatic patients has been facilitated through improved imaging methods; the inclusion of artificial intelligence (AI) shows promising results in more recent studies. Even though the pathophysiology of coronary artery disease in patients with autoimmune rheumatic diseases has been examined in multiple studies, as we continuously gain an increased understanding of this comorbidity, particularly in subclinical cases we still seem to fail in the stratification of who really is at risk—and who is not. A the time being, a multipronged and personalized approach of screening patients for traditional CVD risk factors, integrating modern imaging and further CV diagnostic tools and optimizing treatment seems to be a solid approach. There is promising research on novel biomarkers, likewise, methods using artificial intelligence in imaging provide encouraging data indicating possibilities of risk stratification that might become gold standard in the near future. The present review concentrates on showcasing the newest findings concerning CVD risk in patients with rheumatologic diseases and aims to evaluate screening methods in order to optimize CVD risk evaluation and thus avoiding underdiagnosis and undertreatment, as well as highlighting which patient groups are most at risk.

High-quality compressed sensing imaging with limited detector bits using sparse measurements and multiple dithers.

High-flux measurement characteristics of compressed sensing (CS) imaging causes the imaging system prone to be disturbed by quantization. To realize high-quality CS imaging with limited detector bits, an improved imaging method combining sparse measurements and multiple dithers is proposed to reduce the dynamic range of the measured signals and increase that of effective detection. Simulations and experiments show that compared with traditional CS imaging, the proposed system decreases reconstruction errors caused by quantization distortions and may reduce the required number of detector bits to 1. The effects of detector noise and system parameters are discussed to validate the feasibility and performance of this method.

Neuroendocrine Tumours of Gastrointestinal Tract: Our Experience

<i>Background</i>: TNE-GEPs are rare and originate in the endocrine system located in the gastrointestinal tract (carcinoids) and in the pancreas (island tumours) with a variety of clinical presentations. <i>Design</i>: Cooperative, retrospective. <i>Method</i>: Between January 2005 and December 2018, a cooperative work in the Central Guard Service of the HNC, General Surgery Service "Pablo Luis Mirizzi" of the HNC and Caraffa Private Clinic, 24 patients with TNE-GEP were surgically intervened. Of the total, 14 belonged to the female sex (58.3%) and the remaining 10 men (41.6%), with an age range between 20 and 82 years of age with an average of 55.3 years. <i>Results</i>: The locations were 4 stomachs (16.6%), 14 in the intestine (58.3%) and finally 6 in the head of the pancreas (25%). In relation to the stomach in the 4 patients a total gastrectomy was performed and the pathological anatomy in three demonstrated low-grade neuroendocrine carcinoma and the fourth high degree, the latter dying. 5 patients with clinical presentations of acute appendicitis. The pathological anatomy was further acute appendicitis, a low-grade neuroendocrine carcinoma. In ileum-cecal region, four of it performed right colectomy. In three were low-grade living and fourth high-grade carcinoma with liver mtts who died. In three of the ileum all were occlusive, carrying out intestinal resections, in two low- and last-grade moderate-grade carcinomas with living liver mtts. The colon tumours were, one ascending with hepatic mtts and right colectomy more liver resections, with pathological anatomy being high-grade carcinoma and another a low-grade descending colon. The 6 pancreas lesions, 3 were non-functioning and three other functioning. All patients were operated of CPD. <i>Conclusion</i>: TNE-GEP is a rare pathology but whose frequency is constant onset. With improved imaging methods, we are faced with an increase in preoperative presumption and in the face of its best oncological possibilities, a pathology that every surgeon must know and think about.

Nondestructive testing of bonding defects in multilayered ceramic matrix composites using THz time domain spectroscopy and imaging

The accurate detection and imaging of small debonded regions in a 3-layer ceramic matrix composite (CMC) with two bonded layers is a challenge within terahertz (THz) nondestructive detection. To solve this problem, an improved imaging method for detecting bonding defects is proposed based on the statistical characteristics of variance and kurtosis to detect defects in the upper/lower adhesive layers in a multilayered CMC. The proposed method can ultimately realize a detection accuracy of 50 and 250 μm for bonding defects in the upper and lower adhesive layers, respectively, and achieve a better imaging result compared with power imaging method. Moreover, there is a corresponding relationship between the statistical characteristic value and the bonding defect size—the larger the statistical characteristic value, the larger the bonding defect size—which can be used as a reference to quantify the defect size.

A High Accuracy Ion Conductance Imaging Method Based on the Approach Curve Spectrum

Scanning ion conductance microscopy (SICM), as an emerging non-contact in situ topography measurement tool with nano resolution, has been increasingly used in recent years in biomedicine, electrochemistry and materials science. In the conventional measurement method of SICM, the sample topography is constructed according to the position of the probe at the feedback threshold of the ion current. Nevertheless, for different structures, a constant threshold cannot maintain a constant probe-sample distance. This phenomenon makes the measurement topography inconsistent with the real sample surface. In order to solve this problem and improve the measurement accuracy of SICM, a new ion conductance imaging method based on the approach curve spectrum is proposed in this work. In the new method, the local feature around the measurement point is firstly evaluated according to the change rate of ion current. Secondly, based on the local feature, the corresponding approach curve is searched from the prior approach curve spectrum to accurately evaluate the distance between the probe and the sample. Finally, the sample topography is constructed by the probe position subtracting the probe-sample distance. In this paper, we verify the feasibility of the new imaging method by combining finite element theory and experiments. To examine the measurement accuracy, the standard strip silicon and cylindrical polydimethylsiloxane (PDMS) samples are tested, and the improved imaging method can obtain the topography closer to the real samples and reduce the volumetric measurement error by 5.4%. The implementation of the new imaging method will further promote SICM application in related research fields.

MON-597 Non-Alcoholic Fatty Liver Disease Determined by MRI and Its Association with Metabolic Variables in Non-Diabetic Subjects

Non-alcoholic fatty liver disease determined by MRI and its association with metabolic variables in non-diabetic subjectsBackground: Non-alcoholic fatty liver disease (NAFLD) is defined as the presence of hepatic steatosis (liver fat accumulation higher than 5% of liver weight) in the absence of other causes. Liver biopsy is recognized as a gold standard for diagnosis, but it is limited by the risks of serious complications. Besides that, the increasing prevalence of NASH led to improved imaging methods, such as Magnetic Resonance Imaging (MRI), that enable quantitative assessment of steatosis by quantifying the hepatic fat fraction (HFF), even with steatosis levels as low as 5.56%.Objective: The aim of this study was to evaluate the metabolic profile of patients without T2DM according to hepatic steatosis measured by MRI.Methods: This was cross-sectional study conducted in an Endocrinology Unity in Minas Gerais, Brazil. The study complied with the WMA Declaration of Helsinki and was approved by the Ethical Committee on Human Subject Research from the Faculty Patos de Minas. We recruited non-diabetic subjects aged above 20 years with hepatic steatosis detected by liver sonography. Exclusion criteria were alcohol consumption of more than 20 grams/day for female and 30 grams/day for male, ferritin serum levels above 1000 mg/dL, positive serology for hepatitis B or C and intake of medications known to produce hepatic steatosis. Included subjects underwent HFF quantification by MRI, and the degree of liver fatty infiltration was estimated by using chemical shift imaging. The following biochemical variables were assessed: fasting glucose and HbA1c, HOMA-IR, lipids, AST, ALT and GGT. Analysis: we grouped individuals according to the quartile of HFF and compared clinical and biochemical variables between the groups.Results: A total of 30 subjects (18 male and 12 females) were included. All subjects were overweight (10% overweight and 90% obese); 7 (23.3%) had 3 criteria and 16 (53.3%) had two criteria for MS. The only variable assessed herein that was different between males and females was HDL-c (40.5 vs 50.5 mg/dL, respectively, p=0.0255). ALT serum levels were significantly higher in subjects in the fourth quartile of HFF, when compared to those in the third quartile (76 vs 47 UI/L, respectively, p=0.037). The other clinical of biochemical variables assessed did not differ between the quartiles of HFF.Conclusion: our preliminary findings indicate that the biochemical variables related to metabolic homeostasis are poor predictors of the degree of liver fat in overweight non-diabetic subjects. Although screening for NAFLD is still a matter of debate, our results suggest that future discussions about this should take into account that excess body weight per se, independently from biochemical abnormalities, should be considered in the recommendations for screening non-diabetic subjects.

Placenta accreta spectrum: biomarker discovery using plasma proteomics

Many cases of placenta accreta spectrum are not diagnosed antenatally, despite identified risk factors and improved imaging methods. Identification of plasma protein biomarkers could further improve the antenatal diagnosis of placenta accreta spectrum . The purpose of this study was to determine if women with placenta accreta spectrum have a distinct plasma protein profile compared with control subjects. We obtained plasma samples before delivery from 16 participants with placenta accreta spectrum and 10 control subjects with similar gestational ages (35.1 vs 35.5 weeks gestation, respectively). We analyzed plasma samples with an aptamer-based proteomics platform for alterations in 1305 unique proteins. Heat maps of the most differentially expressed proteins (T test, P<.01) were generated with matrix visualization and analysis software. Principal component analysis was performed with the use of all 1305 proteins and the top 21 dysregulated proteins. We then confirmed dysregulated proteins using enzyme-linked immunosorbent assay and report significant differences between placenta accreta spectrum and control cases (Wilcoxon-rank sum test, P<.05). Many of the top 50 proteins that significantly dysregulated in participants with placenta accreta spectrum were inflammatory cytokines, factors that regulate vascular remodeling, and extracellular matrix proteins that regulate invasion. Placenta accreta spectrum, with the use of the top 21 proteins, distinctly separated the placenta accreta spectrum cases from control cases (P<.01). Using enzyme-linked immunosorbent assay, we confirmed 4 proteins that were dysregulated in placenta accreta spectrum compared with control cases: median antithrombin III concentrations (240.4 vs 150.3 mg/mL; P=.002), median plasminogen activator inhibitor 1 concentrations (4.1 vs 7.1 ng/mL; P<.001), soluble Tie2 (13.5 vs 10.4 ng/mL; P=.02), soluble vascular endothelial growth factor receptor 2 (9.0 vs 5.9 ng/mL; P=.003). Participants with placenta accreta spectrum had a unique and distinct plasma protein signature.

Two improved defocus quantitative phase imaging methods: discussion.

Multifilter phase imaging with partially coherent light (MFPI-PC) and phase optical transfer function recovery (POTFR) are two viable defocus-based, two-dimensional quantitative phase imaging (QPI) methods. While both methods use transfer function inversion, MFPI-PC is based on the in-focus intensity derivative, while POTFR is based on the intensity difference between symmetrically defocused images. This paper compares and contrasts MFPI-PC and POTFR. Six disadvantages (five in MFPI-PC and one in POTFR) are identified. Improvement strategies to overcome each of the six shortcomings are identified and implemented, and both methods are shown to be clearly improved. The revised MFPI-PC is shown to be more accurate than the original MFPI-PC and generally more accurate than the revised POTFR. The revised POTFR is shown to be inherently faster than the original POTFR and also slightly faster than the revised MFPI-PC.

Non-invasive estimation of prostate tumor grade with PET [68Ga] Ga-PSMA-11 imaging

Background and Hypothesis: In the US alone, more than 160,000 men are diagnosed with prostate cancer each year. Prostate cancer grows slowly in many patients such that most die due to unrelated causes, yet 29,000 prostate cancer-related deaths occur annually in the US. The gravity of this mortality rate promotes over-treatment of low- and intermediate-risk cancer patients as well as monitoring of cancer via invasive biopsies to determine cancer grade. We hypothesize that molecular imaging methods can differentiate low- and intermediate- risk prostate cancer, guide optimal treatment, and eliminate morbidity associated with biopsy procedures. &#x0D; Experimental Design or Project Methods: In this work, we used PET [68Ga] Ga-PSMA-11 imaging to estimate cancer grade through direct comparison with whole mount pathology, which is the gold standard for cancer grading. A tool was developed using Interactive Data Language (IDL) to automate 3D spatial registration of whole mount pathology slices with [68Ga] Ga-PSMA-11 PET images. Upon accurate spatial registration, quantitative analysis was performed to establish the relationship between regional [68Ga] Ga-PSMA-11 uptake and prostate cancer grade.&#x0D; Results: Thus far, we have shown qualitatively that the whole mount pathology accurately maps to the correct 3D spatial location on the PET images. Upon spatial registration, using a ROC curve, we have found that [68Ga] Ga-PSMA-11 uptake could be used to detect both low- and high- risk tumor location (AUC = 0.82 and 0.84 respectively). Further, we demonstrated increasing uptake with greater risk.&#x0D; Conclusion and Potential Impact: This study begins to establish the feasibility of noninvasive, imaging-based monitoring alternatives which can mitigate the need for invasive biopsies for prostate cancer. Ultimately, improved imaging methods have the potential for not only bettering prostate cancer monitoring but also for improving cancer outcomes and quality of life for prostate cancer patients.

Experimental studies of two-dimensional complex plasma crystals: waves and instabilities

A review of experimental studies on waves, phonon dispersion relations, and mode-coupling instability in two-dimensional complex plasma crystals is presented. An improved imaging method allowing simultaneous measurements of the three wave modes (compression in-plane, shear in-plane, and out-of-plane) is given. This method is used to evidence the formation of hybrid modes and the triggering of the mode-coupling instability due to wake-mediated interactions. The main stages of the mode-coupling instability are analyzed. In the early stages, synchronization of microparticle motion at the hybrid mode frequency is reported. The spatial orientation of the observed synchronization pattern correlates well with the directions of the maximal increment of the shear-free hybrid mode. When the instability is fully developed, a melting front is formed. The propagation of the melting front has similarities with flame propagation in ordinary reactive matter. Finally, it is experimentally demonstrated that an external mechanical excitation of a stable 2D complex plasma crystal can trigger the mode-coupling instability and lead to the full melting of a two-dimensional complex plasma crystal.

Root cause analysis of diagnostic and surgical failures in the treatment of suspected Cushing’s disease

Cushing’s disease (CD) is a condition characterized by excess glucocorticoid from an ACTH pituitary adenoma. Identifying surgical candidates represents a major diagnostic challenge. We performed a root cause analysis (RCA) of treatment failures for patients with suspected CD. The present study aims to categorize failures in treatment. Medical records were reviewed from 2008 to 2017 for all patients treated surgically for suspected CD. Demographics, past medical history, endocrine outcomes, imaging findings, laboratory studies and clinical features were collected. Eighty-five patients were identified with pre-operative suspicion for CD. Thirty-four (40.0%) had undergone prior surgery confirming ACTH adenoma, leaving 51 (60.0%) for analysis. The average length of follow-up was 18.3 ± 24.1 months, 42 (82.4%) patients had postoperative biochemical remission of hypercortisolism. Forty-three (84.3%) had histologically confirmed CD, two (3.9%) were diagnosed with extracranial ACTH-secreting tumors, four (7.8%) had no obvious tumor upon intraoperative exploration, one (1.9%) had suspected pituitary ACTH hyperplasia, and one (1.9%) had no identifiable pathologic tissue despite apparent gross tumor observed during surgery. Thirty-four (66.7%) patients had remission following surgery alone, four (7.8%) after reoperation, and four (7.81%) after radiosurgery. One patient (1.9%) was found to have an ectopic source of ACTH, and one (1.9%) had immunohistochemically confirmed adrenal tumors. On RCA, we identified six categories of treatment failures. CD is a diagnostic challenge that can be difficult to distinguish from other forms of hypercortisolism. Surgical efficacy can be improved with more accurate patient selection, and perhaps with improved imaging methods.

Reactivity of larger intracranial arteries using 7 T MRI in young adults

The larger intracranial conduit vessels contribute to the total cerebral vascular resistance, and understanding their vasoreactivity to physiological stimuli is required when attempting to understand regional brain perfusion. Reactivity of the larger cerebral conduit arteries remains understudied due to a need for improved imaging methods to simultaneously assess these vessels in a single stimulus. We characterized reactivity of basal intracranial conduit arteries (basilar, right and left posterior, middle and anterior cerebral arteries) and the right and left internal carotid arteries, to manipulations in end-tidal CO2 (PetCO2). Cross-sectional area changes (%CSA) were evaluated from high-resolution (0.5 mm isotropic) images collected at 7 T using a T1-weighted 3D SPACE pulse sequence, providing high contrast between vessel lumen and surrounding tissue. Cerebrovascular reactivity was calculated as %CSA/ΔPetCO2 in eight healthy individuals (18–23 years) during normocapnia (41 ± 4 mmHg), hypercapnia (48 ± 4 mmHg; breathing 5% CO2, balance oxygen), and hypocapnia (31 ± 8 mmHg; via hyperventilation). Reactivity to hypercapnia ranged from 0.8%/mmHg in the right internal carotid artery to 2.7%/mmHg in the left anterior cerebral artery. During hypocapnia, vasoconstriction ranged from 0.9%/mmHg in the basilar artery to 2.6%/mmHg in the right posterior cerebral artery. Heterogeneous cerebrovascular reactivity to hypercapnia and hypocapnia was characterized across basal intracranial conduit and internal carotid arteries.

Fluorescence guided surgery in liver tumors: applications and advantages.

The use of fluorescence-guided surgery for benign and malignant hepatobiliary (HPB) neoplasms has significantly increased and improved imaging methods creating new interesting perspectives. A major challenge in HPB surgery is performing radical resection with maximal preservation of the liver parenchyma and obtaining a low rate of complications. Despite the developments, visual inspection, palpation, and intraoperative ultrasound remain the most utilized tools during surgery today. In laparoscopic and robotic HPB surgery palpation is not possible. Fluorescence imaging enables identification of subcapsular liver tumors through accumulation of indocyanine green (ICG), after preoperative intravenous injection, in cancerous tissues of hepatocellular carcinoma and in noncancerous hepatic parenchyma, around intrahepatic cholangiocarcinoma and liver metastases, and it can also be used for visualizing extrahepatic bile duct anatomy and hepatic segmental borders, increasing the accuracy and the easiness of open and minimally invasive hepatectomy. (www.actabiomedica.it)

An improved imaging method for extended targets

When we use direct imaging methods for solving inverse scattering problems, we observe artificial lines which make it hard to determine the shape of targets. We propose a signal space test to study the cause of the artificial lines and we use multiple frequency data to reduce the effect from them. Finally, we use the active contour without edges (ACWE) method to further improve the imaging results. The final reconstruction is accurate and robust. The computational cost is lower than iterative imaging methods which need to solve the forward problem in each iteration.

MRI Study of the Posterior Visual Pathways in Primary Open Angle Glaucoma.

The purpose of the study was to evaluate neurodegeneration along brain visual pathways in primary open angle glaucoma (POAG) using improved analysis methods of volumetric and diffusion tensor magnetic resonance imaging (MRI) data. Eleven POAG patients (60.0±9.2 y) with primarily mild to moderate POAG and 11 age-matched controls (55.9±7.5 y) were studied using structural and diffusion tensor MRI. Surface-based segmentation was applied to structural MRI to obtain visual cortical area and volume. Fiber tracking was applied to diffusion tensor data to obtain diffusion parameters along the optic tract and optic radiation. MRI parameters in glaucoma patients were compared with the corresponding left and right visual fields and retinal nerve fiber layer thicknesses, instead of with the left and right eye. Area and volume of the primary visual cortex were significantly reduced in POAG patients compared with controls (P<0.05) but did not correlate with visual field loss. Fractional anisotropy was reduced at multiple locations along the optic tracts and optic radiations in POAG patients compared with controls. Axial and radial diffusivity along the fiber tracts showed trends but were not significantly different between POAG patients and controls when averaged over the whole structures. Only fractional anisotropy (P<0.05) of the optic radiations was significantly correlated with visual field loss. No MRI parameters were correlated with retinal nerve fiber layer thickness. Improved analysis techniques of MRI data improves delineation of degeneration in the brain visual pathways and further supports the notion that neurodegeneration is involved with glaucoma pathogenesis.

Improved image method for a holographic description of conical defects

The geodesics prescription in holographic approach in Lorentzian signature is valid only for geodesics which connect spacelike-separated points at the boundary, since there are no timelike geodesics which reach the boundary. There is also no straightforward analytic Euclidean continuation for a general background, such as e. g. moving particle in AdS. We propose an improved geodesic image method for two-point Lorentzian correlators which is valid for arbitrary time intervals in case of the bulk spacetime deformed by point particles. We illustrate that our prescription is consistent with the case when the analytic continuation exists and with the quasigeodesics prescription used in previous work. We also discuss some other applications of the improved image method, such as holographic entanglement entropy and multiple particles in AdS3.