Imaging Cerebral Blood Vessels Using Near-Infrared Optical Tomography: A Simulation Study.

Cerebral veins have received increasing attention due to their importance in preoperational planning and the brain oxygenation measurement. There are different modalities to image those vessels, such as magnetic resonance angiography (MRA) and recently, contrast-enhanced (CE) 3D gradient-echo sequences. However, the current techniques have certain disadvantages, i.e., the long examination time, the requirement of contrast agents or inability to measure oxygenation. Near-infrared optical tomography (NIROT) is emerging as a viable new biomedical imaging modality that employs near infrared light (650-950 nm) to image biological tissue. It was proven to easily penetrate the skull and therefore enables the brain vessels to be assessed. NIROT utilizes safe non-ionizing radiation and can be applied in e.g., early detection of neonatal brain injury and ischemic strokes. The aim is to develop non-invasive label-free dynamic time domain (TD) NIROT to image the brain vessels. A simulation study was performed with the software (NIRFAST) which models light propagation in tissue with the finite element method (FEM). Both a simple shape mesh and a real head mesh including all the segmented vessels from MRI images were simulated using both FEM and a hybrid FEM-U-Net network, we were able to visualize the superficial vessels with NIROT with a Root Mean Square Error (RMSE) lower than 0.079.

Effects of Different Optical Properties of Head Tissues on Near-Infrared Spectroscopy Using Monte Carlo Simulations.

In near-infrared spectroscopy (NIRS), it is crucial to have an accurate and realistic model of photon transport in the adult head for obtaining accurate brain oxygenation values. There are several studies on the influence of thickness, the morphology of extracerebral layers, and source-detector distance on the sensitivity of NIRS to the brain. However, the optical properties of the different layers vary between different publications. How is the performance of NIRS affected when the real optical properties differ from the assumed ones?We aim to investigate the influence of variation in scattering and absorption in a five-layered head model (scalp, skull, CSF, grey and white matter). We performed Monte Carlo simulations focusing on a five-layered slab mesh. The range of optical properties is based on a review of the published literature. We assessed the effect on light propagation by measuring the difference in the mean partial path lengths, attenuation, and the number of the detected photons between the different optical properties performing Monte Carlo simulations. For changes in the reduced scattering, we found that the upper layers tend to have a negative impact. In contrast, changes in lower layers tend to impact the brain's influence metrics positively. Furthermore, for small source-detector distances, the relative percentage difference between lower and higher values is greater than larger distances. Conclusions: We conclude that the assumption of different optical properties has a substantial effect on the sensitivity to the brain. This means that it is important to determine the correct optical properties for NIRS measurements in vitro and in vivo.

Development and Validation of Robust and Cost-Effective Liquid Heterogeneous Phantom for Time Domain Near-Infrared Optical Tomography.

Diffused light imaging techniques, such as near-infrared optical tomography (NIROT), require a stable platform for testing and validation that imitates tissue optical properties. The aim of this work was to build a robust, but flexible liquid phantom for BORL time-domain NIROT system Pioneer. The phantom was designed to assess penetration depth and resolution of the system, and to provide a heterogeneous inner structure that can be changed in controllable manner with adjustable optical properties. We used only in-house produced 3D-printed elements and mechanics of a budget 3D-printer to build the phantom, and managed to keep the overall costs below $500. We achieved stable and repeatable movement of an arbitrary structure in 3+1 degree of freedom inside the phantom and demonstrated its performance in a series of tests. Thus, we presented a universal and cost-effective solution for testing NIROT, that can be easily customised to various systems or testing paradigms.

[Markers of viral hepatitis B. Diagnostic, prognostic and therapeutic relevance]. / I markers della virus-epatite B. Rilevanza diagnostica, prognostica e terapeutica.

Analysis of the behaviour and chronological development of B virus markers (including those most recently identified) in acute and chronic hepatitis gives rise to a diagnostic hypothesis about their presence and association. The prognostic and therapeutic significance of the markers is also emphasised with particular reference to fulminating and chronic active HBSAg and D positive hepatitis and the early diagnosis of liver cell carcinoma.

[Benign monoclonal gammopathies: probable antibody specificity of monoclonal immunoglobulins]. / Gammopatie monoclonali benigne: probabile specificità anticorpale delle immunoglobuline monoclonali.

40 patients with benign paraproteinemia have been studied in relation to their age and associated diseases. Significantly high frequency of liver diseases (CALD, cirrhosis, hepatoma, metastases) has been found (12 over 40 people) and increased incidence of idiopathic paraproteinaemia in the old age has been confirmed. 9 patients have been followed for 5 years, so that one could be sure that they had really benign paraproteinaemia: these patients have been then studied from an immunological point of view, in vivo by means of skin tests (PPD, Candida, Trichophyton, DNCB) and in vitro by searching for circulating immune complexes (using a new highly specific immuno-enzymatic method), and compared to controls without paraproteinaemia. Highly positive skin tests have been found only in 7 over 9 patients (even in old subjects) and 6 of them had circulating immune complexes (C.I.C.) in their sera; all the controls were negative both for skin tests and for C.I.C. Immune complexes have been found also in some cases of idiopathic paraproteinaemia, so that they do not seem to be in relation to the associated diseases. The Authors suggest that a genetically determined defect in regulator/suppressor T lymphocyte activity may cause the growth of a benign B cell neoplasm; and that monoclonal immunoglobulins most probably have antibody specificity and are directed against target antigens.