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An experimental study is performed on electromagnetic time reversal in highly scattering environments, with a particular focus on performance when environmental conditions change. In particular, we consider the case for which there is a mismatch between the Green's function used on the forward measurement and that used for time-reversal inversion. We examine the degradation in the time-reversal image with increasing media mismatch, and consider techniques that mitigate such degradation. The experimental results are also compared with theoretical predictions for time reversal in changing media, with good agreement observed

Objective To characterize MR imaging features of pure mucinous carcinoma of the breast. Materials and methods MR images obtained from 16 women (age range, 29–81; mean age, 57 years) with pure mucinous carcinoma of the breast determined at surgery were reviewed. The MR findings used were shape, margin, internal mass enhancement, kinetic curve pattern on dynamic study, signal intensity on short time inversion recovery (STIR) T2-weighted images, and non-mass-like enhancement around the main tumor. Non-mass-like enhancement was compared with the presence of extensive intraductal component (EIC) on histopathological findings. Results Eleven tumors (69%) had lobular contour, and nine tumors (56%) had smooth margin. Eight tumors (50%) showed rim enhancement and six tumors (38%) showed heterogeneous enhancement. Fourteen tumors (88%) showed a persistent enhancing pattern on kinetic curve. Fifteen tumors exhibited homogenous strongly high signal intensity on STIR T2-weighted images. In six cases with EIC, five cases had non-mass-like enhancement around the main mass. Conclusions MR findings such as lobular shape, rim or heterogeneous enhancement, persistent pattern on kinetic curve, and homogeneous strongly high signal intensity on STIR T2-weighted images may be useful in diagnosing pure mucinous carcinoma. Moreover, linear-ductal enhancement around main mass may indicate presence of EIC.

Introduction: In Graves' Ophthalmopathy, it is important to distinguish active inflammatory phase, responsive to immunosuppressive treatment, from fibrotic unresponsive inactive one. The purpose of this study is, first, to identify the relevant orbital magnetic resonance imaging signal intensities before treatment, so to classify patients according to their clinical activity score (CAS), discriminating inactive (CAS3) subjects and, second, to follow post-steroid treatment disease. Methods: An observational study was executed on 32 GO consecutive patients in different phases of disease, based on clinical and orbital Magnetic Resonance Imaging parameters, compared to 32 healthy volunteers. Orbital Magnetic Resonance Imaging was performed on a 1.5 tesla Magnetic Resonance Unit by an experienced neuroradiologist blinded to the clinical examinations. Results: In pre-therapy patients, compared to controls, a medial rectus muscle statistically significant signal intensity ratio (SIR) in short-time inversion recovery (STIR) (long TR/TE) sequence was found, as well as when comparing patients before and after treatment, both medial and inferior rectus muscle SIR resulted significantly statistically different in STIR. These increased outcomes explain the inflammation oedematous phase of disease, moreover after steroid administration, compared to controls; patients presented lack of that statistically significant difference, thus suggesting treatment effectiveness. Conclusion: In our study, we proved STIR signal intensities increase in inflammation oedematous phase, confirming STIR sequence to define active phase of disease with more sensibility and reproducibility than CAS alone and to evaluate post-therapy involvement. © 2014 Springer-Verlag.

The paper presents a digital method of conversion of the sensor and its hardware implementation. The method is based on excitation of oscillations in the sensitive elements of sensors, analog-digital conversion of signals and their time reversal by re-indexing of array elements, followed by Fourier transformation and determination of the initial phases of the oscillations.

The short TI LGE sequence detected a significant higher number of papillary muscle infarction compared to standard LGE sequence (19/54 versus 15/54 respectively). Moreover, in these images papillary muscle infarction was appeared with more sharpness (84.2% vs 53.3%) The contrast-to-noise ratio was higher between infarcted myocardium and blood (77.9±60 vs 19.3±16, p

In this paper we present a mixed-integer linear programming formulation for performing source inversion in drinking water systems using discrete (yes/no) measurements available from manual grab samples. Given the large size of a typical water distribution system, standard water quality models are inappropriate for use in the mixed-integer framework. In this research, we demonstrate the use of an origin-tracking approach to develop the water quality model, and show how this model can be efficiently and exactly reduced prior to the formulation of the MILP, giving rise to a much smaller MILP. Furthermore, we demonstrate that this formulation can be efficiently solved in a real-time setting on large networks with over 10,000 nodes while considering over 100 time discretizations.

Early production, as well as ultimate oil and gas recovery, from a reservoir often depend on the timeliness and the accuracy of geosteering decisions. Exiting the reservoir during drilling results in costly nonproductive intervals. Even staying within the reservoir but in a nonoptimal location eventually leads to early water breakthrough while leaving behind valuable oil. In recent years, azimuthal deep resistivity measurements have been recognized as beneficial to real-time steering decisions. Because of their deep investigation, azimuthal deep resistivity measurements anticipate exits from the reservoir well before such events occur. In addition, their azimuthal sensitivity clearly points to the direction of preferred evasive actions. Azimuthal wave resistivity measurements take on multiple embodiments with multiple characteristics and multiple depths of investigation. The best results are achieved by jointly interpreting several of these measurements according to workflows that are specific to the particular applications. In the simplest cases, the up-down resistivity curves exhibit an unexpected behavior that has proven valuable both to petrophysicists and to geosteering specialists. When approaching conductive overlaying shale, for example, the up-curve tends to read the resistivity of the reservoir and the down-curve exhibits amplified horns beneficial to reservoir navigation. Resistivity images feature bright spots whose progression with increasing depth of investigation facilitates the avoidance of unwanted boundaries. A new measurement, designated as a geosignal, features strong lateral sensitivity. The geosignal from the deepest spacing is best suited to provide an early indication of the approaching boundary, with a near-exponential dependence on the distance to boundary. Quantitative inversion based on a subset of the azimuthal resistivity logs and the use of limited local knowledge helps to quantify the distance to the reservoir boundaries and their rate of approach. This paper presents some of the most commonly used interpretation methods are demonstrated on computer models, and then applied to various wells, with applications varying from thick reservoirs to interbedded sand-shale sequences.

Eighty-three MR studies for primary bone tumors, performed with both spin echo and short time inversion recovery (STIR) sequences, were reviewed. Twenty-six patients underwent surgery within 10 days after MR imaging. Specimens were cut and directly compared with MR images. In the remainder, pathologic slides were compared in order to obtain a better understanding of MR pattern. All MR images were examined with a traditional morphologic approach and, upon comparison with surgical macroslides and with pathology samples, some MR distinctive patterns were identified: the bulky appearance of osteosarcoma surrounded by muscle edema, the multilobular high signal intensity (SI) chondroid lesions, the subtle infiltration of Ewing's sarcoma, rarely accompanied by muscle edema and prone to MR underestimation, the well defined “multiple shells” pattern of giant cell tumor, and the ill defined “storiform” appearance of malignant fibrous histocytoma are all typical MR features strictly corresponding to pathologic findings. The chondroid origin tumors may be identified based on the lobular high SI pattern whereas a benign fibrous lesion was the only one in this series to be distinguished relying on the SI. Peritumoral soft tissue edema was found by the STIR sequence only in malignant tumors (69%) of this series, and particularly in osteosarcoma (96%), chondrosarcoma (83%), and giant cell tumor (100%): this associate finding may further contribute to the diagnosis.

Background A new fast and robust technique combing CINE imaging with a retrospectively adjustable delayed-enhancement (DE) contrast in a short breath-hold of 4 seconds was recently introduced [1]. As a benefit of this technique, DE images can be reconstructed as a CINE series for any TI contrast, which in turn could be beneficial in the evaluation of CMR images and allow for improved diagnostic accuracy. In this work, we performed an initial clinical evaluation of the technique.

A clinical study of the evolution of the space resolved near infrared reflectance with the subcutaneous layers thickness, at rest, on the vastus lateralis, is used to determine convenient sets of muscle and fat optical coefficients at 850 nm and 780 nm. These coefficients are then used to establish pre-calculated 3 layers MC simulations tables of the reflectance as a function of the fat thickness. Real time inversion during effort is then performed to determine the absolute muscle oxygenation.

The aim was to compare fast short time inversion recovery (FSTIR) images and fat suppression, contrast enhanced T(1) weighted (FSCE T1W) spin echo images in the diagnosis of nasopharyngeal carcinoma (NPC). 102 MR studies were obtained with a 1.0 T or a 1.5 T system in 28 patients with NPC. The MR studies comprised both FSTIR and FSCE T1W images. FSTIR and FSCE T1W images were compared for detection of NPC by means of a receiver operating characteristic (ROC) analysis. The areas under the ROC curves of FSTIR and FSCE T1W images showed no statistical difference (0.87 vs 0.87). There was also no statistical difference in the sensitivity, specificity and accuracy of each sequence (0.74 vs 0.77, 0.81 vs 0.77 and 0.79 vs 0.77, respectively). Both sequences had the same performance for detection of NPC. FSTIR is as useful as FSCE T1W images, especially in the detection of recurrent tumours, but without the cost of contrast medium.

A clinical study of the evolution of the space resolved reflectance with the subcutaneous layers thickness, at rest, on the vastus lateralis, is used to determine convenient sets of muscle and fat optical coefficients at 850 nm. The results are compared to the data available in the literature. When the same study will be completed at 780 nm, these coefficients will be used in 3 layers MC simulations to establish pre-calculated tables of the reflectance as a function of the fat thickness and of the muscle absorption coefficient. The goal of this study is eventually to perform real time inversion during effort in order to determine the muscle oxygenation with this very simple technique (part 2).

In 82 asymptomatic subjects aged 8–62 years we evaluated the menisci by magnetic resonance imaging [MRI; L0 tesla; spin-echo (SE 700/20), PS (partial saturation: 500/10), STIR (short time inversion recovery sequence: 1600/130/30)]. For grading the degeneration of the meniscus we used a standard classification (grades 0–4). MR findings were correlated with the patients' age, weight, profession, and athletic activity. Statistic analysis revealed a correlation between athletic activity and meniscal degeneration of both anterior horns and the posterior horn of the lateral meniscus. Especially the anterior horn of the lateral meniscus seems to be loaded during athletic activities. Correlation of meniscus degeneration with subjects' age showed an increase in grade 3 and grade 4 lesions with advancing age. Among subjects older than 50 years, grade 3 and 4 lesions were present in the SE sequence in 28.5% of cases, in PS sequences in 40.7% of cases, and in STIR sequences in 25% of cases.Clinical relevance: Athletic activity seems to load the anterior knee compartments, especially the lateral compartment. MRI shows meniscal lesions in a significant number of asymptomatic subjects, especially those older than 50 years.

Purpose To assess the diagnostic effectiveness of unenhanced-multiparametric magnetic resonance imaging (mp MRI) as an alternative to gadolinium (Gad)-enhanced MRI in the characterization of vertebral marrow infiltrative lesions. Patients and methods A prospective evaluation of fifty-six patients with suspected or untreated vertebral metastases undergoing MRI of the spine at 1.5 T was carried out. Two groups of sequences were assigned and compared for the characterization of marrow infiltrative lesions: group [A] unenhanced-mp MRI (including T1-weighted, T2-weighted, short time inversion recovery (STIR), diffusion weighted imaging (DWI) and in/opposed phase sequences) and group [B] gadolinium-enhanced MRI (including T1-weighted, T2-weighted, STIR and T1-weighted fat-suppressed gadolinium-enhanced sequence). Qualitative and quantitative image analysis was performed and compared. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy for both imaging techniques were calculated. Results There was no statistical significant difference between unenhanced-multiparametric MRI and gadolinium-enhanced MRI as regards their diagnostic performance in differentiating benign from malignant vertebral marrow infiltrative lesions ( p > 0.05) with calculated sensitivity (94% vs. 97%), specificity (92% vs. 88%), positive predictive value (94% vs. 91%), negative predictive value (92% vs. 95%) and (93% vs. 93%) accuracy. Conclusion Unenhanced-multiparametric MRI is compatible with gadolinium-enhanced MRI in reliable characterization of marrow infiltrative lesions. The routine MRI protocol of cancer patients should be altered to accommodate the evolving MRI technology and cost effectively substitute the need for a gadolinium enhanced scan.

An adaptation of the work by Huber and Muller (see Electronic Letters, vol.33, no.5, p.368-69, 1997) on partial transmit sequences (PTS) for the reduction of the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) is described.