Differentiation of recurrent brain tumor versus radiation injury using diffusion tensor imaging in patients with new contrast-enhancing lesions

BACKGROUND AND PURPOSE: The purpose of this study was to assess the use of diffusion tensor imaging (DTI) in the evaluation of new contrast-enhancing lesions and perilesional edema in patients previously treated for brain neoplasm in the differentiation of recurrent neoplasm from treatment-related injury. METHODS: Twenty-eight patients with new contrast-enhancing lesions and perilesional edema at the site of previously treated brain neoplasms were retrospectively reviewed. Nine directional echoplanar DTIs with b=1000 s/mm(2) were obtained using a single-shot spin-echo echoplanar imaging. Standardized regions of interest were manually drawn in several regions. Mean apparent diffusion coefficient (ADC), fractional anisotropy (FA) and eigenvalue indices (lambda( parallel) and lambda( perpendicular)) and their ratios relative to the contralateral side were compared in patients with recurrent neoplasm versus patients with radiation injury, as established by histological examination or by clinical course, including long-term imaging studies and magnetic resonance spectroscopy. RESULTS: The ADC values in the contrast-enhancing lesions were significantly higher (P=.01) for the recurrence group (range=1.01 x 10(-3) to 1.66 x 10(-3) mm(2)/s; mean+/-S.D.=1.27+/-0.15) than for the nonrecurrence group (range=0.9 x 10(-3) to 1.31 x 10(-3) mm(2)/s; mean+/-S.D.=1.12+/-0.14). The ADC ratios in the white matter tracts in perilesional edema trended higher (P=.09) in treatment-related injury than in recurrent neoplasm (mean+/-S.D.=1.85+/-0.30 vs. 1.60+/-0.27, respectively). FA ratios were significantly higher in normal-appearing white matter (NAWM) tracts adjacent to the edema in the nonrecurrence group (mean+/-S.D.=0.89+/-0.15) than in those in the recurrence group (mean+/-S.D.=0.74+/-0.14; P=.03). Both eigenvalue indices lambda( parallel) and lambda( perpendicular) were significantly higher in contrast-enhancing lesions in the recurrence group than in those in the nonrecurrence group (P=.02). As well, both eigenvalue indices lambda( parallel) and lambda( perpendicular) were significantly higher in perilesional edema than in normal white matter (P<.01 and P<.001, respectively) in both groups. CONCLUSION: The assessment of diffusion properties, especially ADC values and ADC ratios, in contrast-enhancing lesions, perilesional edema and NAWM adjacent to the edema in the follow-up of new contrast-enhancing lesions at the site of previously treated brain neoplasms may add to the information obtained by other imaging techniques in the differentiation of radiation injury from tumor recurrence.     

Differential non-destructive image current detection in a fourier transform quadrupole ion trap

Dual-detector differential non-destructive Fourier transform detection in a quadrupole ion trap is shown to improve signal intensity and reduce noise compared with spectra recorded using a single detector. A larger area detector in each end-cap electrode is machined to fit its hyperbolic shape and so minimize field imperfections on the z-axis. Argon, acetophenone and bromobenzene spectra were recorded to allow a comparison between single- and dual-detector (differential) modes of detection and to demonstrate the improvement achieved with differential detection. Copyright 1999 John Wiley & Sons, Ltd.     

Forests, colorings and acyclic orientations of the square lattice

There is no known polynomial time algorithm which generates a random forest or counts forests or acyclic orientations in general graphs. On the other hand, there is no technical reason why such algorithms should not exist. These are key questions in the theory of approximately evaluating the Tutte polynomial which in turn contains several other specializations of interest to statistical physics, such as the Ising, Potts, and random cluster models.Here, we consider these problems on the square lattice, which apart from its interest to statistical physics is, as we explain, also a crucial structure in complexity theory. We obtain some asymptotic counting results about these quantities on then ×n section of the square lattice together with some properties of the structure of the random forest. There are, however, many unanswered questions.Supported by a grant from D.G.A.P.A.Supported in part by Esprit Working Group No. 21726, RAND2.     

New approaches for neutron depth profiling

The scope of NDP can be expanded by measuring (via time-of-flight) the kinetic energies of the recoils emitted from (n,p) or (n,) reactions. When they occur inside a solid, the energies of the emerging recoils reveal depth from which they originated. The Recoil Nucleus Time-of-Flight NDP (RN-TOF-NDP) technique can reveal the depth distribution of some isotopes (e.g.,¹⁰B,²¹⁰Bi) with a resolution of a few Å. Furthermore, it is possible to detect atomic and molecular species ejected at the surface site where the recoil emerges from the solid. This paper discusses the methodology for RN-TOF-NDP and its applications including surface analysis based on atomic and molecular ions codesorbed with the recoils.     

Chain twisting in long-chain aliphatic compounds and polyethylene

Rate parameters for dielectric relaxation and the thermal properties of long-chain molecular systems are shown to provide evidence for chain twisting at chain lengths shorter than previously suggested. Comparison of the temperatures of maximum absorption at 1 Hz for mechanical and dielectric relaxation suggests that the underlying motion is not the same for the two observed quanties. The evidence for relaxation in polyethylene is shown to be compatible with this suggestion.     

Three-dimensional quantitative structure-property relationship (3D-QSPR) models for prediction of thermodynamic properties of polychlorinated biphenyls (PCBs): enthalpy of vaporization

Three-dimensional Quantitative Structure-Property Relationship (QSPR) models have been derived using Comparative Molecular Field Analysis (CoMFA) to correlate the vaporization enthalpies of a representative set of polychlorinated biphenyls (PCBs) at 298.15 K with their CoMFA-calculated physicochemical properties. Various alignment schemes, such as inertial, as is, and atom fit, were employed in this study. The CoMFA models were also developed using different partial charge formalisms, namely, electrostatic potential (ESP) charges and Gasteiger-Marsili (GM) charges. The most predictive model for vaporization enthalpy (Delta(vap)H(m)(298.15 K)), with atom fit alignment and Gasteiger-Marsili charges, yielded r2 values 0.852 (cross-validated) and 0.996 (conventional). The vaporization enthalpies of PCBs increased with the number of chlorine atoms and were found to be larger for the meta- and para-substituted isomers. This model was used to predict Delta(vap)H(m)(298.15 K) of the entire set of 209 PCB congeners.     

MULTIDIMENSIONAL UPWIND RESIDUAL DISTRIBUTION SCHEMES FOR THE CONVECTION–DIFFUSION EQUATION

Multidimensional residual distribution schemes for the convection–diffusion equation are described. Compact upwind cell vertex schemes are used for the discretization of the convective term. For the diffusive term, two approaches are compared: the classical finite element Galerkin formulation, which preserves the compactness of the stencil used for the convective part, and various residual-based approaches in which the diffusive term, evaluated after a reconstruction step, is upwinded along with the convective term.     

Comparing dissolved reactive phosphorus measured by DGT with ferrihydrite and titanium dioxide adsorbents: anionic interferences, adsorbent capacity and deployment time

Two adsorbents (Metsorb and ferrihydrite) used in binding layers with the diffusive gradients in a thin film technique were evaluated for the measurement of dissolved reactive phosphorous (DRP) in synthetic and natural waters. Possible interferences were investigated with Cl(-) (up to 1.35 mol L(-1)) and SO(4)(2-) (up to 0.056 mol L(-1)) having no affect on either DGT binding layer, and HCO(3)(-) (up to 5.7 mmol L(-1)) having no effect on Metsorb-DGT, over 4 days. However, HCO(3)(-) interfered with the ferrihydrite-DGT measurement at concentrations typical of many natural waters (≥0.7 mmol L(-1)) after a deployment period of 1-2 days. The capacity of the Metsorb binding phase for DGT response was ～37,000 ng P, whereas the capacities of a low-mass (17.8 mg of adsorbent per DGT sampler) and high-mass (29.2mg of adsorbent per DGT sampler) ferrihydrite binding phase were substantially lower (～15,000 ng P and ～25,000 ng P, low-mass and high-mass, respectively). Increasing the capacity of the ferrihydrite adsorbent allowed the ferrihydrite-DGT to be utilized for up to 3 days before interference by HCO(3)(-) was observed. Seawater deployments demonstrated that even high-capacity ferrihydrite-DGT devices underestimated the DRP concentration by 37%, whereas Metsorb-DGT measurements were accurate. The Metsorb-DGT is superior to the ferrihydrite-DGT for determining DRP over deployment times greater than 1 day and in waters with ≥0.7 mmol L(-1) HCO(3)(-). Based on the experience obtained from this detailed validation process, the authors propose a number of key requirements that need to be considered when developing new DGT binding layers, with testing the performance over longer deployment times being critical.