Orbital venous malformation: percutaneous treatment using an electrolytically detachable fibred coil

PURPOSE: To report the efficacy of percutaneous treatment of an orbital venous malformation with an electrolytically detachable fibred coil. METHODS: We report an instance of radiography-guided percutaneous treatment with an electrolytically detachable fibred coil in a 16-year-old boy with acute, spontaneous, painless proptosis on the left side, which progressed with time. RESULTS: Magnetic resonance imaging, angiography and orbitophlebography revealed a low-flow, intraorbital venous malformation. Percutaneous puncture and drainage were followed by a short remission. Following an acute recurrence, a single detachable fibred coil was deployed via a percutaneous approach under angiographic guidance. No radiological or clinical recurrences were observed over 4 years. CONCLUSIONS: Embolization of a deep orbital venous malformation with detachable fibred coils via a percutaneous approach can be highly effective, and may be considered before proceeding with open surgery.

Charge and spin transport in nanoscale junction from first principles

Recently nanoscale junctions consisting of 0-D nanostructures (single molecule) or 1-D nanostructures (semiconducting nanowire) sandwiched between two metal electrodes are successfully fabricated and characterized. What lacks in the recent developments is the understanding of the mechanism behind the observed phenomena at the level of atoms and electrons. For example, the origin of observed switching effect in a semiconducting nanowire due to the influence of an external gate bias is not yet understood at the electronic structure level. On the same context, different experimental groups have reported different signs in tunneling magneto-resistance for the same organic spin valve structure, which has baffled researchers working in this field. In this thesis, we present the answers to some of these subtle questions by investigating the charge and spin transport in different nanoscale junctions. A parameter-free, single particle Green’s function approach in conjunction with a posteriori density functional theory (DFT) involving a hybrid orbital dependent functional is used to calculate the tunneling current in the coherent transport limit. The effect of spin polarization is explicitly incorporated to investigate spin transport in a nanoscale junction. Through the electron transport studies in PbS nanowire junction, a new orbital controlled mechanism behind the switching of the current is proposed. It can explain the switching behavior, not only in PbS nanowire, but in other lead-chalcogenide nanowires as well. Beside this, the electronic structure properties of this nanowire are studied using periodic DFT. The quantum confinement effect was investigated by calculating the bandgap of PbS nanowires with different diameters. Subsequently, we explain an observed semiconducting to metallic phase transition of this nanowire by calculating the bandgap of the nanowire under uniform radial strain. The compressive radial strain on the nanowire was found to be responsible for the metallic to semiconducting phase transition. Apart from studying one dimensional nanostructure, we also present transport properties in zero dimensional single molecular junctions. We proposed a new codoping approach in a single molecular carborane junction, where a cation and an anion are simultaneously doped to find the role of a single atom in the device. The main purpose was to build a molecular junction where a single atom can dictate the flow of electrons in a circuit. Recent observations of both positive and negative sign in tunneling magnetoresistance (TMR) the using same organic spin-valve structure hasmystified researchers. From our spin dependent transport studies in a prototypical organic molecular tunneling device, we found that a 3% change in metal-molecule interfacial distance can alter the sign of TMR. Changing the interfacial distance by 3%, the number of participating eigenstates as well as their orbital characteristic changes for anti-parallel configuration of the magnetization at the two electrodes, leading to the sign reversal of the TMR. Apart from this, the magnetic proximity effect under applied bias is investigated quantitatively, which can be used to understand the observed unexpectedmagnetismin carbon basedmaterials when they are in close proximity with magnetic substrates.

Magnetization transfer contrast and T2 mapping in the evaluation of cartilage repair tissue with 3T MRI

PURPOSE: To use magnetization transfer (MT) imaging in the visualization of healthy articular cartilage and cartilage repair tissue after different cartilage repair procedures, and to assess global as well as zonal values and compare the results to T2-relaxation. MATERIALS AND METHODS: Thirty-four patients (17 after microfracture [MFX] and 17 after matrix-associated autologous cartilage transplantation [MACT]) were examined with 3T MRI. The MT ratio (MTR) was calculated from measurements with and without MT contrast. T2-values were evaluated using a multiecho, spin-echo approach. Global (full thickness of cartilage) and zonal (deep and superficial aspect) region-of-interest assessment of cartilage repair tissue and normal-appearing cartilage was performed. RESULTS: In patients after MFX and MACT, the global MTR of cartilage repair tissue was significantly lower compared to healthy cartilage. In contrast, using T2, cartilage repair tissue showed significantly lower T2 values only after MFX, whereas after MACT, global T2 values were comparable to healthy cartilage. For zonal evaluation, MTR and T2 showed a significant stratification within healthy cartilage, and T2 additionally within cartilage repair tissue after MACT. CONCLUSION: MT imaging is capable and sensitive in the detection of differences between healthy cartilage and areas of cartilage repair and might be an additional tool in biochemical cartilage imaging. For both MTR and T2 mapping, zonal assessment is desirable.

Steady state free precession magnetization transfer imaging

The formerly proposed concept for magnetization transfer imaging (MTI) using balanced steady-state free precession (SSFP) image acquisitions is in this work extended to nonbalanced protocols. This allows SSFP-based MTI of targets with high susceptibility variation (such as the musculoskeletal system), or at ultra-high magnetic fields (where balanced SSFP suffers from considerable off-resonance related image degradations). In the first part, SSFP-based MTI in human brain is analyzed based on magnetization transfer ratio (MTR) histograms. High correlations are observed among all different SSFP MTI protocols and thereby ensure proper conceptual extension to nonbalanced SSFP. The second part demonstrates SSFP-based MTI allowing fast acquisition of high resolution volumetric MTR data from human brain and cartilage at low (1.5T) to ultra-high (7.0T) magnetic fields.

Prevention of radiochemotherapy-induced toxicity with amifostine in patients with malignant orbital tumors involving the lacrimal gland: a pilot study

BACKGROUND: To use amifostine concurrently with radiochemotherapy (CT-RT) or radiotherapy (RT) alone in order to prevent dry eye syndrome in patients with malignancies located in the fronto-orbital region. METHODS: Five patients (2 males, 3 females) with diagnosed malignancies (Non-Hodgkin B-cell Lymphoma, neuroendocrine carcinoma) involving the lacrimal gland, in which either combined CT-RT or local RT were indicated, were prophylactically treated with amifostine (500 mg sc). Single RT fraction dose, total dose and treatment duration were individually adjusted to the patient's need. Acute and late adverse effects were recorded using the RTOG score. Subjective and objective dry eye assessment was performed for the post-treatment control of lacrimal gland function. RESULTS: All patients have completed CT-RT or RT as indicated. The median total duration of RT was 29 days (range, 23 - 39 days) and the median total RT dose was 40 Gy (range, 36 - 60 Gy). Median lacrimal gland exposure was 35.9 Gy (range, 16.8 - 42.6 Gy). Very good partial or complete tumor remission was achieved in all patients. The treatment was well tolerated without major toxic reactions. Post-treatment control did not reveal in any patient either subjective or objective signs of a dry eye syndrome. CONCLUSION: The addition of amifostine to RT/CT-RT of patients with tumors localized in orbital region was found to be associated with absence of dry eye syndrome.

Comparison between intravitreal and orbital floor triamcinolone acetonide after phacoemulsification in patients with endogenous uveitis

PURPOSE: To compare the effect of intravitreal and orbital floor triamcinolone acetonide (TA) on macular edema, visual outcome, and course of postoperative inflammation after cataract surgery in uveitis patients. DESIGN: Prospective, randomized clinical trial. METHODS: Monocenter study (40 patients) with chronic endogenous uveitis who underwent phacoemulsification with intraocular lens implantation with either 4 mg intravitreal TA (n = 20) or 40 mg orbital floor TA (n = 20). The primary outcome was influence on cystoid macular edema (CME). Secondary outcome measures were best-corrected visual acuity (BCVA), anterior chamber cell grade, laser flare photometry, giant cell deposition, posterior capsule opacification (PCO), and intraocular pressure. RESULTS: Mean central foveal thickness decreased in the intravitreal TA group and increased in the orbital floor TA group (P < .001 at one and three months). CME improved in 50% of patients after intravitreal TA, whereas it was unchanged after orbital floor TA (difference between the groups at three months, P = .049). Mean BCVA (logarithm of the minimal angle of resolution) improved postoperatively (P < .001) from 0.76 and 0.74 to 0.22 and 0.23 in the intravitreal TA and orbital floor TA group, respectively. Anterior chamber cell count at one month was lower in the intravitreal TA than in the orbital floor TA group (P = .02). Laser flare photometry values and giant cell numbers were slightly higher after orbital floor TA than after intravitreal TA. The groups did not differ with respect to PCO rate and ocular hypertension. CONCLUSIONS: The CME improvement and anti-inflammatory effect after intravitreal TA was better than after orbital floor TA injection in cataract surgery in uveitis patients.

Multi-parametric classification of Alzheimer's disease and mild cognitive impairment: the impact of quantitative magnetization transfer MR imaging

Multi-parametric and quantitative magnetic resonance imaging (MRI) techniques have come into the focus of interest, both as a research and diagnostic modality for the evaluation of patients suffering from mild cognitive decline and overt dementia. In this study we address the question, if disease related quantitative magnetization transfer effects (qMT) within the intra- and extracellular matrices of the hippocampus may aid in the differentiation between clinically diagnosed patients with Alzheimer disease (AD), patients with mild cognitive impairment (MCI) and healthy controls. We evaluated 22 patients with AD (n=12) and MCI (n=10) and 22 healthy elderly (n=12) and younger (n=10) controls with multi-parametric MRI. Neuropsychological testing was performed in patients and elderly controls (n=34). In order to quantify the qMT effects, the absorption spectrum was sampled at relevant off-resonance frequencies. The qMT-parameters were calculated according to a two-pool spin-bath model including the T1- and T2 relaxation parameters of the free pool, determined in separate experiments. Histograms (fixed bin-size) of the normalized qMT-parameter values (z-scores) within the anterior and posterior hippocampus (hippocampal head and body) were subjected to a fuzzy-c-means classification algorithm with downstreamed PCA projection. The within-cluster sums of point-to-centroid distances were used to examine the effects of qMT- and diffusion anisotropy parameters on the discrimination of healthy volunteers, patients with Alzheimer and MCIs. The qMT-parameters T2(r) (T2 of the restricted pool) and F (fractional pool size) differentiated between the three groups (control, MCI and AD) in the anterior hippocampus. In our cohort, the MT ratio, as proposed in previous reports, did not differentiate between MCI and AD or healthy controls and MCI, but between healthy controls and AD.

Differentiating hippocampal subregions by means of quantitative magnetization transfer and relaxometry: preliminary results

The hippocampal formation (HF) of healthy control subjects and schizophrenic patients was examined using an MRI experiment that implements sequences for relaxometry and magnetization transfer (MT) quantification. In addition to the semi-quantitative magnetization transfer ratio (MTR), all of the observable properties of the binary spin bath model were included. The study demonstrates that, in contrast to the MTR, quantitative MT parameters (especially the T2 relaxation time of restricted protons, T2b) are capable to differentiate functionally significant subregions within the HF. The MT methodology appears to be a promising new tool for the differential microstructural evaluation of the HF in neuropsychiatric disorders accompanied by memory disturbances.