RESUMO
PURPOSE: RapidArc is routinely used for stereotactic radiotherapy for lung cancer. While treatment dose is optimized and calculated on a static CT image, the motion of the target in conjunction with the motion of the MLC may Result in a delivered dose deviating from the planed dose. In this study, we investigate the dosimetric consequences of the inter-play effect by simulating dynamic dose delivery on a dynamic CT dataset of real patients. METHODS: The target motion in 20 patients was analyzed and 5 patients with >10 mm motion were chosen for this study. The RapidArc plan for eachpatient is optimized on a free-breathing CT using 2 arcs. Inherent in each plan is data on the associated parameters such as timestamp, MLC leave position, gantry angle and delivered beam MUs for each control point. Simulated dynamic delivery is performed by associating these parameters with each of the breathing phases of the 4D-CT. The starting breathing phase is selected randomly for each of the two arcs. Dose from the derived partial plans associated with each phase of the 4D-CT dose is recalculated in Eclipse. Accumulation of dose is performed using deformable image registration from each phase of the 4D-CT to the exhale phase of the 4D-CT. RESULTS: The coverage of the GTV and PTV shows negligible variations from the interplay effect. But the Homogeneity Index is affected by the motion. The prescription isodose volume is smaller than what was from the treatment plan dose. There were both intra- and inter-fraction effects seen inthe OARs dose in some patients. CONCLUSIONS: We investigated the motioneffect in RapidArc Lung SBRT delivery in 5 patients. Negligible variations were shown for target coverage. However the motion effects were observed in high dose distribution and volume. Some OARs dose distributions were affected by the motion.
Assuntos
Agricultura , Micoses/diagnóstico , Leucemia-Linfoma Linfoblástico de Células Precursoras/complicações , Sepse/microbiologia , Trichosporon/isolamento & purificação , Adulto , Antifúngicos/uso terapêutico , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Cateterismo Periférico , Emigração e Imigração , Evolução Fatal , Febre/microbiologia , Guatemala/etnologia , Humanos , Masculino , Micoses/complicações , Micoses/tratamento farmacológico , Neutropenia/etiologia , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamento farmacológico , Pirimidinas/uso terapêutico , Sepse/tratamento farmacológico , Triazóis/uso terapêutico , Estados Unidos , Urease/isolamento & purificação , Voriconazol , Leveduras/enzimologiaRESUMO
The reactions of nitric oxide ((.)NO) and alpha-tocopherol (alpha-TH) during membrane lipid oxidation were examined and compared with the pair alpha-TH/ascorbate. Nitric oxide serves as a more potent inhibitor of lipid peroxidation propagation reactions than alpha-TH and protects alpha-TH from oxidation. Mass spectrometry, oxygen and (.)NO consumption, conjugated diene analyses, and alpha-TH fluorescence determinations all demonstrated that (.)NO preferentially reacts with lipid radical species, with alpha-TH consumption not occurring until (.)NO concentrations fell below a critical level. In addition, alpha-TH and (.)NO cooperatively inhibit lipid peroxidation, exhibiting greater antioxidant capacity than the pair alpha-TH/ascorbate. Pulse radiolysis analysis showed no direct reaction between (.)NO and alpha-tocopheroxyl radical (alpha-T(.)), inferring that peroxyl radical termination reactions are the principal lipid-protective mechanism mediated by (.)NO. These observations support the concept that (.)NO is a potent chain breaking antioxidant toward peroxidizing lipids, due to facile radical-radical termination reactions with lipid radical species, thus preventing alpha-TH loss. The reduction of alpha-T(.) by ascorbate was a comparatively less efficient mechanism for preserving alpha-TH than (.)NO-mediated termination of peroxyl radicals, due to slower reaction kinetics and limited transfer of reducing equivalents from the aqueous phase. Thus, the high lipid/water partition coefficient of (.)NO, its capacity to diffuse and concentrate in lipophilic milieu, and a potent reactivity toward lipid radical species reveal how (.)NO can play a critical role in regulating membrane and lipoprotein lipid oxidation reactions.
Assuntos
Antioxidantes/farmacologia , Ácido Ascórbico/farmacologia , Peroxidação de Lipídeos , Óxido Nítrico/metabolismo , Vitamina E/farmacologia , Amidinas/farmacologia , Radicais Livres , Ácido Linoleico/metabolismo , OxirreduçãoRESUMO
Peroxynitrite (ONOO-), the reaction product of superoxide (O2.-) and nitric oxide (.NO), nitrates tyrosine and other phenolics. We report herein that tryptophan is also nitrated by peroxynitrite in the absence of transition metals to one predominant isomer of nitrotryptophan, as determined from spectral characteristics and liquid chromatography-mass spectrometry analysis. At high peroxynitrite to tryptophan ratios, other oxidation products were detected as well. The amount of nitrotryptophan formed from peroxynitrite increased at acidic pH, with an apparent pKa of 7.8. High concentrations of Fe(3+)-EDTA were required to enhance peroxynitrite-induced nitrotryptophan formation, while addition of up to 15 microM Cu/Zn superoxide dismutase had a minimal effect on tryptophan nitration. Cysteine, ascorbate, and methionine decreased nitrotryptophan yield to an extent similar to that predicted by their reaction rates with ground-state peroxynitrite, and typical hydroxyl radical scavengers partially inhibited nitration. Plots of the observed rate constant of nitrotryptophan formation vs tryptophan concentration presented downward curvatures. Thus, the kinetics of metal-independent nitration reactions were interpreted in terms of two parallel mechanisms. In the first one, ground-state peroxynitrous acid nitrated tryptophan with a second-order rate constant of 184 +/- 11 M-1 s-1 at 37 degrees C. The activation enthalpy was 9.1 +/- 0.3 kcal mol-1, and the activation entropy was -19 +/- 1 cal mol-1 K-1. In the second mechanism, ONOOH*, an activated intermediate derived from trans-peroxynitrous acid formed in a steady state, was the nitrating agent.
Assuntos
Nitratos/metabolismo , Nitratos/fisiologia , Triptofano/metabolismo , Desferroxamina/metabolismo , Dimetil Sulfóxido/metabolismo , Etanol/metabolismo , Cinética , Manitol/metabolismo , Metais/metabolismo , Superóxido Dismutase/metabolismoRESUMO
Determinar as populaçöes de barbeiros residuais nas casas depois de borrifaçäo com inseticidas é um componente importante na vigilânica e evoluçäo do controle dos vetores da doença de Chagas. Recentemente, mostramos que folhas de papel, afixadas na parede das casas infestadas, podem ser manchadas com fezes dos triatomíneos, assim revelando a infestaçäo. Apresenta-se uma chave simples para diferenciar as fezes dos triatomíneos de outros artropodos, como baratas, carrapatos e percevejos de cama