A Multimodality Image Guided Precision Radiation Research Platform: Integrating X-ray, Bioluminescence, and Fluorescence Tomography With Radiation Therapy.

Purpose: Small animal irradiation is crucial to the investigation of radiobiological mechanisms. The paradigm of clinical radiation therapy is trending toward high-precision, stereotactic treatment. However, translating this scheme to small animal irradiation is challenging owing to the lack of high-quality image guidance.

Data for optimizing Gamma Knife radiosurgery using the shot within shot technique.

The tables included in this article will allow the user to implement shot within shot optimization for Gamma Knife radiosurgery planning and delivery. The method is intended to reduce treatment time when treating small to medium sized brain metastasis. The tables were previously developed by extracting profiles from Gamma Plan for three collimator settings and modeling their behavior when combined or prescribed at different isodose lines.

Clinical Evaluation of Shot-Within-Shot Optimization for Gamma Knife Radiosurgery Planning and Delivery.

Objective: Shot-within-shot (SWS) optimization is a new planning technique that relies on various combinations of shot weighting and prescription isodose line (IDL) to reduce beam-on time. The method differs from other planning techniques that incorporate mixed collimation, multiple stereotactic coordinates, and traditionally low prescription IDLs (<60%). In this work, we evaluate the percentage of brain metastasis for which the method can be applied, the magnitude of the resultant time savings, and the possible tradeoffs in plan quality.

Technical Note: Minimizing geometrical uncertainties of cylindrical well-type ionization chamber measurements: There is an optimal chamber length.

Purpose: The response of well-type ionization chambers used, for example, in brachytherapy and nuclear medicine, depends on the location of the source. In cases where the source length is variable (typically in nuclear medicine), it is also dependent on length of the source. Here, the combined effect on chamber sensitivity of both source position and length is investigated in detail.

The Phase Behavior and Organization of Sphingomyelin/Cholesterol Membranes: A Deuterium NMR Study.

We have studied the dependence of the phase and domain characteristics of sphingomyelin (SM)/cholesterol model membranes on sterol content and temperature using deuterium nuclear magnetic resonance. NMR spectra of N-palmitoyl(D31)-D-erythro-sphingosylphosphorylcholine (PSM-d31) were taken for temperatures from 25 to 70°C and cholesterol concentrations of 0-40%. Analogous experiments were performed using 1-palmitoyl,2-palmitoyl(D31)-sn-glycero-3-phosphocholine (DPPC-d31)/cholesterol membranes to carefully compare the data obtained using palmitoyl chains that have similar "kinked" conformations.

Constrained Versus Free Cholesterol in DPPC Membranes: A Comparison of Chain Ordering Ability Using Deuterium NMR.

We report here the first exploration of the nature of the hydrophobic region of bilayer membranes formed from sterol-modified phospholipids [Huang, Z.; Szoka, F. C.

Insights into sphingolipid miscibility: separate observation of sphingomyelin and ceramide N-acyl chain melting.

Ceramide produced from sphingomyelin in the plasma membrane is purported to affect signaling through changes in the membrane's physical properties. Thermal behavior of N-palmitoyl sphingomyelin (PSM) and N-palmitoyl ceramide (PCer) mixtures in excess water has been monitored by ²H NMR spectroscopy and compared to differential scanning calorimetry (DSC) data. The alternate use of either perdeuterated or proton-based N-acyl chain PSM and PCer in our ²H NMR studies has allowed the separate observation of gel-fluid transitions in each lipid in the presence of the other one, and this in turn has provided direct information on the lipids' miscibility over a wide temperature range.

Interaction of a charged polymer with zwitterionic lipid vesicles.

The interaction between polyethylenimine (PEI) and phospholipid bilayers plays an important role in several biophysical applications such as DNA transfection of target cells. Despite considerable investigation into the nature of the interaction between PEI and phospholipid bilayers, the physical process remains poorly understood. In this paper, we study the impact of PEI on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) vesicles as a function of salt concentration using several techniques including dynamic (DLS) and static (SLS) light scattering, differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR).

Influence of the nature of the sterol on the behavior of palmitic acid/sterol mixtures and their derived liposomes.

The phase behavior of mixtures formed with palmitic acid (PA) and one of the following sterols (dihydrocholesterol, ergosterol, 7-dehydrocholesterol, stigmasterol and stigmastanol), in a PA/sterol molar ratio of 3/7, has been characterized by IR and (2)H NMR spectroscopy at different pH. Our study shows that it is possible to form liquid-ordered (lo) lamellar phases with these binary non-phospholipid mixtures. The characterization of alkyl chain dynamics of PA in these systems revealed the large ordering effect of the sterols.