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1.
Br J Radiol ; 85(1017): e654-60, 2012 Sep.
Article in English | MEDLINE | ID: mdl-22919015

ABSTRACT

OBJECTIVES: In radiotherapy, delineation uncertainties are important as they contribute to systematic errors and can lead to geographical miss of the target. For margin computation, standard deviations (SDs) of all uncertainties must be included as SDs. The aim of this study was to quantify the interobserver delineation variation for stereotactic body radiotherapy (SBRT) of peripheral lung tumours using a cross-sectional study design. METHODS: 22 consecutive patients with 26 tumours were included. Positron emission tomography/CT scans were acquired for planning of SBRT. Three oncologists and three radiologists independently delineated the gross tumour volume. The interobserver variation was calculated as a mean of multiple SDs of distances to a reference contour, and calculated for the transversal plane (SD(trans)) and craniocaudal (CC) direction (SD(cc)) separately. Concordance indexes and volume deviations were also calculated. RESULTS: Median tumour volume was 13.0 cm(3), ranging from 0.3 to 60.4 cm(3). The mean SD(trans) was 0.15 cm (SD 0.08 cm) and the overall mean SD(cc) was 0.26 cm (SD 0.15 cm). Tumours with pleural contact had a significantly larger SD(trans) than tumours surrounded by lung tissue. CONCLUSIONS: The interobserver delineation variation was very small in this systematic cross-sectional analysis, although significantly larger in the CC direction than in the transversal plane, stressing that anisotropic margins should be applied. This study is the first to make a systematic cross-sectional analysis of delineation variation for peripheral lung tumours referred for SBRT, establishing the evidence that interobserver variation is very small for these tumours.


Subject(s)
Lung Neoplasms/diagnosis , Lung Neoplasms/surgery , Multimodal Imaging/methods , Positron-Emission Tomography , Radiosurgery , Radiotherapy, Image-Guided/methods , Tomography, X-Ray Computed , Aged , Cross-Sectional Studies , Female , Humans , Male , Middle Aged , Observer Variation , Reproducibility of Results , Sensitivity and Specificity
2.
Proteins ; 79(4): 1079-88, 2011 Apr.
Article in English | MEDLINE | ID: mdl-21246631

ABSTRACT

One of the most remarkable characteristics of Brucella lumazine synthase (BLS) is its versatility to undergo reversible dissociation and reassociation as a polymeric scaffold. We have proposed a mechanism of dissociation and unfolding of BLS. Using static light scattering (SLS) analysis, we were able to demonstrate that the decameric assembly dissociates into two different conditions [pH 5 or 2M guanidinium chloride (GdnHCl) pH 7] forming stable folded pentamers. The transition from folded pentamers to unfolded monomers by GdnHCl denaturation is highly cooperative and can be measured by different spectroscopic techniques. In this work, we show the successful insertion of an intrinsic probe to study in more detail the equilibria described in previous publications. For that purpose, we performed single-point mutations of Phe residues 121 and 127, located at the pentamer-pentamer and monomer-monomer interface, respectively, to Trp residues. These mutations produced only a marginal perturbation of the BLS structure. We analyzed the unfolding and stability of the mutants through different techniques: far-and near-UV CD, SLS, dynamic light scattering, and fluorescence spectroscopy. The introduced intrinsic probe could be used to gain insights into the detailed folding and assembly mechanism of this protein.


Subject(s)
Bacterial Proteins/chemistry , Bacterial Proteins/metabolism , Multienzyme Complexes/chemistry , Multienzyme Complexes/metabolism , Point Mutation , Algorithms , Bacterial Proteins/genetics , Brucella/enzymology , Guanidine , Hydrogen-Ion Concentration , Light , Multienzyme Complexes/genetics , Mutagenesis, Site-Directed , Protein Folding , Protein Multimerization , Protein Stability , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Scattering, Radiation , Spectrum Analysis , Thermodynamics , Tryptophan
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