Prosper: image and robot-guided prostate brachytherapy

Brachytherapy for localized prostate cancer consists in destroying cancer by introducing iodine radioactive seeds into the gland through hollow needles. The planning of the position of the seeds and their introduction into the prostate is based on intra-operative ultrasound (US) imaging. We propose to optimize the global quality of the procedure by: i) using 3D US; ii) enhancing US data with MRI registration; iii) using a specially designed needle-insertion robot, connected to the imaging data. The imaging methods have been successfully tested on patient data while the robot accuracy has been evaluated on a realistic deformable phantom

Automatic 3D seed location and orientation in CT images for prostate brachytherapy

International audienceIn prostate brachytherapy, the analysis of the 3D pose information of each individual implanted seed is one of the critical issues for dose calculation and procedure quality assessment. This paper addresses the development of an automatic image processing solution for the separation, localization and 3D orientation estimation of prostate seeds. This solution combines an initial detection of a set of seed candidates in CT images (using a thresholding and connected component method) with an orientation estimation using principal components analysis (PCA). The main originality of the work is the ability to classify the detected objects based on a priori intensity and volume information and to separate groups of seeds using a modified k-means method. Experiments were carried out on CT images of a phantom and a patient aiming to compare the proposed solution with manual segmentation or other previous work in terms of detection performance and calculation time

The choice of statistical methods for comparisons of dosimetric data in radiotherapy

Purpose: Novel irradiation techniques are continuously introduced in radiotherapy to optimize the accuracy, the security and the clinical outcome of treatments. These changes could raise the question of discontinuity in dosimetric presentation and the subsequent need for practice adjustments in case of significant modifications. This study proposes a comprehensive approach to compare different techniques and tests whether their respective dose calculation algorithms give rise to statistically significant differences in the treatment doses for the patient. Methods: Statistical investigation principles are presented in the framework of a clinical example based on 62 fields of radiotherapy for lung cancer. The delivered doses in monitor units were calculated using three different dose calculation methods: the reference method accounts the dose without tissues density corrections using Pencil Beam Convolution (PBC) algorithm, whereas new methods calculate the dose with tissues density correction for 1D and 3D using Modified Batho (MB) method and Equivalent Tissue air ratio (ETAR) method, respectively. The normality of the data and the homogeneity of variance between groups were tested using Shapiro-Wilks and Levene test, respectively, then non-parametric statistical tests were performed. Specifically, the dose means estimated by the different calculation methods were compared using Friedman’s test and Wilcoxon signed-rank test. In addition, the correlation between the doses calculated by the three methods was assessed using Spearman’s rank and Kendall’s rank tests Results: The Friedman’s test showed a significant effect on the calculation method for the delivered dose of lung cancer patients (p 0.001). The density correction methods yielded to lower doses as compared to PBC by on average (−5 ± 4.4 SD) for MB and (−4.7 ± 5 SD) for ETAR. Post-hoc Wilcoxon signed-rank test of paired comparisons indicated that the delivered dose was significantly reduced using density-corrected methods as compared to the reference method. Spearman’s and Kendall’s rank tests indicated a positive correlation between the doses calculated with the different methods. Conclusion: This paper illustrates and justifies the use of statistical tests and graphical representations for dosimetric comparisons in radiotherapy. The statistical analysis shows the significance of dose differences resulting from two or more techniques in radiotherapy

La grotte Mandrin et les premières occupations du Paléolithique supérieur en Occitanie orientale

Le niveau supérieur de la grotte Mandrin présente une courte occupation attribuable au passage d'un groupe hiumain postérieurement à 35 000 BP (Giraud et al. à paraître). Ces éléments présentent de nettes affinités avec les séries attribuées régionalement à un Aurignacien initial méditerranéen (Bazile 1974, 1999), actuellement reconnu comme la première expression du Paléolithique supérieur dans le sud-est de la France, région où le Castelperronien n'est pas représenté (Combler 1960, 1967, 1990). La reconnaissance et la caractérisation d'un faciès de transition non reconnu jusqu'alors est en cours d'élaboration (Slimak 2004). Située sous un promontoire rocheux dominant la vallée du Rhône au sud de Montélimar (France, Fig. 1), la grotte Mandrin se présente comme un petit abri peu profond ouvert au nord. Sondée dès 1990, elle livre depuis une importante stratigraphie comprenant huit niveaux attribuables à un Paléolithique moyen récent. Au sein du niveau Protoaurignacien, les lamelles Dufour rectilignes et de grand module occupent une place prépondérante du système technique. Cette étude permet d'apporter un nouveau regard sur les systèmes techniques protoaurignaciens et élabore une synthèse régionale portant sur les premières occupations du Paléolithique supérieur reconnues dans cette région. L'aire géographique concernée par cette synthèse couvre la Provence, le Languedoc oriental, l'Ardèche et la Drôme, qui appartiennent à la frange orientale de l'Occitanie.El nivel superior de la Cueva Mandrin indica que fue ocupada por grupos humanos durante un brève période después de 35 000 BP (Giraud et al., en prensa). La industrfa leptolitica contenida en este nivel muestra claras afinidades con otras séries de la région, atribuidas a un Aurihaciense inicial (Bazile 1974, 1999), actualmente reconocido como la primera expresiôn del Paleolitico Superior en el sudeste de Francia donde no hay ocupaciones Castelperroniense (Combler 1960, 1967, 1990). El reconocimiento y la caracterizaciôn de una faciès de transiciôn, no reconocida hasta la fecha, esta en proceso de elaboraciôn (Slimak 2004). Situada en un promontorio rocoso que domina el Valle del Rôdano, al sur de Montélimar (fig. 1), la Cueva Mandrin se présenta como un pequeho abrigo, poco profundo y abierto al Morte. Explorada desde 1990, muestra una importante estratigrafia compuesta de 8 nivelés atribuibles a un Paleolitico Medio Reciente. En el nivel Protoaurihaciense, las laminitas Dufour de gran tamano (de màs de 5 cm le longitud) ocupan un papel importante en el sistema técnico. El présente estudio lanza una nueva mirada sobre los sistemas técnicos y procura esquemas especfficos de producciôn de laminitas. Al mismo tiempo propone una síntesis, fundada en la composiciôn de los conjuntos liticos, de las primeras implantaciones durante el Paleolftico Superior en esta région, que incluye la Provenza, el Languedoc oriental, Ardeche y Drome, todos pertenecientes a la franja oriental de la Occitania

A 3D quantitative evaluation for assessing the changes of treatment planning system and irradiation techniques in radiotherapy

Purpose: This work proposes and compares two 3D global evaluation methods for assessing the alteration of calculated dose distributions when treatment planning system algorithms or irradiation techniques is modified in radiation therapy. Methods: The global analysis is based on gamma index (γ) proposed by Low et al.1 and Chi (χ) index proposed by Bakai et al.2. The γ and χ values are signed in order to identify the over and under estimating dosage. The 3D maps, the cumulative Gamma Voxels Histograms (GVHs) and Chi Voxels Histograms (CVHs) were generated using two software. The γ and χ criteria were set to 3 mm for the distance to agreement and 3% for dose. Pearson's Chi-squared test was applied to assess the statistically significance between GVHs and CVHs. We illustrated this method for the change of dose calculation algorithms for lung cancer, and the change of irradiation techniques for breast cancer. For each patient, 2 treatment plans were generated. For the example of change of dose calculation algorithms, a plan 1 was calculated using Pencil Beam Convolution (PBC) algorithm and a plan 2 was calculated using Modified Batho method (PBC-MB). For the example of change of irradiation technique, a plan 1 was calculated using Source Skin Distance SSD technique and a plan 2 was calculated using a single isocenter technique. Results: The 3D analysis based on γ and χ indexes showed a significant effect on the dosimetric representation in the lung cancer when we change the PBC algorithm to PBC-MB method. The comparison between the two irradiation techniques showed that the single isocenter technique produces a better dose distribution for the treatment of breast cancer. Pearson's Chi-squared test showed that there was no statistically significance between GVHs and CVHs generated by γ and χ indexes, (p > 0.05). The global analysis using 3D for γ and χ indexes confirmed the results obtained from dosimetric analysis. Conclusion: The methods proposed in this study provide useful tools for radiotherapy to compare two dose distributions obtained using different algorithms or different irradiation techniques. The χ-index was (~190) times faster than γ-index. The χ-index is thus a valuable and more convenient method for 3D global analysis compared with γ-index.------------------------Cite this article as: Chaikh A, Giraud JY, Balosso J. A 3D quantitative evaluation for assessing the changes of treatment planning system and irradiation techniques in radiotherapy. Int J Cancer Ther Oncol 2014; 2(3):02033. DOI: 10.14319/ijcto.0203.

A method to quantify and assess the dosimetric and clinical impact resulting from the heterogeneity correction in radiotherapy for lung cancer

Purpose: The aim of this study was to propose a method to quantify and assess the differences in dose computations using heterogeneity correction algorithms for the planning target volumes and organs at risk.Methods: Six patients with lung cancer treated with 3-dimensional conformal radiation therapy were included and analysed. Dose calculations were performed using the pencil beam convolution (PBC) algorithm without heterogeneity correction and the Modified Batho method (PBC-MB) with heterogeneity correction. For each patient, 3 treatment plans were generated using exactly the same beam configuration. In plan 1, the dose was calculated using the PBC algorithm. In plan 2, the dose was calculated using the PBC-MB. In plan 3, the dose was calculated using the PBC-MB method but with the same number of monitor units obtained from plan 1. To evaluate the treatment plans computed by the PBC and PBC-MB, the monitor units, dose at the isocenter, spatial isodose distribution, dose volume histograms, conformity index, homogeneity index, planning target volumes conformity index, and geometrical index were compared. A statistical analysis was carried out using Wilcoxon signed rank test. Results: The PBC-MB method in plan 2 produced a lower number of monitor units than in plan 1 using PBC algorithm (p < 0.001). Dosimetric parameters derived from the dose volume histograms were higher for the planning target volumes and organs at risks using PBC-MB method for plans 2 and 3 when compared to plan 1. There was no significant difference for all the quality indices between plan 1 and plan 2, (p > 0.05), but a significant difference for the geometric index between plans 2 and 3 (p = 0.002) was observed.Conclusion: The risks related to the modification from the homogeneity plan to the heterogeneity plan were the reduction of delivered dose in monitor units for the planning target volumes and the increment of the dose to the organs at risk. We suggest the adaption in the dose prescriptions when switching the dose calculation algorithm from the PBC to PBC-MB.------------------------------------------------------Cite this article as: Chaikh A, Giraud J, Balosso J. A method to quantify and assess the dosimetric and clinical impact resulting from the heterogeneity correction in radiotherapy for lung cancer. Int J Cancer Ther Oncol 2014; 2(1):020110.DOI: http://dx.doi.org/10.14319/ijcto.0201.1

The Minisatellite MSB1, in the Fungus Botrytis cinerea, Probably Mutates by Slippage

A minisatellite was identified in the intron of the ATP synthase of the filamentous fungus Botrytis cinerea, and it was named MSB1. This is the second fungal minisatellite described to date. Its 37-bp repeat unit is AT-rich, and it is found at only one locus in the genome. The introns of 47 isolates of Botrytis species were sequenced. The number of tandem repeats varied only from 5 to 11, but there were many repeat variants. The structure of MSB1 is peculiar: the variants are in the same physical order in all individuals, and this order follows the most parsimonious tree. These original characteristics, together with a total lack of recombination between alleles of the flanking regions, suggest that MSB1 probably mutates by slippage. MSB1 was found in the intron of the ATP synthase of all of the Botrytis species analyzed, but the repeat unit was not found in any other genus examined, including Sclerotinia, which is the genus closest to Botrytis

Role of methylotrophy during symbiosis between Methylobacterium nodulans and Crotalaria podocarpa

Some rare leguminous plants of the genus Crotalaria are specifically nodulated by the methylotrophic bacterium Methylobacterium nodulans. In this study, the expression and role of bacterial methylotrophy were investigated during symbiosis between M. nodulans, strain ORS 2060(T), and its host legume, Crotalaria podocarpa. Using lacZ fusion to the mxaF gene, we showed that the methylotroph genes are expressed in the root nodules, suggesting methylotrophic activity during symbiosis. In addition, loss of the bacterial methylotrophic function significantly affected plant development. Indeed, inoculation of M. nodulans nonmethylotroph mutants in C. podocarpa decreased the total root nodule number per plant up to 60%, decreased the whole-plant nitrogen fixation capacity up to 42%, and reduced the total dry plant biomass up to 46% compared with the wild-type strain. In contrast, inoculation of the legume C. podocarpa with nonmethylotrophic mutants complemented with functional mxa genes restored the symbiotic wild phenotype. These results demonstrate the key role of methylotrophy during symbiosis between M. nodulans and C. podocarpa