Almost-Optimal Deterministic Treasure Hunt in Arbitrary Graphs

A mobile agent navigating along edges of a simple connected graph, either finite or countably infinite, has to find an inert target (treasure) hidden in one of the nodes. This task is known as treasure hunt. The agent has no a priori knowledge of the graph, of the location of the treasure or of the initial distance to it. The cost of a treasure hunt algorithm is the worst-case number of edge traversals performed by the agent until finding the treasure. Awerbuch, Betke, Rivest and Singh [3] considered graph exploration and treasure hunt for finite graphs in a restricted model where the agent has a fuel tank that can be replenished only at the starting node $s$. The size of the tank is $B=2(1+\alpha)r$, for some positive real constant $\alpha$, where $r$, called the radius of the graph, is the maximum distance from $s$ to any other node. The tank of size $B$ allows the agent to make at most $\lfloor B\rfloor$ edge traversals between two consecutive visits at node $s$. Let $e(d)$ be the number of edges whose at least one extremity is at distance less than $d$ from $s$. Awerbuch, Betke, Rivest and Singh [3] conjectured that it is impossible to find a treasure hidden in a node at distance at most $d$ at cost nearly linear in $e(d)$. We first design a deterministic treasure hunt algorithm working in the model without any restrictions on the moves of the agent at cost $\mathcal{O}(e(d) \log d)$, and then show how to modify this algorithm to work in the model from [3] with the same complexity. Thus we refute the above twenty-year-old conjecture. We observe that no treasure hunt algorithm can beat cost $\Theta(e(d))$ for all graphs and thus our algorithms are also almost optimal

Profil de l’ionogramme sanguin chez les enfants brûlés du Centre Hospitalier Universitaire Pédiatrique Charles de Gaulle de Ouagadougou (Burkina Faso)

Les brûlures de l’enfant peuvent être à l’origine de troubles ioniques graves, entrainant une morbi-mortalité importante. Ce travail avait pour objectif de décrire les perturbations de l’ionogramme sanguin chez les enfants brûlés, afin de contribuer à l’amélioration des soins. Il s’est agi d’une étude transversale rétrospective allant du 01 janvier 2017 au 30 juin 2019. Ont été inclus les enfants hospitalisés dans le service de chirurgie du CHU pédiatrique Charles de Gaulle pour brûlure et chez lesquels un ionogramme sanguin a été réalisé. L’étude a porté sur 212 enfants, avec un âge moyen de 38,52 mois et un sex ratio de 1,12. La surface corporelle brûlée moyenne était de 26,60% et le délai moyen d’admission de 5,71 heures. La mortalité était de 16,98%. L’ionogramme sanguin à l’entrée a retrouvé une hyponatrémie (27,88%), une hypobicarbonatémie (53,95%), une hypoprotidémie (26,67%) et une hyperchlorémie (53,59%). Au contrôle, ces troubles ioniques étaient toujours présents. S’y sont associées une hypocalcémie (30,43%), une hypomagnésémie (27,27%) et une hyperphosphatémie (28,79%). La natrémie, la bicarbonatémie et la protidémie à l’entrée étaient significativement plus basses chez les patients décédés. Les brûlures de l’enfant sont fréquentes. Leur évolution est marquée par des perturbations de l’ionogramme sanguin et une mortalité élevée.Mots clés : Brûlure, Ionogramme sanguin, Enfants, Burkina Faso.   English title: Blood ionogram profile in burned children at the Charles de Gaulle University Pediatric Hospital of Ouagadougou (Burkina Faso)Burns in children can be the cause of serious ionic disorders, leading to significant morbidity and mortality. The aim of this study was to describe the disturbances in the blood ionogram of burnt children, in order to contribute to the improvement of care. This was a retrospective cross-sectional study from 01 January 2017 to 30 June 2019. Children hospitalised in the surgery department of the Charles de Gaulle Pediatric University Hospital for burns and in whom a blood ionogram was carried out were included. Our study involved 212 children, with an average age of 38.52 months and a sex ratio of 1.12. The average body surface area burned was 26.60% and the average admission time was 5.71 hours. Mortality was 16.98%. The blood ionogram at the entrance showed hyponatremia (27.88%), hypobicarbonatremia (53.95%), hypoprotidemia (26.67%) and hyperchloremia (53.59%). At the control, these ionic disorders were still present. They were associated with hypocalcaemia (30.43%), hypomagnesemia (27.27%) and hyperphosphatemia (28.79%). Natremia, bicarbonateemia and protidemia were significantly lower on admission in patients who died in the course of the evolution. Childhood burns are frequent at the CHUP-CDG; their evolution is marked by disturbances of the blood ionogram and high mortality.Keywords: Burns, Blood Ionogram, Children, Burkina Faso

Diversite Phlebotomienne Dans Trois Villages De La Commune De Bouake (Côte D’ivoire) Durant La Periode De Mars A Juin 2019

La leishmaniose cutanée est une parasitose due à des protozoaires du genre Leishmania et répandue dans le monde. Une enquête médicale réalisée dans trois villages de la ville de Bouaké, autour de cas suspects de leishmaniose cutanée, a permis de confirmer la présence de cette pathologie dans ces villages. Dans le cadre de l’identification des acteurs du cycle épidémiologique de la leishmaniose cutanée, une étude entomologique a été conduite dans ces villages afin d’identifier les phlébotomes potentiels vecteurs de leishmanies. Les pièges huileux et les pièges lumineux CDC, ont été posés entre mars et juin 2019, suivant une méthode de rotation entre les sites de piégeage. Ils ont été posés entre 17h et 18h et relevés le lendemain matin entre 7h et 8h. La diversité spécifique des espèces identifiées a été déterminée à partir des indices écologiques d’équitabilité et de Hill. Ces pièges ont permis la capture de 135 phlébotomes, dont 78 ont été morphologiquement identifiés. Le genre Sergentomyia constituait 91% de nos récoltes contre 9% pour le genre Phlebotomus. Ph. bergeroti, Ph. rodhaini et Ph. sergenti étaient les espèces du genre Phlebotomus, capturées dans ces sites. Des travaux approfondis portant sur l’identification du parasite à la fois chez les phlébotomes et chez l’homme doivent être effectués, afin d’identifier les phlébotomes incriminés dans la transmission des leishmanies à Bouaké. Cutaneous leishmaniasis is a parasitosis caused by protozoa of the genus Leishmania and is widespread worldwide. A medical survey carried out in three villages of the city of Bouaké, around suspected cases of cutaneous leishmaniasis, confirmed the presence of this pathology in these villages. As part of the identification of the actors of the epidemiological cycle of cutaneous leishmaniasis, an entomological study was conducted in these villages in order to identify potential phlebotomus vectors of leishmaniasis. Oil traps and CDC light traps were set between March and June 2019, following a rotation method between trapping sites. They were set between 5:00 pm and 6:00 pm and were collected the next morning between 7:00 am and 8:00 am. The specific diversity of the identified species was determined from the ecological indices of equitability and Hill's ecological indices. These traps allowed the capture of 135 sandfish, 78 of which were morphologically identified. The genus Sergentomyia constituted 91% of our harvests against 9% for the genus Phlebotomus. Ph. bergeroti, Ph. rodhaini and Ph. sergenti were the species of the genus Phlebotomus caught at these sites. Further work on the identification of the parasite in both sandflies and humans should be carried out in order to identify the sandflies incriminated in the transmission of leishmania in Bouaké

Use of fine resolution Voxel S-Values for absorbed dose calculation from SPECT or PET based cumulated activity distributions

International audienc

Almost-Optimal Deterministic Treasure Hunt in Arbitrary Graphs

A mobile agent navigating along edges of a simple connected graph, either finite or countably infinite, has to find an inert target (treasure) hidden in one of the nodes. This task is known as treasure hunt. The agent has no a priori knowledge of the graph, of the location of the treasure or of the initial distance to it. The cost of a treasure hunt algorithm is the worst-case number of edge traversals performed by the agent until finding the treasure. Awerbuch, Betke, Rivest and Singh [3] considered graph exploration and treasure hunt for finite graphs in a restricted model where the agent has a fuel tank that can be replenished only at the starting node $s$. The size of the tank is $B=2(1+\alpha)r$, for some positive real constant $\alpha$, where $r$, called the radius of the graph, is the maximum distance from $s$ to any other node. The tank of size $B$ allows the agent to make at most $\lfloor B\rfloor$ edge traversals between two consecutive visits at node $s$. Let $e(d)$ be the number of edges whose at least one extremity is at distance less than $d$ from $s$. Awerbuch, Betke, Rivest and Singh [3] conjectured that it is impossible to find a treasure hidden in a node at distance at most $d$ at cost nearly linear in $e(d)$. We first design a deterministic treasure hunt algorithm working in the model without any restrictions on the moves of the agent at cost $\mathcal{O}(e(d) \log d)$, and then show how to modify this algorithm to work in the model from [3] with the same complexity. Thus we refute the above twenty-year-old conjecture. We observe that no treasure hunt algorithm can beat cost $\Theta(e(d))$ for all graphs and thus our algorithms are also almost optimal

Semiautomated thoracic and abdominal computed tomography segmentation using the belief functions theory: application to 3D internal dosimetry.

International audienceAIM: Segmentation of computed tomography (CT) images is an important step in three-dimensional (3D) internal dosimetry. To this end, a semiautomated method was developed to delineate organs, using the belief functions theory. MATERIALS AND METHODS: The membership degree of each voxel to each volume of interest is estimated by computing a basic belief assignment (bba). For each voxel V, bbas corresponding to each neighbor are aggregated to obtain a unique bba, using a merging procedure. Before aggregating information, a 3D filter is applied, in order to take into account the fact that the more the voxel V(i) is close to V, the more the information coming from V(i) is reliable. The aim is to weaken the contribution of voxels according to their distance with respect to the voxel to be classified. The algorithm was applied on 10 CT scans (pixel size, 0.98 x 0.98 mm2, slice thickness 3 mm, 120 kV). For each organ (i.e., the lung, liver, kidney, and spleen), the algorithm was applied on a part of the CT volume. First, the lung was segmented using two classes with characteristic values, C, defined by the K-means clustering algorithm. Second, the liver and kidneys were segmented using three classes with C-values defined by local mean Hounsfield Unit (HU) measurements, corresponding to fat, liver, and kidney. Third, the spleen was segmented using three classes corresponding to fat, kidney, and spleen, using local mean HU measurements. The semiautomated segmentation was compared with manual segmentation using the volume difference and the agreement (overlap) index. RESULTS: For organ segmentation, the computation duration was between 5 and 20 minutes (2.5 GHz, RAM of 1 GByte), depending on the number of classes and the volume size to classify. On the 10 patients, manual correction was needed for none on the lung, 1 on the spleen, 2 on the kidneys, and 7 on the liver, mostly owing to intercostal structures. The mean relative volume difference (+/-1 standard deviation [SD]) between manual and automated segmentation was 5.0% +/- 3.7%, 5.7% +/- 3.6%, 6.2% +/- 3.3%, and 7.5% +/- 6.5% for the lung, liver, kidney, and spleen, respectively. The corresponding mean agreement index (+/-1 SD) was 0.94 +/- 0.03, 0.90 +/- 0.01, 0.88 +/- 0.03, and 0.84 +/- 0.04. CONCLUSIONS: The algorithm allows for the delineating of organs on thoracic and abdominal CT images, and will be integrated in a 3D internal dosimetry dedicated software

Implementation and validation of collapsed cone superposition for radiopharmaceutical dosimetry of photon emitters

International audienceTwo collapsed cone (CC) superposition algorithms have been implemented for radiopharmaceutical dosimetry of photon emitters. The straight CC (SCC) superposition method uses a water energy deposition kernel (EDKw) for each electron, positron and photon components, while the primary and scatter CC (PSCC) superposition method uses different EDKw for primary and once-scattered photons. PSCC was implemented only for photons originating from the nucleus, precluding its application to positron emitters. EDKw are linearly scaled by radiological distance, taking into account tissue density heterogeneities. The implementation was tested on 100, 300 and 600 keV mono-energetic photons and (18)F, (99m)Tc, (131)I and (177)Lu. The kernels were generated using the Monte Carlo codes MCNP and EGSnrc. The validation was performed on 6 phantoms representing interfaces between soft-tissues, lung and bone. The figures of merit were γ (3%, 3 mm) and γ (5%, 5 mm) criterions corresponding to the computation comparison on 80 absorbed doses (AD) points per phantom between Monte Carlo simulations and CC algorithms. PSCC gave better results than SCC for the lowest photon energy (100 keV). For the 3 isotopes computed with PSCC, the percentage of AD points satisfying the γ (5%, 5 mm) criterion was always over 99%. A still good but worse result was found with SCC, since at least 97% of AD-values verified the γ (5%, 5 mm) criterion, except a value of 57% for the (99m)Tc with the lung/bone interface. The CC superposition method for radiopharmaceutical dosimetry is a good alternative to Monte Carlo simulations while reducing computation complexity

A new approach for dose calculation in targeted radionuclide therapy (TRT) based on collapsed cone superposition: validation with (90)Y.

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