RESUMEN
Objective.This paper presents a new method for fast reconstruction (compatible with in-beam use) of deposited dose during proton therapy using data acquired from a PET scanner. The most innovative feature of this novel method is the production of noiseless reconstructed dose distributions from which proton range can be derived with high precision.Approach.A new MLEM & simulated annealing (MSA) algorithm, developed especially in this work, reconstructs the deposited dose distribution from a realistic pre-calculated activity-dose dictionary. This dictionary contains the contribution of each beam in the plan to the 3D activity and dose maps, as calculated by a Monte Carlo simulation. The MSA algorithm, usinga prioriinformation of the treatment plan, seeks for the linear combination of activities of the precomputed beams that best fits the observed PET data, obtaining at the same time the deposited dose.Main results.the method has been tested using simulated data to determine its performance under 4 different test cases: (1) dependency of range detection accuracy with delivered dose, (2) in-beam versus offline verification, (3) ability to detect anatomical changes and (4) reconstruction of a realistic spread-out Bragg peak. The results show the ability of the method to accurately reconstruct doses from PET data corresponding to 1 Gy irradiations, both in intra-fraction and inter-fraction verification scenarios. For this dose level (1 Gy) the method was able to spot range variations as small as 0.6 mm.Significance.out method is able to reconstruct dose maps with remarkable accuracy from clinically relevant dose levels down to 1 Gy. Furthermore, due to the noiseless nature of reconstructed dose maps, an accuracy better than one millimeter was obtained in proton range estimates. These features make of this method a realistic option for range verification in proton therapy.
Asunto(s)
Terapia de Protones , Método de Montecarlo , Terapia de Protones/métodos , Protones , Dosificación Radioterapéutica , Planificación de la Radioterapia Asistida por Computador/métodos , Programas Informáticos , Tomografía Computarizada por Rayos X/métodosRESUMEN
A retrospective study on the incidence in our hospital of hypernatremic dehydration was performed. Authors observed a linear decrease both in the frequency of hypernatremic dehydration and in the incidence of hypernatremias above 160 mmol/l, during the 8-year period included in the study. For the past few years a tendency to see affected babies of older age was also observed. We believe that the reasons for these facts are the new dietary habits in infancy feeding and specially the greater use of formulas with low solute and protein content.
Asunto(s)
Deshidratación/etiología , Gastroenteritis/complicaciones , Hipernatremia/etiología , Deshidratación/epidemiología , Femenino , Gastroenteritis/epidemiología , Humanos , Hipernatremia/epidemiología , Lactante , Alimentos Infantiles , Recién Nacido , Enfermedades del Recién Nacido/epidemiología , Masculino , Estudios Retrospectivos , EspañaRESUMEN
Three cases of congenital cerebral arteriovenous malformation are presented. They all developed congestive heart failure in the first day of life. The main clinical findings were a continuous murmur heard over the scalp, an ejection murmur at the upper left sternal border, gallop rhythm, cardiomegaly and hepatomegaly. Diagnosis was confirmed in all by carotideal arterography. Two had aneurysm of the vena cerebri interna Galeni and in the other, the aneurysm was localized in the area irrigated by the sylvian artery. The two former died after surgery was considered not feasible. The latter had his malformation resected. Two years after operation he is doing well.