Monte Carlo simulation of the effect of magnetic fields on brachytherapy dose distributions in lung tissue material.

The aim of this work was to use TOPAS Monte Carlo simulations to model the effect of magnetic fields on dose distributions in brachytherapy lung treatments, under ideal and clinical conditions. Idealistic studies were modeled consisting of either a monoenergetic electron source of 432 keV, or a polyenergetic electron source using the spectrum of secondary electrons produced by 192Ir gamma-ray irradiation. The electron source was positioned in the center of a homogeneous, lung tissue phantom (ρ = 0.26 g/cm3). Conversely, the clinical study was simulated using the VariSource VS2000 192Ir source in a patient with a lung tumor. Three contoured volumes were considered: the tumor, the planning tumor volume (PTV), and the lung. In all studies, dose distributions were calculated in the presence or absence of a constant magnetic field of 3T. Also, TG-43 parameters were calculated for the VariSource and compared with published data from EGS-brachy (EGSnrc) and PENELOPE. The magnetic field affected the dose distributions in the idealistic studies. For the monoenergetic and poly-energetic studies, the radial distance of the 10% iso-dose line was reduced in the presence of the magnetic field by 64.9% and 24.6%, respectively. For the clinical study, the magnetic field caused differences of 10% on average in the patient dose distributions. Nevertheless, differences in dose-volume histograms were below 2%. Finally, for TG-43 parameters, the dose-rate constant from TOPAS differed by 0.09% ± 0.33% and 0.18% ± 0.33% with respect to EGS-brachy and PENELOPE, respectively. The geometry and anisotropy functions differed within 1.2% ± 1.1%, and within 0.0% ± 0.3%, respectively. The Lorentz forces inside a 3T magnetic resonance machine during 192Ir brachytherapy treatment of the lung are not large enough to affect the tumor dose distributions significantly, as expected. Nevertheless, large local differences were found in the lung tissue. Applications of this effect are therefore limited by the fact that meaningful differences appeared only in regions containing air, which is not abundant inside the human.

[Scooter-related injuries in pediatrics patients]. / Lesiones asociadas al uso del patín del diablo (scooter) en pacientes pediátricos.

The authors undertook an analysis of all the pediatric patients who presented at their hospital with scooter-related injuries. A total of 37 patients seen at Dr. Victorio de la Fuente Narváez Trauma Hospital were studied. Findings included a wide variety of injuries, from skull fracture to limb factures, as well as one open fracture and a chondral knee fracture. Diagnoses were made clinically and radiologically and various treatments were provided, both conservative and surgical. Findings showed a high frequency of scooter-related fractures in children. The use of protective equipment by children and their supervision are necessary to prevent these injuries.

[Li-Fraumeni familial cancer syndrome: case report and review of the literature]. / Síndrome de Li Fraumeni. Cáncer familiar comunicación de un caso y revisión de la literatura.

INTRODUCTION: Multiple familial cancer is a rare entity as is also Li-Fraumeni Syndrome (LFS), which involves a mutation in the germ cell line of Tp53 suppresor gene that is expressed in chromosome 17p13.1 and occurs as an autosomal dominant condition. OBJECTIVE: Presentation of one case of LFS. CLINICAL CASE: Family history: maternal grandfather had melanoma and maternal aunt had osteoblastic osteosarcoma of the left distal femur. Eight-and-a-half year-old child with a history of a CNS tumor (choroid plexus carcinoma) and two years later, a melanoma (Spitz nevus). SYMPTOMS: impaired motor function of the left half of the body and pain upon ipsilateral gait. The physical exam showed swelling of the left iliac crest. The X-rays showed osteoblastic osteosarcoma and the fine needle aspiration biopsy (FNAB) was positive. The diagnosis was made according to the clinical criteria for LFS. DISCUSSION: We report a case of LFS diagnosed based on clinical criteria. We suggest that the questioning of patients with cancer be aimed at finding out the family history of neoplasias. The case presented herein shows an evident association between both choroid plexus carcinoma and osteoblastic osteosarcoma and the patient's family history. We think that any physician treating children with cancer should consider these multiple familial cancer syndromes.