Biomaterial Database

Monte Carlo calculation of the dose distributions of two 106Ru eye applicators. 1998

A Sánchez-Reyes, and J I Tello, and B Guix, and F Salvat, and J J Tello

Servicio de Oncología Radioterápica, Hospital Clínic Universitari de Barcelona, Spain.

OBJECTIVE Beta emitting 106Ru applicators are widely used to treat choroidal melanoma. In view of the importance of clinical applications of this radioisotope and the relative lack of knowledge of the dose distributions, three-dimensional dose maps of two concave applicators were calculated by means of Monte Carlo simulation. METHODS Simulations of small CCA and CCB concave applicators manufactured by Bebig were performed using the Monte Carlo code PENELOPE, which allows the description of the structure (geometry and materials) of the applicator in detail. Electrons are emitted from the 106Ru nuclei isotropically, with initial energy randomly sampled from the corresponding Fermi spectra and with initial positions uniformly distributed on the radioactive layer. Primary electrons, as well as the produced delta-rays, are assumed to be absorbed in the medium when they slow down to an energy of 70 keV. Bremsstrahlung photons with energies larger than 7 keV are also simulated. The simulation code has been run on a 166 MHz PENTIUM PC. RESULTS Three-dimensional dose distributions produced by the CCA and CCB applicators in a water sphere, concentric with the applicator, were evaluated. To minimize the magnitude of statistical uncertainties, advantage has been taken of the cylindrical symmetry of the problem. The relative depth-dose (along the symmetry axis of the applicator) was also evaluated from the applicator surface up to distances larger than I cm, with statistical uncertainties of a few percent. Results compare well with data supplied by the manufacturer. CONCLUSIONS We have performed accurate Monte Carlo calculations of three-dimensional dose distributions from CCA and CCB 106Ru applicators. The results, presented in the form of two-dimensional maps, depth-dose distributions along the symmetry axis and lateral dose profiles, provide a detailed description of the dose delivered in treatments of choroidal melanoma.

UI	MeSH Term	Description	Entries
D008545	Melanoma	A malignant neoplasm derived from cells that are capable of forming melanin, which may occur in the skin of any part of the body, in the eye, or, rarely, in the mucous membranes of the genitalia, anus, oral cavity, or other sites. It occurs mostly in adults and may originate de novo or from a pigmented nevus or malignant lentigo. Melanomas frequently metastasize widely, and the regional lymph nodes, liver, lungs, and brain are likely to be involved. The incidence of malignant skin melanomas is rising rapidly in all parts of the world. (Stedman, 25th ed; from Rook et al., Textbook of Dermatology, 4th ed, p2445)	Malignant Melanoma,Malignant Melanomas,Melanoma, Malignant,Melanomas,Melanomas, Malignant
D009010	Monte Carlo Method	In statistics, a technique for numerically approximating the solution of a mathematical problem by studying the distribution of some random variable, often generated by a computer. The name alludes to the randomness characteristic of the games of chance played at the gambling casinos in Monte Carlo. (From Random House Unabridged Dictionary, 2d ed, 1993)	Method, Monte Carlo
D011879	Radiotherapy Dosage	The total amount of radiation absorbed by tissues as a result of radiotherapy.	Dosage, Radiotherapy,Dosages, Radiotherapy,Radiotherapy Dosages
D001918	Brachytherapy	A collective term for interstitial, intracavity, and surface radiotherapy. It uses small sealed or partly-sealed sources that may be placed on or near the body surface or within a natural body cavity or implanted directly into the tissues.	Curietherapy,Implant Radiotherapy,Plaque Therapy, Radioisotope,Radioisotope Brachytherapy,Radiotherapy, Interstitial,Radiotherapy, Intracavity,Radiotherapy, Surface,Brachytherapy, Radioisotope,Interstitial Radiotherapy,Intracavity Radiotherapy,Radioisotope Plaque Therapy,Radiotherapy, Implant,Surface Radiotherapy,Therapy, Radioisotope Plaque
D002830	Choroid Neoplasms	Tumors of the choroid; most common intraocular tumors are malignant melanomas of the choroid. These usually occur after puberty and increase in incidence with advancing age. Most malignant melanomas of the uveal tract develop from benign melanomas (nevi).	Choroidal Neoplasms,Choroid Neoplasm,Choroidal Neoplasm,Neoplasm, Choroid,Neoplasm, Choroidal,Neoplasms, Choroid,Neoplasms, Choroidal
D003198	Computer Simulation	Computer-based representation of physical systems and phenomena such as chemical processes.	Computational Modeling,Computational Modelling,Computer Models,In silico Modeling,In silico Models,In silico Simulation,Models, Computer,Computerized Models,Computer Model,Computer Simulations,Computerized Model,In silico Model,Model, Computer,Model, Computerized,Model, In silico,Modeling, Computational,Modeling, In silico,Modelling, Computational,Simulation, Computer,Simulation, In silico,Simulations, Computer
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D012429	Ruthenium Radioisotopes	Unstable isotopes of ruthenium that decay or disintegrate emitting radiation. Ru atoms with atomic weights 93-95, 97, 103, and 105-108 are radioactive ruthenium isotopes.	Radioisotopes, Ruthenium