RESUMO
PURPOSE: The aim of this study was to determine the optimal number of coplanar and noncoplanar external beams in the setting of stereotactic body radiotherapy (SBRT). METHODS AND MATERIALS: Spherical targets were delineated within 2 separate extracranial sites, the lung and liver, with diameters varying from 2 cm to 7 cm to cover the range of volumes used in SBRT. Treatment plans were created for all target volumes using 5 to 15 geometrically optimized coplanar and noncoplanar conformal beams. Dose gradient and normal tissue complication probability (NTCP) were evaluated for each set of beam configurations and for each target size. RESULTS: For all lung and liver target volumes, the dose gradient improved with an increase in beam number from 5 to 15 for both coplanar and noncoplanar beam configurations. NTCP decreased as the beam number increased from 5 to 9 beams for all target sizes for both coplanar and noncoplanar beams. There is no significant improvement in NTCP when more than 9 beams were used for treatment planning regardless of target size. CONCLUSION: Based on dosimetric criteria, the optimal number of external beams is 13 to 15 for SBRT using either coplanar or noncoplanar beam bouquets. Simple biologic models indicate that the optimal number of beams is 9 for SBRT of lung and liver lesions >2 cm, whereas smaller lesions may benefit from plans using up to 13 beams.
Assuntos
Algoritmos , Neoplasias Hepáticas/radioterapia , Neoplasias Pulmonares/radioterapia , Técnicas Estereotáxicas , Humanos , Masculino , Radioterapia/métodos , Dosagem RadioterapêuticaRESUMO
Adult medulloblastoma is a rare intracranial tumor. Our patient is a 61 year old woman treated with cranial irradiation 15 years previously for a low grade astrocytoma in the left posterior temporal lobe that was recently diagnosed with medulloblastoma in the right cerebellum. This is the first reported case of radiation induced adult medulloblastoma.
Assuntos
Neoplasias Cerebelares/etiologia , Meduloblastoma/etiologia , Neoplasias Induzidas por Radiação/patologia , Astrocitoma/radioterapia , Neoplasias Encefálicas/radioterapia , Neoplasias Cerebelares/patologia , Neoplasias Cerebelares/cirurgia , Craniotomia , Feminino , Humanos , Imageamento por Ressonância Magnética , Meduloblastoma/patologia , Meduloblastoma/cirurgia , Pessoa de Meia-Idade , Procedimentos Neurocirúrgicos , Lobo Temporal/patologiaRESUMO
Intracranial atypical teratoid/rhabdoid tumors (AT/RT) are rare with a poor prognosis. We report one case of a 7-year old girl living over 17 months after the diagnosis of AT/RT in the left frontal lobe. Treatment was partial surgical resection and post-operative radiation therapy. Radiation therapy resulted in complete response with no evidence of residual or recurrent disease more than 17 months after diagnosis. The patient has been maintained on an extensive regimen of alternative therapies since completion of radiation therapy.
