نتایج جستجو برای: isocenter
تعداد نتایج: 707 فیلتر نتایج به سال:
Stereotactic radiosurgery is a minimally invasive procedure that uses a focused beam of radiation as an ablative instrument to destroy brain tumors. To deposit a high dose of radiation in a tumor, while reducing the dose to healthy tissue, a large number of beams are crossfired at the tumor from multiple directions. The treatment planning problem (also called the inverse dosimetry problem) is t...
The operation of the bowtie filter in x-ray CT is correct if the object being scanned is properly centered in the scanner's field-of-view. Otherwise, the dose delivered to the patient and image noise will deviate from optimal setting. We investigate the effect of miscentering on image noise and surface dose on three commercial CT scanners. Six cylindrical phantoms with different size and materi...
PURPOSE To improve patient safety and treatment quality, verification of dose delivery in radiotherapy is desirable. We present a simple, easy-to-implement, open-source method for in vivo planar dosimetry of conformal radiotherapy by electronic portal imaging device (EPID). METHODS Correlation ratios, which relate dose in the mid-depth of slab phantoms to transit EPID signal, were determined ...
Monte Carlo simulation with PENELOPE (v. 2003) is applied to calculate Leksell Gamma Knifer dose distributions for heterogeneous phantoms. The usual spherical water phantom is modified with a spherical bone shell simulating the skull and an air-filled cube simulating the frontal or maxillary sinuses. Different simulations of the 201 source configuration of the Gamma Knife have been carried out ...
AIMS AND BACKGROUND The aim of this report was to investigate the feasibility in terms of treatment time prolongation of an on-line no-action level correction protocol, based on daily electronic portal image verification. METHODS AND STUDY DESIGN The occupation of a linear accelerator (LINAC) delivering 3-D conformal treatments was monitored for two weeks (from Monday to Friday, 10 working da...
The Leksell stereotactic Gamma Knifetrade mark uses radiation from 201 (60)Co sources that are focused to the center of a collimator helmet to deliver a high dose of radiation with minimal irradiation of proximal structures. This paper presents a method for fast verification of the irradiation time as calculated by the Leksell Gamma Knifetrade mark treatment planning software GammaPlan((R)). To...
This study investigated radiation dose variations in pre-clinical irradiation due to the photon beam energy and presence of tissue heterogeneity. Based on the same mouse computed tomography image dataset, three phantoms namely, heterogeneous, homogeneous and bone homogeneous were used. These phantoms were generated by overriding the relative electron density of no voxel (heterogeneous), all vox...
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