RESUMO
A synchrotron light source dedicated to medical applications has been designed at National Institute of Radiological Sciences. The storage ring, with circumference of 80 m, is designed for acceleration of 2.3 GeV and a stored current of 420 mA. It is equipped with two multipole wigglers to produce sufficient photon flux in a hard x-ray region required for medical applications. The purposes of the synchrotron light source are clinical performance of medical diagnoses clinically and research and development relating with medical applications. One of the most interesting applications for us is dual-energy x-ray computed tomography (CT). It gives the information about electron density of human tissue. The information plays an important role in advancing heavy-ion radiotherapy of cancers. Electron density can be derived from attenuation coefficients measured by different energy x rays. In this paper, a practical method of the dual-energy x-ray CT with synchrotron radiation is proposed with the theoretical consideration. The primitive experiment using monochromatic x rays emitted from radioisotopes proved the procedure of analysis mentioned here effective to derive electron densities from linear attenuation coefficients for two x rays of a different energy. The beamline dedicated to dual-energy x-ray CT is also proposed. It has a multipole wiggler as a light source and it mainly consists of a dual crystal monochromator and a rotating filter for attenuating photon flux of x rays and two-dimensional detector.
Assuntos
Iluminação , Imagem Radiográfica a Partir de Emissão de Duplo Fóton , Síncrotrons , Tomografia Computadorizada por Raios X , Desenho de Equipamento , Modelos Teóricos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/instrumentação , Tomografia Computadorizada por Raios X/instrumentação , Tomografia Computadorizada por Raios X/métodosRESUMO
NASA: Researchers explore the use of Bragg Ionization Peak in radiotherapy for tumors. Considerations for the production of a high quality radioactive beam include secondary beam production efficiency, primary beam survival, and multiple scattering. A Positron Emitting Beam Analyzing camera was developed and tested at BEVALAC using a neon-19 beam stopping point. Results indicate that in homogeneous brain tissues, CT measurements and radioactive beam measurements are between 1-2 mm; there can be substantial difference between CT measurements and radioactive beam estimates if the beam stopping point crosses the fossae; random coincidences due to detector activation also appear as diffused images in the image plane of the beam stopping point; and further enhancements are necessary to make reliable measurements in the human trunk and complex brain regions.^ieng
Assuntos
Elétrons , Neoplasias/diagnóstico por imagem , Aceleradores de Partículas , Radioatividade , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia de Alta Energia/métodos , Radioisótopos de Carbono , Humanos , Neônio , Neoplasias/radioterapia , Doses de Radiação , Radioisótopos , Cintilografia , Tomografia Computadorizada por Raios XRESUMO
A synchrotron light source dedicated to medical applications is required to be compact for installation in limited spaces at hospitals. The NIRS storage ring, with a circumference of 44.8 m, is designed to accelerate electrons up to 1.8 GeV and to store a beam of 400 mA. The ring is composed of superconducting bending magnets for downsizing. A beam of 300 MeV is injected into the ring from a microtron operated at an L-band RF frequency. There are two superconducting multipole wigglers with nine poles and a maximum field of 8 T, which can produce a photon flux of about 1.4 x 10(13) photons s(-1) mrad(-1) (0.1% bandwidth)(-1) at 33 keV used for coronary angiography.