11/7/2023 0 Comments Astro byond v13General consensus is that there is a need to conduct randomized trials and/or collect outcomes data in multi-institutional registries to unequivocally demonstrate the advantage of protons. Considering the high cost or establishing and operating proton therapy centers, questions have been raised about their cost effectiveness. Although promising results have been and continue to be reported for many other types of cancers, they are based on small studies. It is generally acknowledged that proton therapy is safe, effective and recommended for many types of pediatric cancers, ocular melanomas, chordomas and chondrosarcomas. The latter technique can be used to treat patients with optimized intensity modulated proton therapy (IMPT), the most powerful proton modality.ĭespite the high potential of proton therapy, the clinical evidence supporting the broad use of protons is mixed. Spreading and shaping can be achieved by electro-mechanical means to treat the patients with “passively-scattered proton therapy (PSPT) or using magnetic scanning of thin “beamlets” of protons of a sequence of initial energies. The initial thin beams of protons are spread laterally and longitudinally and shaped appropriately to deliver treatments. Protons, accelerated to therapeutic energies ranging from 70 to 250 MeV, typically with a cyclotron or a synchrotron, are transported to the treatment room where they enter the treatment head mounted on a rotating gantry. These may, in turn, allow escalation of tumor doses, greater sparing of normal tissues, thus potentially improving local control and survival while at the same time reducing toxicity and improving quality of life. This is because of the unique depth-dose characteristics of protons, which can be exploited to achieve significant reductions in normal tissue doses proximal and distal to the target volume. Free from this restriction and far away from the heat radiated by Earth, L2 provides a much more stable viewpoint.In principle, proton therapy offers a substantial clinical advantage over the conventional photon therapy. It offers a clearer view of the cosmos than an orbit around Earth, which would result in the spacecraft passing in and out of Earth's shadow and causing it to heat up and cool down, distorting its view. This special location, known as the L2 Lagrangian point, keeps pace with Earth as we orbit the Sun. Gaia is mapping the stars from an orbit around the Sun, at a distance of 1.5 million km beyond Earth’s orbit. The underside of the shield is partially covered with solar panels and always faces the Sun, generating electricity to operate the spacecraft and its instruments. This acts as both a sunshade to permanently shade the telescopes and allow their temperatures to drop to below –100☌, and as a power generator for the spacecraft. Gaia launched on a Soyuz-STB/Fregat-MT launch vehicle from the European Spaceport in Kourou, French Guiana.Īfter launch, Gaia unfolded a ‘skirt’ just over 10 m in diameter. The vast catalogue of celestial objects created from Gaia’s scientific haul is not only benefiting studies of our own Solar System and Galaxy, but also the fundamental physics that underpins our entire Universe. Even stars near the Galactic centre, some 30 000 light-years away, will have their distances measured to within an accuracy of 20%. This is allowing the nearest stars to have their distances measured to the extraordinary accuracy of 0.001%. This is comparable to measuring the diameter of a human hair at a distance of 1000 km. Gaia is achieving its goals by repeatedly measuring the positions of all objects down to magnitude 20 (about 400 000 times fainter than can be seen with the naked eye).įor all objects brighter than magnitude 15 (4000 times fainter than the naked eye limit), Gaia is measuring their positions to an accuracy of 24 microarcseconds. By watching for the large-scale motion of stars in our Galaxy, it is also probing the distribution of dark matter, the invisible substance thought to hold our Galaxy together. This huge stellar census is providing the data needed to tackle an enormous range of important open questions relating to the origin, structure and evolutionary history of our Galaxy.įor example, Gaia is identifying which stars are relics from smaller galaxies long ago ‘swallowed’ by the Milky Way. Gaia is creating an extraordinarily precise three-dimensional map of nearly two billion objects throughout our Galaxy and beyond, mapping their motions, luminosity, temperature and composition. What's special? The density of stars from Gaia’s Early Data Release 3
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