9 General introduction Newer techniques in radiotherapy The last decades, radiation technologies have been significantly improved. In the 90’s, three-dimensional conformal radiotherapy (3D-CRT) was commonly used. More recently, more advanced technologies like intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) became the new standard. These technologies can deliver highly conformal dose distributions with improved ratios between target coverage and sparing of critical OARs, like the heart and lungs (Figure 1). Moreover, these techniques provide additional flexibility in prioritizing which OARs should be avoided. This prioritizing of dose to critical organs remains a key issue as, especially in photon radiotherapy, as decreasing the dose to one organ, for example the heart, will come at the expense of the radiation dose to other organs, like the lungs. The new kid on the block, proton radiotherapy is an even more advanced technology, which allows a further reduction of the radiation dose to both heart and lungs. However, its availability is limited and therefore it is important to select the patients that benefit most[3]. Figure 1, evolution of radiotherapy planning techniques in recent years, techniques do become more conformal Red=target volume, Green=prescribed dose, Blue=intermediate dose, 40-80% prescribed dose, Grey=low dose, up to 20% prescribed dose. 1
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