Abstract
To achieve a good therapeutic ratio the radiation dose to the tumor should be as high as possible with the lowest possible dose to the surrounding normal tissue. This is especially the case for brain tumors. Technological advancements in diagnostic imaging, dose calculations, and radiation delivery systems, combined with a better understanding of the pathophysiology of brain tumors have led to improvements in the therapeutic results. The widely used technology of delivering 3-D conformal therapy with photon beams (gamma rays) produced by Linear Accelerators has progressed into the use of Intensity modulated radiation therapy (IMRT). Particle beams have been used for several decades for radiotherapy because of their favorable depth dose characteristics. The introduction of clinically dedicated proton beam therapy facilities has improved the access for cancer patients to this treatment. Proton therapy is of particular interest for pediatric malignancies. These technical improvements are further enhanced by the evolution in tumor physiology imaging which allows for improved delineation of the tumor. This in turn opens the potential to adjust the radiation dose to maximize the radiobiological effects. The advances in both imaging and radiation therapy delivery will be discussed.
Highlights
After the discovery of x-rays in 1895, irradiation became used as a therapeutic modality. The application of these radiation treatments was hampered by a lack of understanding of the radiobiology of ionizing radiation and technical factors such as lack of tissue penetration due to the low energy of the photons and inadequate information on the dose distribution in and around the tumor
Modern radiotherapy depends on good quality imaging to define the target and surrounding organs at risk (OAR), rapid and accurate dose calculations by treatment planning systems (TPS), equipment to deliver these complicated treatment plans, and imaging to verify the correctness of the radiation delivered
This consists of a flat panel detector and either uses a separate KV source or the primary beam for cone beam ct scanning of the patient in the treatment position. The delivery of such high quality beams can be done under stereotactic conditions due to improved mechanical accuracy of the rotation of gantry and couch around the isocenter with an accuracy of ≤1 mm. This combined with improved patient immobilization devices and position verification using the on board imaging, as described above, allows for the delivery of fractionated stereotactic radiotherapy (FSRT)
Summary
After the discovery of x-rays in 1895, irradiation became used as a therapeutic modality. The application of these radiation treatments was hampered by a lack of understanding of the radiobiology of ionizing radiation and technical factors such as lack of tissue penetration due to the low energy of the photons and inadequate information on the dose distribution in and around the tumor. Over the decades radiation has always played a role in managing brain tumors either as the primary modality or as adjuvant therapy. Technological advancements in diagnostic imaging, radiation delivery systems, and a better understanding of the radiobiology have consolidated and expanded this role. The purpose of this paper is to discuss recent technological advances in these areas, discuss the clinical benefit and to look at future developments
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