ABSTRACT
Introducing simulators to relate the treatment area to • internal bony landmarks rened the earlier technique of drawing elds on the patient’s skin, a method relying on the anatomical knowledge of organ and tumor projection on the patient’s surface. Simulators appeared concomitantly with megavoltage units (rst telecobalt, then linear accelerators), and contributed enormously to the development of modern radiotherapy. With the dissemination of 3D-conformal irradiation techniques, there is a trend to replace simulators with CT scanners, and to move away from bony landmarks as a reference for volume denition. Indeed, CT (and MRI and PET) allows the denition of tumor regions (GTV, CTV) and organs at risk (OAR) directly in a volumetric manner, instead of indirectly from bony landmarks. Portal imaging, rst with lms (gammagraphy) and later • with electronic portal imaging, permitted verication that the areas dened at simulation were eectively covered by the treatment beams. It also demonstrated that day-to-day variations exist in a fractionated treatment. is led to the concept and denition of the PTV. In vivo dosimetry has been developed and is promoted as • the simplest and most ecient end-to-end test for individual QC of a treatment. In many countries, it is a legal requirement to proceed with in vivo dosimetry at the rst treatment session. It does not apply, however, to recent developments in treatment techniques like intensity-modulated radiation therapy (IMRT) or rotational therapy (VMAT, RapidArc, tomotherapy) since there is no longer any use of static, uniform beams that can be simply measured at the entrance on the patient skin. More elaborate and indirect verication techniques are currently being developed for the verication of these particular techniques. Complex quality control (QC) of radiotherapy techniques • are currently being developed (asymmetric phantoms, phantoms with density heterogeneities, etc.) to control for equipment performances and accuracy of dose calculations in complex treatments (nonuniform dose distributions, IMRT, rotational therapy), as well as for verication of the information quality of imaging that is used as a source for treatment preparation and dose calculation. Record and verify systems have been developed as a mean • of securing data transfer from planning systems to treatment machines. It allowed the development, in a secure environment, of techniques for the transfer of many thousands of numerical parameters from the planning to the treatment unit.
