Introduction and Overview of the Contents of the Book

Authored by: Ben Mijnheer

Clinical 3D Dosimetry in Modern Radiation Therapy

Print publication date:  October  2017
Online publication date:  October  2017

Print ISBN: 9781482252217
eBook ISBN: 9781315118826
Adobe ISBN:

10.1201/9781315118826-1

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Abstract

In the last two decades of the twentieth century, radiotherapy showed a fundamental change in approach by the transition from conventional two-dimensional radiotherapy (2DRT) to three-dimensional conformal radiotherapy (3DCRT). In 2DRT, tumor volume and critical structures were drawn on orthogonal simulator films or on a few computed tomography (CT) images, simple setups with a few fields were used, treatment planning was performed with isodose plans in only one or a few planes, and generally broad margins were used. When implementing 3DCRT, tumor volume and critical structures were drawn on slice-by-slice CT or magnetic resonance (MR) images in combination with beam's eye views created from digitally reconstructed radiographs. Furthermore, complex setups of four or more fields with rigid immobilization were used, 3D treatment planning was introduced with 3D visualization and 3D plan analysis, while tight margins became general practice. The additional efforts for a clinic when starting 3DCRT have been elucidated in many reports published by national and international organizations such as the International Commission on Radiation Units and Measurements (ICRU, 1993, 1999) and the International Atomic Energy Agency (IAEA, 2008). The consequences with respect to dosimetric issues when introducing 3DCRT were enormous. The possibilities of the newly developed 3D treatment planning systems (TPSs) had to be well understood and extensive sets of commissioning and validation measurements were required to ensure the safe introduction of 3DCRT techniques in the clinic. Capabilities of a 3D TPS that had to be tested included the use of irregularly shaped treatment fields, 3D dose calculation algorithms, display of 3D anatomy and 3D dose distributions, and treatment plan evaluation tools. For all these activities, new dosimetric approaches were introduced, often based on the use of the same type of dosimeters as applied in conventional 2DRT, but measurements were now required in many more points in multiple planes.

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