**1. Introduction**

Wedged techniques are routinely used in external beam radiotherapy delivery to improve the dose distribution. In earlier years, physical wedges were typically constructed from highdensity materials and fixed to certain wedge angles; they were standard accessories shipped

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with linear accelerators. Such wedges are usually mounted externally or internally in the gantry head of the linear accelerators. Nonphysical wedges, first proposed in the late 1970s by Kijewski et al., produce modulated dose distributions that were similar to those of physical wedges [1]. They rely on the dynamic movements of a pair of independent collimating jaws during treatment and have been widely implemented in modern radiotherapy machines. Both modalities possess unique advantages and limitations in terms of dosimetric characteristics, treatment accuracy, and efficiency.

In this chapter, we discuss and compare the clinical implementation and application of wedge techniques in radiation therapy.
