In external beam Radiotherapy, transverse and longitudinal dose measurements are taken by a radiation detector in order to characterise the radiation beams from medical linear accelerators.
[1] Typically, an ionisation chamber and water phantom are used to create these radiation dose profiles.
Water is used due to its tissue equivalence.
Transverse dose measurements are performed in the x (crossplane) or y (inplane) directions perpendicular to the radiation beam, and at a given depth (z) in the phantom.
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