Dose Outside the Treatment Volume in External Beam Therapy

Authored by: Stephen F. Kry , Rebecca M. Howell , Bryan P. Bednarz

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:


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Dose outside the planning target volume (PTV) is defined as “nontarget dose.” In radiation therapy, any “nontarget” dose should be minimized, as it offers no therapeutic benefit. Nontarget dose is delivered by nontarget radiation and can be in-field or out-of-field. “In-field nontarget dose” is that within a primary field border, such as entrance and exit dose along the beam path. “Out-of-field nontarget dose” is not only outside of the PTV but also outside of any primary field edge; dose deposited by leakage, scatter, or secondary radiation, i.e., stray radiation.

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