Which factor may decrease the Planning Target Volume (PTV) margin?

Image-guided radiation therapy (IGRT) can decrease the Planning Target Volume (PTV) margin by enhancing the precision of radiation delivery. IGRT uses imaging techniques during treatment to ensure that the patient is positioned accurately and that the tumor is targeted precisely. This increased accuracy allows for smaller margins around the tumor, as the risk of missing the target due to positional variations is significantly reduced. By localizing the tumor more precisely, clinicians can safely minimize the PTV margin, thus allowing for higher doses of radiation to the tumor while sparing surrounding healthy tissue.

The other factors, while they may influence treatment planning or delivery, do not directly relate to the ability to accurately pinpoint the tumor location during each treatment session in the same way that IGRT does. For instance, patient weight might affect treatment logistics but does not inherently improve the localization of the tumor, while the experience of the radiation therapist could contribute to overall treatment quality but does not specifically address the precision that IGRT offers. The type of cancer might require different considerations in treatment planning, but it does not directly impact the ability to decrease PTV margins like IGRT does.