How can dose non-uniformity be minimized when using adjacent photon fields for treatment?

Minimizing dose non-uniformity at the junction of adjacent photon fields is essential in radiotherapy to ensure that the treatment is effective and that surrounding healthy tissue is spared. Increasing the penumbra width at the junction allows for a gradual transition in dose rather than a sudden change, which helps to blend the dose distribution from the adjacent fields more smoothly.

When the penumbra width is increased, it creates a softer edge where the dose can overlap, reducing the chance of hot or cold spots at the treatment site. This overlapping area allows for a more uniform dose distribution, which is crucial for effectively targeting the tumor while minimizing exposure to surrounding tissues.

In contrast, the other strategies would not achieve this goal effectively. Decreasing the penumbra width would create a sharper edge, potentially leading to more pronounced dose discrepancies at the junction. Blocking the junction completely would disrupt the treatment field and could inadvertently increase dose non-uniformity, rather than addressing it. Finally, simply adding additional radiation fields does not directly address dose uniformity at the junction and could complicate treatment planning without resolving the underlying issue.