What is the primary concern when using small penumbra beams in treatment?

The primary concern when using small penumbra beams in treatment is the accuracy of field placement. Small penumbra refers to the gradient of radiation exposure at the edges of the treatment field. A smaller penumbra indicates a sharper transition between treated and untreated areas. This precision is critical for ensuring that the radiation dose is delivered precisely to the target tissue while minimizing exposure to surrounding healthy tissue. If the field placement is not accurate, it can lead to underdosing of the tumor or overdosing of healthy structures, potentially resulting in ineffective treatment or increased side effects.

The other options, while relevant to radiation therapy, do not represent the most immediate concern related to small penumbra beams. Increased radiation leakage pertains to secondary radiation issues, which may not be the primary focus. The level of absorbed dose is a crucial aspect, but it is typically addressed through careful planning and calculation based on accurate field placement. Lastly, the type of radiation used can influence treatment but is not directly tied to the issues specifically related to small penumbra beams and their precision in field placement. Therefore, ensuring accurate positioning of the treatment field is fundamental when utilizing small penumbra beams.