When is a wedge typically used in a treatment field?

A wedge is typically used in a treatment field to compensate for missing tissue. This is especially relevant in radiation therapy, where achieving an even dose distribution is critical for the treatment's effectiveness. When there are variations in tissue density or missing areas due to surgical resection or anatomical irregularities, wedges help to modulate the radiation beam. By altering the angle and intensity of the radiation at different depths, wedges ensure that the prescribed dose is delivered uniformly to the target area, enhancing the therapeutic outcome while minimizing exposure to surrounding healthy tissues.

In contrast, the other options do not accurately describe the primary usage of a wedge in treatment settings. Increasing dosage, decreasing treatment time, or enhancing image quality are not primary functions of a wedge in radiation therapy; rather, those aspects are managed through other means and techniques in the treatment planning process.