If the hinge angle is 90°, what wedge angle must be chosen for uniform dose to the region of overlap?

When the hinge angle is set at 90°, the choice of wedge angle directly influences the dose distribution in the overlapping region of the treatment fields. A wedge is used to modify the dose distribution and achieve a more uniform dose in areas where beams might otherwise produce hot spots due to collimation adjustments.

To achieve uniform dose distribution between the two overlapping beams, the wedge angle must equal half of the hinge angle. Since the hinge angle is 90°, the corresponding wedge angle calculated should be 90°/2, which results in a wedge angle of 45°. This wedge angle is designed to effectively blend the two treatment fields, reducing the discrepancies in dose delivery.

Using a wedge angle of 45° allows the beams to come together more harmoniously, distributing the dose effectively across the region of overlap and minimizing any potential dose gradients. Thus, the choice of a wedge angle of 45° is crucial in ensuring a balanced dose distribution in the specific treatment area addressed by the overlap.