If the collimated field size is doubled during a radiographic exam, how does the Dose Area Product (DAP) change?

• A. The DAP remains unchanged.
• B. The DAP decreases.
• C. The DAP increases but not proportionally.
• D. The DAP is doubled

Answer: (D)

DAP is the product of the dose to the patient and the irradiated area. If you double the collimated field size, you double the area that is being irradiated. Assuming the dose per unit area stays the same (the exposure factors are not changed to compensate), the total energy delivered to the patient increases in direct proportion to the area, so the DAP doubles. In other words, DAP scales with the field area when the dose per unit area is unchanged.