What is the recommended collimation for an anteroposterior (AP) projection of the tibia and fibula?

What is the recommended collimation for an anteroposterior (AP) projection of the tibia and fibula?

• A. 2 inches (5 cm) on either side of the tibia/fibula and from the knee to the ankle joint
• B. 3 inches (7.5 cm) on either side and from knee to ankle joint
• C. 1 inch (3 cm) on either side of the tibia/fibula and from the knee to the ankle joint
• D. 1 inch (3 cm) on one side only

Answer: (C)

For an AP tibia and fibula projection, the field should be tightly limited to just around the tibia and fibula on both sides and cover from the knee joint to the ankle joint. This focused collimation includes the entire length of the bones and their joints, which is essential for accurate assessment of alignment and fractures, while minimizing radiation exposure to surrounding tissues and reducing scatter that can degrade image contrast. A wider field would increase dose and scatter, while a field that's not centered or too narrow could clip bone ends or miss important anatomy.

For an AP tibia and fibula projection, the field should be tightly limited to just around the tibia and fibula on both sides and cover from the knee joint to the ankle joint. This focused collimation includes the entire length of the bones and their joints, which is essential for accurate assessment of alignment and fractures, while minimizing radiation exposure to surrounding tissues and reducing scatter that can degrade image contrast. A wider field would increase dose and scatter, while a field that's not centered or too narrow could clip bone ends or miss important anatomy.