Shield placement: effect on exposure

Area of Science:

• Radiological sciences
• Pediatric imaging
• Radiation protection

Background:

• Red marrow, crucial for hematopoiesis, is abundant in children's long bones.
• Collimation in radiography reduces radiation dose but does not eliminate exposure outside the primary beam.
• Adjacent radiosensitive tissues, like bone marrow, can receive significant radiation dose from scatter and off-focus radiation.

Purpose of the Study:

• To determine optimal shield placement for adjacent bone marrow during pediatric knee imaging.
• To evaluate shield placement strategies for maximizing radiation dose reduction outside the collimated field.

Main Methods:

• Radiation exposure was quantified using an ion chamber and cassette with a knee phantom.
• Measurements were taken at two locations relative to the collimated field: anterior and posterior surfaces.
• Exposure sources outside collimation, including leakage, off-focus, scatter, and remnant primary radiation, were considered.

Main Results:

• Shielding placed on the anterior surface (facing the primary beam) resulted in a statistically significant reduction in radiation exposure outside the collimated field.
• This anterior shielding placement proved more effective than posterior placement in reducing extraneous radiation.

Conclusions:

• Collimation alone is insufficient to eliminate all radiation exposure outside the intended field of view.
• Shielding is essential in conjunction with collimation for comprehensive radiation dose reduction in pediatric imaging.
• Placing shielding on the patient's surface directly facing the primary X-ray beam is the most effective strategy for minimizing radiation exposure to adjacent bone marrow.