Dose reduction to breast tissue using bithmus breast shields for PET/CT: Effects of bithmus shield on SUV values during PET/CT acquisition

Objectives Previous studies demonstrated that bithmus shields can reduce radiation dose to breasts during CT scanning up to 55%. The purpose of the study was to determine the effects of bithmus shields on SUV values and counts in a PET/CT acquisition.

Methods Standard PET/CT scans were acquired using a water filled phantom with and without a bithmus shield with a lead equivalency of 0.035 mm. 1 mCi of F18-FDG was utilized for each scan. Scans were performed using our standard auto mA CT protocol. The attenuation correction and non-attenuation correction PET 3D images were obtained. On each of 35 slices per scan, mean and maximum SUV values and counts were obtained in a 1 cm circular ROI at the periphery of the phantom, 1 cm from the edge of the phantom covered by the shield and at a similar site not covered. In a similar fashion, mean and maximum SUV values and counts were obtained in the center of the phantom covered with a shield and without a shield in a 10 cm circular ROI.

Results On the attenuation corrected PET images, the SUV values and counts within 2 cm from the shield were 10 % higher than the SUV values and counts in the central portion of the phantom, likely secondary to the beam hardening attenuation artifact. These values had a statistically significant difference.On the non-CT attenuation corrected PET images, the values were 8 % lower than the SUV values and counts in the central portion of the phantom, but the difference was still statistically significant as well. The SUV values and counts in the central portion of the phantom, covered by the shield and in the same region without a shield showed less than 1 % variability and demonstrated no statistically significant difference.

Conclusions The bithmus shield does not affect the SUV values and counts in the phantom except for a very small area at the edge of the phantom immediately adjacent to the shield. Therefore, the bithmus shield can be used for effective dose reduction to the breast without compromise in accurate reading