Impact of Using Uniform Attenuation Coefficients for Heterogeneously Dense Breasts in a Dedicated Breast PET/X-ray Scanner.

We investigated PET image quantification when using a uniform attenuation coefficient () for attenuation correction (AC) of anthropomorphic density phantoms derived from high-resolution breast CT scans. A breast PET system was modeled with perfect data corrections except for AC. Using uniform for AC resulted in quantitative errors roughly proportional to the difference between used in AC ( ) and local , yielding approximately ± 5% bias, corresponding to the variation of for 511 keV photons in breast tissue. Global bias was lowest when uniform was equal to the phantom mean ( ). Local bias in 10-mm spheres increased as the sphere deviated from , but remained only 2-3% when the was 6.5% higher than . Bias varied linearly with and was roughly proportional to local mismatch. Minimizing local bias, e.g., in a small sphere, required the use of a uniform value between the local and the . Thus, biases from using uniform- AC are low when local is close to . As the increasingly differs from the phantom , bias increases, and the optimal uniform is less predictable, having a value between and the phantom .