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 (μ) 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 μ for AC resulted in quantitative errors roughly proportional to the difference between μ used in AC (μ
_AC
) and local μ, yielding approximately ± 5% bias, corresponding to the variation of μ for 511-keV photons in breast tissue. Global bias was lowest when uniform μ
_AC
was equal to the phantom mean μ (μ
_mean
). Local bias in 10-mm spheres increased as the sphere μ deviated from μ
_mean
, but remained only 2%-3% when the μ
_sphere
was 6.5% higher than μ
_mean
. Bias varied linearly with and was roughly proportional to local μ mismatch. Minimizing local bias, e.g., in a small sphere, required the use of a uniform μ value between the local μ and the μ
_mean
. Thus, biases from using uniform-μ AC are low when local μ
_sphere
is close to μ
_mean
. As the μ
_sphere
increasingly differs from the phantom μ
_mean
, bias increases, and the optimal uniform μ is less predictable, having a value between μ
_sphere
and the phantom μ
_mean
.