Effects of attenuation correction on tumor detection in PET oncology

In this work the authors studied the effect of attenuation correction on tumor detection in PET oncology through simulation, phantom, and patient studies. Images were reconstructed from attenuated projection data with and without performing attenuation correction (AC and non-AC). The simulation and phantom studies showed that when the ratio of the activity concentration in the tumor to that in the torso background was at a critical value, the tumor was invisible in the non-AC image. Above the critical value, the tumor was visible in both AC and non-AC images, while below the critical value, the tumor appeared as a cold spot in non-AC images. Theoretical explanations of these phenomena were approached through examining the attenuated sinograms and the FBP reconstruction without AC. This work suggests that whole-body PET images should not be reconstructed without attenuation correction.