Respiration-averaged CT for attenuation correction in non-small-cell lung cancer

Purpose: Breathing causes artefacts on PET/CT images. Cine CT has been used to reduce respiratory artefacts by acquiring multiple images during a single breathing cycle. The aim of this prospective study in non-small-cell lung cancer (NSCLC) patients was twofold. Firstly, we sought to compare the motion artefacts in PET/CT images attenuation-corrected with helical CT (HCT) and with averaged CT (ACT), which provides an average of cine CT images. Secondly, we wanted to evaluate the differences in maximum standardized uptake values (SUV_max) between HCT and ACT. Methods: Enrolled in the study were 80 patients with NSCLC. PET images attenuation-corrected with HCT (PET/HCT) and with ACT (PET/ACT) were obtained in all patients. Misregistration was evaluated by measurement of the curved photopenic area in the lower thorax of the PET images for all patients and direct measurement of misregistration for selected lesions. SUV_max was measured separately at the primary tumours, regional lymph nodes, and background. Results: A total of 80 patients with NSCLC were included. Significantly lower misregistrations were observed in PET/ACT images than in PET/HCT images (below-thoracic misregistration 0.25±0.58 cm vs. 1.17±1.17 cm, p<0.001; lesion misregistration 1.38±2.10 vs. 3.10±4.09, p=0.013). Significantly higher SUV_max were noted in PET/ACT images than in PET/HCT images in the primary tumour (p<0.001) and regional lymph nodes (p<0.001). Compared with PET/HCT images, the magnitude of SUV_max in PET/ACT images was higher by 0.35 for the main tumours and 0.34 for lymph nodes. Conclusion: Due to its significantly reduced misregistration, PET/ACT provided more reliable SUV _max and may be useful in treatment planning and monitoring the therapeutic response in patients with NSCLC.