Deep-inspiration breath-hold PET/CT versus free breathing PET/CT and respiratory gating PET for reference: evaluation in 95 patients with lung cancer

Objective The objective of this study was to define the factors that correlate with differences in maximum standardized uptake value (SUV(max)) in deep-inspiration breath-hold (DIBH) and free breathing (FB) PET/CT admixed with respiratory gating (RG) PET for reference. Methods Patients (n = 95) with pulmonary lesions were evaluated at one facility over 33 months. After undergoing whole-body PET/CT, a RG PET and FB PET/CT scans were obtained, followed by a DIBH PET/CT scan. All scans were recorded using a list-mode dynamic collection method with respiratory gating. The RG PET was reconstructed using phase gating without attenuation correction; the FB PET was reconstructed from the RG PET sinogram datasets with attenuation correction. Respiratory motion distance, breathing cycle speed, and waveform of RG PET were recorded. The SUV(max) of FB PET/CT and DIBH PET/CT were recorded: the percent difference in SUV(max) between the FB and DIBH scans was defined as the % BH-index. Results The % BH-index was significantly higher for lesions in the lower lung area than in the upper lung area. Respiratory motion distance was significantly higher in the lower lung area than in the upper lung area. A significant relationship was observed between the % BH-index and respiratory motion distance. Waveforms without steady end-expiration tended to show a high % BH-index. Significant inverse relationships were observed between % BH-index and cycle speed, and between respiratory motion distance and cycle speed. Conclusion Decrease in SUV(max) of FB PET/CT was due to (1) tumor size, (2) distribution of lower lung, (3) long respiratory movement at slow breathing cycle speeds, and (4) respiratory waveforms without steady end-expiration.