Comparison between 20 seconds breath-hold acquisition and respiratory gating on PET: Effect on detection and quantification

554 Objectives Respiratory movements are an important concern impairing PET acquisition accuracy, leading to a decrease in SUVmax of the moving targets. Nevertheless, respiratory gating system is time-consuming and not always friendly to implement. We aimed to compare the respiratory gating (G) and 20s breath-hold (BH) inspiratory acquisitions on PET scans in terms of detectability and quantification. Methods We compared on a Siemens (mCT), the maximal uptake level using the SUVmax and the signal to noise (S/N) ratio of 28 lung target lesions in 22 consecutive patients (43 to 81 years). The SUV max were measured : - on the sum of three consecutive 20s BH PET acquisitions, coupled with a single breath 5s CT, - on PET images obtained by G-PET using an Anzai system (belt with pressure sensor) by computing the average value of each of the six phases for both parameters, - on a standard free-breathing whole body (SWB) acquisition. S/N was defined as the ratio of targets9 SUVmax and a spherical ROI of 2 cm3 drawn on the pulmonary artery. Results were expressed as mean ± sd. Results All patients sustained the 3 series of 20s apnea. For each BH-PET acquisition, reproducibility of SUVmax and S/N was high (respectively r = 0.97, p = 0.001 and r = 0.93, p = 0.001 between two consecutive acquisitions). 100% of lesions were detected on both BH and G-PET images. Lesion size (11 in the lower and 10 in the upper lobe) varied from 4 to more than 20 mm with movements in the three directions from 0 to 35 mm. Compared to SWB, SUVmax and S/N increased significantly on 20s BH-PET images (respectively 57 ± 68 %, p Conclusions Compared to respiratory gating, three consecutive apneas of 20s, increased similarly SUVmax and improved S/N ratio while reducing the examination time and improving the simplicity of patients9 workflow