Advanced PET imaging simultaneously improves image noise and patient throughput in 68Ga DOTATATE scans

189 Objectives: The benefits of both advanced digital detectors and larger field of view, available on modern PET scanners, have been well characterized in the scientific literature. However, the clinical benefits to patient imaging from the radiologists’ perspective and from the technologists’ perspective have not been well quantified. Generally, the higher sensitivity of modern devices has allowed PET imaging facilities to consider changes to imaging protocols including shorter bed durations. This is often handled qualitatively with physicians noting that the image quality is better on new devices, however, this is a relatively subjective assessment. Recently, our facility has replaced a smaller field of view analog PET/CT scanner with a modern digital device with an extended axial field of view. The purpose of this study is to quantify improvements in image quality as measured by image noise as well as quantify improvement in patient throughput as measured by total scan time. Methods: To quantitatively assess differences in image quality between older and modern devices, regions of interest (ROI) were drawn in the blood pool (aorta) and liver for 20 68Ga DOTATATE patients. The first 10 studies were acquired on an older Discovery STE (General Electric, Waukesha WI) with an approximately 15 cm axial extent and the second 10 from the new Discovery MI PET / CT (General Electric, Waukesha WI) with an approximately 25 cm axial extent. All scans were performed with 5 minutes per bed, iterative reconstruction, and used 5 mm post reconstruction gaussian smoothing. Care was taken to ensure the ROIs avoided tissue boundaries and areas of heterogeneous uptake. SUVmean and standard deviation were measured in each region and the coefficient of variation within each region was calculated. To determine if differences in these parameters were statistically significant, a two tailed t-test was performed. To assess changes in patient throughput, the number of bed positions was tracked for each patient and used to calculate total scan time. Additionally, the time that the patient entered and exited the PET/CT scanner room was tracked for the 10 Discovery MI patients to relate differences in scan time, to the total time the patient occupies the imaging suite. Results: The average SUVmean in the liver was 5.21 ± 1.38 and 6.20 ± 2.67 for the Discovery STE and Discovery MI, respectively. The difference was not statistically significant (p = 0.30). The average standard deviation in the liver was 1.03 ± 0.38 and 0.30 ± 0.11 for the Discovery STE and Discovery MI, respectively. This difference was statistically significant (p < 0.001). Similar findings were observed in the blood pool with the average values of SUVmean of 1.00 ± 0.29 and 1.11 ± 0.37 (not significantly different, p = 0.38) and average standard deviations of 0.23 ± 0.07 and 0.13 ± 0.04 (significantly different, p < 0.01), for Discovery STE and Discovery MI PET / CT, respectively. Regarding throughput, patients imaged on the Discovery STE required either 6 or 7 bed positions (average = 6.64) resulting in an average imaging time of 33.2 minutes. Patients imaged on the Discovery MI all required 5 bed positions resulting in a 25-minute imaging time. Tracking the total room time for Discovery MI patients indicated that the amount of time spent in the room, not during scanning was on average 9.5 minutes. Consequently, use of the new scanner reduced total room time on average from 42.7 minutes per exam to 34.5 minutes per exam. Conclusions: Modern digital PET / CT system with a large field of view can simultaneously achieve reduced total clinical imaging time and improvement in image quality while maintaining the same time per bed position. Quantification of imaging times and imaging metrics can support the rational design of clinical protocols which optimize the acquisition parameters and simultaneously improve image quality.