{'fraction_non_alphanumeric': 0.05307599517490953, 'fraction_numerical': 0.037997587454764774, 'mean_word_length': 4.368932038834951, 'pattern_counts': {'":': 0, '<': 6, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
SU-E-I-184: Variation of SUV in Time of Flight and Non-Time of Flight Dual Time Oncologic PET-CT

Purpose: To investigate the differences of SUV obtained in dual PET‐CT using time of flight (TOF) and non‐TOF iterative reconstruction. Methods: : List mode PET/CT scan of the chest was performed using average of 10 mCi of F‐18 FDG at 1 and 2 hour post‐injection under fasting condition. The maximum standard uptake value (SUVmax) was measured in lungcancer during radiation therapy on ungated PET‐CT images using TOF and non‐ TOF iterative reconstruction in a Philips Big Bore PET‐CT system. 94 pairs of SUV were measured in TOF and non‐TOF PETimages obtained at 1 hr after injection and another 94 pairs were measured at 2 hr post‐inection. Paired t‐tests were used for differences in SUV with cut‐off values of <5, <7.5 <10. A p‐value <0.05 was considered to be significant. Results: Significant variability of SUV is demonstrated between TOF and non‐TOF PETimages obtained at 1 and 2‐hr post‐injection (p<0.0001 in both time points) (Table attached). Mean and SD non‐TOF SUV1hr = 8.82 +/− 4.81 and SUV2hr = 10.66 +/− 6.02. Mean TOF SUV1hr = 8.10 +/− 4.17 and SUV2hr = 10.05 +/− 5.31. There were no significant differences for tumor SUV < 5 between TOF and non‐TOF measured at 1 or 2 hr (Curve attached). These results were also observed in phantom studies. Conclusions: While image quality may be improved with PET scanners having TOF options, the SUV is in general higher in non‐TOF reconstruction due to scatter activity. Recognition of such differences is important when patients are scanned on different PET scanners during the course of their disease.