Activity Dose Reduction in ⁶⁴Cu-DOTATATE PET in Patients with Neuroendocrine Neoplasms: Impact on Image Quality and...

Patients with neuroendocrine neoplasms (NEN) engage in lifelong follow-up with frequent somatostatin receptor PET, e.g. [⁶⁴Cu]Cu-DOTATATE PET, and continued measures to reduce radiation exposures should be in pursued in accordance with the as-low-as-reasonably-achievable (ALARA) principle. We therefore aimed to determine the lowest achievable [⁶⁴Cu]Cu-DOTATATE dose while maintaining image quality and lesion detection rate.

We included scans from 38 patients with NEN referred to routine [⁶⁴Cu]Cu-DOTATATE PET/CT. Using reconstruction of under-sampled PET list-mode data, we simulated [⁶⁴Cu]Cu-DOTATATE activity dose-reduced PET equivalents with median [range] 142 MBq [127;157], 95 MBq [85;105], and 48 MBq [42;52], corresponding to 75% (PET_75%), 50% (PET_50%), and 25% (PET_25%) of the full-dose 191 MBq [169;209] (PET_100%). Three blinded readers independently assessed image quality (scores 1-5), lesion confidence (scores 0-2), and counted lesions grouped by organs and regions. Number of lesions, proportions of patients with diagnostic image quality (reader-median image quality ≥ 4), diagnostic lesion confidence (reader-median lesion confidence ≥ 1), and per-patient sensitivities and specificities for organ-specific disease on PET_75-25% were compared with PET_100%.

The median [⁶⁴Cu]Cu-DOTATATE activity dose could be reduced from 191 to 142 MBq without decline in diagnostic image quality (P = 0.62), diagnostic lesion confidence (P = 1.0), or number of lesions detected in major organs or regions (P = 0.19-0.71). Sensitivity and specificity for detection of liver disease were 100% (26/26 patients) and 100% (12/12), respectively, for both PET_75% and PET_50%. Overall sensitivity for detection of NEN was 100% (26/26) for both PET_75% and PET_50%, and overall specificities were 92% (11/12) and 100% (12/12) for PET₇₅ and PET₅₀, respectively. Following dose-blinded post hoc review, the PET_75% specificity was adjusted to 100% (12/12).

The [⁶⁴Cu]Cu-DOTATATE activity dose can be reduced from 191 MBq to at least 142 MBq without losing image quality or lesion detection ability and further reduced to 95 MBq without loss of clinically relevant information.