Parametric net influx rate imaging of 68Ga-DOTATATE in patients with neuroendocrine tumors: assessment of lesion detectability

Objectives

There has been developed a clinical dynamic total-body ⁶⁸Ga-DOTATATE PET/CT imaging protocol that allows quantitative imaging of net influx rate (K_i). Using qualitative and quantitative analyses of clinical studies, this retrospective study aims to assess whether parametric K_i images improve lesion detectability.

Methods

Using a 194-cm axial field-of-view PET/CT scanner, 52 patients with neuroendocrine tumors underwent a 60-min dynamic total-body ⁶⁸Ga-DOTATATE scan. Parametric K_i images and static standardized uptake value (SUV) images were generated. In addition to visual inspection of both sets of images, a quantitative analysis of 249 individual lesions was conducted using the target-to-background (TBR) metric.

Results

There were 52 patients who underwent dynamic total-body ⁶⁸Ga-DOTATATE PET/CT scans. A total of 249 lesions were evaluated, of which 66 lesions were biopsy-proven and 183 lesions were unproven. K_i images produced two fewer false positives than the SUV images. Overall, our results from 66 proven NET lesions suggested similar sensitivity (98.5%) but improved accuracy (from 95.6 to 97.1%) and potentially enhanced specificity with K_i over SUV imaging. Besides, there was no difference in the number of pathological lesions identified visually in both images. However, K_i TBR was significantly higher than SUV TBR quantitatively (P < 0.001).

Conclusions

Patlak K_i imaging provides nuclear physicians with a PET image with higher tumor contrast which may enhance confidence in diagnosis with possibly reduced false positive results, albeit an equivalent detectability, compared to static SUV image.