A personal acquisition time regimen of 68Ga-DOTATATE total-body PET/CT in patients with neuroendocrine tumor (NET)：A feasible study.

Jie Xiao; Hongcheng Shi

Abstract

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Introduction: The injection activity and acquisition time of ⁶⁸Ga-DOTATATE varied from current literature. As a result, the comparability of image quality between different studies was reduced. The regimen of a variable-acquisition time of ⁶⁸Ga-DOTATATE PET/CT for an acceptable and constant image has not been investigated so far. Therefore, the aim of the present study was to propose a variable-acquisition time regimen to balance the influence of scanner, BM, and to obtain a homogeneous image quality of patients with neuroendocrine tumor.

Methods: The development cohort consisting of 19 consecutive patients with full activity (88.7-204.9MBq, 1.9±0.2 MBq/kg) was to establish the acquisition time regimen. The liver SNR (signal-to-noise ratio, SNR_L) was normalized (SNR_norm) by the product of injected activity and acquisition time. Fits of SNR_normagainst body mass (BM) in linear correlation were performed. A subjective assessment of image quality was performed using a 5-point Likert scale to determine the acceptable threshold of SNR_L. Then, an optimized acquisition regimen based on BM was proposed and then validated based on a cohort consisting of 57 NET patients with half activity (66.9±11.3 MBq, 1.0±0.1 MBq/kg) in a fix-acquisition time regimen.

Results: The linear correlation (R²=0.63) between SNR_norm and BM was presented as: SNR_norm=-0.01*BM+1.50. The threshold SNR_L of acceptable image quality was 11.2. Then, the patient-specific variable-acquisition time regimen was determined as: t (min) = 125.4/(injective activity)*(-0.01*BM+1.50)². Based on the regimen, the average acquisition time for acceptable image quality in the validation cohort was 2.99±0.91 min, ranging from 2.18 to 6.35 min, which was reduced by 36.50%~78.20% compared with the fix-acquisition time of 10 min. The subjective evaluation showed the acceptable image quality could be obtained at 3.00 min in low-activity group with an average score of 3.44±0.53 (kappa = 0.97, 95% CI: 0.96~0.98). Bland-Altman analysis showed good agreement between the proposed regimen and the fix-acquisition time cohort.

Conclusions: A personal acquisition time regimen was proposed and validated its feasibility for patients with NET of ⁶⁸Ga-DOTATATE total-body PET/CT imaging. Based on the regimen, the image quality could be feasible for a constant level independent of body mass with reasonable acquisition time.