Automated liver lesion detection in 68Ga DOTATATE PET/CT using a deep fully convolutional neural network

Background Gastroenteropancreatic neuroendocrine tumors most commonly metastasize to the liver; however, high normal background Ga-68-DOTATATE activity and high image noise make metastatic lesions difficult to detect. The purpose of this study is to develop a rapid, automated and highly specific method to identify Ga-68-DOTATATE PET/CT hepatic lesions using a 2D U-Net convolutional neural network. Methods A retrospective study of Ga-68-DOTATATE PET/CT patient studies (n = 125; 57 with Ga-68-DOTATATE hepatic lesions and 68 without) was evaluated. The dataset was randomly divided into 75 studies for the training set (36 abnormal, 39 normal), 25 for the validation set (11 abnormal, 14 normal) and 25 for the testing set (11 abnormal, 14 normal). Hepatic lesions were physician annotated using a modified PERCIST threshold, and boundary definition by gradient edge detection. The 2D U-Net was trained independently five times for 100,000 iterations using a linear combination of binary cross-entropy and dice losses with a stochastic gradient descent algorithm. Performance metrics included: positive predictive value (PPV), sensitivity, F-1 score and area under the precision-recall curve (PR-AUC). Five different pixel area thresholds were used to filter noisy predictions. Results A total of 233 lesions were annotated with each abnormal study containing a mean of 4 +/- 2.75 lesions. A pixel filter of 20 produced the highest mean PPV 0.94 +/- 0.01. A pixel filter of 5 produced the highest mean sensitivity 0.74 +/- 0.02. The highest mean F-1 score 0.79 +/- 0.01 was produced with a 20 pixel filter. The highest mean PR-AUC 0.73 +/- 0.03 was produced with a 15 pixel filter. Conclusion Deep neural networks can automatically detect hepatic lesions in Ga-68-DOTATATE PET. Ongoing improvements in data annotation methods, increasing sample sizes and training methods are anticipated to further improve detection performance.

Automated summary

This study developed a rapid and specific method using a 2D U-Net convolutional neural network to identify hepatic lesions in Ga-68-DOTATATE PET/CT images. The results showed promising performance metrics, indicating the potential for automatic detection of lesions in future studies.